Thermoresponsive zwitterionic poly(phosphobetaine) microgels: Effect of macro‐RAFT chain length and cross‐linker molecular weight on their antifouling properties

Abstract

Adsorption of proteins on biological surfaces is a detrimental phenomenon that reduces the work‐life of the implants in various biomedical applications. Here, we synthesized a new class of thermoresponsive zwitterionic poly(phosphobetaine) (PMPC) microgel with excellent surface antifouling property by macro‐RAFT mediated thiol‐epoxy click reaction. End‐group modified zwitterionic PMPC homopolymers with well‐defined molecular weight and narrow dispersity were grafted onto poly(N‐vinylcaprolactam‐co‐glycidyl methacrylate) (PVG) copolymer backbone followed by addition of a cross‐linker, leading to microgel formation. While no upper critical solution temperature (UCST) was found in poly(N‐vinylcaprolactam‐co‐glycidyl methacrylate‐g‐2‐methacryloyloxyethyl phosphorylcholine) (PVGP) graft copolymers, the corresponding microgels exhibited both UCST and lower critical solution temperature (LCST) transitions, related to the swelling and collapse of PMPC and poly (N‐vinylcaprolactam) (PVCL) components respectively. An increase in the molecular chain length of the PMPC increased the shifting of UCST and LCST of the microgels to higher temperatures, due to the ability of zwitterionic groups to coordinate a large number of water molecules. The effect of the variation in the molecular weights of amphiphilic poly(ethylene glycol) diamine (PEG‐NH2) cross‐linker was also reflected in both temperature and salt responsiveness of the microgels. The efficacy of the microgels as potential antifouling materials was further studied by fluorescence microscopy and XPS analysis on microgel coatings treated with FITC‐BSA solution and pure BSA solution respectively. Lower protein adsorption was observed for microgels grafted with higher molecular chain length of PMPC, whereas, the microgels synthesized using higher molecular weight PEG‐NH2 diamine cross‐linker displayed greater protein adsorption on their surfaces.

Rational design of dual-functional surfaces on polypropylene with antifouling and antibacterial performances via a micropatterning strategy

“…7A(b)). 60 After the construction of QPDMAEMA micropatterns on the PP-PMPC surface, the number of adhered platelets was slightly increased (∼37) compared with that of PP-PMPC (Fig. 7A(c)).…”

Zwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications

“…[ 138 ] In a similar approach, we also synthesized zwitterionic phosphobetaine (PMPC) microgels and showed for the first time their UCST behavior with varying PMPC chain length and semi‐quantitatively measured their protein repellent behavior by X‐ray photoelectron (XPS) studies. [ 139 ]…”

In-Line Characterization of the Temperature-Responsive Behavior of Surface-Bound Microgel Coatings by QCM-D: A Novel Strategy for Protein Repellence Evaluation

“…A microgel coating with a defined size and rigidity features was carefully selected to allow the continuous characterization of its thermoresponsiveness in the absence of protein deposition and to serve as a baseline. This suitably small and rigid p­(NIPAm- co -GMA) microgel was then copolymerized with poly­(2-methacryloyloxyethyl-phosphorylcholine) (PMPC) with antifouling properties already described in the literature. − The adsorption of the fluorescein-tagged bovine serum albumin protein (FITC-BSA) was then monitored and quantitatively determined by QCM-D. The same experiments were carried on using a p­(NIPAm- co -GMA) coating and a clean sensor for reference.…”