Biofunctionalization Of Polylactide-polyethylene Glycol(PLA-PEG) Nanoparticles For Targeting To Brain Glioma

A series of biotinylated PLA-PEG(PLA-PEG-B) copolymers with different molecular weight were synthesized using D,L-lactide copolymerizing with biotinylated PEG (PEG-B), which was first synthesized via esterifying the hydroxyl groups of PEG with biotinyl chloride. The optimum condition for the preparation of heterofunctional biotinylated PEG was investigated by controlling the ratio of reactant. The copolymers were demonstrated by 1H NMR and 13C-NMR. The molecule weight and distribution were measured through gel permeation chromatography (GPC).PLA-PEG-B nanoparticles were prepared by nanoprecipitation method. The mean diameter , morphology and Zeta potentials were characterized by Laser particle-size analyzer, Transmission electron microscope and Microelectrophoresis, respectively. The results showed that the PLA-PEG-B nanoparticles were mostly spherical with the sizes round about 80–100 nm. The sizes of nanoparticles increased with the increase of lactide/PEG ratio, while the zeta potential of the nanoparticles decreased as the molecule weight increased. The zeta potential of all the nanoparticles obtained was lower than that of PLA nanoparticles, indicating the existence of PEG on the surface of the particles. The conjugation of ligands onto the PLA-PEG-B nanoparticles through biotin-avidin interaction were characteristized by fluorescence microscopy observation and ELISA analysis. The results domenstrated that the PLA-PEG-B nanoparticles had strong abilities for ligands conjugation.The biofunctionalization of PLA-PEG-B nanoparticles was performed using Transferrin as a functional protein based on biotin-avidin interaction. The content of transferrin on the surface of PLA-PEG-B-Tf nanoparticles was evaluated by UV-spectrophotometer method. The uptake of the nanoparticles by U251 tumor cells in vitro was investigated using fluorescence microscopy obseravtion to evaluate the target activity of PLA-PEG-B-Tf nanoparticles. The results suggested that PLA-PEG-B-Tf nanoparticles could find and adhere the U251 tumor cells in 1hour, and enter the cytoplasm in 2 hours, and the cytoplast were the major compartment of their distribution. The PLA-PEG-B-Tf nanoparticles, which were delivered into the cells more rapidly than PLA-PEG nanoparticles, showed glioma cell-targeting ability.The biodistribution of PLA-PEG-B-Tf nanoparticles in SD rats after intravenous injection was also studied using fluorescence microscopy method. The results showed that PLA-PEG-B-Tf nanoparticles were concentrated mainly at liver and spleen, The PLA-PEG-B-Tf nanoparticles could also be found in brain, while PLA-PEG nanoparticles were not found in brain.