Adsorption of antibiotic-resistant bacteria and their cell-free deoxyribonucleic acid harbouring resistance genes in drinking water with metal oxides
- Authors: Tobechukwu, Anthony Eric
- Date: 2022
- Subjects: Metallic oxides , DNA -- Synthesis , Drinking water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27787 , vital:69494
- Description: Access to cleaner water is essential to human health. The incidence of Antibiotic Resistant Bacteria ARB in drinking water and subsequent proliferation of Antibiotic Resistance Genes ARGs in drinking water is a concern for public health. The free DNA cassette harboring antibiotic resistance gene in drinking water has been linked with impaired public health. The ARGs allows bacteria to develop resistance towards antibiotics while ARB render antibiotics ineffective. Existing drinking water treatment technologies eg adsorption, ozonation and chlorination, have shown different levels of potency in the removal of conventional water pollutant. These technologies, which operating principles is based on oxidation or mass transfer, have been explored to gained an insight into their efficiency in the removal of ARB ARGs in water treatment. In general, methods that functions by mass transfer of the ARB ARGs is more effectively than bacteria oxidation. Consequently, adsorption technology was chosen using common metal oxide adsorbents. The adsorbents ZnOAg CeO2 and Al2O3 were synthesized via the self propagation combustion method. This method was selected because of the purity of the final product and the energy requirement. One of the challenges in the removal of ARB in drinking water is the release of ARGs. To address this concern, five different ZnOAg heterostructures were synthesized for the removal of Enterococci faecium. ZnOAg was chosen because of the bactericidal and bacteriostatic characteristics. The study revealed that the concentration of the precursors influences the microstructures of the adsorbents; however, it did not significantly affect the adsorption efficiency. The maximum adsorption capacity q34.11 CFUg was obtained for Ag1Zn3.5. The kinetic studies revealed that Ag1Zn1 and Ag1Zn2 adsorbents agreed to the pseudofirst-order kinetic equation and adsorbents Ag2Zn1 Ag3.5Zn1 and Ag1Zn3.5 agreed to the pseudo-second-order kinetic equation. Initial tap-water pH range was beneficial for the adsorption and the pH of the treated tap-water was within the WHO tap water recommendation 6.5 – 8.5 whereas the effect of ionic strength, anionic and cationic interference was insignificant in the adsorption of MDREF onto the different heterostructure. Interestingly the MDREF could retain its cell membrane integrity and resistance genes, suggesting that surface adsorption was the primary mechanism for the removal. Cerium IV oxide CeO2 was selected because of high adsorption towards phosphate, backbone base for DNA. To prevent the problem of antibiotic resistance, we have synthesized a CeO2 adsorbent that exhibit highly positive character in a wide pH range, via the simple self-propagation combustion protocol, for the removal of free DNA harboring antibiotic resistance genes. Molecular characterization of the extracted genes showed that the sizes for E. coli and inherent gyrB genes are 147 and 460 bp with a purity between 19 2.0. The XRD SEM TEM, and PZC results of the as-synthesized CeO2 showed an agglomerate of pure cubic-faced centered material and highly crystalline, with a net charge at pH 6.2. Experimental results revealed that the reaction proceeded via pseudo first-order kinetic, and it is governed by electrostatic attraction. The free- DNA solution pH electrolyte, and competing ions impacted on the adsorption process. Further experimental results showed that the as-synthesized CeO2 adsorbent has the potential to be used for the removal of free DNA harboring ARGs from tap-water even under oxic conditions. Alumina Al2O3 is an abundant adsorbent that has also shown high removal capacity towards phosphate. The highly pure synthesized Al2O3 adsorbent exhibit fluid-like behaviour under Scanning Electron Microscope SEM. The XRD pattern corresponds to αAl2O3. The adsorption kinetics was described by pseudo second orderadsorption capacity 11.7 μgg implying chemisorption, which agrees with the electrostatic force of attraction caused by opposing ions. This result was evident by the effect of different ions in the tap water. The synthesized α-Al2O3 has the potential for the removal of cell free DNA harbouring multiply resistant genes. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Authors: Tobechukwu, Anthony Eric
- Date: 2022
