Orthogonally Functionalizable Redox-Responsive Polymer Brushes: Catch and Release Platform for Proteins and Cells

Polymer brushes engineered to "specifically capture" and "release on demand" analytes such as dyes, proteins, and cells find biomedical applications ranging from protein immobilization to cell death. Utilizing a disulfide-linker-containing monomer as a building block enables the fabrication of a redox-responsive polymer brush platform with the "catch and release" attribute. Herein, thiol-reactive redox-responsive polymer brushes are fabricated using a pyridyl disulfide-based monomer, and their postpolymerization functionalization is demonstrated via thiol-disulfide exchange reaction with thiol-containing dyes, (bio)molecules, and cell adhesive ligands. After establishing reversible conjugation using a fluorescent dye and other model compounds, copolymer brushes postmodified with thiol-containing mannose demonstrated selective immobilization of concanavalin A in the presence of peanut agglutinin. In addition, a thiolated RGD peptide was conjugated to the side chain of polymer brushes to facilitate cell adhesion, followed by on-demand harvesting. To enable localized drug delivery to surface-adhered cells, orthogonal chain end and side chain functionalization using the thiol-Michael addition and thiol-disulfide exchange reaction, respectively, was used to conjugate the cell adhesive RGD peptide and the anticancer drug doxorubicin (DOX). On-demand DOX release and internalization by surface-bound cancer cells were demonstrated via cleavage of disulfide linkages in the presence of a reducing agent. This approach may provide an attractive methodology to deliver therapeutic agents precisely to specific cells.