Philosophiae Doctor - PhD / Persistent root canal pathogens are one of the main causes of endodontic treatment failure. These pathogens are usually isolated in areas within the root canals that are inaccessible to mechanical instrumentation, chemical irrigants and medicaments resulting in incomplete sterilization of the root canal system. Furthermore, the development of resistant microbial species renders it difficult to disinfect the root canal system using commonly available root canal irrigants and intra-canal medicaments. Intra-canal medicaments are antimicrobial agents that are placed inside the root canal system in order to eliminate the remaining microorganisms that persist after mechanical instrumentation and irrigation. However, their antimicrobial efficacy is effective only against some of the root canal pathogens. Furthermore, the presence of tissue inhibitory factors such as dentine powder and serum albumine within the root canal system inhibits their antimicrobial activity. The use of nanoparticles as antimicrobial agents has recently attracted considerable attention especially in the medical field as a result of their unique antibacterial properties. These properties include their ability to use multiple mechanisms to eradicate microbial cells and their low potentiality to produce microbial resistance. Polymeric nanoparticles such as chitosan nanoparticles (Ch-Np) gained significant interest as a result of their biocompatible and antimicrobial properties. In medicine, several vehicles were designed to carry these antibacterial nanoparticles. Zeolites (Ze) are microporous crystalline hydrated sodium aluminosilicate material that is utilized in the chemical sciences as a carrier for various nanoparticles.

Osteomyelitis or infection of bone is painful and difficult to treat due to limited tissue penetration by antibiotics. A resulting chronic infection has around a 30% chance of never resolving and resulting in amputation of the limb. The current standard of care for osteomyelitis is debridement and systemic antibiotics for two to six months, which can cause systemic toxicity and increase the emergence of antibiotic-resistant bacteria. It is therefore necessary to develop a localized biodegradable treatment that can deliver high concentrations of antimicrobials while minimizing the risk of systemic side effects. The overall objective of this work was to develop, characterize, and challenge locally delivered chitosan-based biomaterials loaded with either antibiotic or alternative antimicrobial agent(s) in either chronic or acute rat osteomyelitis models. The specific aims were to: (i) determine the chemical and biological interactions between chitosan hydrogels and fosfomycin in vitro, (ii) evaluate the antimicrobial efficacy of chitosan hydrogel loaded with fosfomycin antibiotic, either in the gel, in polylactic acid microparticles, or in both gel and microparticles in vitro and in a chronic rat osteomyelitis model, compared to blank chitosan hydrogel, and (iii) evaluate the antimicrobial efficacy of electrospun chitosan membranes loaded with cis-2-decenoic acid and/or bupivacaine in an acute rat osteomyelitis model, compared to current standard Celox™gauze. As hypothesized, chitosan biomaterials loaded with antimicrobial(s) reduced the bacterial burden and disease symptoms when compared to the standard treatment or blank materials. In closing, locally administrated antibiotics with prolonged availability via engineered biomaterials such as chitosan may allow for increased therapeutic efficacy against osteomyelitis.

Localized drug delivery systems have been widely studied as potential replacements for conventional chemotherapy with the capability of providing sustained and controlled drug release in specific targeted sites. They offer numerous benefits over conventional chemotherapy such as enhancing the stability of embedded drugs and preserving their anticancer activity, providing sustained and controlled drug release in the tumor site, reducing toxicity and diminishing subsequent side effects, minimizing the drug loss, averting the need for frequent administrations, and minimizing the cost of therapy. The aim of this study is to develop a localized drug delivery system with niosomes embedded in a chitosan hydrogel with targeting capabilities. The incorporation of niosomes into a chitosan hydrogel has several advantages over each individually being used. First, embedding niosomes in a chitosan hydrogel can yield control over drug release especially for small molecule drugs. Second, chitosan hydrogel may improve the release time and dosage of drugs from niosomes by protecting them with an extra barrier, resulting in tunable release rates. Third, as a localized delivery system, chitosan hydrogels can prevent the migration of niosomes away from the targeted tumor sites. Finally, chitosan has mucoadhesive property which can be used in the targeting of the tumor cells with the mucin over expression. To enhance the specific targeting, the capacity of chitosan to target MUC1 overexpression in cancer cells will be analyzed. Similarly, the incorporation of chlorotoxin in this system will be achieved and evaluated. Chlorotoxin, a 36-amino acid peptide, is purified from Leiurus quinquestriatus scorpion venom with a distinct characteristic of binding preferentially to neuroectoderma tumors such as glioma, but not to normal tissue. The overexpression of MUC1, a mucin antigen, in certain cancer cells has been used as an attractive therapeutic target in the design of a drug delivery system consisting of chitosan with a distinct mucoadhesive property. To determine the level of MUC1expression in different cell lines, Cell based Enzyme Linked Immunosorbent Assay (Cell ELISA) was developed for the first time. Attenuated Total Reflectance- Fourier Transform Infra-Red (ATR-FTIR) Spectroscopy is used to investigate the possible molecular interaction between chlorotoxin and glioma cells. This study presents a new approach in monitoring the biochemical and biophysical changes in glioma cells after being exposed to CTX. In addition to characterizing the signature spectra of CTX and glioma cells, we evaluated the differences in biochemical compositions of the spectra of the glioma cells treated with and without CTX over different incubation time periods. The results indicate that the proposed localized drug delivery system with the distinct tumor targeting features and extended release profiles would tune and control the specific delivery of chemotherapeutics in tumor sites.