Preparation and Properties of UCST‐Type Thermoresponsive Polypeptide Bearing Amide Pendants

Abstract

AbstractThermoresponsive polypeptides bearing amide pendants with an upper critical solution temperature (UCST) under physiologically relevant solution conditions are developed. A series of poly(γ‐propanyl‐l‐glutamate)s bearing amide pendants (PPLGn‐Am) with different molecular weight (or degree of polymerization, DP) is prepared by copper mediated 1,3‐dipolar cycloaddition. While fourier transform infra‐red and CD analysis reveal random coil conformation of the PPLGn‐Am in the solid‐state and in aqueous solutions, respectively, PPLGn‐Am shows reversible UCST‐type phase behaviors in deionized water (DI) water and phosphate‐buffered saline. Variable temperature UV–vis spectroscopy indicates that the UCST‐type cloud point temperature (Tcp) in the range of 25–75 °C can be readily tuned by molecular weight (or DP), polymer concentration, and incorporation of hydrophobic (i.e., n‐hexyl) pendants. Moreover, PPLGn‐Am is readily degraded by proteinase K within 48 h. The results indicate that UCST‐type thermoresponsive and biodegradable polypeptides in aqueous solutions can be constructed by conjugation of amide pendants which shall provide guidance for future UCST polymer designs.