Design, formulation and evalauation of liposomes co-loaded with human serum Albumin and Rifampicin
- Authors: Bapolisi, Alain Murhimalika
- Date: 2020
- Subjects: Liposomes , Serum albumin , Rifampin , Mycobacterium tuberculosis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/161780 , vital:40670
- Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interestingbenefits such as low immunogenicity, antioxidant properties and improving cellular uptake ofdrugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA)seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates.Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
- Full Text:
- Date Issued: 2020
- Authors: Bapolisi, Alain Murhimalika
- Date: 2020
- Subjects: Liposomes , Serum albumin , Rifampin , Mycobacterium tuberculosis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/161780 , vital:40670
- Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interestingbenefits such as low immunogenicity, antioxidant properties and improving cellular uptake ofdrugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA)seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates.Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
- Full Text:
- Date Issued: 2020
Design, formulation and evaluation of liposomes co-loaded with human serum albumin and rifampicin
- Authors: Bapolisi, Alain Murhimalika
- Date: 2020
- Subjects: Liposomes , Rifampin , Antitubercular agents , Serum albumin , Albumins , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163179 , vital:41016
- Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interesting benefits such as low immunogenicity, antioxidant properties and improving cellular uptake of drugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA) seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates. Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. iv The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
- Full Text:
- Date Issued: 2020
- Authors: Bapolisi, Alain Murhimalika
- Date: 2020
- Subjects: Liposomes , Rifampin , Antitubercular agents , Serum albumin , Albumins , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163179 , vital:41016
- Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interesting benefits such as low immunogenicity, antioxidant properties and improving cellular uptake of drugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA) seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates. Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. iv The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
- Full Text:
- Date Issued: 2020
Formulation and evaluation of liposomal films for buccal delivery of antiretroviral drug
- Authors: Okafor, Nnamdi Ikemefuna
- Date: 2020
- Subjects: Liposomes , Highly active antiretroviral therapy , Antiretroviral agents , HIV infections -- Prevention
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/117161 , vital:34485
- Description: The human immune deficiency virus (HIV) infection has been ranked as one of the most devastating microbial infections in the world. This status is a result of the HIV rapid genetic variation, which limits discovery of a vaccine. Use application of antiretroviral therapy (ARVT) in treatment of the disease caused by the HIV infection (known as acquired immunodeficiency syndrome, HIV-AIDS) is frequently compromised by several factors such as the low bioavailability and severe adverse effects associated with the existing antiretroviral drugs (ARVDs). This underlines the need for controlling the pharmacokinetics profiles of ARVD using effective vehicles that can modify drug biodistribution. The same is true for many other conditions, where delivery systems can determine the success or failure of treatment by controlling pharmacokinetic and dynamic properties. The mucosal linings of the oral cavities in addition offer adorable route of administration for systematic drug delivery, improving drug therapeutic performance and often preferred by clinicians and patients. Liposomes are tiny spherical sacs of phospholipid molecules enclosing water droplets, formed (artificially) to carry drugs or other substances into the tissues by crossing and targeting to specific organelles. This work therefore focused on preparation of liposomes and liposomal buccal films (BFs) for potential buccal delivery of efavirenz, an ARVD model endowed with poor solubility and several side effects. The liposomes were prepared by thin film hydration method using crude soybean lecithin (CL) and cholesterol. Efavirenz loaded liposomes were evaluated for particle size, Zeta potential (ZP), morphology, encapsulation efficiency (EE%) and release kinetics studies. The physiochemical properties of the liposomes were also evaluated using Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), energy dispersity spectroscopy (EDS), and Fourier transform infrared (FTIR), while the formulation with the best encapsulation efficiency was used as the solvent medium for the buccal film formation. The buccal films were prepared using solvent casting method, where the liposomal suspension was used as the dispersing medium. The films were optimized for physical properties (thickness, weight variation and folding endurance) using digital Vernier calliper and digital weighing balance. The physiochemical properties of the selected BFs films made of Carbopol (CP) and its combination with Pluronic F127 (PF127) were further characterized using XRD, DSC, FTIR, Transmission Electron Microscopy (TEM), EDS and Scanning Electron Microscopy (SEM). The permeation study of the selected BFs was investigated using Franz diffusion cell. The BFs composed of CP alone or its combination with PF127 demonstrated much better bio-adhesive properties than the films made of other polymers (like Hydroxyl propyl methyl cellulose, HPMC) alone or in combination with PF127. The developed liposome formulation showed high encapsulation 98.8 ± 0.01 % in CL to cholesterol mass ratio of 1:1 and total lipid to drug mass ratio of 2:1. The average particle size 104.82 ± 2.29 nm and Zeta potential -50.33 ± 0.95 mV of these liposomes were found to be attractive for targeted delivery to the HIV infected cells. The CP based BFs (without and with PF127) exhibited good film thickness 0.88 ± 0.10 and 0.76 ± 0.14 mm, with weight uniformity 68.22 ± 1.04 and 86.28 ± 2. 16 mg, satisfactory flexibility values 258 and 321, and slightly acidic pH 6.43 ± 0.76 and 6.32 ± 0.01. The swelling percentage was found to be 50 % for CP film alone and 78 % for CP film with PF127. The cumulative amount of drug that permeated through the buccal epithelium over 24 hours was about 66 % from CP film alone and 75 % from CP film with PF127. Since no evidence of the liposomal encapsulation of EFV have been reported to our knowledge, we find the insights from the present study valuable as a set of preliminary data to encourage further investigations of the encapsulation and delivery of EFV like antiretrovirals for enhanced solubility, site targeting and prolonged release using crude soybean lecithin and mucoadhesive polymers, which holds some added economical values as naturally occurring lipid and polymeric mixtures as a promising delivery systems for buccal delivery of ARVDs.
