A cost effective approach to the delivery of therapeutic gene products in vivo is to immunoprotect genetically-engineered, universal, non-autologous cells in biocompatible microcapsules before implantation. Myoblasts may be an ideal cell type for encapsulation due to their inherent ability to differentiate into myotubes, thereby eliminating the problem of cell overgrowth within the capsular space. To evaluate the interaction between the differentiation program and the secretory activity of the myoblasts within the microcapsule environment, we transfected C2C12 myoblasts to express human growth hormone and followed their expression of muscle differentiation markers, such as creatine phosphate kinase (CPK) protein and up-regulation of muscle-specific genes (ie. myosin light chains 2 & 1/3, Troponin I slow, Troponin T, myogenin and MyoD1). As the transfected myoblasts were induced to differentiate for up to two weeks, their myogenic index (i.e. the percentage of multinucleate myoblasts) increased from 0 to ~50%. Concomitantly, up-regulation of differentiation marker RNA levels, and as much as a 23-fold increase in CPK activity, were observed. After encapsulation and the induction of differentiation, the myoblasts showed a lag phase of ~3 days before an increase in CPK was observed, although the level of CPK activity increased by as much as 63-fold. The myogenic index of the encapsulated cells remained at zero. The rate of human growth hormone secretion was relatively constant throughout the two-week differentiation period, at an average of 7.78 x 10^-2 ng hGH per hour per (mu)g protein, however, human growth hormone secretion was slightly decreased by about twofold during the differentiation of encapsulated myoblasts. In conclusion, the differentiation of myoblasts into myotubes is retarded after encapsulation while the secretion of a recombinant product is slightly reduced. Further studies are necessary to elucidate the cause of this atypical differentiation pattern such that the proliferation and differentiation of the encapsulated myoblasts may be optimized to provide a stable vehicle for gene delivery. / Thesis / Master of Science (MS)

A new design of dual-functional polyurea microcapsules was proposed for chronic wound dressings to provide both non-leaching infection control and sustained topical drug delivery functionalities. Quaternary ammonium functionalized polyurea microcapsules (MCQs) were synthesized under mild conditions through an interfacial crosslinking reaction between branched polyethylenimine (PEI) and 2,4-toluene diisocyanate (TDI) in a dimethylformamide/cyclohexane emulsion. An in-situ modification method was developed to endow non-leaching surface antimicrobial properties to MCQs via bonding antimicrobial surfactants to surface isocyanate residues on the polyurea shells. The resultant robust MCQs with both non-leaching antimicrobial properties and sustained drug releasing properties have potential applications in medical textiles, such as chronic wound dressings, for infection control and drug delivery.

A new design of dual-functional polyurea microcapsules was proposed for chronic wound dressings to provide both non-leaching infection control and sustained topical drug delivery functionalities. Quaternary ammonium functionalized polyurea microcapsules (MCQs) were synthesized under mild conditions through an interfacial crosslinking reaction between branched polyethylenimine (PEI) and 2,4-toluene diisocyanate (TDI) in a dimethylformamide/cyclohexane emulsion. An in-situ modification method was developed to endow non-leaching surface antimicrobial properties to MCQs via bonding antimicrobial surfactants to surface isocyanate residues on the polyurea shells. The resultant robust MCQs with both non-leaching antimicrobial properties and sustained drug releasing properties have potential applications in medical textiles, such as chronic wound dressings, for infection control and drug delivery.

