Kinetics of the nanohydrogel flattening at a hydrophobic interface

Hydrophobitized polysaccharides were designed to form the self-assembled nanohydrogels (hydrogel nanoparticles) in the aqueous conditions. For improving their biocompatibilities, they were decorated with the biomembrane-mimetic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers. The interfacial roles of the decorated membrane-mimetic nanohydrogels were investigated by choosing MPC branched choresteryl-bearing pullulan (CHP). Tapping-mode atomic force microscopy was used to study its adsorption mechanism on the hydrophobic highly oriented pyrolytic graphite (HOPG) surface in aqueous conditions. Dynamic observation at the interfaces revealed two distinctive patterns: the immobilized nanohydrogel particles and the flatten layers. The flattening (unfolding) kinetics with and without MPC branched nanohydrogel revealed that the flattening energy was at approximately 37 k(B)T. The flattening rate of the MPC decorated nanohydrogels was approximately 1.7 times faster than that without MPC decoration, corresponding to minor reduction of the flattening activation energy.