Textile structures made of biocompatible, osteoconductive and resorbable chitosan-filaments provide excellent preconditions as scaffolds for Bone Tissue Engineering applications. The novel Net Shape Nonwoven (NSN) technique that enables short fibers to be processed into three-dimensional net-shaped nonwoven structures with adjustable pore size distributions is described. NSN scaffolds made of pure chitosan fibers were fabricated. NSN hybrid scaffolds for improved initial cell adhesion were realized by combining the NSN technique with electrospinning and dip-coating with collagen, respectively. Scanning electron microscopy and liquid displacement porosimetry revealed an interconnecting open porous scaffold structure. The novel chitosan-hybrid scaffolds provide proper conditions for adhesion, proliferation and differentiation of the seeded human bone marrow stromal cells, proving that they are suitable for usage in hard-tissue regeneration.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / This work investigates the possible use of chitosan beads and polyaniline grafted chitosan beads (PGCB) for the adsorption of copper ions from copper contaminated water. For this purpose chitosan flakes were converted to chitosan beads. However, a variable from a number of reaction variables (aniline concentration, chitosan concentration, temperature, acid concentration, reaction time and initiator concentration) was varied while others was kept constant, in an attempt to determine the best conditions for grafting of polyaniline onto chitosan beads. Percentage (%) grafting and % efficiency were key parameters used to determine such conditions. The chitosan beads and PGCB were characterized using physical techniques such as Fourier transformed infra red (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The beads were used as an adsorbent for copper ions removal. The effect of pH on the removal rate of copper (II) by PGCB was investigated on by varying the pH values from pH 3 to 8 at an initial concentration of 40 mg/l. The effect of contact time, initial concentration and temperature was also investigated. The Langmuir and Freundlich model were used to describe adsorption isotherms for chitosan beads and PGCB, with correlation coefficient (R2) as the determining factor of best fit model. The thermodynamics of adsorption of copper (II) onto PGCB was described by parameters such as standard Gibb’s free energy change (ΔGo), standard enthalpy change (ΔHo), and standard entropy change (ΔSo) while the pseudo first-order and pseudo second-order kinetic model was used to describe kinetic data for the PGCB, with R2 and chi- square test (  2) as the determinant factor of best fit model. From the desorption studies, the effect of eluants (HCl and HNO3) and contact time on percentage desorption of PGCB loaded copper (II) ion was investigated upon. In determining the reusability of the PGCB loaded copper (II) ion, three cycles of adsorption/desorption studies was carried out. The results obtained from determining the best conditions for grafting polyaniline onto chitosan beads revealed the following grafting conditions; [Aniline] 0.1 g/l, [temperature] 35oC, [chitosan] 0.45 g/l, [HCl] 0.4 g/l, [(NH4)2S2O8] 0.35 g/l, and [time] 1 h. These conditions were applied in the grafting of polyaniline onto chitosan beads. FTIR analysis showed increase intensity in the grafted beads which provided evidence of grafting, XRD measurement showed a decrease in crystallinity in the PGCB as against the partial crystalline nature of chitosan. In SEM analysis, evidence of grafting was revealed by the closed gap between the polysaccharide particles in the PGCB. From the investigation carried out on the effect of pH on the percentage removal of Cu(II) ions by PGCB, the optimal pH value was found to be pH 5 with a percentage removal of 100% and this value was used for all adsorption experiment. Also from the investigation performed on the effect of contact time and initial concentration, it was observed that there was a sharp increase in the amount of Cu(II) ions adsorbed by PGCB up until contact time of 30 min and thereafter, it increases gradually. From the experiment carried out on the effect of temperature on adsorption capacity, there was an increase in adsorption capacity with increase in temperature. Moreover, at temperatures of 25oC, 35 oC and 45oC the Langmuir model gave the best fit for the chitosan beads having R2 values that are equal and greater than 0.942 in contrast to Freundlich having R2 values that is equal and greater than 0.932. The maximum adsorption capacity (Qm) from Langmuir model at these temperatures were 30.3 mg/g, 47.6 mg/g and 52.6 mg/g respectively. Also, the Langmuir model gave the best fit for the PGCB having R2 values that are equal and greater than 0.956 in contrast to Freundlich model with R2 values that is equal and greater than 0.935. The Qm from Langmuir model at these temperatures were 80.3 mg/g, 90.9 mg/g and 100 mg/g respectively. The values of Qm for PGCB appears to be significantly higher when compared to that of chitosan beads and this makes PGCB a better adsorbent than chitosan beads. From the thermodynamic studies carried out on PGCB, the values of ΔGo were negative and this denotes that the adsorption of copper ions onto PGCB is favorable and spontaneous, the positive value of ΔHo shows the adsorption process is endothermic and the positive value of ΔSo illustrate increased randomness at the solid-liquid interface during the adsorption process. Also, from the kinetic studies carried out on the PGCB, the pseudo second-order kinetic model best described the kinetic data having R2 values that are equal and greater than 0.994 in contrast to the pseudo first-order kinetic model with R2 values that is equal and greater than 0.913. The  2 values for the pseudo first-order and pseudo second-order kinetic model were similar; however, there was a large difference for qe between the calculated (qeCal) values of the first-order kinetic model and experimental (qeExp) values. In the case of the pseudo second-order model, the calculated qe values agree very well with the experimental data. Desorption of the metal ions from PGCB was efficient. 0.5 M HCl was successfully used in desorbing the beads loaded with copper ions and a percentage desorption of 97.1% was achieved at contact time of 180 min. PGCB were successfully re-used for adsorption/desorption studies were a Qm of 83.3 mg/g, 83.3 mg/g and 76.9 mg/g was achieved in the first, second and third cycle respectively.