- Subjects: Metallic oxides , DNA -- Synthesis , Drinking water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27787 , vital:69494
- Description: Access to cleaner water is essential to human health. The incidence of Antibiotic Resistant Bacteria ARB in drinking water and subsequent proliferation of Antibiotic Resistance Genes ARGs in drinking water is a concern for public health. The free DNA cassette harboring antibiotic resistance gene in drinking water has been linked with impaired public health. The ARGs allows bacteria to develop resistance towards antibiotics while ARB render antibiotics ineffective. Existing drinking water treatment technologies eg adsorption, ozonation and chlorination, have shown different levels of potency in the removal of conventional water pollutant. These technologies, which operating principles is based on oxidation or mass transfer, have been explored to gained an insight into their efficiency in the removal of ARB ARGs in water treatment. In general, methods that functions by mass transfer of the ARB ARGs is more effectively than bacteria oxidation. Consequently, adsorption technology was chosen using common metal oxide adsorbents. The adsorbents ZnOAg CeO2 and Al2O3 were synthesized via the self propagation combustion method. This method was selected because of the purity of the final product and the energy requirement. One of the challenges in the removal of ARB in drinking water is the release of ARGs. To address this concern, five different ZnOAg heterostructures were synthesized for the removal of Enterococci faecium. ZnOAg was chosen because of the bactericidal and bacteriostatic characteristics. The study revealed that the concentration of the precursors influences the microstructures of the adsorbents; however, it did not significantly affect the adsorption efficiency. The maximum adsorption capacity q34.11 CFUg was obtained for Ag1Zn3.5. The kinetic studies revealed that Ag1Zn1 and Ag1Zn2 adsorbents agreed to the pseudofirst-order kinetic equation and adsorbents Ag2Zn1 Ag3.5Zn1 and Ag1Zn3.5 agreed to the pseudo-second-order kinetic equation. Initial tap-water pH range was beneficial for the adsorption and the pH of the treated tap-water was within the WHO tap water recommendation 6.5 – 8.5 whereas the effect of ionic strength, anionic and cationic interference was insignificant in the adsorption of MDREF onto the different heterostructure. Interestingly the MDREF could retain its cell membrane integrity and resistance genes, suggesting that surface adsorption was the primary mechanism for the removal. Cerium IV oxide CeO2 was selected because of high adsorption towards phosphate, backbone base for DNA. To prevent the problem of antibiotic resistance, we have synthesized a CeO2 adsorbent that exhibit highly positive character in a wide pH range, via the simple self-propagation combustion protocol, for the removal of free DNA harboring antibiotic resistance genes. Molecular characterization of the extracted genes showed that the sizes for E. coli and inherent gyrB genes are 147 and 460 bp with a purity between 19 2.0. The XRD SEM TEM, and PZC results of the as-synthesized CeO2 showed an agglomerate of pure cubic-faced centered material and highly crystalline, with a net charge at pH 6.2. Experimental results revealed that the reaction proceeded via pseudo first-order kinetic, and it is governed by electrostatic attraction. The free- DNA solution pH electrolyte, and competing ions impacted on the adsorption process. Further experimental results showed that the as-synthesized CeO2 adsorbent has the potential to be used for the removal of free DNA harboring ARGs from tap-water even under oxic conditions. Alumina Al2O3 is an abundant adsorbent that has also shown high removal capacity towards phosphate. The highly pure synthesized Al2O3 adsorbent exhibit fluid-like behaviour under Scanning Electron Microscope SEM. The XRD pattern corresponds to αAl2O3. The adsorption kinetics was described by pseudo second orderadsorption capacity 11.7 μgg implying chemisorption, which agrees with the electrostatic force of attraction caused by opposing ions. This result was evident by the effect of different ions in the tap water. The synthesized α-Al2O3 has the potential for the removal of cell free DNA harbouring multiply resistant genes. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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Development and in vitro biological studies of polymer-based wound dressings with a high haemostatic ability for the management of wounds
- Nqoro, Xhamla https://orcid.org/0000-0002-2065-3629
- Authors: Nqoro, Xhamla https://orcid.org/0000-0002-2065-3629
- Date: 2022
