Toward preclinical evaluation of a thermosensitive PEG-poly(L-alanine) hydrogel: A study on sterilization, storage stability, and in vivo performance.

Poly(amino acid)-based thermosensitive hydrogels hold great potential for clinical translation. Herein, we employ a thermosensitive methoxy poly(ethylene glycol)-block-poly(_L-alanine) (mPEG-PAla) hydrogel that undergoes a sol-to-gel transition upon heating as the model system to systematically evaluates its sterilizability, storage stability, in vivo degradation and in vivo drug release profiles-critical factors for clinical translation. mPEG-PAla copolymers are synthesized via ring-opening polymerization using the optimized amount of crown ether as the catalyst, ensuring controlled polymerization while minimizing catalyst usage. The powder form of the synthesized polymer facilitates efficient UV irradiation sterilization, and its aqueous solution can be rapidly prepared within 15 min. When pre-loaded into syringes, the mPEG-PAla hydrogel demonstrates storage stability for over 6 months. After subcutaneous injection into mice, traditional anatomic observation combined with nondestructive fluorescence imaging and magnetic resonance imaging (MRI) confirms that the mPEG-PAla hydrogel exhibits a stable in vivo degradation pattern, persisting for over 1.5 months, and its degradation products are metabolized primarily by the liver and kidneys. Histological analysis and MRI further validate the good biocompatibility of hydrogel. Fluorescence imaging reveals that the in vivo release profiles of three distinct fluorescent molecules, used as model drugs, present significant differences but follow the first-order release kinetics. STATEMENT OF SIGNIFICANCE: Intelligent hydrogels have garnered significant attention for various biomedical applications. Nevertheless, few have entered clinical practice, and their successful clinical translation depends on fundamental research related to effective sterilization, long-term storage stability, and in vivo fate estimation. In this study, we systematically evaluated the translation potential of an injectable and thermosensitive mPEG-PAla hydrogel by optimizing the synthesis of mPEG-PAla copolymer and validating its sterilization efficacy, convenience of preparation, storage stability, in vivo degradation and in vivo drug release profiles. This study enhances the understanding of PEG-poly(amino acid) hydrogels and provides valuable insights for their preclinical studies and future applications.