Metrological framework for selecting morphological characters to identify species and estimate developmental maturity of forensically significant insect specimens
- Midgley, John M, Villet, Martin H
- Authors: Midgley, John M , Villet, Martin H
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440784 , vital:73813 , https://doi.org/10.1080/20961790.2020.1794347
- Description: Accurate age estimates of immature necrophagous insects associated with a human or animal body can provide evidence of how long the body has been dead. These estimates are based on species-specific details of the insects’ aging processes, and therefore require accurate species identification and developmental stage estimation. Many professionals who produce or use identified organisms as forensic evidence have little training in taxonomy or metrology, and appreciate the availability of formalized principles and standards for biological identification. Taxonomic identifications are usually most readily and economically made using categorical and qualitative morphological characters, but it may be necessary to use less convenient and potentially more ambiguous characters that are continuous and quantitative if two candidate species are closely related, or if identifying developmental stages within a species. Characters should be selected by criteria such as taxonomic specificity and metrological repeatability and relative error. We propose such a hierarchical framework, critique various measurements of immature insects, and suggest some standard approaches to determine the reliability of organismal identifications and measurements in estimating postmortem intervals. Relevant criteria for good characters include high repeatability (including low scope for ambiguity or parallax effects), pronounced discreteness, and small relative error in measurements. These same principles apply to individuation of unique objects in general.
- Full Text:
- Date Issued: 2021
- Authors: Midgley, John M , Villet, Martin H
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440784 , vital:73813 , https://doi.org/10.1080/20961790.2020.1794347
- Description: Accurate age estimates of immature necrophagous insects associated with a human or animal body can provide evidence of how long the body has been dead. These estimates are based on species-specific details of the insects’ aging processes, and therefore require accurate species identification and developmental stage estimation. Many professionals who produce or use identified organisms as forensic evidence have little training in taxonomy or metrology, and appreciate the availability of formalized principles and standards for biological identification. Taxonomic identifications are usually most readily and economically made using categorical and qualitative morphological characters, but it may be necessary to use less convenient and potentially more ambiguous characters that are continuous and quantitative if two candidate species are closely related, or if identifying developmental stages within a species. Characters should be selected by criteria such as taxonomic specificity and metrological repeatability and relative error. We propose such a hierarchical framework, critique various measurements of immature insects, and suggest some standard approaches to determine the reliability of organismal identifications and measurements in estimating postmortem intervals. Relevant criteria for good characters include high repeatability (including low scope for ambiguity or parallax effects), pronounced discreteness, and small relative error in measurements. These same principles apply to individuation of unique objects in general.
- Full Text:
- Date Issued: 2021
Modulation of the optical properties of chiral porphyrin dimers by introducing bridged chiral amide-bonds
- Qin, Mingfeng, Zhang, Zhen, Zhu, Weihua, Mack, John, Soy, Rodah C, Nyokong, Tebello, Liang, Xu
- Authors: Qin, Mingfeng , Zhang, Zhen , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190815 , vital:45031 , xlink:href="https://doi.org/10.1142/S1088424620500492"
- Description: The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.
- Full Text:
- Date Issued: 2021
- Authors: Qin, Mingfeng , Zhang, Zhen , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190815 , vital:45031 , xlink:href="https://doi.org/10.1142/S1088424620500492"
- Description: The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.
- Full Text:
- Date Issued: 2021
Muco-adhesive clarithromycin-loaded nanostructured lipid carriers for ocular delivery: Formulation, characterization, cytotoxicity and stability
- Makoni, Pedzisai A, Khamanga, Sandile M, Walker, Roderick B
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Walker, Roderick B
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183150 , vital:43916 , xlink:href="https://doi.org/10.1016/j.jddst.2020.102171"
- Description: Topical ophthalmic formulations are the preferred approach to treat the anterior segment of the eye as it is a non-invasive therapeutic approach. The ocular bioavailability of drugs is generally limited, due to the presence of impervious anatomical barriers and low residence time and contact with the target tissue. Optimization of clarithromycin-loaded nanostructured lipid carriers using Design of Experiments was undertaken. Manufacture of nanostructured lipid carriers was achieved using hot emulsification ultrasonication. Formulation and process parameters were successfully identified following screening and subsequently optimized using Tween® 20, as a stabilizer. Muco-adhesive properties that could potentially increase ocular residence time, in vitro clarithromycin release and cytotoxicity against HeLa cells were evaluated. Short term stability studies of the optimized lipidic formulations was assessed at 4 °C and 22 °C. The optimized formulation exhibited muco-adhesive properties under stationary conditions assessed using Laser Doppler Anemometry, sustained release of API over 24 h under in vitro conditions. In vitro cytotoxicity studies revealed that the NLC were less cytotoxic to HeLa cells in comparison to pure API. The results suggest that the optimized carriers may have the potential to enhance precorneal retention, increase ocular availability and permit dose reduction or permit use of a longer dosing frequency.
- Full Text:
- Date Issued: 2021
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Walker, Roderick B
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183150 , vital:43916 , xlink:href="https://doi.org/10.1016/j.jddst.2020.102171"
- Description: Topical ophthalmic formulations are the preferred approach to treat the anterior segment of the eye as it is a non-invasive therapeutic approach. The ocular bioavailability of drugs is generally limited, due to the presence of impervious anatomical barriers and low residence time and contact with the target tissue. Optimization of clarithromycin-loaded nanostructured lipid carriers using Design of Experiments was undertaken. Manufacture of nanostructured lipid carriers was achieved using hot emulsification ultrasonication. Formulation and process parameters were successfully identified following screening and subsequently optimized using Tween® 20, as a stabilizer. Muco-adhesive properties that could potentially increase ocular residence time, in vitro clarithromycin release and cytotoxicity against HeLa cells were evaluated. Short term stability studies of the optimized lipidic formulations was assessed at 4 °C and 22 °C. The optimized formulation exhibited muco-adhesive properties under stationary conditions assessed using Laser Doppler Anemometry, sustained release of API over 24 h under in vitro conditions. In vitro cytotoxicity studies revealed that the NLC were less cytotoxic to HeLa cells in comparison to pure API. The results suggest that the optimized carriers may have the potential to enhance precorneal retention, increase ocular availability and permit dose reduction or permit use of a longer dosing frequency.