- Subjects: Wound healing , Surgical wound infections , Wound treatment equipment industry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27970 , vital:71404
- Description: Wounds are usually accompanied by complications such as excessive bleeding and bacteria invasion. The design of wound dressings that rapidly stop excessive bleeding and inhibit bacterial invasion is crucial to promoting accelerated wound healing. To meet the abovementioned requirements in wound dressings, topical gels were prepared from sodium alginate SA and carboxymethylcellulose CMC. The wound dressings were loaded with an antifibrinolytic agent, tranexamic acid TA, essential oils, and a variety of metal-based nanoparticles, and carbon-based biomaterials. The scanning electron microscopy SEM and X-ray diffraction XRD confirmed the successful formation of the nanoparticles. The prepared formulations exhibited in vitro drug release kinetics that best fitted with the Korsmeyer-Peppas model. These gels exhibited good spreadability and viscosity, showing a shear-thinning behaviour with pH between 6.7 and 7.3, signifying suitability for skin application and ease of application. The prepared topical gels exhibited significant antibacterial effects against gram-negative and gram-positive strains of bacteria. SA EO-based formulations showed high antibacterial activity across all bacterial strains, followed by SA-based formulations compared to CMC-based formulations, which exhibited moderate antibacterial activity. Moreover, the prepared gels showed good cytocompatibility, promoted cell proliferation, and exhibited 80 percent wound closure on day 3 compared to the untreated group, which showed a 38 percent wound reduction in vitro. Excellent blood clotting properties were observed with CMC-based gels compared to other formulations. However, all the prepared formulations exhibited outstanding blood clotting ability compared to the control, showing that they can promote rapid blood coagulation. The features presented by the prepared gels reveal that they are suitable for rapid wound healing , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Authors: Nqoro, Xhamla https://orcid.org/0000-0002-2065-3629
- Date: 2022
- Subjects: Wound healing , Surgical wound infections , Wound treatment equipment industry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27970 , vital:71404
- Description: Wounds are usually accompanied by complications such as excessive bleeding and bacteria invasion. The design of wound dressings that rapidly stop excessive bleeding and inhibit bacterial invasion is crucial to promoting accelerated wound healing. To meet the abovementioned requirements in wound dressings, topical gels were prepared from sodium alginate SA and carboxymethylcellulose CMC. The wound dressings were loaded with an antifibrinolytic agent, tranexamic acid TA, essential oils, and a variety of metal-based nanoparticles, and carbon-based biomaterials. The scanning electron microscopy SEM and X-ray diffraction XRD confirmed the successful formation of the nanoparticles. The prepared formulations exhibited in vitro drug release kinetics that best fitted with the Korsmeyer-Peppas model. These gels exhibited good spreadability and viscosity, showing a shear-thinning behaviour with pH between 6.7 and 7.3, signifying suitability for skin application and ease of application. The prepared topical gels exhibited significant antibacterial effects against gram-negative and gram-positive strains of bacteria. SA EO-based formulations showed high antibacterial activity across all bacterial strains, followed by SA-based formulations compared to CMC-based formulations, which exhibited moderate antibacterial activity. Moreover, the prepared gels showed good cytocompatibility, promoted cell proliferation, and exhibited 80 percent wound closure on day 3 compared to the untreated group, which showed a 38 percent wound reduction in vitro. Excellent blood clotting properties were observed with CMC-based gels compared to other formulations. However, all the prepared formulations exhibited outstanding blood clotting ability compared to the control, showing that they can promote rapid blood coagulation. The features presented by the prepared gels reveal that they are suitable for rapid wound healing , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
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Evaluation of functionalized silver and silica nanoparticles for the removal of deoxyribonucleic acid conveying antibiotics resistance genes from water
- Authors: Ezeuko, Adaora Stella
- Date: 2022
- Subjects: DNA , Silica , Water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27765 , vital:69414
