Nanostructured biomaterials assembled from PEGylated poly-L-lysine

Nature has many examples of the bottom-up fabrication to produce various functional materials. This method is expected to be utilized to create intelligent and stimuli-responsive materials in medical, food, and cosmetic fields. The secondary structure of poly-L-lysine (PLL) changed responding to pHs and temperatures among random, α helix, and β sheet forms. Poly(ethylene glycol) (PEG) was coupled with the backbone of PLL (mPEG-PLL graft polymers). PEG-rich graft polymers formed nanoparticles spontaneously by the formation of β-sheet structures when both pHs and temperatures were raised. We founded that nanoparticles crosslinked with a cleavable reagent that contains a disulfide bond collapsed and released drugs in response to reductive environment in cytoplasm. On the other hand, PEG-poor graft polymers at higher concentrations exhibited heat-induced gelation. They could disassociate again by lowering pHs or temperatures. Such biomimetic fabrication method enabled us to create nanostructured materials with huge expectations of diverse applications.