- Full Text:
- Date Issued: 2021
Naked Eye and Colorimetric Detection of Cyanide with a 1, 3‐Diethyl‐2‐thiobarbituric Acid Substituted Ferrocene Chemosensor
- Babu, Balaji, Mack, John, Nyokong, Tebello
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190567 , vital:45006 , xlink:href="https://doi.org/10.1002/slct.202100163"
- Description: A 1,3-diethyl-2-thiobarbituric-acid-substituted ferrocene (FET) has been evaluated for its cyanide sensing ability by UV-visible absorption spectroscopy and other characterization methods. FET provides a ratiometric colorimetric chemosensor for the CN− anion detection in 1 : 1 DMSO/H2O (v/v) solution. The addition of CN− results in an immediate color change from dark blue to pale orange that is visible to the naked eye. Mechanism studies and molecular modelling with TD-DFT calculations demonstrate that nucleophilic addition of CN− to an electrophilic sp2-hybridized carbon atom blocks charge transfer from the ferrocene ring complex to the thiobarbituric acid moiety. The FET sensor exhibits excellent selectivity for CN− and a limit of detection of 0.2 μM.
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190567 , vital:45006 , xlink:href="https://doi.org/10.1002/slct.202100163"
- Description: A 1,3-diethyl-2-thiobarbituric-acid-substituted ferrocene (FET) has been evaluated for its cyanide sensing ability by UV-visible absorption spectroscopy and other characterization methods. FET provides a ratiometric colorimetric chemosensor for the CN− anion detection in 1 : 1 DMSO/H2O (v/v) solution. The addition of CN− results in an immediate color change from dark blue to pale orange that is visible to the naked eye. Mechanism studies and molecular modelling with TD-DFT calculations demonstrate that nucleophilic addition of CN− to an electrophilic sp2-hybridized carbon atom blocks charge transfer from the ferrocene ring complex to the thiobarbituric acid moiety. The FET sensor exhibits excellent selectivity for CN− and a limit of detection of 0.2 μM.
- Full Text:
- Date Issued: 2021
Nano Co-Crystal Embedded Stimuli-Responsive Hydrogels: A Potential Approach to Treat HIV/AIDS
- Witika, Bwalya A, Stander, Jessé-Clint, Smith, Vincent J, Walker, Roderick B
- Authors: Witika, Bwalya A , Stander, Jessé-Clint , Smith, Vincent J , Walker, Roderick B
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183137 , vital:43915 , xlink:href="https://doi.org/10.3390/pharmaceutics13020127"
- Description: Currently, the human immunodeficiency virus (HIV) that causes acquired immunodeficiency syndrome (AIDS) can only be treated successfully, using combination antiretroviral (ARV) therapy. Lamivudine (3TC) and zidovudine (AZT), two compounds used for the treatment of HIV and prevention of disease progression to AIDS are used in such combinations. Successful therapy with 3TC and AZT requires frequent dosing that may lead to reduced adherence, resistance and consequently treatment failure. Improved toxicity profiles of 3TC and AZT were observed when combined as a nano co-crystal (NCC). The use of stimuli-responsive delivery systems provides an opportunity to overcome the challenge of frequent dosing, by controlling and/or sustaining delivery of drugs. Preliminary studies undertaken to identify a suitable composition for a stimulus-responsive in situ forming hydrogel carrier for 3TC-AZT NCC were conducted, and the gelation and erosion time were determined. A 25% w/w Pluronic® F-127 thermoresponsive hydrogel was identified as a suitable carrier as it exhibited a gelation time of 5 min and an erosion time of 7 days. NCC-loaded hydrogels were evaluated using in vitro dissolution and cytotoxicity assays. In vitro dissolution undertaken using membrane-less diffusion over 168 h revealed that 3TC and AZT release from NCC-loaded hydrogels was complete and followed zero-order kinetic processes, whereas those loaded with the micro co-crystal and physical mixture were incomplete and best described using the Korsmeyer–Peppas kinetic model. The release of AZT and 3TC from the physical mixture and MCC-loaded gel exhibited a value for n of 0.595 for AZT release from the physical mixture and 0.540 for the MCC technology, whereas the release exponent for 3TC was 0.513 for the physical mixture and 0.557 for the MCC technology indicating that diffusion and erosion controlled 3TC and AZT release. In vitro cytotoxicity assay data revealed that the addition of NCC to the thermoresponsive hydrogel resulted in an improved cell viability of 88.0% ± 5.0% when compared to the cell viability of the NCC of 76.9% ± 5.0%. The results suggest that the use of a thermoresponsive nanosuspension may have the potential to be delivered as an intramuscular injection that can subsequently increase bioavailability and permit dose reduction and/or permit use of a longer dosing frequency.
- Full Text:
- Date Issued: 2021
- Authors: Witika, Bwalya A , Stander, Jessé-Clint , Smith, Vincent J , Walker, Roderick B
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183137 , vital:43915 , xlink:href="https://doi.org/10.3390/pharmaceutics13020127"
- Description: Currently, the human immunodeficiency virus (HIV) that causes acquired immunodeficiency syndrome (AIDS) can only be treated successfully, using combination antiretroviral (ARV) therapy. Lamivudine (3TC) and zidovudine (AZT), two compounds used for the treatment of HIV and prevention of disease progression to AIDS are used in such combinations. Successful therapy with 3TC and AZT requires frequent dosing that may lead to reduced adherence, resistance and consequently treatment failure. Improved toxicity profiles of 3TC and AZT were observed when combined as a nano co-crystal (NCC). The use of stimuli-responsive delivery systems provides an opportunity to overcome the challenge of frequent dosing, by controlling and/or sustaining delivery of drugs. Preliminary studies undertaken to identify a suitable composition for a stimulus-responsive in situ forming hydrogel carrier for 3TC-AZT NCC were conducted, and the gelation and erosion time were determined. A 25% w/w Pluronic® F-127 thermoresponsive hydrogel was identified as a suitable carrier as it exhibited a gelation time of 5 min and an erosion time of 7 days. NCC-loaded hydrogels were evaluated using in vitro dissolution and cytotoxicity assays. In vitro dissolution undertaken using membrane-less diffusion over 168 h revealed that 3TC and AZT release from NCC-loaded hydrogels was complete and followed zero-order kinetic processes, whereas those loaded with the micro co-crystal and physical mixture were incomplete and best described using the Korsmeyer–Peppas kinetic model. The release of AZT and 3TC from the physical mixture and MCC-loaded gel exhibited a value for n of 0.595 for AZT release from the physical mixture and 0.540 for the MCC technology, whereas the release exponent for 3TC was 0.513 for the physical mixture and 0.557 for the MCC technology indicating that diffusion and erosion controlled 3TC and AZT release. In vitro cytotoxicity assay data revealed that the addition of NCC to the thermoresponsive hydrogel resulted in an improved cell viability of 88.0% ± 5.0% when compared to the cell viability of the NCC of 76.9% ± 5.0%. The results suggest that the use of a thermoresponsive nanosuspension may have the potential to be delivered as an intramuscular injection that can subsequently increase bioavailability and permit dose reduction and/or permit use of a longer dosing frequency.
