Construction And Application In Tumor Therapy Chitosan Fund Nanorods

Gold nanorods(GNRs) have attracted considerable attention for their unique properties in photothermal therapy, biosensing, molecular imaging, and gene or drug delivery for biomedical applications. Chitosan derivatives are widely used in biomedical materials, gene and drug delivery system with biocompatibility, non-toxicity, biodegradability and strong adhesion of biological mucosa. Expecially, chitosan nanoparticles as a carrier of anticancer drugs has been used very extensively.In this study, a new hybrid nanomaterials were designed and synthesized based on the conjugates of GNRs and chitosan derivatives with low toxicity and biocompatibility. A synergistic effect of combined photothermo-and chemo-therapy was expected to treat with cancer cells. The main contents of this work are as follows:1. The chitosan derivatives were designed and synthesized with different substitution degree of PEG and PEI. First, double carboxy-terminated PEG (compound1) was synthesized by esterification of poly(ethylene) glycol (PEG) and succinic acid anhydride (SA). The structure of1was characterized by1H and13C NMR, and the results show that synthetic product was1and transformation completely. Second, partly thioled polyethylenimine (compound2) was prepared by branched polyethylenimine (PEI) and methyl thioglycolate. The degrees of substitution of the thiol moiety determined by Ellman’s method were PEI-SH2、PEI-SH2.4and PEI-SH2.7. A modified version of the NHS/EDC coupling approach was used to synthesize PEG2000-g-chitosan conjugate (compound3) and PEI-PEG-g-chitosan conjugate (compound4). The structures of3and4were characterized by1H and13C NMR and FT-IR spectra. The degrees of substitution of the PEG or PEI moiety were influenced by the molar ratio.2. GNRs were synthesized through seed mediated growth procedure, and the surface was capped by CTAB bilayer while the end faces relatively bare, thus makes the ends much easier to be modified. The2preferentially attached onto the surface of GNRs through Au-S bond. TEM images chearly showed the end-to-end assembly of GNRs when the molar ratio of2and GNRs was low. But with the increae of molar ratios, the side-by-side assembly of GNRs was observed. The chitosan-modified-GNRs nanoparticles (CS-GNRs) were prepared by mixing4and GNRs. The mixture was treated by dialysis and the result was mainly to assemble GNRs into side by side structure. The high degrees of substitution of PEI and high molar ratio of4were suitable for inducing the side by side structure. The CS-GNRs with core-shell structure were prepared by still-setting method when the molar ratio of4and GNRs was low. Chitosan derivatives were wrapped in internal, and GNRs arrayed outside. And the high molar ratio led to side-by-side assembly of GNRs. Therefore, CS-GNRs with side by side structure was more suitable for following research considering the stability and biocompatibility.3. The CS-GNRs were used for drug delivery system. Doxorubicin (DOX) conjugated to chitosan derivatives by NHS/EDC coupling approach (compound5). The DOX content of5was calculated by fluorescence detection at480nm according to a standard curve of DOX in DMSO, and the degrees of substitution of DOX was18.4%. The stability of optical, temperture and NIR irradiation of CS-GNRs were detected by UV-vis spectra, and the results showed CS-GNRs can be used for following research. The DOX-CS-GNRs with side-by-side structure was prepared by5and GNRs.4. The raw GNRs showed heavy cytotoxic effect on cells even at low concentration. However, the CS-GNRs and DOX-CS-GNRs did not show any cyctotoxic. The confocal image analysis revealed that DOX-CS-GNRs appeared in cells after incubation for2h. CS-GNRs inhibited cancer cells by photothermal effect under near-infrared laser irradiation. A synergistic effect of DOX-CS-GNRs combined photothermo-and chemo-therapy was found at moderate power intensity of NIR irradiation based on the DOX release and the photothermal effect of GNRs.In summary, DOX-CS-GNRs was prepared by chitosan derivatives and GNRs through the strong metal sulfur chemical bond between thiols and the surface of GNRs. And the inhibition of DOX-CS-GNRs combined photothermo-and chemo-therapy was more effective than by photothermal therapy alone.