- Description: Antibiotic resistance genes ARGs are recognized as a serious public health emergency linked to extensive use of antibiotics by humans and animals as a prophylactic agent that treats and prevents infections. The occurrence of high concentrations being identified in wastewater treatment plants, rivers, etc is due to untreated effluents being discharged from households, hospitals, agriculture, and pharmaceutical industries. The application of adequate treatment techniques and material for the removal of bacteria DNA conveying ARGs from the effluents before their release to the environment cannot be overemphasized. Adsorption techniques seem to be effective due to their easy design, operation, and ability to regenerate adsorbents for use without producing toxic by-products. This concept was employed for the removal of bacteria DNA conveying ARGs from simulated aqueous solution, effluents from hospital, river and WWTPs using silver and silica metallic nanoparticles. This thesis investigated the effectiveness of metallic nanoparticles containing silver AgNPs and mesoporous silica nanoparticles MSNPs as well as magnetite Fe3O4 functionalized with 4 4hydroxyphenyl 2 262-terpyridine onto their surface, for the removal of bacteria DNA conveying antibiotic resistance genes from water samples from hospitals, river, and wastewater treatment plants WWTPs. Silver nanoparticles AgNPs of different molar concentrations 0.1M, 0.5M and 1.0 M and mesoporous silica nanoparticles MSNPs adsorbents were successfully synthesized in their original states and surface functionalization achieved by incorporating magnetite Fe3O4 and 4 4 hydroxyphenyl 2 2 6 2 terpyridine on the silver AgNPs Fe3O4 and silica MSNPs TPPY surfaces respectively. Their effectiveness as adsorbent for the removal of bacteria DNA conveying ARGs from aqueous solutions and real water/wastewater samples were investigated. The DNA uptake by the as-synthesized AgNPs and MSNPs were compared to the functionalized AgNPs Fe3O4 and MSNPsTPPY by determining the adsorbents with the highest removal efficiencies. All as synthesized and functionalized adsorbents were characterized by SEM, EDX, FTIR, XRD, UV spectroscopy and PZC before the removal process. The extraction of genomic DNA from antibiotic-resistant Enterococcus faecium and Vibrio parahaemolyticus was successfully achieved via the boiling method. Antibiotic susceptibility test was conducted using the disk diffusion method before the commencement of genomic DNA extraction. Molecular characterization via gel electrophoresis confirmed the presence of resistance genes at different base pairs. Adsorption batch experiment were investigated, and the best optimum parameters were evaluated through the influence of pH, contact time, initial DNA concentration, adsorbent dose, and competitive ions for each sorption process. The rate determining step were determined by fitting kinetic models such as Natarajan and Khalaf first order, pseudo first order, pseudo second order, Elovich model to experimental data. Also, the adsorption mechanisms determining adsorption equilibrium were investigated by fitting Freundlich, Langmuir and Sips model into the experimental data. The application of AgNPsFe3O4 nanocomposite and MSNPsTPPY for the removal of bacteria DNA demonstrated much enhancement for DNA uptake than the as-synthesized AgNPs and MSNPs materials. The incorporation of magnetite and 4 4hydroxyphenyl 2 2 6 2-terpyridine onto AgNPs and MSNPs significantly enhanced the binding affinity towards the removal the bacteria DNA via strong electrostatic attraction between the active sites on the adsorbent and the negative DNA molecules. Finally, high adsorption capacities were recorded with AgNPsFe3O4 nanocomposite and MSNPsTPPY compared to AgNPs and MSNPs with chaotropic salts. The kinetic adsorption models were mostly best fitted by the pseudo-second order and Elovich models while the adsorption equilibrium was best described by Langmuir and Sips isotherm models. MSNPs with different chaotropic salts, AgNPsFe3O4 nanocomposite and MSNPsTPPY also proved its effectiveness in DNA removal not only in the simulated aqueous solution but in three different real life water samples obtained from Cofimvaba hospital, Ndevana river and Uitenhage WWTPs. High adsorption efficiencies above 90 percent were achieved during the removal of DNA in all the three real water samples. Therefore, application of these adsorbents for the removal of bacteria DNA conveying ARGs may be a promising option that would tackle the consequences of consuming ARGs infected water globally. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Authors: Ezeuko, Adaora Stella
- Date: 2022
- Subjects: DNA , Silica , Water
