A Self-healing Thermogelling Polymer with Tunable Transparency Based on Biomolecule Alginate Grafting Phenylboronic Acid

Thermogelling polymers with transparency, structure stability and biocompatibility are promising for biomedicine application. In this study, a thermogelling polymer P-CPEG with tunable transparency was developed by the reaction between alternating copolymer CPEG and chemically modified biomolecule Alg-PBA via boronic ester bonds. The sol-to-gel transition of P-CPEG aqueous solution sensitively responded to changes in temperature, and the critical value could be adjusted between 15 and 40 °C by varying the content of CPEG and Alg-PBA. As the weight ratio of Alg-PBA to CPEG was over 0.3, the transparency of as-synthesized hydrogel kept above 75 % at 37 °C. Meanwhile, immersion P-CPEG hydrogel in CaCl solution significantly increased its mechanical strength by 3 times due to chelation effect. The shear-resistance and self-healing properties were ensured by dynamic boronic ester bonds due to the protective effect of hydrophobic gel network. As a drug delivery, P-CPEG hydrogel had a swelling rate of 3748.7 ± 103 % in PBS and could continuously release fluorescein sodium within 24 h. Moreover, the in vitro degradability and cytotoxicity of P-CPEG was confirmed. Finally, the mechanisms behind the thermogelling property and tunable transparency were revealed. Overall, this thermogelling P-CPEG polymer, with tunable transparency and thermo-responsiveness, exhibits great potential for biomedicine application.