Preparation And Property Of Environment Responsive Polysaccharide-based Anticancer Drug Delivery Systems

During the last decade, polymeric micelles have become a hot research object as drug nanocarriers for clinical cancer chemotherapy as they possess various advantages in their applications for drug delivery: their intrinsic core-shell structure allows them load poorly water-soluble anticancer drugs in the hydrophobic core to improve bioavailability; they can also serve as drug reservoirs to allow sustain release to prevent or decrease tissue damage upon accidental extravasations; micelles with nano-size could get to the lesion place(tumor site) by the passive targeting due to enhanced permeability and retention(EPR) effect. However, several challenges still remain for clinical applications. For example, the raw materials are almost expensive and synthetic process is complex, which make it difficult to mass product of polymeric micelles; the degradation of synthetic polymer micelles is very slow, metabolite may cause side effects to body; micelles are lack of tumor targeting, making low bioavailability in vivo. In view of these problems, we synthesized a series of novel polysaccharide-based polymeric micelles and micellar complexes, and investigated their potential applications in drug delivery.A series of novel polysaccharide-based polymeric micelles and micellar complexes were developed, and were characterized by Fourier transform infrared(FTIR) spectroscopy and 1H NMR. Fluorescence Spectroscopy was employed to investigate the micelle behavior. Dynamic light scattering(DLS) was used to test the particle size and particle size distribution of micelles. Transmission electron microscopy(TEM) and scanning electron microscopy(SEM) were employed to observe the morphology of micelles or the internal structure of gel. Dialysis method was used to study the drug loading and release behavior in vitro. Cytotoxicity evaluation of the micelles were performed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide(MTT) assay and the cell morphology was observed by crystal violet staining. Confocal laser scanning microscopy(CLSM) was employed to examine the cellular uptake of drug-loaded micelles. The detailed research contents are as follows:1. ChS-Cur polymeric micelles derived from oxidized chondroitin sulfate(ChS), curcumin(Cur) and bis-acrylamide cysteine(BAC) were prepared by radical polymerization. The morphology, Zeta potential, cytotoxic and drug release behavior were explored. ChS-Cur polymeric micelles hold a spherical structure with a particle size of about 250 nm, and micelles showed a good dispersion stability. DOX and quercetin were used as the model drug. Release studies showed that the controlled release profile of drug was obtained and the micelles has redox sensitivity. In vitro cytotoxicity studies showed that the ChS-Cur micelles were non-cytotoxic.2. Pluronic PF127(PF127) was modified with chondroitin sulfate(ChS) to form tumor-specific micelles using Schiff bases reaction. A series of PF127-ChS micelles with different ratio of PF127 and ChS were fabricated and evaluated in terms of size, morphology, drug loading efficiency and drug release behavior. Spherical micelles with a mean diameter of 155-241 nm were obtained and their critical micelle concentration(CMC) was significantly reduced contrast to PF127 micelles and their stability was enhanced. Doxorubicin(DOX) was loaded into the micelles and in vitro DOX release studies showed that DOX release from the micelles was enhanced at acid pH compared to physiological pH. Cytotoxicity assay determined that the micelles possess significantly lower toxicity and confocal microscopy analysis indicated that DOX-loaded micelles could efficiently release DOX inside cells by the specific cellular uptake.3. A smart dual drug delivery system of injectable micelle/hydrogel composite based on curcumin(Cur) loaded shell-crosslinked PF127 micelle and 5-fluorouracil(Fu) dispersed chitosan/oxidized dextran(CS/ODex) hydrogel was developed. Both of the shell-crosslinked PF127 micelle and CS/ODex hydrogel were prepared based on Schiff base bonds. Disulfide bonds were introduced in the shell of PF127 micelle. The system was detailed characterized by 1H NMR, FTIR, TEM, SEM, DLS and fluorescence spectroscopy. Independent release behaviors of the two drugs are observed under conditions of different precursor concentration, different CS/ODex proportion, different pH and different concentration of DTT. The results show that the drug carrier has pH and redox sensitivity and the release rate can be adjusted by the concentration of the precursor solution. In vitro degradation experiment and cytotoxicity assay determine that the system has good biodegradability and biocompatibility.