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27765 , vital:69414
- Description: Antibiotic resistance genes ARGs are recognized as a serious public health emergency linked to extensive use of antibiotics by humans and animals as a prophylactic agent that treats and prevents infections. The occurrence of high concentrations being identified in wastewater treatment plants, rivers, etc is due to untreated effluents being discharged from households, hospitals, agriculture, and pharmaceutical industries. The application of adequate treatment techniques and material for the removal of bacteria DNA conveying ARGs from the effluents before their release to the environment cannot be overemphasized. Adsorption techniques seem to be effective due to their easy design, operation, and ability to regenerate adsorbents for use without producing toxic by-products. This concept was employed for the removal of bacteria DNA conveying ARGs from simulated aqueous solution, effluents from hospital, river and WWTPs using silver and silica metallic nanoparticles. This thesis investigated the effectiveness of metallic nanoparticles containing silver AgNPs and mesoporous silica nanoparticles MSNPs as well as magnetite Fe3O4 functionalized with 4 4hydroxyphenyl 2 262-terpyridine onto their surface, for the removal of bacteria DNA conveying antibiotic resistance genes from water samples from hospitals, river, and wastewater treatment plants WWTPs. Silver nanoparticles AgNPs of different molar concentrations 0.1M, 0.5M and 1.0 M and mesoporous silica nanoparticles MSNPs adsorbents were successfully synthesized in their original states and surface functionalization achieved by incorporating magnetite Fe3O4 and 4 4 hydroxyphenyl 2 2 6 2 terpyridine on the silver AgNPs Fe3O4 and silica MSNPs TPPY surfaces respectively. Their effectiveness as adsorbent for the removal of bacteria DNA conveying ARGs from aqueous solutions and real water/wastewater samples were investigated. The DNA uptake by the as-synthesized AgNPs and MSNPs were compared to the functionalized AgNPs Fe3O4 and MSNPsTPPY by determining the adsorbents with the highest removal efficiencies. All as synthesized and functionalized adsorbents were characterized by SEM, EDX, FTIR, XRD, UV spectroscopy and PZC before the removal process. The extraction of genomic DNA from antibiotic-resistant Enterococcus faecium and Vibrio parahaemolyticus was successfully achieved via the boiling method. Antibiotic susceptibility test was conducted using the disk diffusion method before the commencement of genomic DNA extraction. Molecular characterization via gel electrophoresis confirmed the presence of resistance genes at different base pairs. Adsorption batch experiment were investigated, and the best optimum parameters were evaluated through the influence of pH, contact time, initial DNA concentration, adsorbent dose, and competitive ions for each sorption process. The rate determining step were determined by fitting kinetic models such as Natarajan and Khalaf first order, pseudo first order, pseudo second order, Elovich model to experimental data. Also, the adsorption mechanisms determining adsorption equilibrium were investigated by fitting Freundlich, Langmuir and Sips model into the experimental data. The application of AgNPsFe3O4 nanocomposite and MSNPsTPPY for the removal of bacteria DNA demonstrated much enhancement for DNA uptake than the as-synthesized AgNPs and MSNPs materials. The incorporation of magnetite and 4 4hydroxyphenyl 2 2 6 2-terpyridine onto AgNPs and MSNPs significantly enhanced the binding affinity towards the removal the bacteria DNA via strong electrostatic attraction between the active sites on the adsorbent and the negative DNA molecules. Finally, high adsorption capacities were recorded with AgNPsFe3O4 nanocomposite and MSNPsTPPY compared to AgNPs and MSNPs with chaotropic salts. The kinetic adsorption models were mostly best fitted by the pseudo-second order and Elovich models while the adsorption equilibrium was best described by Langmuir and Sips isotherm models. MSNPs with different chaotropic salts, AgNPsFe3O4 nanocomposite and MSNPsTPPY also proved its effectiveness in DNA removal not only in the simulated aqueous solution but in three different real life water samples obtained from Cofimvaba hospital, Ndevana river and Uitenhage WWTPs. High adsorption efficiencies above 90 percent were achieved during the removal of DNA in all the three real water samples. Therefore, application of these adsorbents for the removal of bacteria DNA conveying ARGs may be a promising option that would tackle the consequences of consuming ARGs infected water globally. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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Preparation, characterization, and in vitro evaluation of polymer-based wound dressings for the management of chronic wounds