- Full Text:
- Date Issued: 2021
Nanohybrid electrocatalyst based on cobalt phthalocyanine-carbon nanotube-reduced graphene oxide for ultrasensitive detection of glucose in human saliva
- Adeniyi, Omotayo, Nwahara, Nnamdi, Mwanza, Daniel, Nyokong, Tebello, Mashazi, Philani N
- Authors: Adeniyi, Omotayo , Nwahara, Nnamdi , Mwanza, Daniel , Nyokong, Tebello , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231356 , vital:49880 , xlink:href="https://doi.org/10.1016/j.snb.2021.130723"
- Description: The current diabetes management systems require collecting blood samples via an invasive and painful finger pricking leading to the formation of callus, scarring and loss of sensibility to patients due to continuous monitoring. Therefore, a non-invasive and painless method of determining glucose levels would be desirable to diabetes patients who need constant monitoring. Saliva glucose measurement is a non-invasive alternative for diabetes management. A highly sensitive, stable, and selective non-enzymatic electrochemical sensor that can accurately quantify saliva glucose is required. A single-walled carbon nanotube/reduced graphene oxide/cobalt phthalocyanines nanohybrid modified glassy carbon electrode (GCE-SWCNT/rGO/CoPc) has been fabricated for the non-enzymatic determination of glucose in human saliva. The SWCNT/rGO/CoPc was characterized using various spectroscopic, microscopic, and electrochemical techniques. The synergistic effect between SWCNT, rGO, and CoPc facilitated excellent electron transfer process that improved the sensor sensitivity. The GCE-SWCNT/rGO/CoPc sensor exhibited two linear responses in the 0.30 μM to 0.50 mM and 0.50–5.0 mM glucose concentration ranges, and the detection limit was 0.12 μM. The sensor had an excellent saliva glucose detection sensitivity of 992.4 μA·mM−1·cm−2 and high specificity for glucose in the presence of other coexisting analytes. In addition, it showed good storage stability, reusability, and a fast response time of about 1.2 s. The GCE-SWCNT/rGO/CoPc nanohybrid electrode showed excellent potential for developing accurate, non-invasive, and painless glucose sensing.
- Full Text:
- Date Issued: 2021
- Authors: Adeniyi, Omotayo , Nwahara, Nnamdi , Mwanza, Daniel , Nyokong, Tebello , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231356 , vital:49880 , xlink:href="https://doi.org/10.1016/j.snb.2021.130723"
- Description: The current diabetes management systems require collecting blood samples via an invasive and painful finger pricking leading to the formation of callus, scarring and loss of sensibility to patients due to continuous monitoring. Therefore, a non-invasive and painless method of determining glucose levels would be desirable to diabetes patients who need constant monitoring. Saliva glucose measurement is a non-invasive alternative for diabetes management. A highly sensitive, stable, and selective non-enzymatic electrochemical sensor that can accurately quantify saliva glucose is required. A single-walled carbon nanotube/reduced graphene oxide/cobalt phthalocyanines nanohybrid modified glassy carbon electrode (GCE-SWCNT/rGO/CoPc) has been fabricated for the non-enzymatic determination of glucose in human saliva. The SWCNT/rGO/CoPc was characterized using various spectroscopic, microscopic, and electrochemical techniques. The synergistic effect between SWCNT, rGO, and CoPc facilitated excellent electron transfer process that improved the sensor sensitivity. The GCE-SWCNT/rGO/CoPc sensor exhibited two linear responses in the 0.30 μM to 0.50 mM and 0.50–5.0 mM glucose concentration ranges, and the detection limit was 0.12 μM. The sensor had an excellent saliva glucose detection sensitivity of 992.4 μA·mM−1·cm−2 and high specificity for glucose in the presence of other coexisting analytes. In addition, it showed good storage stability, reusability, and a fast response time of about 1.2 s. The GCE-SWCNT/rGO/CoPc nanohybrid electrode showed excellent potential for developing accurate, non-invasive, and painless glucose sensing.
- Full Text:
- Date Issued: 2021
Nationwide Assessment of Population Structure, Stability and Plant Morphology of Two Mimusops Species along a Social-Ecological Gradient in Benin, West Africa
- Sinasson, Gisèle K, Shackleton, Charlie M, Sinsin, Brice
- Authors: Sinasson, Gisèle K , Shackleton, Charlie M , Sinsin, Brice
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/399805 , vital:69560 , xlink:href="https://doi.org/10.3390/f12111575"
- Description: Understanding tree species autecology and population structure supports effective conservation actions. Of particular importance are multipurpose trees that provide non-timber forest products (NTFPs). We assessed the population structures and morphologies of two species of NTFP trees in the genus Mimusops across bioclimatic zones in Benin by sampling 288 plots within 11 forests. Structural characteristics were compared between species, forests and zones. Correlations were also observed between Mimusops tree regeneration density, tree features and ecological characteristics. The density of trees ≥5 cm and of regeneration and mean tree height were higher for M. andongensis (within more protected forest) than M. kummel (in forests with access to people), while the highest mean diameter was observed for M. kummel. Tree and regeneration densities and mean height were greatest in the humid zone of Benin, whilst the largest mean diameter was obtained in the sub-humid zone. The results showed significant correlations between regeneration density and soil properties for M. andongensis but not for M. kummel. The correlations between tree morphology and soil characteristics were weak for both species. Ecological characteristics, along with the species’ functional traits and pressures, are important factors related to the observed differences between the species. All diameter classes were represented, and the population seemed more stable in the more protected forest relative to other forests. Mimusops trees with a diameter of 5–15 cm represented more than 30% of this species in most forests; this suggests, for M. kummel, whose trees flower when quite small (≥6 cm dbh), that there are sufficient reproductive trees. Thus, as a long-lived species, its populations could be maintained even with low/episodic recruitment. However, we found no regeneration in many forests and climate change could threaten populations. Therefore, it is important to investigate regeneration growth and dynamics, seed production and germination of the species in relation to the biophysical conditions and disturbances experienced by Mimusops stands.
