| Biodegradable polymers play an important role in the biomedical field. Polyurethane has been widely studied as biodegradable polymers due to its biocompatibility and its controllable structures and properties. With proper structure, the polyurethane is expected to assembly into nanoparticles and exhibit environmental-sensitivity.L-lysine ethyl ester diisocyanate was synthesized from L-lysine, and condensed with polyethylene glycol (PEG) and bis-1,4-(hydroxyl-ethyl) piperazine (HEP), respectively, to form amphiphilic polyurethanes. The structure and molecule weight of the polymers were examined by 1H NMR, FT-IR, gel permeation chromatography (GPC).Polyurethanes consisting of poly (ethylene glycol) (PEG) and L-Lysine ester diisocyanate (LDI) could self-assembly into nanoparticles in aqueous solution, temperature-sensitivity in aqueous solution was gradually disappeared with PEG chain extending. Only LDI-PEG600 exhibited a reversible temperature-responsive behavior in aqueous solution. The transition temperature (Tc) of LDI-PEG600 with methyl ester of LDI was higher than that of LDI-PEG600 with butyl ester side chain. Polymeric nanoparticles incorporated with adriamycin showed a dramatic temperature-responsive drug release on/off switching behavior according to the temperature responsive structural changes.Polyurethanes consisting of bis-1,4-(hydroxyl-ethyl) piperazine (HEP) and L-Lysine ester diisocyanate (LDI) could also form nanoparticle using dialysis method. With the extending of L-lysine side chain, the hydrophobicity of polyurethanes gradually increased, which induced the polymer to be responsive at lower pH value. The polyurethanes were then used to incorporate and release an anti-cancer drug, adriamycin (ADR). The polyurethanes could encapsulate ADR efficiently and the release rate of ADR was related to the environmental pH value and showed a dramatic pH-responsive drug release on/off switching behavior according to the temperature responsive structural changes.
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