Natural polymers and alternative drug delivery systems

Abstract

Natural polymers are promising candidates for biomedical applications such as wound healing and drug delivery. For the latter, oral administration is preferred since it’s non-invasive, and is convenient to patients improving compliance. In this thesis we describe an oral delivery system for heparin that exploits the formation of an ionic complex that is pH sensitive. In addition, natural polymers can be processed into matrices that are effective wound healing agents. Herein, we describe the development of bacterial cellulose matrices with varied morphologies that control the rate of drug diffusion to the wound site. Ionically Complexed Nanoparticles for Heparin Oral DeliveryIonically complexed nanoparticles were prepared from an anionic polysaccharide drug, heparin, entrapped by a positively charged chitosan polysaccharide. In this study, the encapsulation of heparin was studied to optimize the properties needed for its oral drug delivery. Chitosan, used in various biomedical applications, was selected as a cationic polymer for heparin encapsulation. These particles were prepared with a slightly positive charge and an appropriate size for oral drug delivery. In addition, the release profiles of these ionically complexed nanoparticles were improved by using FDA-approved stabilizers, such as pluronic non-ionic surfactant and polyvinyl alcohol. These results obtained in vitro suggest that these stabilized, ionically complexed nanoparticles may be well-suited for the oral drug delivery of heparin into the gastrointestinal tract. Drug Diffusion Through the Bacterial Cellulose Membrane with Varied MorphologyBacterial cellulose (BC) is a naturally derived polymer from the bacterium G. xylinus. BC has high mechanical strength, water holding capacity, and biocompatibility such that it is a useful matrix for drugs that can diffuse at controlled rates to wound sites such as burns. A critical challenge is to develop methods that lead to BC matrices with controlled morphological parameters such as nanofiber orientation and lamellar structure. Gelatin proved to have a strong effect on these organization parameters. The fraction of BC with lamellar and random nanofiber order as a function of gelatin added to BC forming cultures was characterized. Multiple scanning electron microscope images were recorded and analyzed to estimate the lamellar content throughout the matrix. The important learning is that BC morphology is a critical parameter controlling drug diffusion such that it is continuous or leads to blocking of diffusion pathways such that ceasing further diffusion of drug.