- Full Text:
- Date Issued: 2021
- Authors: Sinasson, Gisèle K , Shackleton, Charlie M , Sinsin, Brice
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/399805 , vital:69560 , xlink:href="https://doi.org/10.3390/f12111575"
- Description: Understanding tree species autecology and population structure supports effective conservation actions. Of particular importance are multipurpose trees that provide non-timber forest products (NTFPs). We assessed the population structures and morphologies of two species of NTFP trees in the genus Mimusops across bioclimatic zones in Benin by sampling 288 plots within 11 forests. Structural characteristics were compared between species, forests and zones. Correlations were also observed between Mimusops tree regeneration density, tree features and ecological characteristics. The density of trees ≥5 cm and of regeneration and mean tree height were higher for M. andongensis (within more protected forest) than M. kummel (in forests with access to people), while the highest mean diameter was observed for M. kummel. Tree and regeneration densities and mean height were greatest in the humid zone of Benin, whilst the largest mean diameter was obtained in the sub-humid zone. The results showed significant correlations between regeneration density and soil properties for M. andongensis but not for M. kummel. The correlations between tree morphology and soil characteristics were weak for both species. Ecological characteristics, along with the species’ functional traits and pressures, are important factors related to the observed differences between the species. All diameter classes were represented, and the population seemed more stable in the more protected forest relative to other forests. Mimusops trees with a diameter of 5–15 cm represented more than 30% of this species in most forests; this suggests, for M. kummel, whose trees flower when quite small (≥6 cm dbh), that there are sufficient reproductive trees. Thus, as a long-lived species, its populations could be maintained even with low/episodic recruitment. However, we found no regeneration in many forests and climate change could threaten populations. Therefore, it is important to investigate regeneration growth and dynamics, seed production and germination of the species in relation to the biophysical conditions and disturbances experienced by Mimusops stands.
- Full Text:
- Date Issued: 2021
Nothing forever
- Authors: Krueger, Anton
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225533 , vital:49233 , xlink:href="https://doi.org/10.5920/pam.1013"
- Description: Thank you to everybody who made contributions to this bumper 2021 Special Issue on Improvisation. Many thanks to our peer reviewers and especially to co-editors Deborah and Daniel for their help with the selection and editing process which has now culminated in a baker’s dozen texts. With contributions from Australia, South Africa, and New Zealand, as well as from France, the USA and the UK, the issue includes five interviews, four articles, two book reviews, a reflection and a score.
- Full Text:
- Date Issued: 2021
- Authors: Krueger, Anton
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225533 , vital:49233 , xlink:href="https://doi.org/10.5920/pam.1013"
- Description: Thank you to everybody who made contributions to this bumper 2021 Special Issue on Improvisation. Many thanks to our peer reviewers and especially to co-editors Deborah and Daniel for their help with the selection and editing process which has now culminated in a baker’s dozen texts. With contributions from Australia, South Africa, and New Zealand, as well as from France, the USA and the UK, the issue includes five interviews, four articles, two book reviews, a reflection and a score.
- Full Text:
- Date Issued: 2021
Partial Purification and Characterization of Endoxylanase from a fungus, Leohumicola incrustata
- Adeoyo, Olusegun R, Pletschke, Brett I, Dames, Joanna F
- Authors: Adeoyo, Olusegun R , Pletschke, Brett I , Dames, Joanna F
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440393 , vital:73779 , 10.4314/br.v19i1.2
- Description: Xylanases are glycoside hydrolases (GH) that degrade β-1, 4-xylan, a linear polysaccharide found as hemicellulose in cell wall of plants. Endoxylanase (Endo-1, 4-β-xylanase, EC 3.2. 1.8) randomly catalyses xylan to produce varying short xylooligosaccharides (XOS). This study aimed to determine the characteristics of a partially purified endoxylanase from Leohumicola incrustata. Enzyme production was carried out using beechwood (BW) xylan, after which the cell-free crude filtrate was concentrated using the ammonium sulphate precipitation method. The hydrolysed products were analysed by thin-layer chromatography (TLC) and zymography. The result showed that the enzyme produced varying smaller-sized linear xylooligosaccharides with R f values corresponding to those of xylobiose, xylotriose, xylotetraose, xylopentaose, xylohexaose and other higher oligomers. The endoxylanase had a molecular mass of 72 kDa. The enzyme is stable in the presence of K+, Na+, Ca 2+, Fe 2+, Mg 2+, Zn 2+, Co 2+, pH of 5.0 and temperature of 37 o C. However, the activity gradually decreased after 60 min at 50 o C and retained over 69% activity after 120 min, while at 60 and 70 o C, the enzyme activity sharply decreased (pre-incubation periods). Endoxylanase from L. incrustata is comparable to those of other microorganisms and should be considered an attractive candidate for future industrial applications.
- Full Text:
- Date Issued: 2021
- Authors: Adeoyo, Olusegun R , Pletschke, Brett I , Dames, Joanna F
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440393 , vital:73779 , 10.4314/br.v19i1.2
- Description: Xylanases are glycoside hydrolases (GH) that degrade β-1, 4-xylan, a linear polysaccharide found as hemicellulose in cell wall of plants. Endoxylanase (Endo-1, 4-β-xylanase, EC 3.2. 1.8) randomly catalyses xylan to produce varying short xylooligosaccharides (XOS). This study aimed to determine the characteristics of a partially purified endoxylanase from Leohumicola incrustata. Enzyme production was carried out using beechwood (BW) xylan, after which the cell-free crude filtrate was concentrated using the ammonium sulphate precipitation method. The hydrolysed products were analysed by thin-layer chromatography (TLC) and zymography. The result showed that the enzyme produced varying smaller-sized linear xylooligosaccharides with R f values corresponding to those of xylobiose, xylotriose, xylotetraose, xylopentaose, xylohexaose and other higher oligomers. The endoxylanase had a molecular mass of 72 kDa. The enzyme is stable in the presence of K+, Na+, Ca 2+, Fe 2+, Mg 2+, Zn 2+, Co 2+, pH of 5.0 and temperature of 37 o C. However, the activity gradually decreased after 60 min at 50 o C and retained over 69% activity after 120 min, while at 60 and 70 o C, the enzyme activity sharply decreased (pre-incubation periods). Endoxylanase from L. incrustata is comparable to those of other microorganisms and should be considered an attractive candidate for future industrial applications.
- Full Text:
- Date Issued: 2021
Photo-sonodynamic combination activity of cationic morpholino-phthalocyanines conjugated to nitrogen and nitrogen-sulfur doped graphene quantum dots against MCF-7 breast cancer cell line in vitro
- Nene, Lindokhule Cindy, Nyokong, Tebello
- Authors: Nene, Lindokhule Cindy , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231334 , vital:49878 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102573"
- Description: In this work, we explore the reactive oxygen species (ROS) generation abilities of cationic morpholino-substituted-phthalocyanine (Pc) conjugated to nitrogen (NGQDs) and nitrogen-sulfur (NSGQDs) doped-graphene quantum dots upon irradiation with light for photodynamic therapy (PDT), ultrasound for sonodynamic therapy (SDT) and the combination of both in photo-sonodynamic therapy (PSDT). The in vitro cytotoxicity studies were conducted using the Michigan Cancer Foundation-7 breast cancer cell lines (MCF-7 cells). For PDT treatments, only the 1O2 was detected for all the sensitizers, whereas both the 1O2 and •OH radicals were evident after SDT and PSDT treatments. An increase in the 1O2 generation was observed for the conjugates compared to the GQDs and the Pc alone. However, the •OH radicals were reduced in the conjugates compared to the GQDs and the Pc alone. The NGQDs generally showed better ROS generation efficacy compared to the NSGQDs, alone and in the conjugates. The combination therapy also shows improved efficacy compared to the monotherapies for the Pcs and Pc-GQDs conjugates.
