Light-Responsive Polyion Complex Micelles with Switchable Surface Charge for Efficient Protein Delivery

In this letter, light-responsive protein-encapsulated polyion complex (PIC) micelles were prepared by self-assembly of cationic block copolymer poly(N,N-dimethyl-N-(2-(methacryloyloxy)ethyl)-N-((2-nitrobenzyl)oxy)-2-oxoe-thanaminium bromide)-block-poly(carboxybetaine methacrylate) (PDMNBMA-b-PCBMA) and negatively charged bovine serum albumin (BSA). The PIC micelles were well characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). From the zeta potential measurement, the increase of the zeta potential of PIC micelles from similar to 10 to similar to 20 mV was observed when the solution pH decreased from 7.4 to 6.5, which could enhance the intracellular protein delivery efficiency. Moreover, the positively charged PDMNBMA blocks can be transformed to zwitterionic carboxybetaine units under UV irradiation, which could result in the disassembly of the PIC micelles. The release of BSA can therefore be drastically accelerated in the presence of UV irradiation. Meanwhile, the circular dichroism (CD) spectroscopy confirmed that the secondary structure of BSA was unaffected during the UV irradiation process.