Kinetics of swelling/shrinking rearrangement of a self-aggregated nanohydrogel at solid/liquid interfaces

Abstract

The hydrogel nanoparticles (nanohydrogels) have great potentials in numerous biomedical applications. Biomembrane-mimetic self-assemble nanohydrogel MC n (n repeated 2-methacryloyloyloxyethyl phosphoryl choline grafted cholesteryl group-bearing pullulan) was designed. In order to mimic the interfacial responses of fibrinogen at the hydrophobic/hydrophilic surfaces, MC n molecules were controlled by the chain length of the decorated MPC in term(s) of n ¼ 0, 6.2, 14.3 and 180, respectively. The dynamic rearrangements of MC n hydrogel molecular layer on the hydrophobic highly ordered pyrolytic graphite surface were observed by the atomic force microscopy. The results showed that there were biphasic transitions at the liquid/solid interfaces from the initial solute state to metastable state to the equilibrium state. The length of MPC branches, n, governed the changes of layer thickness to the equilibrium state appearing as swelling or shrinking. The time evolution of the thickness was fitted by a single exponential model, and the kinetics parameters of surface rearrangements to the equilibrium state were obtained.