- Full Text:
- Date Issued: 2021
- Authors: Nene, Lindokhule Cindy , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231334 , vital:49878 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102573"
- Description: In this work, we explore the reactive oxygen species (ROS) generation abilities of cationic morpholino-substituted-phthalocyanine (Pc) conjugated to nitrogen (NGQDs) and nitrogen-sulfur (NSGQDs) doped-graphene quantum dots upon irradiation with light for photodynamic therapy (PDT), ultrasound for sonodynamic therapy (SDT) and the combination of both in photo-sonodynamic therapy (PSDT). The in vitro cytotoxicity studies were conducted using the Michigan Cancer Foundation-7 breast cancer cell lines (MCF-7 cells). For PDT treatments, only the 1O2 was detected for all the sensitizers, whereas both the 1O2 and •OH radicals were evident after SDT and PSDT treatments. An increase in the 1O2 generation was observed for the conjugates compared to the GQDs and the Pc alone. However, the •OH radicals were reduced in the conjugates compared to the GQDs and the Pc alone. The NGQDs generally showed better ROS generation efficacy compared to the NSGQDs, alone and in the conjugates. The combination therapy also shows improved efficacy compared to the monotherapies for the Pcs and Pc-GQDs conjugates.
- Full Text:
- Date Issued: 2021
Photocatalytic and solar radiation harvesting potential of a free-base porphyrin-zinc (II) phthalocyanine heterodyad functionalized polystyrene polymer membrane for the degradation of 4-chlorophenol
- Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185772 , vital:44422 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113142"
- Description: In this work a novel porphyrin-phthalocyanine heterodyad (complex 4) was synthesized and embedded in polystyrene polymer membranes. The singlet oxygen generation of 4 improved in comparison to the parent porphyrin and phthalocyanine complexes giving singlet oxygen quantum yields of 0.67 and 0.51 (in dimethyl sulfoxide) where the porphyrin and phthalocyanine complementarily absorb respectively. Successful Buchwald-Hartwig coupling of complex 4 to amine functionalized polystyrene ((NH2)PS) gave a complex loading of 24.6 mg complex/g 4-PS. Embedding of 4-PS in polystyrene polymer membrane yielded the photoactive 4-memb which proved to be capable of degrading 4-chlorophenol at reaction rates of at least 1.12 × 10−7 molL-1 min-1 and half-life of 193 min in a pseudo first order reaction at an initial concentration of 3.10 × 10-5. Also, light harvesting experiments proved 4-memb to be active in the whole 300–700 nm wavelength range with the greatest activity being under white light.
- Full Text:
- Date Issued: 2021
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185772 , vital:44422 , xlink:href="https://doi.org/10.1016/j.jphotochem.2021.113142"
- Description: In this work a novel porphyrin-phthalocyanine heterodyad (complex 4) was synthesized and embedded in polystyrene polymer membranes. The singlet oxygen generation of 4 improved in comparison to the parent porphyrin and phthalocyanine complexes giving singlet oxygen quantum yields of 0.67 and 0.51 (in dimethyl sulfoxide) where the porphyrin and phthalocyanine complementarily absorb respectively. Successful Buchwald-Hartwig coupling of complex 4 to amine functionalized polystyrene ((NH2)PS) gave a complex loading of 24.6 mg complex/g 4-PS. Embedding of 4-PS in polystyrene polymer membrane yielded the photoactive 4-memb which proved to be capable of degrading 4-chlorophenol at reaction rates of at least 1.12 × 10−7 molL-1 min-1 and half-life of 193 min in a pseudo first order reaction at an initial concentration of 3.10 × 10-5. Also, light harvesting experiments proved 4-memb to be active in the whole 300–700 nm wavelength range with the greatest activity being under white light.
- Full Text:
- Date Issued: 2021
Photocatalytic desulfurization of dibenzothiophene using asymmetrical zinc (II) phthalocyanines conjugated to silver-magnetic nanoparticles
- Mgidlana, Sithi, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185953 , vital:44451 , xlink:href="https://doi.org/10.1016/j.ica.2020.119970"
- Description: Asymmetrical Zn(II) phthalocyanines: mono (4-carboxy phenoxy) tris (phenylazo phenoxy) (1), mono (4-amino phenoxy) tris (phenylazo phenoxy) (2), mono (4-propanoic acid phenoxy) tris (phenylazo phenoxy) (3) zinc(II) phthalocyanines are synthesized and covalently linked to mercaptohexanol (mph) or mercaptopropionic acid (mpa) functionalized dimerized silver-magnetic nanoparticles (Ag-M). Complexes 1 and 3 are covalently linked to nanomaterials via ester bond whereas complex 2 is covalently linked to nanoparticles (NPs) via amide bond. The conjugates of complexes 1–3 with NPs gave higher singlet oxygen quantum than the Pcs alone. Electrospun fibers were fabricated from polystyrene (PS) solutions containing complexes 1 to 3 and their conjugates. The functionalized PS fibers were used for the phototransformation of dibenzothiophene. The increase in photocatalytic properties of phthalocyanines was observed in the presence of Ag-M with 3 alone and its conjugate with mph capped silver-magnetic nanoparticles showing the larger catalytic activity towards the transformation of dibenzothiophene.
- Full Text:
- Date Issued: 2021
- Authors: Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185953 , vital:44451 , xlink:href="https://doi.org/10.1016/j.ica.2020.119970"
- Description: Asymmetrical Zn(II) phthalocyanines: mono (4-carboxy phenoxy) tris (phenylazo phenoxy) (1), mono (4-amino phenoxy) tris (phenylazo phenoxy) (2), mono (4-propanoic acid phenoxy) tris (phenylazo phenoxy) (3) zinc(II) phthalocyanines are synthesized and covalently linked to mercaptohexanol (mph) or mercaptopropionic acid (mpa) functionalized dimerized silver-magnetic nanoparticles (Ag-M). Complexes 1 and 3 are covalently linked to nanomaterials via ester bond whereas complex 2 is covalently linked to nanoparticles (NPs) via amide bond. The conjugates of complexes 1–3 with NPs gave higher singlet oxygen quantum than the Pcs alone. Electrospun fibers were fabricated from polystyrene (PS) solutions containing complexes 1 to 3 and their conjugates. The functionalized PS fibers were used for the phototransformation of dibenzothiophene. The increase in photocatalytic properties of phthalocyanines was observed in the presence of Ag-M with 3 alone and its conjugate with mph capped silver-magnetic nanoparticles showing the larger catalytic activity towards the transformation of dibenzothiophene.
