Interactions between bovine serum albumin and Langmuir films composed of charged and uncharged poly(N-isopropylacrylamide) block copolymers

The thermoresponsive poly(N-isopropylacrylamide) (PNIPAAM) and NIPAAM block copolymer derivatives are attractive for drug delivery applications as they contract reversibly at lower critical solution temperatures (LCST) close to physiological conditions. In order to investigate biomaterial-protein compatibility, we have studied the interaction between PNIPAAM copolymer films spread at the air–water surface and bovine serum albumin (BSA) injected below the precompressed polymer films, using the Langmuir technique coupled with Brewster angle microscopy (BAM). A PNIPAAM homopolymer was applied together with a number of PNIPAAM-based di- and triblock copolymers, to assess effects of e.g., charge and hydrophobicity on protein–polymer interactions. The nature and strength of protein–polymer interaction was found to be tunable, ranging from complex formation (PNIPAAM homopolymer) to mixed monolayers and electrostatic cross-linking, according to the nature of the co-monomer. Results show that intercalation versus adsorption can be controlled through polymer composition.