- Full Text:
- Date Issued: 2020
- Authors: Okafor, Nnamdi Ikemefuna
- Date: 2020
- Subjects: Liposomes , Highly active antiretroviral therapy , Antiretroviral agents , HIV infections -- Prevention
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/117161 , vital:34485
- Description: The human immune deficiency virus (HIV) infection has been ranked as one of the most devastating microbial infections in the world. This status is a result of the HIV rapid genetic variation, which limits discovery of a vaccine. Use application of antiretroviral therapy (ARVT) in treatment of the disease caused by the HIV infection (known as acquired immunodeficiency syndrome, HIV-AIDS) is frequently compromised by several factors such as the low bioavailability and severe adverse effects associated with the existing antiretroviral drugs (ARVDs). This underlines the need for controlling the pharmacokinetics profiles of ARVD using effective vehicles that can modify drug biodistribution. The same is true for many other conditions, where delivery systems can determine the success or failure of treatment by controlling pharmacokinetic and dynamic properties. The mucosal linings of the oral cavities in addition offer adorable route of administration for systematic drug delivery, improving drug therapeutic performance and often preferred by clinicians and patients. Liposomes are tiny spherical sacs of phospholipid molecules enclosing water droplets, formed (artificially) to carry drugs or other substances into the tissues by crossing and targeting to specific organelles. This work therefore focused on preparation of liposomes and liposomal buccal films (BFs) for potential buccal delivery of efavirenz, an ARVD model endowed with poor solubility and several side effects. The liposomes were prepared by thin film hydration method using crude soybean lecithin (CL) and cholesterol. Efavirenz loaded liposomes were evaluated for particle size, Zeta potential (ZP), morphology, encapsulation efficiency (EE%) and release kinetics studies. The physiochemical properties of the liposomes were also evaluated using Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), energy dispersity spectroscopy (EDS), and Fourier transform infrared (FTIR), while the formulation with the best encapsulation efficiency was used as the solvent medium for the buccal film formation. The buccal films were prepared using solvent casting method, where the liposomal suspension was used as the dispersing medium. The films were optimized for physical properties (thickness, weight variation and folding endurance) using digital Vernier calliper and digital weighing balance. The physiochemical properties of the selected BFs films made of Carbopol (CP) and its combination with Pluronic F127 (PF127) were further characterized using XRD, DSC, FTIR, Transmission Electron Microscopy (TEM), EDS and Scanning Electron Microscopy (SEM). The permeation study of the selected BFs was investigated using Franz diffusion cell. The BFs composed of CP alone or its combination with PF127 demonstrated much better bio-adhesive properties than the films made of other polymers (like Hydroxyl propyl methyl cellulose, HPMC) alone or in combination with PF127. The developed liposome formulation showed high encapsulation 98.8 ± 0.01 % in CL to cholesterol mass ratio of 1:1 and total lipid to drug mass ratio of 2:1. The average particle size 104.82 ± 2.29 nm and Zeta potential -50.33 ± 0.95 mV of these liposomes were found to be attractive for targeted delivery to the HIV infected cells. The CP based BFs (without and with PF127) exhibited good film thickness 0.88 ± 0.10 and 0.76 ± 0.14 mm, with weight uniformity 68.22 ± 1.04 and 86.28 ± 2. 16 mg, satisfactory flexibility values 258 and 321, and slightly acidic pH 6.43 ± 0.76 and 6.32 ± 0.01. The swelling percentage was found to be 50 % for CP film alone and 78 % for CP film with PF127. The cumulative amount of drug that permeated through the buccal epithelium over 24 hours was about 66 % from CP film alone and 75 % from CP film with PF127. Since no evidence of the liposomal encapsulation of EFV have been reported to our knowledge, we find the insights from the present study valuable as a set of preliminary data to encourage further investigations of the encapsulation and delivery of EFV like antiretrovirals for enhanced solubility, site targeting and prolonged release using crude soybean lecithin and mucoadhesive polymers, which holds some added economical values as naturally occurring lipid and polymeric mixtures as a promising delivery systems for buccal delivery of ARVDs.
