Influencing bacterial S-layer protein recrystallization on polymer brushes through surface charge and accessible volume: A combined AFM and QCMD analysis

S-layer recrystallization is part of, at least, two major scientific and technological challenges: a model system to study 2-D polymer crystal formation and a bottom-up approach to build biomimetic and functional interfaces. In particular, the self-assembly process of the bacterial surface layer protein (SbpA) might be influenced by two different interactions: protein/substrate and protein/protein. In this work, we are taking advantage of the versatility of already well known polymer brushes to study the self-assembly mechanism of the S-protein SbpA. In particular, the recrystallization pathway of the protein has been modified by the underlying polymer charge and accessible volume offered by the positively charged poly{[2-(methacryloyloxy)ethyl] trimethylammonium chloride} (PMETAC), the negative poly(sulfo propyl methacrylate) (PSPM) and the non-charged poly(N -isopropyl acrylamide) (PNIPAAm). The recrystallization pathways on polymer brushes have been compared with the bacterial biomimetic case represented by the secondary cell wall polymer (SCWP). Results concerning protein adsorption kinetics, viscoelastic properties, crystal lattice parameters and domain formation are presented, and have been obtained with Quartz Crystal Microbalance with Dissipation Monitoring (QCMD) and Atomic Force Microscopy (AFM).