- Authors: Alven, Sibusiso
- Date: 2022
- Subjects: Toxicity testing -- In vitro , Wound healing , Chronic diseases
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27992 , vital:71414
- Description: Microbial infections are responsible for the retarded recovery process of chronic wounds. Polymer-based scaffolds possess features suitable for the treatment of chronic injuries. However, these scaffolds are commonly encapsulated with therapeutic agents to enhance their biological activities, including antibacterial efficacy. In this research, two types of polymer-based scaffolds were formulated and evaluated as effective formulations for the treatment of chronic wounds: sponges and topical gels. Sponges were formulated from cross-linking of gelatin and PEG. Ag nanoparticles and metronidazole were incorporated into the sponges to improve their antibacterial activity. Topical gels were loaded with essential oils and Ag nanoparticles and prepared from CMC and poloxamer. The prepared sponges and topical gels were evaluated using various analysis and characterization techniques. SEM/EDX, FTIR, and TGA were employed to characterize gelatin/PEG hybrid sponges followed by porosity, in vitro biodegradability, cytotoxicity, and antibacterial studies. FTIR, SEM/EDX, and TGA confirmed their physicochemical properties and successful fabrication of sponges loaded with metronidazole and Ag nanoparticles. The sponges were biodegradable, indicating their capability to induce skin regeneration. The drug release studies showed a rapid release of metronidazole 28.32-71.97 percent from the sponges over the first hour, followed by a sustained drug release. The Ag nanoparticles were released in a sustained manner, suggesting that these sponges can rapidly destroy bacteria and inhibit persisting bacterial infections as well as protect the lesion bed from further bacteria infections. The in vitro antibacterial studies of sponges displayed superior antibacterial activity against most of the Gram-negative and Gram-positive bacteria strains commonly found in chronic wound infections with a MIC value of 15.625 μg/mL. In vitro cytotoxicity experiments revealed excellent biocompatibility with a percent cell viability of more than 70 percent. The in vitro wound scratch healing assay exhibited that the sponges encapsulated with only metronidazole promoted high cell migration than the dual drug-loaded sponges and untreated cells, suggesting its potential to quicken the wound healing process. CMC/Poloxamer topical gels were also characterized by FTIR, followed by pH, viscosity, spreadability, cytotoxicity, and antibacterial studies. FTIR showed successful preparation of CMC/Poloxamer topical gels loaded with essential oils and Ag nanoparticles. The topical gels exhibited pH in the range of 5.20-6.68, spreadability between 5.4 and 5.9 cm, and viscosity ranged from 216 to 1200 cP at 50 rpm and 210–858 cP at 100 rpm. The in vitro drug release studies demonstrated that Ag nanoparticles were released from the topical gels in a sustained manner. Most formulated topical gels demonstrated superior antimicrobial efficacy against Gram-positive and Gram-negative bacteria strains than the blank gel and controls. The cytotoxicity analysis displayed more than 90.83 percent cell viability for the topical gels, revealing excellent biocompatibility. The outcomes revealed that the topical gels enriched with essential oils lavender and tea tree and Ag nanoparticles and sponges incorporated with metronidazole and Ag nanoparticles are potential wound dressing scaffolds that can be employed for the treatment of chronic infected injuries. The in vitro wound healing experiments showed that the HaCaT cells cultured with gels co-enriched with lavender oil and Ag nanoparticles possessed a higher rate of closure in comparison to the untreated cells for 96 hours. , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Authors: Alven, Sibusiso
- Date: 2022
- Subjects: Toxicity testing -- In vitro , Wound healing , Chronic diseases
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27992 , vital:71414