- Full Text:
- Date Issued: 2021
Photocatalytic desulfurization of dibenzothiophene using methoxy substituted asymmetrical zinc (II) phthalocyanines conjugated to metal tungstate nanomaterials
- Mgidlana, Sithi, Nwahara, Nnamdi, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Nwahara, Nnamdi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185760 , vital:44421 , xlink:href="https://doi.org/10.1016/j.poly.2021.115053"
- Description: We report on the syntheses of three asymmetrical zinc(II) phthalocyanine endowed with benzoic acid, phenylpropanoic acid, and phenylacetic acid units: (1), (2), and (3), respectively. Metal tungstate nanoparticles, capped with glutathione were prepared and characterized using analytical techniques. Complexes were covalently linked to nickel tungstate (NiWO4) and bismuth tungstate (Bi2WO6) through an amide bond. The complexes and the conjugates with nanomaterial were evaluated for singlet oxygen generating ability. Complexes 1–2 and their conjugates generate higher singlet oxygen compared to 3 and its corresponding conjugates. The conjugates show degradation of dibenzothiophene (DBT) in fuel with shorter half-lives and greater initial rate values compared to phthalocyanines alone.
- Full Text:
- Date Issued: 2021
- Authors: Mgidlana, Sithi , Nwahara, Nnamdi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185760 , vital:44421 , xlink:href="https://doi.org/10.1016/j.poly.2021.115053"
- Description: We report on the syntheses of three asymmetrical zinc(II) phthalocyanine endowed with benzoic acid, phenylpropanoic acid, and phenylacetic acid units: (1), (2), and (3), respectively. Metal tungstate nanoparticles, capped with glutathione were prepared and characterized using analytical techniques. Complexes were covalently linked to nickel tungstate (NiWO4) and bismuth tungstate (Bi2WO6) through an amide bond. The complexes and the conjugates with nanomaterial were evaluated for singlet oxygen generating ability. Complexes 1–2 and their conjugates generate higher singlet oxygen compared to 3 and its corresponding conjugates. The conjugates show degradation of dibenzothiophene (DBT) in fuel with shorter half-lives and greater initial rate values compared to phthalocyanines alone.
- Full Text:
- Date Issued: 2021
Photocytotoxicity of heavy-atom-free thiobarbituric acid functionalized pyrene derivatives against MCF-7 cancer cells
- Babu, Balaji, Ali, Thaslima A, Ochappan, Thivagar, Mack, John, Nyokong, Tebello, Sethuraman, Mathur G
- Authors: Babu, Balaji , Ali, Thaslima A , Ochappan, Thivagar , Mack, John , Nyokong, Tebello , Sethuraman, Mathur G
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190556 , vital:45005 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102102"
- Description: Two thiobarbituric acid-functionalized pyrene derivatives (P1, P2) have been synthesized to explore the photophysical properties and photodynamic activity of dyes of this type. Both compounds exhibit an intense intramolecular charge transfer (ICT) band at ca. 470 nm, which is absent in the spectra of the precursor. P1 and P2 exhibit singlet oxygen generation on irradiation with light with moderate singlet oxygen yields of 0.36 and 0.32, respectively, in DMSO. P1 showed better photodynamic activity against MCF-7 cells with an IC50 value of 18.3 μM under illumination at 455 nm for 60 min with a Thorlabs M455L3 LED (330 mW.cm−2).
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Ali, Thaslima A , Ochappan, Thivagar , Mack, John , Nyokong, Tebello , Sethuraman, Mathur G
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190556 , vital:45005 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102102"
- Description: Two thiobarbituric acid-functionalized pyrene derivatives (P1, P2) have been synthesized to explore the photophysical properties and photodynamic activity of dyes of this type. Both compounds exhibit an intense intramolecular charge transfer (ICT) band at ca. 470 nm, which is absent in the spectra of the precursor. P1 and P2 exhibit singlet oxygen generation on irradiation with light with moderate singlet oxygen yields of 0.36 and 0.32, respectively, in DMSO. P1 showed better photodynamic activity against MCF-7 cells with an IC50 value of 18.3 μM under illumination at 455 nm for 60 min with a Thorlabs M455L3 LED (330 mW.cm−2).
- Full Text:
- Date Issued: 2021
Photodynamic activity of 2, 6-dibrominated dimethylaminophenylbuta-1, 3-dienylBODIPY dyes
- Khubeka, Gugu, Babu, Balaji, Prinsloo, Earl, Kobayashi, Nagao, Mack, John, Nyokong, Tebello
- Authors: Khubeka, Gugu , Babu, Balaji , Prinsloo, Earl , Kobayashi, Nagao , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190804 , vital:45030 , xlink:href="https://doi.org/10.1142/S1088424620500509"
- Description: Mono- and disubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes were successfully prepared, and their in vitro photodynamic activities against MCF-7 breast cancer cells were evaluated with a Thorlabs M660L4 660 nm LED (336 J · cm−2)−2). The IC5050 value of the monophenylbuta-1,3-dienylBODIPY was ca. 2.1 μμM, while that of the diphenylbuta-1,3-dienylBODIPY was > 50 μμM. Both dyes exhibited minimal dark toxicity. The results demonstrate that monosubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes merit further in-depth study for use as photosensitizer dyes in photodynamic therapy.
- Full Text:
- Date Issued: 2021
- Authors: Khubeka, Gugu , Babu, Balaji , Prinsloo, Earl , Kobayashi, Nagao , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190804 , vital:45030 , xlink:href="https://doi.org/10.1142/S1088424620500509"
- Description: Mono- and disubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes were successfully prepared, and their in vitro photodynamic activities against MCF-7 breast cancer cells were evaluated with a Thorlabs M660L4 660 nm LED (336 J · cm−2)−2). The IC5050 value of the monophenylbuta-1,3-dienylBODIPY was ca. 2.1 μμM, while that of the diphenylbuta-1,3-dienylBODIPY was > 50 μμM. Both dyes exhibited minimal dark toxicity. The results demonstrate that monosubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes merit further in-depth study for use as photosensitizer dyes in photodynamic therapy.
