Preparation And In Vivo/In Vitro Evaluation Of Amphiphilic Dextran Decorated Poly(D, L-lactide) Nanoparticles

Cholesterol-3-hemisuccinyl chloride was synthesized using cholesterol and succinic anhydride in anhydrous pyridine. Cholesterol hydrophobically modified dextran (DEX-CH) was obtained by esterification of dextran cholesterol 3-hemisuccinyl chloride using anhydrous dimethyl sulfoxide (DMSO) as a solution and terethylamine as a catalyst. Substituted degree can be controlled by the ratio of dextran and cholesterol 3-hemisuccinate, the actual substituted degree was determined to be 2.2%, 3.4%, and 8% by 1H-NMR spectra.Cholesterol hydrophobically modified dextran-decorated poly(D,L-lactic acid) (DEX-CH/PLA) nanoparticles were prepared using dialysis and O/W emulsion/evaporation methods respectively. The effects of various factors, such as substituted degree (DS) of dextran, sonication during dialysis process and molecular weight of PLA et al., on the size distribution and morphology of DEX-CH/PLA NPs were investigated for the dialysis method. While the effects of another group of factors, such as solution properties, concentration of DEX-CH, DS values of dextran and power of sonication et al., on size distribution of NPs were investigated for O/W emulsion/evaporation method. Then their merits and shortages were evaluated. The results of DLS and TEM indicated that DEX-CH/PLA NPs can be obtained with almost uniform sizes about 104 nm and spherical figures under the condition of CDEX-CH=0.5 mg/ml and DS=5%. These NPs would abstractly satisfy the requirements for long-circulating drug delivery system. The results of stability experiment demonstrated that all of the DEX-CH NPs are stable under 4℃and 37℃, while only the DS=2% NPs were unstable when freeze-dried.The non-specific interaction of DEX-CH/PLA NPs with blood proteins was evaluated using bovine serum albumin (BSA) as a model protein. The result showed that FITC-BSA absorded much less onto DEX-CH/PLA=10:1 and DEX-CH/PLA=3:1 NPs than PLA NPs, suggesting that the decoration of amphiphilic dextran significantly decreased the non-specific protein adsorption onto PLA NPs.The blood half-life and biodistribution of 99mTc-labelled DEX-CH/PLA NPs were investigated using Sprague-Dawley rats as model animals. It was evaluated compared to PVA/PLA NPs, which was PLA NPs stabilized by PVA. The half-life of DEX-CH/PLA was found to be 6.1 min, while PVA/PLA NPs was 13.8 min. Accumulation of DEX-CH/PLA NPs in liver, spleen, lungs was rather much and also in kidney, but almost no radioactivity was observed in brain. These results suggested that the surface decoration of DEX-CH to PLA could not significantly prolong the blood circulation time of PLA NPs nor improve their biodistribution. This could be attributed to the conformation of dextran chains on the PLA NPs'surface, which was suggested to be a strong activator of the complement system.