[EN] The aim of tissue engineering is to develop functional biological substitutes to replace or restore damaged tissues by preparing three-dimensional scaffolds able to accommodate cells plus signaling factors to promote the regeneration of damaged tissue. There is a special interest in developing scaffolds that while providing a favourable environment for cells also possess a degradation rate that can be adapted to the tissue's rate of regeneration. Scaffolds should be porous and possess a pore morphology adapted to the application for which they are designed. They must also be able to hold large quantities of water (hydrogels) while presenting suitable cell/biomaterial interaction. The aim of this thesis is to create chitosan-based three-dimensional porous structures with tunable degradation rates with particular interest in fast degradation rate. Hydrogels of block-copolymer networks were prepared to crosslink the chitosan (CHT) or carboxymethyl chitosan (CmCHT) with either a hydrophobic polymer of low molecular weight, such as poly(ε-caprolactone), (PCL) or a hydrophilic polymer such as poly(ethylene glycol), (PEG). The hypothesis was that the degradation of the cross-linker polymer leaves behind large water-soluble polymer chains (protonated chitosan or carboxymethyl chitosan). However, in spite of chitosan's favourable properties, the polymer has relatively slow biodegradation times in enzymatic media that contain lysozyme and even slower in hydrolytic conditions. Chitosan's physical and chemical properties largely depend on its deacetylation degree (DD). In order to analyze these properties, chitosan was synthesized with various DD ranging from 85% to 45%. Water absorption was seen to rise rapidly as deacetylation was reduced. This would appear to contradict the fact that chitin water absorption (low DD) is much lower than that of chitosan. In order to understand this behaviour, it was analyzed the dependence of the degree of network swelling on the parameters determined by the Flory Rhener theory, the elastic properties of the network and the density of the cross-linking according to the sample's water content. The thermal stability of chitosan according to its DD was analysed by thermogravimetry. Different methods were applied to obtain the activation energy. Electrospinning was chosen as the porous membrane preparation technique as it provides thin membranes that can be handled with fiber sizes in the order of microns. The influence of the electrospinning and cross-linking processes on the thermal stability of chitosan was analyzed. Chitosan and carboxymethyl chitosan hydrogels covalently cross-linked with short chains of poly(ε-caprolactone), (PCL) and poly(ethylene glycol) (PEG) were synthesized. The formation of networks was confirmed by solubility tests with appropriate solvents for each polymer. Hydrogels that absorbed large quantities of water were obtained, with values that ranged between 90 and 5000%. The calorimetric tests together with the Studies on the kinetics of hydrolytic and enzymatic biodegradation showed three different systems: CmCHT-PEG system that can be classified as stable hydrogel, CHT-PCL system as semidegradable hydrogel and degradable hydrogels with degradation kinetics in the order of days for the CmCHT-PCL system. Finally, biological studies were carried out on porous CmCHT-PCL hydrogels. Mesenchymal stem cells (MSCs) from pig adipose tissue were then cultivated and the results showed that these networks can be used in the organism in tissue engineering applications with degradation times of around a week. / [ES] La ingeniería tisular tiene como finalidad desarrollar sustitutos biológicos funcionales que reemplacen o restauren los tejidos dañados. Se trata de preparar andamiajes tridimensionales (scaffolds) que sean capaces de albergar células y factores de señalización que favorezcan la regeneración del tejido dañado. Existe un especial interés en el desarrollo de scaffolds que proporcionando un entorno favorable a las células, tengan una tasa de degradación que se adapte a velocidad de regeneración del tejido. Los scaffolds deben ser porosos y poseer una morfología del poro adaptada a la aplicación para la que son diseñados. Deben ser capaces de albergar gran cantidad de agua (hidrogeles) al tiempo que presentan una interacción célula/biomaterial adecuada. El objetivo de esta tesis es el de crear estructuras porosas tridimensionales basadas en quitosano con velocidades de degradación ajustables con particular interés en velocidades de degradación altas. Se han preparado hidrogeles de redes de copolimeros en bloque entrecruzando el quitosano, (CHT) o el carboximetil quitosano, (CmCHT) con un polímero hidrófobo de bajo peso molecular como la poli(ε-caprolactona), (PCL) o bien con un polímero hidrófilo como es el poli(etilenglicol), (PEG). La hipótesis de trabajo fue que la degradación del polímero que actúa como entrecruzador debe dejar grandes cadenas del polímero (quitosano protonado o carboximetil quitosano) que son solubles en agua. A pesar de las buenas propiedades del quitosano, el polímero presenta tiempos de biodegradación bastante lentos en medio enzimático conteniendo lisozima y aún más lentos en condiciones