- Full Text:
- Date Issued: 2021
Photodynamic activity of Sn (IV) tetrathien-2-ylchlorin against MCF-7 breast cancer cells
- Babu, Balaji, Mack, John, Nyokong, Tebello
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185920 , vital:44448 , xlink:href="https://doi.org/10.1039/d0dt03958f"
- Description: A new readily-synthesized Sn(IV) tetraarylchlorin with thien-2-yl substituents (SnC) has been prepared and fully characterized by various spectroscopic techniques and its photophysical and photochemical properties, such as the singlet oxygen quantum yield (ΦΔ), fluorescence quantum yield (ΦF), triplet lifetime (τT) and photostability, have been evaluated. SnC has an unusually high ΦΔ value of 0.89 in DMF. Studies on the photodynamic activity against MCF-7 breast cancer cells exhibited a very low IC50 value of 0.9 μM and high phototoxicity (dark versus light) indices of >27.8 after irradiation with a 660 nm Thorlabs LED (280 mW cm−2). The results demonstrate that Sn(IV) tetraarylchlorins of this type are suitable candidates for further in-depth PDT studies.
- Full Text:
- Date Issued: 2021
- Authors: Babu, Balaji , Mack, John , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185920 , vital:44448 , xlink:href="https://doi.org/10.1039/d0dt03958f"
- Description: A new readily-synthesized Sn(IV) tetraarylchlorin with thien-2-yl substituents (SnC) has been prepared and fully characterized by various spectroscopic techniques and its photophysical and photochemical properties, such as the singlet oxygen quantum yield (ΦΔ), fluorescence quantum yield (ΦF), triplet lifetime (τT) and photostability, have been evaluated. SnC has an unusually high ΦΔ value of 0.89 in DMF. Studies on the photodynamic activity against MCF-7 breast cancer cells exhibited a very low IC50 value of 0.9 μM and high phototoxicity (dark versus light) indices of >27.8 after irradiation with a 660 nm Thorlabs LED (280 mW cm−2). The results demonstrate that Sn(IV) tetraarylchlorins of this type are suitable candidates for further in-depth PDT studies.
- Full Text:
- Date Issued: 2021
Photodynamic antimicrobial action of asymmetrical porphyrins functionalized silver-detonation nanodiamonds nanoplatforms for the suppression of Staphylococcus aureus planktonic cells and biofilms
- Openda, Yolande I, Ngoy, Bokolombe P, Nyokong, Tebello
- Authors: Openda, Yolande I , Ngoy, Bokolombe P , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190544 , vital:45004 , xlink:href="https://doi.org/10.3389/fchem.2021.628316"
- Description: New asymmetrical porphyrin derivatives containing a p-hydroxyphenyl moiety and p-acetylphenyl moieties along with their functionalized silver-detonation nanodiamonds nanohybrids were characterized and their photophysicochemical properties were established. The study provides evidence that the metalated porphyrin derivatives were red-shifted in absorption wavelength and possessed high singlet oxygen quantum yield comparative to the unmetalated core, thus making them suitable agents for photodynamic antimicrobial chemotherapy. As a result of conjugation to detonation nanodiamonds and silver nanoparticles, these compounds proved to be more effective as they exhibited stronger antibacterial and anti-biofilm activities on the multi-drug resistant S. aureus strain due to synergetic effect, compared to Ps alone. This suggests that the newly prepared nanohybrids could be used as a potential antimicrobial agent in the treatment of biofilms caused by S. aureus strain.
- Full Text:
- Date Issued: 2021
- Authors: Openda, Yolande I , Ngoy, Bokolombe P , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190544 , vital:45004 , xlink:href="https://doi.org/10.3389/fchem.2021.628316"
- Description: New asymmetrical porphyrin derivatives containing a p-hydroxyphenyl moiety and p-acetylphenyl moieties along with their functionalized silver-detonation nanodiamonds nanohybrids were characterized and their photophysicochemical properties were established. The study provides evidence that the metalated porphyrin derivatives were red-shifted in absorption wavelength and possessed high singlet oxygen quantum yield comparative to the unmetalated core, thus making them suitable agents for photodynamic antimicrobial chemotherapy. As a result of conjugation to detonation nanodiamonds and silver nanoparticles, these compounds proved to be more effective as they exhibited stronger antibacterial and anti-biofilm activities on the multi-drug resistant S. aureus strain due to synergetic effect, compared to Ps alone. This suggests that the newly prepared nanohybrids could be used as a potential antimicrobial agent in the treatment of biofilms caused by S. aureus strain.
- Full Text:
- Date Issued: 2021
Photodynamic inactivation of Staphylococcus Aureus with Schiff base substituted Zinc phthalocyanines through conjugation to silver nanoparticles
- Sen, Pinar, Nyokong, Tebello
- Authors: Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185688 , vital:44415 , xlink:href="https://doi.org/10.1016/j.molstruc.2021.130012"
- Description: We present the preparation of Schiff base substituted neutral phthalocyanines derived from aldehyde-substituted phthalocyanine which are conjugated to silver nanoparticles through covalent-like strong interactions. The photophysicochemical properties of the nanoconjugates and the Pcs alone were studied comparatively. The photodynamic antimicrobial chemotherapy (PACT) activities. of prepared photosensitizers was investigated against Gram-positive bacterium (Staphylococcus aureus). Unlike Pcs alone, conjugated phthalocyanines to silver nanoparticles showed excellent photodynamic antimicrobial activity with the 100% reduction percentage upon illumination.
- Full Text:
- Date Issued: 2021
- Authors: Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185688 , vital:44415 , xlink:href="https://doi.org/10.1016/j.molstruc.2021.130012"
- Description: We present the preparation of Schiff base substituted neutral phthalocyanines derived from aldehyde-substituted phthalocyanine which are conjugated to silver nanoparticles through covalent-like strong interactions. The photophysicochemical properties of the nanoconjugates and the Pcs alone were studied comparatively. The photodynamic antimicrobial chemotherapy (PACT) activities. of prepared photosensitizers was investigated against Gram-positive bacterium (Staphylococcus aureus). Unlike Pcs alone, conjugated phthalocyanines to silver nanoparticles showed excellent photodynamic antimicrobial activity with the 100% reduction percentage upon illumination.
