Design, synthesis, characterization and evaluation of Chitosan-based hydrogel for controlled drug delivery system
- Authors: Safari, Justin Bazibuhe
- Date: 2022-04
- Subjects: Chitosan , Drug delivery systems , Drugs Controlled release , Tenofovir , Colloids , Hepatitis B Chemotherapy , Hydrogel
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/232182 , vital:49969
- Description: Hepatitis B infection is a deadly infectious disease caused by the hepatitis B virus and is responsible for many deaths every year worldwide. Despite medication and vaccines against hepatitis B infection, it still presents high morbidity and mortality among populations. This is partly due to factors such as a long medication period of the existing treatments, resulting in poor patient compliance and leading to treatment failure. In addition, this situation can be responsible for the observed emerging drug resistance. Hence, novel drugs and drug delivery systems are needed to tackle this matter. Many strategies have been used to develop long-acting drug delivery systems treatment for several infectious diseases. Hydrogel drug delivery systems have shown interesting results as controlled drug delivery systems for several drugs. Therefore, the present study aimed to develop chitosan grafted poly (acrylamide-co-acrylic acid) hydrogel and apply it as a pH-sensitive controlled delivery system of tenofovir disoproxil fumarate (TDF). TDF is a nucleoside reverse transcriptase inhibitor used as first-line treatment of hepatitis B chronic infection and in the treatment of other viral infections. The free-radical polymerization method was utilized to modify chitosan by grafting acrylamide and acrylic acid and using N, N’-methylene bisacrylamide as the crosslinking agent to prepare the hydrogel, followed by an optimization of parameters that could affect the swelling capacity. The prepared chitosan-g-poly(acrylamide-co-acrylic acid) hydrogel was characterized using Fourier Transmission Infra-red spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Energy-dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopy (SEM), and was evaluated for cytotoxicity using a HeLa cell assay. TDF was used as a drug model, it was loaded by the swelling equilibrium method, following by the investigation of the release profile of TDF-loaded hydrogel at pH 1.2 and 7.4. A successful synthesis of chitosan grafted poly(acrylamide-co-acrylic acid) hydrogel was confirmed by Fourier Transmission Infra-red spectroscopy (FTIR), X-Ray Diffraction Spectroscopy (XRD), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Energy-dispersive X-ray spectroscopy (EDS) and Scanning Electron Microscopy (SEM). Optimization results showed that the ratio of monomers impacted the swelling ratio of the hydrogel and both the concentration of the crosslinking agent, and the reaction initiator also affected the swelling ratio. The synthesized hydrogels were sensitive to pH and ionic strength. Hydrogel swelling was lower in acidic solutions and higher in neutral and basic solutions and decreased with the increasing ionic strength. Furthermore, SEM results revealed that hydrogel have a rough and fibrous surface structure with numerous pores. Cytotoxicity studies demonstrated that the hydrogel was non-cytotoxic at 50 μg/ml against HeLa cells which suggested a good biocompatibility of the material. TDF was loaded and released from the hydrogels and showed an encapsulation efficiency and drug loading percentage ranging from 81-96% and 8-10%, respectively. TDF release profile was found to be low in buffer solution of pH 1.2 (in the range of 5-10%) and much higher (38-53%) at pH 7.4 within 96 hours. TDF maintained its chemical integrity after release and the hydrogels can therefore be proposed as a new controlled-release drug delivery system for hepatitis B treatment. , Thesis (MSc) -- Faculty of Science, Chemistry, 2022
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The mechanisms conditioning doctoral supervision development in public universities across South Africa
- Authors: Motshoane, Puleng Lorraine
- Date: 2022-04
- Subjects: Doctoral students South Africa , Graduate students Supervision of South Africa , Agent (Philosophy) , Public universities and colleges South Africa , Supervisors Training of South Africa , Supervision South Africa , Mentoring in education South Africa
- Language: English
- Type: Doctoral thesis , text
- Identifier: http://hdl.handle.net/10962/232305 , vital:49980 , DOI 10.21504/10962/232305