hidrolíticas. Las propiedades físico-químicas del quitosano dependen en gran medida del grado de desacetilación, DD. Con el fin de analizar dichas propiedades se ha llevado a cabo la síntesis de quitosano con DD variando entre 85% y el 45%. Se ha comprobado que la absorción de agua aumenta rápidamente a medida que el grado de desacetilación disminuye. Esto parece contradecir el hecho de que la absorción de agua de la quitina (DD bajo) es mucho menor que la de quitosano. Para entender dicho comportamiento se han analizado los parámetros que determinan la teoría de Flory Rhener, las propiedades elásticas de la red y la densidad de entrecruzamiento en función del contenido en agua de la muestra. La estabilidad térmica del quitosano en función de DD ha sido analizada por termogravimetría. Se han aplicado diferentes métodos para obtener la energía de activación. Como técnica de preparación de membranas porosas se ha elegido el electrohilado, ya que permite obtener membranas delgadas y manipulables con tamaños de fibra del orden de micras. Se ha analizado la influencia de los procesos de electrohilado y entrecruzamiento en la estabilidad térmica del quitosano. Se han sintetizado hidrogeles de quitosano, y carboximetil quitosano entrecruzados covalentemente con cadenas cortas de poli(ε-caprolactona), y poli(etilenglicol). La formación de las redes se ha confirmado mediante ensayos de solubilidad con buenos solventes para cada polímero. En todos los casos se han obtenido hidrogeles que absorben gran cantidad de agua con valores que oscilan entre 90 y 5000%. Los estudios de las cinéticas de biodegradación tanto hidrolítica como enzimática revelan la obtención de tres sistemas que se pueden clasificar como hidrogeles estables, para los hidrogeles formados por CmCHT-PEG, hidrogeles semidegradables para el sistema CHT-PCL y finalmente hidrogeles degradables con cinéticas de degradación del orden de días, para el sistema CmCHT-PCL. Finalmente se ha llevado a cabo estudios biológicos de los hidrogeles porosos de CmCHT-PCL. Se realizaron cultivos con células mesenquimales del tejido adiposo de cerdo (MSCs). Los resultados han revelado que dichas redes pueden ser utilizadas como sistemas de liberación de células en el organismo con tiempos de degradación / [CA] L'enginyeria tissular té com a finalitat desenvolupar substituts biològics funcionals que reemplacen o restauren els teixits danyats. Es tracta de preparar suports tridimensionals (esquelets o scaffolds) que siguen capaços d'albergar cèl.lules i factors de senyalització que afavorisquen la regeneració del teixit danyat. Hi ha un interès especial en el desenvolupament d'esquelets que, proporcionant un entorn favorable a les cèl.lules, tinguen una taxa de degradació que s'adapte a la velocitat de regeneració del teixit. Els scaffolds han de ser porosos i han de tenir una morfologia del porus adaptada a l'aplicació per a la qual són dissenyats. Han de ser capaços d'albergar una gran quantitat d'aigua (hidrogels) alhora que presenten una interacció cèl.lula/biomaterial adequada. L'objectiu d'aquesta tesi és crear estructures poroses tridimensionals basades en quitosan amb velocitats de degradació sintonizables amb un interés particular de rutes de degradació altes. S'han preparat hidrogels de xarxes de copolímers en bloc entrecreuant el quitosan o el carboximetil quitosan amb un polímer hidròfob de baix pes molecular com la poli (ε-caprolactona), o bé amb un polímer hidròfil com és el poli (etilenglicol). Es tracta d'aconseguir que quan el polímer que actua com a entrecreuador es degrade, deixe grans cadenes del polímer (quitosan protronat o carboximetil quitosan) que són solubles en aigua. A pesar de les bones propietats del quitosan, el polímer presenta cinètiques de biodegradació lentes en condicions enzimàtiques quan conté lisozima i encara més lentes en condicions hidrolítiques. Les propietats fisicoquímiques del quitosan depenen en gran mesura del grau de desacetilació, DD. A fi d'analitzar aquestes propietats, s'ha dut a terme la síntesi de quitosan amb un DD que variava entre el 85% i el 45%. S'ha comprovat que l'absorció d'aigua augmenta ràpidament a mesura que el grau de desacetilació disminueix. Això sembla que contradiu el fet que l'absorció d'aigua de la quitina (DD baixos) és molt menor que no la de quitosan. Per a entendre aquest comportament s'ha analitzat la dependència del grau d'unflament de la xarxa amb els paràmetres que determina la teoria de Flory Rhener, les propietats elàstiques de la xarxa i la densitat d'entrecreuament en funció del contingut en aigua de la mostra. L'estabilitat tèrmica del quitosan en funció del DD ha sigut analitzada per termogravimetria. S'han aplicat diversos mètodes per obtenir l'energia d'activació. Com a tècnica de preparació de membranes poroses s'ha utilitzat l'electrofilatura, ja que permet obtenir membranes primes i manipulables amb grandàries de fibra de l'ordre de micres. S'ha analitzat la influència dels processos d'electrofilatura i entrecreuament amb l'estabilitat tèrmica del quitosan. S'han sintetitzat hidrogels de quitosan i carboximetil quitosan entrecreuats covalentment amb cadenes curtes de poli(ε-caprolactona) i poli(etilenglicol). La formació de les