Preparation Of Nano-hydroxyapatite/Poly (Lactic-co-glycolic Acid)Electrospun Composite Nanofibers For Drug Delivery Applications

Electrospun nanofibers, with controllable diameters, high specific surface area and porosity, and three dimensional network structures, which closely mimic the structure of nature extracellular matrix, are widely used in the fields of drug delivery systems and tissue engineering. Poly(lactide-co-glycolide acid)(PLGA) is a copolymer with excellent biocompatibility and biodegradability. Nano-hydroxyapatite (n-HA), with high surface activity and strong mechanical property, is a good inorganic carrier material. In this thesis, we used n-HA and PLGA to develop a double-container composite nanofibrous drug delivery system. Amoxicillin (AMX) and doxorubicine hydrochloride (DOX) used as model drugs were firstly loaded onto n-HA surface, respectively, to fabricate the double-container composite nanofibrous drug delivery system of AMX/n-HA/PLGA and DOX/n-HA/PLGA through electrospinning method. We discussed the characteristics of drug delivery system, such as mechanical durability, drug loading and release properties, drug activity, and biocompatibility, and explored the prospects for biomedical applications as drug carrier material or tissue engineering scaffold.The second chapter of the thesis reports a facile approach to fabricating electrospun drug-loaded organic/inorganic hybrid nanofibrous system for antibacterial applications. In this study, nano-hydroxyapatite (n-HA) particles loaded with a model drug, amoxicillin (AMX) were dispersed into poly(lactic-co-glycolic acid)(PLGA) solution to form electrospun hybrid nanofibers. The loading of AMX onto n-HA surfaces (AMX/n-HA) and the formation of AMX/n-HA/PLGA composite nanofibers were characterized using different techniques. We show that AMX can be successfully adsorbed onto the n-HA surface and the formed AMX/n-HA/PLGA composite nanofibers have a uniform and smooth morphology with improved mechanical durability. Cell viability assay and cell morphology observation reveal that the formed AMX/n-HA/PLGA composite nanofibers are cytocompatible. Importantly, the loaded AMX within the n-HA/PLGA hybrid nanofibers shows a sustained release profile and a non-compromised activity to inhibit the growth of a model bacterium. Staphylococcus aureus. With the significantly reduced burst-release prfile, good cytocompatibility, improved mechanical durability, as well as the remained antibacterial activity, the developed AMX/n-HA/PLGA composite nanofibers should find various potential applications in the fields of tissue engineering and pharmaceutical science.In the third chapter, we attempted to first encapsulate the anticancer drug doxorubicin (DOX) using inorganic rod-like nano-hydroxyapatite (n-HA) as a carrier. Then, the DOX-loaded n-HA particles were mixed with poly(lactic-co-glycolic acid)(PLGA) solution to fabricate electrospun hybrid nanofibers. The formation of drug-n-HA complexes and the drug-loaded composite nanofibers were characterized using different techniques. In vitro DOX release behavior was examined using UV-vis spectroscopy under both neutral and acidic conditions. The anticancer activity of the drug-loaded composite nanofibers was evaluated via the3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) viability assay and phase contrast microscopic morphology observation of a model KB cancer cell line (a human epithelial carcinoma cell line). We show that DOX can be successfully loaded onto the surface of the n-HA and the formed composite fibers have a uniform and continuous fibrous morphology. Importantly, the loaded DOX shows a sustained release profile, and the released DOX from the nanofibers displays non-compromised antitumor activity towards the growth inhibition of KB cells.With the significantly reduced burst release profile and the improved mechanical durability of the composite nanofiber system compared with n-HA-free PLGA nanofibers, the designed organic-inorganic hybrid nanofibers nanofibers could be used as a versatile drug delivery system for encapsulation and sustained release of different drugs with prolonged therapeutic efficacy for different biomedical applications.Due to the extremely strong dye sorption capability of porous electrospun nanofiber mats, it is possible to lead to a false negative result of cell viability by MTT colorimetric assay. Therefore, it is necessary to explore a more reliable technology to evaluate cell biocompatibility of electrospun nanofibers. The fourth part of the thesis systematically studied the possibility of evaluating electrospun nanofibers’biocompatibility by resazurin microtiter assay (REMA). The results showed that unreduced resazurin has the highest fluorescence intensity at a concentration of0.1mg/mL. The reduced product of resazurin displayed a good linear relationship in a cell concentration range from0to50×104cells/mL and then a decreasing tend with the increasing cell concentration. It also showed a secondary growth curve relationship within culture time from0to10hours. There was no obvious adsorption of the resazurin reduction product on nanofibrous mats. All experimental results show that the viability of cells cultivated on the electrospinning composite nanofibers can be more accurately evaluated by REMA method than by MTT method.