Biodegradable and temperature-responsive polyurethanes for adriamycin delivery.

To develop biodegradable polymers with temperature-sensitivity, a series of polyurethanes consisting of poly (ethylene glycol) (PEG) and L-lysine ester diisocyanate (LDI) were synthesized, and the structure and molecule weight of the polymers were examined by (1)H NMR, FT-IR, gel permeation chromatography (GPC). The solution properties of the copolymers were studied by turbidity measurement and size measurement. Polyurethanes could form nanoparticles by sonication in water. No temperature-sensitivity was observed with the polyurethane nanoparticles composed of PEG1000 and PEG1500. On the contrary, LDI-PEG600 exhibited a reversible temperature-responsive behavior in aqueous solution. The transition temperature (T(c)) of LDI-PEG600 with methyl ester of LDI was higher than that of LDI-PEG600 with butyl ester side chain. The polymers were then used to encapsulate adriamycin (ADR) by the dialyzing method from dimethylformamide solution against water. ADR could be successfully encapsulated into the polyurethane nanoparticles. The ratio of ADR release from polymeric nanoparticles increased sharply above the T(c), while the release was suppressed below the T(c). Crown