xarxes s'ha confirmat per mitjà d'assajos de solubilitat amb bons solvents per a cada polímer. En tots els casos s'han obtingut hidrogels que absorbeixen una gran quantitat d'aigua, compresa en valors que oscil.len entre el 90 i el 5.000%. Els estudis de les cinètiques de biodegradació tant hidrolítica com enzimàtica revelen l'obtenció de tres sistemes que es poden classificar com a hidrogels estables (per als hidrogels formats per CmCHT-PEG), hidrogels semidegradables (per al sistema CHT-PCL) i, finalment, hidrogels degradables amb cinètiques de degradació de l'ordre de dies (per al sistema CmCHT-PCL). Finalment s'ha dut a terme estudis biològics dels hidrogels porosos de CmCHT-PCL. Es van realitzar cultius amb cèl.lules mesenquimals del teixit adipós de porc (MSCs). Els resultats han revelat que aquestes xarxes poden ser utilitzades com a sistemes d'alliberament de cèl.lules en l'organisme amb temps de degradació de l'ordre d'una setm / Gámiz González, MA. (2016). Biodegradable hydrogels based on water-soluble chitosan for cell transplant [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73070

Malaria is an infectious disease caused by various forms of the Plasmodium parasite. It is responsible for thousands of deaths yearly with 90 % of those deaths being in sub-Saharan Africa, thus making it a disease of global importance. The global burden of malaria is worsened by resistance to current treatment, a lack in funding and limited research outputs. More alternative ways of treatment must be explored and may include the co-formulation of antimalarial drug substances as well as alternative ways of drug delivery. Antifolates are drugs which interfere with an organism’s folate metabolism by inhibiting dihydropteroate synthase (DHPS) or dihydrofolate reductase (DHFR). Dapsone is a synthetic sulfone which has a mechanism of action that is very similar to that of sulphonamides. The mechanism of action is characterised by the inhibition of folic acid synthesis through the inhibition of dihydropteroate synthase (DHPS). Another antifolate drug, proguanil, is the prodrug of cycloguanil. Its mechanism involves the inhibition of dihydrofolate reductase (DHFR), thus inhibiting the malaria parasite to metabolise folates and therefore stunting its growth. Unfortunately, dapsone has a serious side-effect in people with a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) causing oxidative stress on the red blood cells leading to the rupturing of these cells. The main objective of this study was to formulate and characterise TMC-TPP microparticles loaded with the effective but toxic drug combination of dapsone and proguanil and to determine if these drug-containing microparticles had in vivo efficacy against malaria. N-trimethyl chitosan chloride (TMC), a partially quaternised chitosan derivative, shows good water solubility across a wide pH range thus having mucoadhesive properties and excellent absorption enhancing effects even at neutral pH. A faster, more efficient microwave irradiation method was developed as an alternative to the conventional synthesising method of TMC. TMC with the same degree of quaternisation (DQ), ± 60 %, was obtained in a quarter of the reaction time (30 min) by using the newly developed method. The TMC synthesised with the microwave irradiation method also exhibited less degradation of the polymer structure, thus limiting the chance for the formation of any unwanted by-products (Omethylation, N,N-dimethylation and N-monomethylation). The formation of complexes by ionotropic gelation between TMC and oppositely charged macromolecules, such as tripolyphosphate (TPP), has been utilised to prepare microparticles which are a suitable drug delivery system for the dapsone-proguanil combination. Both these drugs were successfully entrapped. These particles were characterised and the in vivo efficacy against the malaria parasites was determined. The microparticles with both the drugs, separately and in combination, displayed similar or better in vivo efficacy when compared to the drugs without the TMC microparticles. An in vitro dissolution study was also performed by subjecting the dapsone and proguanil TMC formulations to 0.1N HCl dissolution medium. Samples were withdrawn after predetermined time points and the drug concentration was determined with HPLC. It was found that the TMC microparticles resulted in a sustained release profile since only 73.00 ± 1.70 % (dapsone) and 55.00 ± 1.90 % (proguanil) was released after 150 minutes. The in vivo bioavailability of the dapsone and proguanil TMC formulations was evaluated in mice by collecting blood samples at predetermined time points and analysing the samples with a sensitive and accurate LC-MS/MS method. The in vivo bioavailability of the dapsone TMC formulation relative to the normal dapsone formulation was found to be 244 % and 123 % for the proguanil TMC formulation relative to the normal proguanil formulation. These TMC-TPP microparticles formulations showed better in vivo efficacy and bioavailability when compared to the normal formulation. Together with the sustained release, these formulations may be a promising cheaper and more effective treatment against malaria. / PhD (Pharmaceutics), North-West University, Potchefstroom Campus, 2015

