Electrospun Nanotube/Poly(Lactic-co-glycolic Acid) Composite Nanofibers For Drug Delivery Applications:Preparation,Characterization, Drug Release Properties, And Drug Actibity Evaluation

Electrospinning is a simple and effective method for fabricating ultrafine fibers. Generally, electrospun biodegradable and biocompatible polymeric nanofibrous scaffolds with controllable diameters, high specific surface and porosity and three dimensional network structures, have the ability to closely mimic the biological function and structure of nature extracellular matrix (ECM). And electrospun nanofibrous scaffolds could provide favorable environment for cell adhesion, migration and growth, thus a three dimensional fiber/cell integrated network could be constructed due to cell-cell and cell-matrix interaction. Beyond the application of electrospun nanofibers in tissue engineering, the application in drug delivery is another direction.The objective of this research is to develop electrospun nanofiber-based scaffolding materials for both tissue engineering and pharmaceutical sciences. Traditional polymer nanofibers lack enough mechanical strength and often have a burst release profile when drug molecules are incorporated within the nanofibers. In addition, the formulation of drug-loaded nanotubes (multiwalled carbon nanotubes (MWCNTs) or halloysite nanotubes (HNTs)) is not in the status of device but often presented as powders. Therefore, we combined drug-loaded nanotubes and electrospinning to improve the mechanical properties of the fibers, to develop a double-container drug delivery system, and to avoid the burst release of the incorporated drugs.In this study, poly(lactic-co-glycolic acid)(PLGA) is used as the electrospinning fibrous matix. Tetracycline hydrochloride (TCH) and Doxorubicine hydrochloride (DOX) used as model drugs were loaded into or onto HNTs and CNTs, respectively. Then, the drug-loaded TCH/HNTs and DOX/CNTs with optimized encapsulation efficiency were mixed with PLGA polymer solution for subsequent electrospinning to form nanotube/polymer double-container composite nanofibrous drug delivery system.Firstly, the main research is about the electrospun TCH/HNTs/PLGA nanofibers. Electrospun PLGA nanofibers and HNTs/PLGA composite nanofibers were fabricated, and the affection of the doped HNTs into PLGA on the morphology, structure, fiber diameter, porosity, mechanical and thermal properties was investigated. The results showed that HNTs were successfully incorporated into PLGA fibers, and the incorporation of HNTs did not significantly influence the morphology, structure and porosity of PLGA fibers. While the fiber diameters were increased with the quantity of the doped HNTs. Importantly, the mechanical properties of PLGA fibrous mats were significantly improved and the thermal properties were slightly enhanced with the incorporation of HNTs. All these properties give the priority for the application in tissue engineering.A key step to develop a nanofibrous scaffold for tissue engineering is to evaualte the biocompatibility of the materials. The adhesion and proliferation of L929mouse fibroblast cells cultured on both PLGA and HNT-doped PLGA fibrous scaffolds were compared through MTT assay of cell viability and SEM observation of cell morphology. And protein adsorption behavior on nanofibrous scaffolds was investigated. Similar to electrospun PLGA nanofibers, HNTs-doped PLGA nanofibers were able to promote cell attachment and proliferation and fibroblasts displayed a phenotypic shape, suggesting that the incorporation of HNTs within PLGA nanofibers does not compromise the biocompatibility of the PLGA nanofibers. In addition, compared with PLGA, HNTs-doped PLGA scaffolds allow more protein adsorption, which is favorable for cell adhesion and proliferation. The developed electrospun HNT-doped composite fibrous scaffold may find applications in tissue engineering and pharmaceutical sciences.As a popular method, MTT colorimetric assay is often used to evaluate the viability of cells cultured onto various fibrous tissue engineering scaffolds. While sometimes the cell viability determined from MTT assay is relatively lower than other characterization method, which probably due to the strong dye sorption capability of porous scaffolding materials. Therefore, we proposed that the OD values obtained from MTT assay likely has a false negative result. In this study, the adsorption of MTT formazan onto porous electrospun PLGA based nanofibrous mats was investigated. We show that PLGA, and the HNTs-or CNTs-doped PLGA nanofibers display appreciable MTT formazan dye sorption, corresponding to35.58～50.23%deviation from the real cell viability assay data. By quantifying the MTT formazan dye sorption amount, the MTT assay data could be rectified to reflect the real cell viability. Our study provides a general insight into the deviation and rectification of MTT cell viability assay, which is likely applicable to other colorimetric assays of different porous scaffolding materials for various biomedical applications.On the basis of previous characterization of electrospun PLGA and HNTs/PLGA nanofibers, electrospun TCH/HNTs/PLGA double container drug delivery systems were fabricated. The morphology, structure, fiber diameter, mechanical properties, in-vitro biocompatibility, drug release behavior and antibacterial activity of the drug-loaded composite nanofibrous mats were investigated. The results showed that the mechanical properties of TCH/HNTs/PLGA fibers were also improved by comparing with PLGA fibers. And drug-loaded fibrous mats had good compatibility for the adhesion and proliferation of L929mouse fibroblasts. Compared with drug-loaded TCH/HNTs and TCH/PLGA nanofibers with obvious burst release, electrospun TCH/HNTs/PLGA double container nanofibrous drug delivery system prolonged the release rate of the drug and appreciably eliminated the initial burst release, and sustained release was obtained for more than one month. The TCH-medicated HNTs/PLGA scaffolds displayed effective activity to inhibit the growth of S. aureus both in liquid medium and on solid medium in vitro. These medicated PLGA-based electrospun scaffolds hold a promising potential in wound dressing applications and in preventing in vivo postsurgical adhesions and infections.Electrospun DOX/CNTs/PLGA drug-loaded nanofibrous mat is an antitumer formulation. For this formulation, the morphology, structure, and mechanical properties of electrospun CNTs/PLGA composite nanofibers and DOX/CNTs/PLGA drug-loaded nanofibers were investigated. Similar to electrospun CNTs/PLGA composite nanofibrous mats, DOX (1,2%)/CNTs/PLGA drug-loaded nanofibrous mats could improve the mechanical properties of PLGA fibers. In addition, DOX/CNTs/PLGA double container nanofibrous drug delivery system prolonged the release rate of drug-loaded DOX/CNTs and appreciably eliminated the initial burst release, and sustained release was obtained. The DOX/CNTs/PLGA and DOX/PLGA drug-loaded scaffolds displayed effective anticancer bioactivity on KB cells. In summary, this drug delivery system with controllable release will find various applications in cancer treatment area.