- Description: This study offers a social realist account of how South African public institutions develop emerging supervisors. The study addresses the need for supervision development across South African public higher education universities. The purpose of the study was to answer the question “What mechanisms condition the development and support of emerging doctoral supervisors across South African public universities?” To examine this question, analytical dualism was used to separate the roles of the ‘people’ (agents) from the ‘parts’ (structure and culture) to examine their interplay. The study was qualitative, and the data was generated through documents, an online survey, and semi-structured interviews. One hundred and eighty-six participants responded to the survey and fifty-four people were interviewed. The participants came from twenty of the twenty-six public higher education universities and represent a large range of disciplines. The study findings revealed that emerging supervisors were often simply ‘thrown into the deep-end’ as they had to work out how to supervise by learning from their students and using the experience gained while they were being supervised. This was experienced as highly problematic by the participants who shared this understanding. Secondly, the findings suggest that where there were developmental events in place, some were not well received. For example where those providing the training were not regarded as credible because they lacked the supervision experience or because the interventions were seen to be too ad hoc and generic. There were calls for more discipline-specific interventions and collaborative spaces where emerging supervisors could engage with experienced supervisors rather than being instructed in a generic best-practice of ‘how to supervise’. The findings indicated that the lines between co-supervision and mentoring were often blurred, and both were used as another form of supervision development. Such relationships provided a useful means for emerging supervisors to come to understand the complex pedagogy of postgraduate supervision but were at times constrained by power imbalances. It was evident across the data that supervision is a special form of teaching and needs to be conceptualised at least in part as a pedagogy. Moreover, the issue of institutional differentiation needs to be considered for the sector to achieve its intended goals of increasing doctoral output and to be able to participate fully in the knowledge economy. , Phuputso ena e fana ka tlaleho ea 'nete ea kahisano ea kamoo litsi tsa Afrika Boroa li ntlafatsang batsamaisi ba ntseng ba hlaha. Phuputso ena e sebetsana le tlhokeho ya ntshetsopele ya bolebedi ho tswa ho diyunibesithing tsa thuto e phahameng tsa setjhaba tsa Aforika Borwa. Sepheo sa phuputso e ne e le ho araba potso e mabapi le "Ke mekhoa efe e behang nts'etsopele le tšehetso ea baokameli ba ntseng ba tsoela pele ho pholletsa le liunivesithi tsa sechaba tsa Afrika Boroa?" E le ho hlahloba potso ena, ho ile ha sebelisoa li-analytical dualism ho arola likarolo tsa "batho" (baemeli) ho "likarolo" (sebopeho le setso) ho hlahloba likamano tsa bona. Thuto e ne e le ea boleng, 'me lintlha li ile tsa hlahisoa ka litokomane, phuputso ea inthaneteng, le lipuisano tse hlophisitsoeng hantle. Barupeluoa ba lekholo le mashome a robeli a metso e tšeletseng ba ile ba arabela phuputsong eo, 'me batho ba 54 ba botsoa. Barupeluoa ba ne ba tsoa liunivesithing tse mashome a mabeli ho tse mashome a mabeli a metso e tšeletseng tsa thuto e phahameng ea sechaba 'me ba emetse mefuta e mengata ea lithuto. Liphuputso tsa phuputso li senotse hore baokameli ba ntseng ba hlaha hangata ba ne ba ‘lahleloa botebong ba pelo kaha ba ne ba lokela ho etsa qeto ea ho laola ka ho ithuta ho liithuti tsa bona le ho sebelisa phihlelo eo ba e fumaneng ha ba ntse ba behiloe leihlo. Phihlelo ena e bile bothata haholo ho barupeluoa ba arolelanang boiphihlelo bona. Taba ea bobeli, liphuputso li fana ka maikutlo a hore ha liketsahalo tsa nts'etsopele li ntse li le teng, tse ling ha lia ka tsa amoheloa hantle, mohlala, hobane ba fanang ka koetliso ba ne ba sa nkoe e le ba ka tšeptjoang hobane ba ne ba se na boiphihlelo ba bolebeli kapa hobane ho ne ho bonahala hore ho na le mehato ea nakoana. . Ho bile le meipiletso ea hore ho be le litšebetso tse khethehileng tsa khalemelo le libaka tse kopanetsoeng moo baokameli ba neng ba ka buisana le baokameli ba nang le phihlelo ho e-na le ho rutoa ka mokhoa o tloaelehileng oa 'ho laola'. Liphuputso li bonts'itse hore litsela tse pakeng tsa ts'ebelisano-'moho le boeletsi hangata li ne li sa hlaka. Ho feta moo, ka bobeli li ne li sebelisoa e le mofuta o mong oa ntlafatso ea tlhokomelo. Likamano tse joalo li ne li fana ka mokhoa oa bohlokoa bakeng sa baokameli ba ba qalang ho utloisisa thuto e rarahaneng ea bolebeli ba morao-rao empa ka linako tse ling ba ne ba sitisoa ke ho se leka-lekane ha matla. Ho ile ha totobala ho pholletsa le data hore tsamaiso ke mokhoa o ikhethileng oa ho ruta 'me o hloka ho nahanoa bonyane e le mokhoa oa ho ruta. Ho feta moo, taba ea karohano ea litsi e lokela ho shejoa hore lekala le fihlele lipheo tsa lona tse reriloeng tsa ho eketsa tlhahiso ea bongaka le ho kenya letsoho ka botlalo moruong oa tsebo. , Thesis (PhD) -- Faculty of Education, Education, 2022
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