- Description: Microbial infections are responsible for the retarded recovery process of chronic wounds. Polymer-based scaffolds possess features suitable for the treatment of chronic injuries. However, these scaffolds are commonly encapsulated with therapeutic agents to enhance their biological activities, including antibacterial efficacy. In this research, two types of polymer-based scaffolds were formulated and evaluated as effective formulations for the treatment of chronic wounds: sponges and topical gels. Sponges were formulated from cross-linking of gelatin and PEG. Ag nanoparticles and metronidazole were incorporated into the sponges to improve their antibacterial activity. Topical gels were loaded with essential oils and Ag nanoparticles and prepared from CMC and poloxamer. The prepared sponges and topical gels were evaluated using various analysis and characterization techniques. SEM/EDX, FTIR, and TGA were employed to characterize gelatin/PEG hybrid sponges followed by porosity, in vitro biodegradability, cytotoxicity, and antibacterial studies. FTIR, SEM/EDX, and TGA confirmed their physicochemical properties and successful fabrication of sponges loaded with metronidazole and Ag nanoparticles. The sponges were biodegradable, indicating their capability to induce skin regeneration. The drug release studies showed a rapid release of metronidazole 28.32-71.97 percent from the sponges over the first hour, followed by a sustained drug release. The Ag nanoparticles were released in a sustained manner, suggesting that these sponges can rapidly destroy bacteria and inhibit persisting bacterial infections as well as protect the lesion bed from further bacteria infections. The in vitro antibacterial studies of sponges displayed superior antibacterial activity against most of the Gram-negative and Gram-positive bacteria strains commonly found in chronic wound infections with a MIC value of 15.625 μg/mL. In vitro cytotoxicity experiments revealed excellent biocompatibility with a percent cell viability of more than 70 percent. The in vitro wound scratch healing assay exhibited that the sponges encapsulated with only metronidazole promoted high cell migration than the dual drug-loaded sponges and untreated cells, suggesting its potential to quicken the wound healing process. CMC/Poloxamer topical gels were also characterized by FTIR, followed by pH, viscosity, spreadability, cytotoxicity, and antibacterial studies. FTIR showed successful preparation of CMC/Poloxamer topical gels loaded with essential oils and Ag nanoparticles. The topical gels exhibited pH in the range of 5.20-6.68, spreadability between 5.4 and 5.9 cm, and viscosity ranged from 216 to 1200 cP at 50 rpm and 210–858 cP at 100 rpm. The in vitro drug release studies demonstrated that Ag nanoparticles were released from the topical gels in a sustained manner. Most formulated topical gels demonstrated superior antimicrobial efficacy against Gram-positive and Gram-negative bacteria strains than the blank gel and controls. The cytotoxicity analysis displayed more than 90.83 percent cell viability for the topical gels, revealing excellent biocompatibility. The outcomes revealed that the topical gels enriched with essential oils lavender and tea tree and Ag nanoparticles and sponges incorporated with metronidazole and Ag nanoparticles are potential wound dressing scaffolds that can be employed for the treatment of chronic infected injuries. The in vitro wound healing experiments showed that the HaCaT cells cultured with gels co-enriched with lavender oil and Ag nanoparticles possessed a higher rate of closure in comparison to the untreated cells for 96 hours. , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
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Synthesis and in vitro biological studies of ursolic acid-based hybrid compounds
- Authors: Khwaza, Vuyolwethu
- Date: 2022
- Subjects: Herbal medicine , Herbs -- Therapeutic use , Antineoplastic antibiotics
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27797 , vital:69689
- Description: Ursolic acid UA, a pentacyclic triterpenoid that is commonly found in many medicinal herbs and fruits, has been identified as a potential source of therapeutic agents because of its potent biological effects, which include its potential anticancer and antimicrobial activities. However, its limited solubility, rapid metabolism and poor bioavailability inhibit its clinical applications. Numerous UA derivatives have been prepared over the past years in an effort to mitigate the drawbacks associated with UA, as new chemical entities for the treatment of various infections. There is very little progress in the discovery of efficient UA derivatives. In this study, a class of ester and amide-linked ursolic acid-based hybrid compounds fused with selected pharmaceutical scaffolds were successfully synthesized using amidation and esterification reactions and tested for antibacterial and cytotoxicity activities. Hybridizing UA with other known pharmaceutical scaffolds has the potential of overcoming its