- Full Text:
- Date Issued: 2020
Uptake of liposomes into bacterial cells
- Authors: Oidu, Benjamin
- Date: 2013
- Subjects: Liposomes , Drug carriers (Pharmacy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10165 , http://hdl.handle.net/10948/d1021010
- Description: Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. A variety of liposome formulations are presently under clinical trial exploration, while others have already been approved for clinical use. The aim of this study was to optimize liposome uptake into bacterial cells. Both gram-positive and gram-negative bacteria were used in the study as well as Candida albicans.Response surface methodology (RSM) using a central composite design (CCD) model was used to optimize liposomal formulations of carboxyfluorescien (CF) for each of the three microbes, and also the three microbes in combination namely; Staphylococcus aureus (Sa), Escherichia coli (Ec) and Candida albicans (Ca). Percentage of CF encapsulated and CF increase in Uptake were investigated with respect to two independent variables that were, cholesterol (CHOL) and stearylamine (SA) content. Design Expert 8 was used for the purpose of finding the combination of independent variables that would yield an optimal formulation for each microbe and the three microbes in combination. The model selected by the software managed to reasonably correlate the predicted models to the experimental data. Encapsulation of carboxyfluorescien (CF) into a liposome formulation enhanced its uptake by Staphylococcus aureus and Escherichia coli as well as Candida albicans. This was evident in the increase in CF uptake when the uptake rate of free CF was compared with that of liposomal CF.
- Full Text:
- Date Issued: 2013
- Authors: Oidu, Benjamin
- Date: 2013
- Subjects: Liposomes , Drug carriers (Pharmacy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10165 , http://hdl.handle.net/10948/d1021010
- Description: Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. A variety of liposome formulations are presently under clinical trial exploration, while others have already been approved for clinical use. The aim of this study was to optimize liposome uptake into bacterial cells. Both gram-positive and gram-negative bacteria were used in the study as well as Candida albicans.Response surface methodology (RSM) using a central composite design (CCD) model was used to optimize liposomal formulations of carboxyfluorescien (CF) for each of the three microbes, and also the three microbes in combination namely; Staphylococcus aureus (Sa), Escherichia coli (Ec) and Candida albicans (Ca). Percentage of CF encapsulated and CF increase in Uptake were investigated with respect to two independent variables that were, cholesterol (CHOL) and stearylamine (SA) content. Design Expert 8 was used for the purpose of finding the combination of independent variables that would yield an optimal formulation for each microbe and the three microbes in combination. The model selected by the software managed to reasonably correlate the predicted models to the experimental data. Encapsulation of carboxyfluorescien (CF) into a liposome formulation enhanced its uptake by Staphylococcus aureus and Escherichia coli as well as Candida albicans. This was evident in the increase in CF uptake when the uptake rate of free CF was compared with that of liposomal CF.
- Full Text:
- Date Issued: 2013
Development and testing of liposome encapsulated cyclic dipeptides
- Authors: Kilian, Gareth
- Date: 2011
- Subjects: Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10136 , http://hdl.handle.net/10948/1397 , Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Description: Cyclic dipeptides have been well characterized for their multitude of biological activities, including antimicrobial and anticancer activities. Cyclo(His-Gly) and cyclo(His-Ala) have also recently been shown to possess significant anticancer activity against a range of cell lines, despite the limitations of these two molecules with respect to their physicochemical properties. Low Log P results in poor cell permeability which can often be problematic for drugs with intracellular mechanisms of action. It can also results in poor biodistribution, and theoretical Log P values for cyclo(His-Gly) and cyclo(His-Ala) were extremely low making them ideal candidates for inclusion into a nanoparticulate drug delivery system. The aim of this study was therefore to formulate and evaluate liposome-encapsulated cyclic dipeptides that increase the tumour-suppressive actions of the cyclic dipeptides, while showing a high degree of specificity for tumour cells. While liposomes are relatively simple to prepare, inter batch variation, low encapsulation and poor stability are often problematic in their production and this has lead to very few liposomal products on the market. This study aimed at using a comprehensive statistical methodology in optimizing liposome formulations encapsulating cyclo(His-Gly) and cyclo(His-Ala). Initial screening of potential factors was conducted using a 25-1 fractional factorial design. This design made use of two levels for each of the five factors and abbreviated the design to minimize runs. Although not much information is provided by these types of designs, the design was sufficient in identifying two critical factors that would be studies further in a more robust design. The