| Cyclodextrin-based pseudo-block copolymer micelles are drawing more and more attention. Compared to conventional polymeric micelles, pseudo-block copolymer endows them with enhanced structural versatility, flexibility and tunability. By further using a biodegradable and biocompatible material, these materials are expected as protein drug delivery system and gene carrier.The new pseudo-graft copolymer micelles was constructed and used as a protein carrier. Polysuccinimide(PSI) was synthesized by thermal condensation with L-aspartic acid as the raw material, and then PASP-CD was synthesized by aminolysis ring-opening reaction of PSI with the ethylene diamine modified beta-cyclodextrin(β-CDen). Cholesterol-modified poly(D,L-lactide)(PLA-Chol) was synthesized by polymerizing D,L-lactide under vacuum using stannous octoate(Sn-oct) as a catalyst and cholesterol as an initiator. Finally,we synthesized three different molecular weight of PLA-Chol by adjusting the feed ratio of cholesterol and D, L-lactide. The chemical structures and the molecular weight of polymers were confirmed by Fourier transform infrared spectroscopy(FT-IR), proton nuclear magnetic resonance spectroscopy(NMR) and gel permeation chromatography(GPC). Based on the host-guest interation of β-cyclodextrin and cholesterol, PASP-CD and PLA-Chol were dissolved in DMSO, and then form micelles by dialyzed against water. By adjusting the ratio of hydrophilic and hydrophobic micelles and the hydrophobic molecular, we get a variety of different micelle composition. These components were then investigated for their ability to form nanoparticles and encapsulate protein. The diameter of micelles in water ranged from 70 to 200 nm as determined by dynamic light scattering(DLS), and the micelles were spherical in shape as observed by transmission electron microscopy(TEM). A model protein, bovine serum albumin(BSA), was encapsulated into the pseudo-graft copolymer micelles. The encapsulation efficiency(EE) and loading capacity(LC) of BSA in the micelles could be well tuned by adjusting the composition of the pseudo-graft copolymers. The micelles with a lower molar ratio of CD and cholesterol(hydrophilic/hydrophobic ratio) exhibited a higher EE and LC. While in vitro release studies showed that a shorter chain of hydrophobic segment and higher hydrophilic/hydrophobic molar ratio could enhance the release rate. Cell viability studies showed that these materials possessed good cell viability(>95%). These results suggest that the degradable copolymers with appropriate hydrophilic and hydrophobic composition are able to self-assemble into micelles that are an effective and biocompatible vehicle for delivering protein, paving a new way for the application of pseudo-graft copolymers in protein or peptide delivery.Additionally, PASP-CD/DNA complexes at different nitrogen-to-phosphate(N/P) ratios were prepared. In addition, we prepared PASP-CD/PLA-Chol/DNA at different N/P to compare with PASP-CD/DNA complexes. The diameter of micelles in water ranged from 90 to 270 nm as determined by DLS, and the micelles were spherical in shape as observed by scanning electron microscopy(SEM). Gel electrophoresis assay showed that under the complexes can be well condense DNA at lower N/P(≥ 10). The in vitro cytotoxicity and transfection assay showed that compared with the conventional transfection polymer PEI, PASP-CD or PASP-CD/PLA-Chol exhibit lower cytotoxicity, while to some of N/P ratio the transfection efficiency was lower. Research indicates that the cyclodextrin-based pseudo-graft copolymer has a potential application as a gene carrier. |
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