Malaria is an infectious disease caused by various forms of the Plasmodium parasite. It is responsible for thousands of deaths yearly with 90 % of those deaths being in sub-Saharan Africa, thus making it a disease of global importance. The global burden of malaria is worsened by resistance to current treatment, a lack in funding and limited research outputs. More alternative ways of treatment must be explored and may include the co-formulation of antimalarial drug substances as well as alternative ways of drug delivery. Antifolates are drugs which interfere with an organism’s folate metabolism by inhibiting dihydropteroate synthase (DHPS) or dihydrofolate reductase (DHFR). Dapsone is a synthetic sulfone which has a mechanism of action that is very similar to that of sulphonamides. The mechanism of action is characterised by the inhibition of folic acid synthesis through the inhibition of dihydropteroate synthase (DHPS). Another antifolate drug, proguanil, is the prodrug of cycloguanil. Its mechanism involves the inhibition of dihydrofolate reductase (DHFR), thus inhibiting the malaria parasite to metabolise folates and therefore stunting its growth. Unfortunately, dapsone has a serious side-effect in people with a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) causing oxidative stress on the red blood cells leading to the rupturing of these cells. The main objective of this study was to formulate and characterise TMC-TPP microparticles loaded with the effective but toxic drug combination of dapsone and proguanil and to determine if these drug-containing microparticles had in vivo efficacy against malaria. N-trimethyl chitosan chloride (TMC), a partially quaternised chitosan derivative, shows good water solubility across a wide pH range thus having mucoadhesive properties and excellent absorption enhancing effects even at neutral pH. A faster, more efficient microwave irradiation method was developed as an alternative to the conventional synthesising method of TMC. TMC with the same degree of quaternisation (DQ), ± 60 %, was obtained in a quarter of the reaction time (30 min) by using the newly developed method. The TMC synthesised with the microwave irradiation method also exhibited less degradation of the polymer structure, thus limiting the chance for the formation of any unwanted by-products (Omethylation, N,N-dimethylation and N-monomethylation). The formation of complexes by ionotropic gelation between TMC and oppositely charged macromolecules, such as tripolyphosphate (TPP), has been utilised to prepare microparticles which are a suitable drug delivery system for the dapsone-proguanil combination. Both these drugs were successfully entrapped. These particles were characterised and the in vivo efficacy against the malaria parasites was determined. The microparticles with both the drugs, separately and in combination, displayed similar or better in vivo efficacy when compared to the drugs without the TMC microparticles. An in vitro dissolution study was also performed by subjecting the dapsone and proguanil TMC formulations to 0.1N HCl dissolution medium. Samples were withdrawn after predetermined time points and the drug concentration was determined with HPLC. It was found that the TMC microparticles resulted in a sustained release profile since only 73.00 ± 1.70 % (dapsone) and 55.00 ± 1.90 % (proguanil) was released after 150 minutes. The in vivo bioavailability of the dapsone and proguanil TMC formulations was evaluated in mice by collecting blood samples at predetermined time points and analysing the samples with a sensitive and accurate LC-MS/MS method. The in vivo bioavailability of the dapsone TMC formulation relative to the normal dapsone formulation was found to be 244 % and 123 % for the proguanil TMC formulation relative to the normal proguanil formulation. These TMC-TPP microparticles formulations showed better in vivo efficacy and bioavailability when compared to the normal formulation. Together with the sustained release, these formulations may be a promising cheaper and more effective treatment against malaria. / PhD (Pharmaceutics), North-West University, Potchefstroom Campus, 2015

Thesis (MSc)--Stellenbosch University, 2016. / ENGLISH ABSTRACT: Tuberculosis (TB) is one of the world’s deadliest diseases, with one third of the population being infected by it. The diagnosis of active tuberculosis entails finding and identifying Mycobacterium tuberculosis (Mtb), the causative pathogen in a specimen of bodily fluid from the patient. Multiple samples will improve the diagnostic yield and specimen volumes should therefore be as large as possible, which is often challenging for patients and especially younger children. Alternatively, a smaller volume could be required if there was a manner in which to concentrate the bacteria within a specimen, through use of a substrate which has an affinity for the pathogenic species. Polymers having intrinsic cellular activity are of interest as such substrates, one such being the natural polysaccharide, chitosan. In this thesis, a variety of modified chitosan derivatives were prepared as potential Mtb-capturing substrates. This was achieved by