drawbacks. FT-IR, Mass Spectroscopy, and 1H13C-NMR spectroscopy were used to confirm the structures of the synthesized hybrid compounds. Among the tested ester-linked hybrid compounds in Chapter three, compounds 3.14-3.19,3.21, 3.34, 3.31, and 3.30 demonstrated significant antibacterial activities against some tested bacteria, with MIC values of 15.625 μgml. Furthermore, the in vitro cytotoxicity of these hybrids was determined using the MTT assay against three human tumor cell lines MCF7, MDA-MB-231, and HeLa cells. Compounds 3.19 and 3.34 were found to have better cytotoxic activity when compared to ursolic acid, with IC50 values of 46.99 and 48.18 μg ml respectively. Both compounds revealed more promising docking results, presenting favourable binding interactions as well as better docking energy against the MCF 7 protein target compared to the parent compound ursolic acid. In Chapter Four, among the tested amide-linked hybrid compounds, Compounds 4.17 and 4.24 demonstrated significant antibacterial activity against the majority of bacterial strains with MIC values of 15.625 gml. Compound 4.24 exhibited a MIC value of 15.625gmL against BS, SA, PV, KO, PM, and EC. Compound 4.23 was more cytotoxic to HeLa cells than ursolic acid. Furthermore, molecular docking calculations revealed that compound 4.16 strongly binds to the protein epidermal growth factor receptor while e compounds 4.17 and 4.24 showed a strong binding affinity for the methionyl-tRNA synthetase. In both cases, the hybrid compounds showed better conformational fittings in the active site of the targeted proteins as compared to the parent ursolic acid. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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- Authors: Khwaza, Vuyolwethu
- Date: 2022
- Subjects: Herbal medicine , Herbs -- Therapeutic use , Antineoplastic antibiotics
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27797 , vital:69689
- Description: Ursolic acid UA, a pentacyclic triterpenoid that is commonly found in many medicinal herbs and fruits, has been identified as a potential source of therapeutic agents because of its potent biological effects, which include its potential anticancer and antimicrobial activities. However, its limited solubility, rapid metabolism and poor bioavailability inhibit its clinical applications. Numerous UA derivatives have been prepared over the past years in an effort to mitigate the drawbacks associated with UA, as new chemical entities for the treatment of various infections. There is very little progress in the discovery of efficient UA derivatives. In this study, a class of ester and amide-linked ursolic acid-based hybrid compounds fused with selected pharmaceutical scaffolds were successfully synthesized using amidation and esterification reactions and tested for antibacterial and cytotoxicity activities. Hybridizing UA with other known pharmaceutical scaffolds has the potential of overcoming its drawbacks. FT-IR, Mass Spectroscopy, and 1H13C-NMR spectroscopy were used to confirm the structures of the synthesized hybrid compounds. Among the tested ester-linked hybrid compounds in Chapter three, compounds 3.14-3.19,3.21, 3.34, 3.31, and 3.30 demonstrated significant antibacterial activities against some tested bacteria, with MIC values of 15.625 μgml. Furthermore, the in vitro cytotoxicity of these hybrids was determined using the MTT assay against three human tumor cell lines MCF7, MDA-MB-231, and HeLa cells. Compounds 3.19 and 3.34 were found to have better cytotoxic activity when compared to ursolic acid, with IC50 values of 46.99 and 48.18 μg ml respectively. Both compounds revealed more promising docking results, presenting favourable binding interactions as well as better docking energy against the MCF 7 protein target compared to the parent compound ursolic acid. In Chapter Four, among the tested amide-linked hybrid compounds, Compounds 4.17 and 4.24 demonstrated significant antibacterial activity against the majority of bacterial strains with MIC values of 15.625 gml. Compound 4.24 exhibited a MIC value of 15.625gmL against BS, SA, PV, KO, PM, and EC. Compound 4.23 was more cytotoxic to HeLa cells than ursolic acid. Furthermore, molecular docking calculations revealed that compound 4.16 strongly binds to the protein epidermal growth factor receptor while e compounds 4.17 and 4.24 showed a strong binding affinity for the methionyl-tRNA synthetase. In both cases, the hybrid compounds showed better conformational fittings in the active site of the targeted proteins as compared to the parent ursolic acid. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
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