Supercritical Carbon Dioxide Impregnation of Gold Nanoparticles Demonstrates a New Route for the Fabrication of Hybrid Silk Materials

How many nanoparticles can we load in a fiber? How much will leak? Underlying is the relatively new question of the “space available” in fibers for nanoparticle loading. Here, using supercritical carbon dioxide (scCO2) as a carrier fluid, we explored the impregnation in four Indian silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold nanoparticles (5, 20, 50, 100 and 150 nm in diameter). All silks could be permanently impregnated with nanoparticles up to 150 nm in size under scCO2 impregnation. Accompanying structural changes indicated that the amorphous silk domains reorganized to accommodate the gold NPs. The mechanism was studied in detail in degummed Mulberry silk fibers (i.e., without the sericin coating) with the 5 nm nanoparticle. The combined effects of concentration, time of impregnation, scCO2 pressure, and temperature showed that only a narrow set of conditions allowed for permanent impregnation without deterioration of the properties of the silk fibers.

Grape Seed-Inspired Smart Hydrogel Scaffolds for Melanoma Therapy and Wound Healing

Grape-seed extracts contain rich flavonoids with oligomeric proanthocyanidins (OPC). In this study, OPC containing hydrogel scaffolds can function as a natural photothermal agent for melanoma therapy and bioactive biomaterial for wound healing. Inspired by grape-seed extracts, OPC were explored as a photothermal agent and endowed the hydrogel scaffolds with excellent and controlled photothermal ability. The rheological property of the hydrogel scaffolds responded to irradiation time of near infrared (NIR) laser, and OPC contents. The compressive mechanical property of the hydrogel scaffolds was well modulated by NIR laser irradiation with different impact durations. The controlled high temperature induced by OPC-containing hydrogel scaffolds under NIR laser irradiation could effectively kill melanoma cells and suppress tumor growth. In addition, OPC-containing hydrogel scaffolds supported the proliferation and migration of human dermal fibroblasts and human umbilical vein endothelial cells, as well as obviously promoted angiogenesis and skin regeneration in both tumor-caused and chronic wounds. Therefore, OPC-containing hydrogel scaffolds possessed controlled photothermal, rheological, and compressive mechanical properties under NIR laser stimuli, as well as excellent biocompatibility and bioactivity for melanoma therapy and wound healing.