modifying chitosan with a variety of moieties, selected based on possible interactions with the Mtb cell wall, to render various quaternary ammonium salts of the polymer chitosan. The quaternized chitosan derivatives were then used to synthesize nano-substrates having an affinity for Mtb. Polymer coated superparamagnetic magnetite nanoparticles (SPMNs) were synthesized via an in situ co-precipitation technique, in which modified chitosan is able to chelate with the metal core. Polymer nanofibers were also electrospun via the electrospinning technique. The prepared derivative, N-trimethylammonium chitosan chloride (TMC), was electrospun into nanofibers by blending with suitable non-ionogenic polymers, namely polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinyl pyrrolidone (PVP) and polyacrylamide (PAM), required to facilitate nanofiber formation. Affinity studies were conducted between the modified chitosan nano-substrates and the bacillus Calmette-Guérin (BCG) strain of Mycobacterium bovis, the attenuated Mtb-mimic bacteria, for evaluation as mycobacterium capturing substrates. The successful capture of BCG onto the surfaces of the various modified chitosan nanofibers and modified chitosan coated superparamagnetic nanoparticles was confirmed by fluorescence microscopy (FM), light microscopy (LM), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). Analysis of the FM, TEM and FE-SEM images indicated that the chitosan coated nanoparticles functionalized with a C12 aliphatic quaternary ammonium moiety (CS-qC12), captured the most BCG through a combination of ionic and hydrophobic interaction. TMC blended with PVA, to produce nanofibers crosslinked with genipin, were found to have the strongest interaction with BCG of the nanofibrous mats tested. These findings were corroborated by water contact angle measurements, which established that PVA was the least hydrophilic of the non-ionogenic polymers and had hydrogen bond donating groups only, factors influencing the cellular adhesive properties of affinity substrates. / AFRIKAANSE OPSOMMING: Tuberkulose (TB) is een van die wêreld se mees dodelikste siektes, met ‘n derde van die bevolking wat geïnfekteer is daarmee. Ten einde aktiewe TB te diagnoseer moet Mycobacterium tuberculosis (Mtb), die voorsakende patogeen in ʼn monster van die pasiënt se liggaamlike vloeistof, gevind en ïdentifiseer word. Veelvuldige monsters sal die diagnotiese opbrengs verhoog en monster volumes moet dus so groot as moontlik wees wat dikwels ʼn uitdaging vir pasiënte en veral jonger kinders kan bied. Alternatiewelik kan ʼn kleiner monster van die pasiënt vereis word indien daar ʼn manier was om die bakterieë in ʼn monster te konsentreer deur die gebruik van ʼn substraat wat ʼn affiniteit toon vir die patogeniese spesie. Polimere met ʼn intrinsieke sellulêre aktiwiteit, wek belangstelling as sodanige substraat, een synde die natuurlike polisakkaried, chitosan. In hierdie tesis is ʼn verskeidenheid gemodifiseerde chitosan afgeleides voorberei as potensiële Mtb-vaslegging substrate. Dit is gedoen deur chitosan te modifiseer met ʼn verskeidenheid funksionele groepe, gekies op grond van moontlike interaksies met die Mtb selwand, ten einde ʼn verskeidenheid kwaternêre ammonium soute van die chitosan polimeer te bekom. Die kwaternêre chitosan afgeleides is gevolglik gebruik om nano-substrate te sintetiseer wat ʼn affiniteit toon vir Mtb. Polimeer bedekte superparamagnetiese magnetiet nanopartikels (SPMNs) is gesintetiseer via ʼn in situ mede-neerslag metode, waarvolgens die gemodifiseerde chitosan polimere in staat is om met die metaal kern te chelaat. Polimeer nanovesels is ook geëlektrospin deur die elektrospin tegniek te gebruik. Die voorbereide afgeleide N-trimetielammonium chitosan chloried (TMC) is tot nanovesels geëlektrospin deur vermenging met geskikte nie-ionogeniese polimere, naamlik poliviniel-alkohol (PVA), polietilene-oksied (PEO), poliviniel-pirrolidoon (PVP) en poliakrielamied (PAM), wat vereis word ten einde nanovesels te produseer. Affiniteit studies is uitgevoer tussen die gemodifiseerde chitosan nano-substrate en die bacillus Calmette-Guérin (BCG) stam van Mycobacterium bovis, die verswakte Mtb-mimiek bakterieë vir evaluering as mycobakterium-vaslegging substrate. Die suksesvolle vasvang van BCG op die oppervlaktes van die verskillende gemodifiseerde chitosan nanovesels en gemodifiseerde chitosan bedekte SPMNs is bevestig deur fluoressensie mikroskopie (FM), lig mikroskopie (LM), transmissie elektron mikroskopie (TEM) en veld-emissie-skandering elektron mikroskopie (FE-SEM). Analise van die FM, TEM en FE-SEM beelde het getoon dat die chitosan bedekte nanopartikels met byvoeging van ʼn C12 alifatiese kwaternêre ammonium groep, die meeste BCG vasgevang het deur ʼn kombinasie van ioniese en hidrofobiese interaksie. TMC vermeng met PVA om nanovesels te vorm, gekruisbind met genipin, is gevind om die sterkste interaksie met BCG te toon. Hierdie bevindings is bevestig deur water-kontak-hoek-metings, wat getoon het dat PVA die minste hidrofilies van die nie-ionogeniese polimere was en slegs waterstof-binding skenkings groepe het, alles faktore wat die sellulêre bindingskwaliteite van affiniteit-substrate sal beïnvloed.

