Stimuli-Responsive Proteinosomes Based on Biohybrid Shell Cross-Linked Micelles

A new method of stimuli-responsive proteinosome fabrication with the shell cross-linked micelle as a template is reported in this research. A thermoresponsive diblock copolymer poly­[di­(ethylene glycol) methyl ether methacrylate]-<i>b</i>-poly­[poly­(ethylene glycol) methyl ether methacrylate-<i>co</i>-pyridyl disulfide methacrylamide] [PDEGMA-<i>b</i>-P­(PEGMA-<i>co</i>-PDSMA)] was synthesized and self-assembled into micelles with PDEGMA cores and P­(PEGMA-<i>co</i>-PDSMA) shells at the temperature above its lower critical solution temperature (LCST). Reduced bovine serum albumin (BSA) molecules with six thiol groups were used to cross-link the shells of the micelles by reacting with the pendant pyridyl disulfide groups on the P­(PEGMA-<i>co</i>-PDSMA) block. At a temperature below the LCST of the polymer, the PDEGMA cores were dissolved in water, affording proteinosomes with a size of about 50 nm and capsule-like structures. The proteinosome was also thermoresponsive with a phase transition temperature at 35 °C. The fabrication of the proteinosome had no obvious influence on the structure and activity of BSA, and BSA retained most of its secondary structure and esterase-like activity. Because the BSA molecules were connected to the polymer chains through disulfide bonds, they could be released upon addition of dithiothreitol. The <i>in vitro</i> cell viability evaluation and the cellular uptake assay demonstrated that the proteinosome showed low toxicity to NIH 3T3 and 4T1 cells and could be internalized into the 4T1 cells.