Investigation of soy protein hydrogels for biomedical applications: Materials characterization, drug release, and biocompatibility

Soy protein is emerging as a novel material for biomedical applications due to its abundance in nature, ease of isolation and processing, and inherent properties for mediating cell adhesion and growth. In this study, mechanically robust soy protein hydrogels were fabricated with varying weight percentages in water (15, 18, and 20 wt.%) without the use of chemical modifiers or crosslinkers. This fabrication method is beneficial because it allows for the direct injection of these soy hydrogels in vivo. The material properties, drug releasing capability, and biocompatibility in vitro and in vivo were assessed. The different concentrations of soy protein varied the rheological, swelling, and mechanical properties and affected the release of the model drug fluorescein from the hydrogels in vitro. Higher weight percent of soy increased the robustness of the hydrogels and released a lower amount of fluorescein over one week. Viability and growth of seeded L929 mouse fibroblasts demonstrated that the hydrogels were biocompatible in vitro for one week. Soy hydrogels were injectable in vivo into the subcutaneous pocket of mice, and histological staining showed minimal fibrous capsule formation for up to 20 days. The ease of fabrication and tailorable properties of soy hydrogels render it a promising biomaterial for tissue engineering and drug delivery applications, particularly for wound healing.