An alternative gene therapy method, non-autologous somatic-gene therapy, is the use of a genetically modified universal cultured cell line that can be implanted into different allogeneic recipients. When used as recombinant cells in microcapsules, myoblasts possess several advantages over other cell types, namely their ability to terminally differentiate thus preventing overcrowding within the capsular space. However, encapsulated myoblasts demonstrate decreased proliferation and myogenic differentiation when compared to unencapsulated myoblasts due to the unnatural capsule environment. This study aims to improve the microcapsule environment by incorporating basic fibroblast growth factor (bFGF) and insulin-like growth factor-11 (IGF-11) and the extracellular matrix materials, collagen, laminin-1 and merosin (laminin-2) within the microcapsules in an attempt to mimic the natural surrounding required for myoblast growth and differentiation. While bFGF lead to significant increases in encapsulated myoblast proliferation, it did not appear to be an ideal choice for optimizing the microcapsule environment due to its inhibitory effect on differentiation and the relative cost in therapeutic delivery of proteins. Both merosin and the combination of laminin and merosin together provide a better alternative for increasing myoblast growth and survival within microcapsules since they have no apparent inhibitory effect on myogenic differentiation, and produce similar proliferative results seen when using bFGF. In terms of differentiation, the addition of IGF-11 to the microcapsules or the use of a myoblast cell line overexpressing IGF-11, aid in increasing the myogenic differentiation of encapsulated myoblasts, however, differentiation levels still do not approach those seen in unencapsulated myoblasts. The positive results obtained with the growth factors and matrix materials employed in this study are important steps towards the optimization of microcapsules by improving both the proliferation and differentiation of encapsulated myoblasts. However, more study is needed to elucidate possible solutions to the continued problem of decreased differentiation of myoblasts within APA microcapsules in order to achieve myogenic differentiation that is comparable to what is seen in unencapsulated myoblasts. / Thesis / Master of Science (MS)

L'acide hyaluronique est un polysaccharide fortement hydraté. Grâce à sa présence naturelle dans le corps humain et aux nombreuses possibilités de modifications chimiques de ce polysaccharide, l'acide hyaluronique est un bon candidat pour la conception de transporteurs de principes actifs. Dans cette thèse, nous avons synthétisé différents types de dérivés du HA en milieu aqueux. Ceux-ci comprennent les dérivés alkylés du HA, HA-cyclodextrine conjugués et des copolymères «hybrides» composés de HA et d'un copolymère thermosensible de l'éthylène glycol.Basé sur la capacité d'accueillir des molécules hydrophobes paclitaxel dans leurs hydrophobes "nanocavités", nous avons ensuite montré la formation de multicouches de polyélectrolytes de capsules à partir de ces dérivés du HA. L'insertion des molécules paclitaxel dans la paroi des capsules a été réalisée par pré-complexation avec les dérivés du HA en solution, et ensuite déposition ces PTX-polyélectrolytes avec le poly(L-lysine) selon la technique de couche par couche.Dans les deux cas, les capsules chargées de PTX ont été trouvés qu'elles permettent de réduire la viabilité et la prolifération des cellules cancéreuses. Ces multicouches ouvrent de nouvelles voies vers des applications en nanomédecine, comme systèmes transporteurs de médicaments hydrophobes. L'acide hyaluronique modifié par maleimide a été réagit avec poly(diethyleneglycolmethacrylate - oligoethyleneglycolmethacrylate (poly(DEGMA-co-OEGMA)) modifié par thiol afin d'obtenir le copolymère «hybrides» thermosensible. La valeur de la LCST de ce copolymère de HA est autour de 35 °C en déterminant par les mesures du point de trouble des solutions. Au-dessus de cette température, le HA-poly(DEGMA-co-OEGMA) conduit à la formation des nanogels avec la capacité d'encapsuler des molécules hydrophobes dans leur domaine hydrophobe.Les nanogels chargés en PTX ont montré une cytotoxicité plus élevée avec des cellules du cancer surexprimant le récepteur CD44. Ces résultats suggèrent que ces nanogels thermosensible pourraient s'avérer être des candidats intéressants pour la libration thérapeutique dans le traitement de cancer. / Hyaluronic acid is a highly hydrated polysaccharide of great biological interest. It can be easily chemically modified, resulting in many kinds of functional polysaccharide derivatives. In this thesis, we have synthesized different types of HA derivatives in aqueous media. These comprise alkylated HA derivatives, HA-cyclodextrin conjugates, and hybrid copolymers made of HA and of a thermosensitive ethylene glycol copolymer. Based on the ability of alkylated HA and cyclodextrin grafted HA to accomodate hydrophobic molecules paclitaxel into their hydrophobic “nanocavities”, we then demonstrated the formation of polyelectrolyte multilayer capsules based on these HA derivatives. The loading of PTX in the nanoshell was achieved by first complexing PTX with HA derivatives in solution and then, depositing these PTX-containing polyelectrolytes alternately with poly(L-lysine) according to the layer-by-layer technique. In the two cases, the PTX loaded capsules were found to decrease the viability and proliferation of MDA MB 231 breast cancer cells, while unloaded capsules did not impact cell viability. Due to these promising results, these hydrophobic polysaccharide nanoshells open new avenues for applications of hydrophobic drug-carrier systems in nanomedicine.Thiol modified poly(diethyleneglycolmethacrylate - oligoethyleneglycolmethacrylate (poly(DEGMA-co-OEGMA)) was reacted with a HA-maleimide conjugate to obtain HA- poly(DEGMA-co-OEGMA). The LCST value of this HA-copolymer was determined to be around 35°C via turbidity measurements. At the body temperature, HA-copolymer was thus shown to self-assemble into nanogels with the ability to encapsulate hydrophobic molecules into their hydrophobic domain. . In vitro cell culture studies showed that with incorporating the hydrophobic anti-cancer drug paclitaxel, the nanogels exhibited high efficiency and selectivity in the eradication of CD44 positive human ovarian cancer cells. These results suggest that these temperature-triggered nanogels hold great potential for the delivery of chemotherapeutics in anti-cancer therapy.