- Full Text:
- Date Issued: 2021
Photodynamic therapy activities of phthalocyanine-based macromolecular photosensitizers on MCF-7 breast cancer cells
- Ahmetali, Erem, Sen, Pinar, Süer, N Ceren, Nyokong, Tebello, Erin, Tarik, Sener, M Kasim
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Nyokong, Tebello , Erin, Tarik , Sener, M Kasim
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185655 , vital:44407 , xlink:href="https://doi.org/10.1080/10601325.2021.1934012"
- Description: Poly(oxanorbornene)s with zinc(II) phthalocyanine side chains have been synthesized by ring-opening metathesis polymerization. The incorporation of zinc(II) phthalocyanine into cationic polymer has given poly(oxanorbornene)s noteworthy photophysicochemical properties and the capacity to generate singlet oxygen under light irradiation. To investigate photosensitizer’s properties of the newly synthesized polymers P6 and P7: fluorescence (ΦF), singlet oxygen (ΦΔ) and triplet (ΦT) quantum yields of polymers have been measured in dimethyl sulfoxide and aqueous medium. Singlet oxygen quantum yields of P6 and P7 have been found to be 0.22 and 0.20 in dimethyl sulfoxide, respectively. Then, photodynamic therapy activities of polymers (P1-P7) against human breast adenocarcinoma cell line (MCF-7 cells) have been investigated. The copolymer P5 bearing pendant zinc(II) phthalocyanine and triethyl phosphonium functionalities has showed enhanced PDT activity with less than 10% viable cells at 60 μg/mL.
- Full Text:
- Date Issued: 2021
- Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Nyokong, Tebello , Erin, Tarik , Sener, M Kasim
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185655 , vital:44407 , xlink:href="https://doi.org/10.1080/10601325.2021.1934012"
- Description: Poly(oxanorbornene)s with zinc(II) phthalocyanine side chains have been synthesized by ring-opening metathesis polymerization. The incorporation of zinc(II) phthalocyanine into cationic polymer has given poly(oxanorbornene)s noteworthy photophysicochemical properties and the capacity to generate singlet oxygen under light irradiation. To investigate photosensitizer’s properties of the newly synthesized polymers P6 and P7: fluorescence (ΦF), singlet oxygen (ΦΔ) and triplet (ΦT) quantum yields of polymers have been measured in dimethyl sulfoxide and aqueous medium. Singlet oxygen quantum yields of P6 and P7 have been found to be 0.22 and 0.20 in dimethyl sulfoxide, respectively. Then, photodynamic therapy activities of polymers (P1-P7) against human breast adenocarcinoma cell line (MCF-7 cells) have been investigated. The copolymer P5 bearing pendant zinc(II) phthalocyanine and triethyl phosphonium functionalities has showed enhanced PDT activity with less than 10% viable cells at 60 μg/mL.
- Full Text:
- Date Issued: 2021
Photophysicochemical behaviour of phenoxy propanoic acid functionalised zinc phthalocyanines when grafted onto iron oxide and silica nanoparticles: Effects in photodynamic antimicrobial chemotherapy
- Dube, Edith, Soy, Rodath, Shumba, Mumyaradzi, Nyokong, Tebello
- Authors: Dube, Edith , Soy, Rodath , Shumba, Mumyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185465 , vital:44389 , xlink:href="https://doi.org/10.1016/j.jlumin.2021.117939"
- Description: This work reports on the covalent linkage of (3-aminopropyl)triethoxysilane (APTES) functionalised iron oxide (IONPs–APTES) and silica (SiNPs–APTES) nanoparticles with zinc(II) tetra–([3–(4–phenoxy) propanoic acid) phthalocyanine] (1) and zinc(II) mono–([3–(4–phenoxy) propanoic acid) phthalocyanine (2) via an amide bond to form the conjugates, 1–IONPs-APTES, 1–SiNPs–APTES, 2-IONPs-APTES and 2-SiNPs-APTES). The photophysicochemical behaviour of the conjugates was investigated. These were characterized by a decrease in the fluorescence quantum yields and lifetimes, and an increase in the triplet quantum yield and singlet oxygen quantum yield when compared to complex 1 and 2 alone. The conjugates to IONPs-APTES displayed higher ΦT than those of SiNPs-APTES probably due to the heavy atom effect of iron compared to silica and the high loading capacity of the relatively smaller iron oxide NPs, however, there was no significant difference in the ΦΔ values of 2-IONPs-APTES (ΦΔ=0.59) and 2-SiNPs-APTES (ΦΔ=0.58), suggesting that the energy transfer process between the excited triplet state of 2-IONPs-APTES and ground state molecular oxygen was not effective. Photodynamic antimicrobial chemotherapy (PACT) studies showed that linkage of Pcs to NPs improves their photoinactivation capability against Staphylococcus aureus and Escherichia coli. IONPs-APTES and its conjugates generally displayed the highest log reductions than SiNPs-APTES and its conjugates except for studies after 75 min of irradiation for S. Aureus where the log reductions are the same. 2-IONP-APTES was recovered using a magnet after each photodegradation cycle and its stability after 3 cycles confirmed re-usability.
- Full Text:
- Date Issued: 2021
- Authors: Dube, Edith , Soy, Rodath , Shumba, Mumyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185465 , vital:44389 , xlink:href="https://doi.org/10.1016/j.jlumin.2021.117939"
- Description: This work reports on the covalent linkage of (3-aminopropyl)triethoxysilane (APTES) functionalised iron oxide (IONPs–APTES) and silica (SiNPs–APTES) nanoparticles with zinc(II) tetra–([3–(4–phenoxy) propanoic acid) phthalocyanine] (1) and zinc(II) mono–([3–(4–phenoxy) propanoic acid) phthalocyanine (2) via an amide bond to form the conjugates, 1–IONPs-APTES, 1–SiNPs–APTES, 2-IONPs-APTES and 2-SiNPs-APTES). The photophysicochemical behaviour of the conjugates was investigated. These were characterized by a decrease in the fluorescence quantum yields and lifetimes, and an increase in the triplet quantum yield and singlet oxygen quantum yield when compared to complex 1 and 2 alone. The conjugates to IONPs-APTES displayed higher ΦT than those of SiNPs-APTES probably due to the heavy atom effect of iron compared to silica and the high loading capacity of the relatively smaller iron oxide NPs, however, there was no significant difference in the ΦΔ values of 2-IONPs-APTES (ΦΔ=0.59) and 2-SiNPs-APTES (ΦΔ=0.58), suggesting that the energy transfer process between the excited triplet state of 2-IONPs-APTES and ground state molecular oxygen was not effective. Photodynamic antimicrobial chemotherapy (PACT) studies showed that linkage of Pcs to NPs improves their photoinactivation capability against Staphylococcus aureus and Escherichia coli. IONPs-APTES and its conjugates generally displayed the highest log reductions than SiNPs-APTES and its conjugates except for studies after 75 min of irradiation for S. Aureus where the log reductions are the same. 2-IONP-APTES was recovered using a magnet after each photodegradation cycle and its stability after 3 cycles confirmed re-usability.
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- Date Issued: 2021