two factors selected, based on the screening study, were cholesterol and stearylamine content. These two factors were then used in designing a response surface methodology (RSM) design making use of a central composite rotatable vii design (CCRD) at five levels (-1.5, -1, 0, 1, 1.5) for each factor in order to better understand the design space. Various factors influenced the measured responses of encapsulation efficiency, zeta potential, polydispersity index, cellular uptake and leakage, but most notable were the adverse effects of increasing stearylamine levels on encapsulations efficiency and cholesterol levels on leakage for both cyclo(His-Gly) and cyclo(His-Ala) liposomes. Optimized formulations were derived from the data and prepared. Fair correlation between the predicted and measured responses was obtained. The cytotoxic activity of the encapsulated cyclic dipeptides were assessed against HeLa and MCF-7 cells and found to have limited improvement in activity. However, modification of the polyethylene glycol (PEG) grafted to the liposome surface in order to target folate receptors showed good benefit in significantly decreasing the IC50 values recorded in all cells lines tested, particularly low folate HeLa cells with the lowest IC50 being recorded as 0.0962 mM for folate targeted cyclo(His-Ala). The results therefore indicate that hydrophilic cyclic dipeptides are ideal candidates for inclusion into targeted drug delivery systems such as liposomes. Key words: Liposomes, cyclo(His-Gly), cyclo(His-Ala), cyclic dipeptides, HeLa, MCF-7, folate receptors, factorial design, response surface methodology (RSM), central composite rotatable design (CCRD).
- Full Text:
- Date Issued: 2011
- Authors: Kilian, Gareth
- Date: 2011
- Subjects: Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10136 , http://hdl.handle.net/10948/1397 , Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Description: Cyclic dipeptides have been well characterized for their multitude of biological activities, including antimicrobial and anticancer activities. Cyclo(His-Gly) and cyclo(His-Ala) have also recently been shown to possess significant anticancer activity against a range of cell lines, despite the limitations of these two molecules with respect to their physicochemical properties. Low Log P results in poor cell permeability which can often be problematic for drugs with intracellular mechanisms of action. It can also results in poor biodistribution, and theoretical Log P values for cyclo(His-Gly) and cyclo(His-Ala) were extremely low making them ideal candidates for inclusion into a nanoparticulate drug delivery system. The aim of this study was therefore to formulate and evaluate liposome-encapsulated cyclic dipeptides that increase the tumour-suppressive actions of the cyclic dipeptides, while showing a high degree of specificity for tumour cells. While liposomes are relatively simple to prepare, inter batch variation, low encapsulation and poor stability are often problematic in their production and this has lead to very few liposomal products on the market. This study aimed at using a comprehensive statistical methodology in optimizing liposome formulations encapsulating cyclo(His-Gly) and cyclo(His-Ala). Initial screening of potential factors was conducted using a 25-1 fractional factorial design. This design made use of two levels for each of the five factors and abbreviated the design to minimize runs. Although not much information is provided by these types of designs, the design was sufficient in identifying two critical factors that would be studies further in a more robust design. The two factors selected, based on the screening study, were cholesterol and stearylamine content. These two factors were then used in designing a response surface methodology (RSM) design making use of a central composite rotatable vii design (CCRD) at five levels (-1.5, -1, 0, 1, 1.5) for each factor in order to better understand the design space. Various factors influenced the measured responses of encapsulation efficiency, zeta potential, polydispersity index, cellular uptake and leakage, but most notable were the adverse effects of increasing stearylamine levels on encapsulations efficiency and cholesterol levels on leakage for both cyclo(His-Gly) and cyclo(His-Ala) liposomes. Optimized formulations were derived from the data and prepared. Fair correlation between the predicted and measured responses was obtained. The cytotoxic activity of the encapsulated cyclic dipeptides were assessed against HeLa and MCF-7 cells and found to have limited improvement in activity. However, modification of the polyethylene glycol (PEG) grafted to the liposome surface in order to target folate receptors showed good benefit in significantly decreasing the IC50 values recorded in all cells lines tested, particularly low folate HeLa cells with the lowest IC50 being recorded as 0.0962 mM for folate targeted cyclo(His-Ala). The results therefore indicate that hydrophilic cyclic dipeptides are ideal candidates for inclusion into targeted drug delivery systems such as liposomes. Key words: Liposomes, cyclo(His-Gly), cyclo(His-Ala), cyclic dipeptides, HeLa, MCF-7, folate receptors, factorial design, response surface methodology (RSM), central composite rotatable design (CCRD).
- Full Text:
- Date Issued: 2011
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