Synthesis of pH/ temperature sensitive gelatin/peptide composite hydrogels and its characterization for potential controlled drug release applications

Conventional self-assembled peptide hydrogels have poor mechanical properties and tend to release abruptly when they are used as drug carriers, limiting the application of these materials in biomedical field. In this work, gelatin was embedded in a pH-responsive peptide Ac-FALNLAKD-NH2 (PEP) to construct gelatin/peptide composite hydrogels (Gel/PEP) for controlling the delivery of the anticancer drug chelerythrine (CHE). The physicochemical properties of Gel/PEP composite hydrogels were evaluated. The results of circular dichroism and Fourier transform infrared spectroscopy characterization showed that compared with PEP hydrogels and gelatin, the Gel/PEP composite hydrogel has a superposition of two secondary structures, in which β-sheet and random coil accounted for 44.7 % and 55.3 % of the conformation, respectively. Rheology and scanning electron microscope characterization confirmed that the Gel/PEP hydrogel has a highly dense nanofibrous meshwork structure, which enhances mechanical and injectable properties. In addition, the encapsulation rate of CHE could reach more than 97 % at a gelatin/peptide mass ratio of 7:1. More importantly, in vitro results showed that the composite hydrogel still had good pH and thermal response performance, which can achieve controlled release of CHE. Therefore, it is possible to synthesize supramolecular drug release soft materials by composite of gelatin and peptide hydrogels.