Pagrindinis šio darbo tikslas buvo susintetinti vandenyje tirpius norimos struktūros bei skirtingo pakeitimo laipsnio skiepytuosius chitozano-polietilenglikolio (MPEG) kopolimerus bei katijonizuotus chitozano darinius ir ištirti jų savybes. „Klik“ chemijos reakcijų pagalba susintetinti nauji įvairaus pakeitimo laipsnio chitozano-MPEG skiepytieji kopolimerai, turintys triazolilliekaną. Pasiūlyti nauji chitozano-C(6)-MPEG bei N-2,3-epoksipropil-N,N,N-trimetilamonio chloridu C(6)-katijonizuoto chitozano sintezės būdai, chitozano aminogrupių apsaugai naudojant chitozano kompleksus su dodecilsulfatu. Dalinai N-katijonizuoto chitozano darinius papildomai katijonizuojant šarminėje terpėje, gauti N,O-katijonizuoti chitozano dariniai, turintys labai didelį katijonizavimo laipsnį. Pasiūlytas katijonizuoto chitozano fermentinės hidrolizės metodas, kurį naudojant chitozano darinio molekulinę masę lengvai galima sumažinti dešimtimis kartų. Chitozaną modifikuojant vyno, citrinų, adipo rūgštimis, susintetinti dalinai tinklinti chitozano dariniai. Prie chitozano ir karboksirūgštimis modifikuotų chitozano nanodalelių prijungus (4-cianpentano rūgšties)-4-ditiobenzenkarboksilatą, susintetintas makroiniciatorius gyvybingajai radikalinei polimerizacijai RAFT metodu. / The main aim of this work was to synthesize water-soluble chitosan-methoxy poly(ethylene glycol) (MPEG) graft copolymers and quaternized derivative of chitosans of various structure and desirable graft density and to study their properties. Novel chitosan-MPEG derivatives containing triazolyl moiety with different degree of substitution of chitosan were prepared for the first time by “click chemistry”. Several new schemes of the synthesis of chitosan-C(6)-TMPEG and C(6)-quaternized chitosan derivatives were suggested based on protection of amino functionality by using chitosan-dodecyl sulfate complexes. Additional cationization of cationic chitosan through its hydroxyl groups in alkaline medium enabled to prepare N,O-quaternized chitosans derivatives with very high degree of quaternization. It was suggested method of enzymatic hydrolysis of quaternized chitosans which allow a tenfold decrease the molecular weight of chitosans derivatives. Modification of chitosan by tartaric, citric or adipic acid yielded partially crosslinked chitosan derivatives. Modification of chitosan and further modification of chitosan nanoparticles by dithiobenzendicarboxylate resulted in RAFT macroinitiators which are precursors of functionalized nanoparticles.