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

No description available.

Developing a drug delivery vehicle that can control the release kinetics of a therapeutic drug on demand has great potential to improve health by allowing health care professionals to maintain the drug concentration in its therapeutic window and increase the efficiency at which treatment is administered. On-demand release can be triggered by a range of stimuli including magnetic, radiation, and ultrasound activation. Of the three, ultrasound is the only one indiscriminate of the chemical properties of the material and is the most widely available clinically, which makes it versatile and applicable for many systems. However, existing strategies that use ultrasound as a release stimulus either pop the microcapsules altogether (enabling no subsequent effective control over the kinetics of drug release) or require continuous ultrasonic administration (typically impractical in a clinical setting), both of which are suboptimal. Overcoming at least of these shortcomings would vastly improve on the technology. In this thesis, microcapsules with a complex shell were fabricated using a modified electrohydrodynamic approach named immersion coaxial electrospraying, which allowed for an increased polymer loading in the shell and improved manipulation of microcapsule size. The complex shell structure of the microcapsules incorporated silica microparticles that acted as corks plugging pores between the inside and outside of the microcapsule. The modified microcapsules were shown to release their payload in the presence of a focused ultrasound signal, while uncorked microcapsules do not release. Release kinetics were shown to be adjustable based on the number of corks initially present in the shell of the microcapsule material. Altogether, the cork-shell microcapsules fabricated in this thesis show promise as a tunable on-demand drug delivery vehicle that is able to better control release compared to conventional ultrasound triggered microcapsules. / Thesis / Master of Applied Science (MASc) / This thesis focuses on the fabrication of complex microcapsules that can be deliver therapeutic drugs on-demand using ultrasound waves. These microcapsules are composed of a water-based core and a biologically inert shell into which particles are embedded. Upon the application of ultrasound, these embedded particles (like corks on a bottle) are popped out to release the “corks” from the shell, creating pores from which the drug in the microcapsule core can be released. In the absence of ultrasound signals, the microcapsules do not release any of their contents, making these effective for “on-demand” release. These microcapsules are made using a modified process based on electrospraying which allows very precise control over the microcapsules’ physical properties, incorporating a key modification that overcomes an inherent issue with the general technique. These microcapsules also improve on currently used ultrasound triggered drug delivery systems by requiring shorter periods of ultrasound and/or enabling better control over the dynamics of drug release following the ultrasound pulse.