The main aim of this work was to synthesize water-soluble chitosan – methoxy poly(ethylene glycol) (MPEG) graft copolymers and cationized chitosan derivatives of various structure and desirable graft density, and to study their properties. Novel chitosan-MPEG derivatives with different degree of substitution of chitosan were prepared for the first time by “click” chemistry. Several new schemes of the synthesis of chitosan-MPEG and additionally cationized chitosan derivatives were suggested based on protection of amino functionality by using chitosan-dodecyl sulphate complexes. Additional cationization of chitosan through its hydroxyl groups in alkaline medium enabled to prepare chitosan derivatives with very high charge density. A method of enzymatic hydrolysis of the cationized chitosans was proposed which allowed a tenfold decrease of the molecular weight of chitosan derivatives. Modification of chitosan by tartaric, citric or adipic acid yielded chitosan nanoparticles. Further modification of chitosan nanoparticles by dithiobenzendicarboxylate resulted in RAFT macroinitiators used as precursors of functionalized nanoparticles. / Pagrindinis šio darbo tikslas buvo susintetinti vandenyje tirpius norimos struktūros bei pakeitimo laipsnio skiepytuosius chitozano – polietilenglikolio (MPEG) kopolimerus bei katijonizuotus chitozano darinius ir ištirti jų savybes. Įvairaus pakeitimo laipsnio chitozano-MPEG skiepytieji kopolimerai susintetinti vykdant „klik“ chemijos reakcijas. Pasiūlyti nauji chitozano-MPEG bei papildomai katijonizuoto chitozano sintezės būdai, chitozano aminogrupių apsaugai naudojant chitozano kompleksus su dodecilsulfatu. Dalinai katijonizuoto chitozano darinius papildomai katijonizuojant šarminėje terpėje, gauti chitozano dariniai, turintys labai didelį krūvio tankį. Pasiūlytas katijonizuoto chitozano fermentinės hidrolizės metodas, kurį naudojant chitozano darinio molekulinę masę lengvai galima sumažinti dešimtimis kartų. Chitozaną modifikuojant vyno, citrinų arba adipo rūgštimis, susintetintos nanodalelės. Prie chitozano nanodalelių prijungus (4-cianpentano rūgšties)-4-ditiobenzenkarboksilatą, susintetintas makroiniciatorius gyvybingajai radikalinei polimerizacijai RAFT metodu.

Cell adhesion is the first step of cell response to materials and the extracellular matrix (ECM), and is essential to all cell behaviours such as cell proliferation, differentiation, migration and apoptosis for anchor-dependent cells. Therefore, studies of cell attachment have important implications to control and study cell behaviours. During many developed techniques for cell attachment, the manipulation of surface chemistry is a very important method to control initial cell attachment. To control cell adhesion on a two-dimensional surface is a simple model to study cell behaviours, and is a fundamental topic for cell biology, tissue engineering, and the development of biosensors. From the engineering point of view, the preparation of a material with controllable surface chemistry can help studies of cell behaviours and help scientists understand how surface features and chemistry influence cell behaviours. During the fabrication, the challenge is to create a surface with heterogeneous surface properties in the micro scale and subsequently to guide cell initial adhesion. In order to control cell adhesion in a spatial and temporal manner, a photochemical method to control surface chemistry was employed to control the surface property for cell adhesion in this project. Two photocleavable derivatives of the nitrobenzyl group were tried on two types of surfaces: a model self-assembled monolayer (SAM) with alkanethiol-gold surface and biodegradable chitosan. Reactive functional groups on two different surfaces can be inactivated by covalent binding with these photocleavable molecules, and light can be further introduced into the system as a stimulus to recover their reactivity. By simply applying a photomask with diffe

In controlled release applications a drug is molecularly dispersed in a polymer phase. In the presence of a thermodynamically compatible solvent, swelling occurs and the polymer releases its content to the surrounding medium. The rate of the drug release can be controlled by interfering with the swelling rate of the beads or by influencing diffusion through the viscosity of the polymer. Beads that contain chitosan were prepared through the ionotropic gelation method where tripolyphosphate (TPP) was used as the crosslinking agent. Beads that consisted of 3% w/v isoniazid (lNH) and 5% w/v chitosan were prepared in a 5% w/v TPP solution (pH 8.7) as the primary beads. To improve the drug loading of chitosan isoniazid beads (ClB) the TPP concentration, pH of the TPP solution and the INH concentrations were altered for maximum drug loading. To increase the porosity of the beads of chitosan beads Explotab® (EXPL), Ac-Di-Sol® (ADS) and Vitamin C (VC) were added individually to chitosan solutions at concentrations of 0.1, 0.25 and 0.5% w/v before adding the mixture to the TPP solution. Morphology, swelling and drug loading studies were used to evaluate the different formulations. After these excipients were added individually they were also added in combinations of two excipients respectively and characterised. From the results of the drug loading studies the beads that contained only chitosan and isoniazid showed a percentage drug loading of (43.92%) which is the best of all the beads that were analyzed. The multi excipient combination of Ac-Di-Sol® and Explotab® showed the best swelling capability at both pH levels. Dissolution studies were conducted on all the formu lations over a period of 6 hours (360 minutes) at pH 5.6 and pH 7.4. From the dissolution results it were clear that no chitosan dissolved at both pH values. The dissolution of single pharmaceutical excipient (SPE) and multi pharmaceutical excipient (MPE) formulations can be arranged in the following order: VC/ADS < VC < ADS/EXPL < ADS < VC/EXPL < CIB < EXPL. Explotab® is a potential excipient for enhanced drug release over a wide pH range. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.