Silk Fibroin Particle-Laden Sponges as a Multiphase Controlled Release Platform

Silk fibroin-based biomaterials have shown utility across regenerative medicine applications due to their ability to provide robust mechanical support and deliver bioactive cargo. To achieve diverse functions, fibroin can be fabricated into material formats with varied morphology including sponge-like scaffolds and microparticles. This study investigates the potential of a dual-component silk fibroin system (particle-laden sponges) to enable two-phase controlled release and assesses the impact of cytokine release on RAW 264.7 polarization.

Silk fibroin microparticles (SFMPs) were prepared through phase separation from PVA before being combined with aqueous fibroin polymer solution at desired mass ratios. This solution was frozen and lyophilized to form a particle-laden sponge. The sponge was then water annealed to induce crystallinity at a set temperature. Sponge morphology was assessed with SEM and crystallinity was assessed with FTIR. In vitro accelerated degradation studies were used to identify candidate formulations for functional release experiments. For functional release analysis, M1 and M2 promoting cytokines were loaded into the sponge and the particle portions, respectively. Cytokine release was assessed using ELISA and using RT-qPCR, the polarization state of RAW 264.7 cells was captured following 1 and 3 days of incubation with the material.

Both formulation and temperature during water annealing were found to impact morphology and total crystalline content. Degradation studies showed disruption of the sponge like structures prior to SFMP degradation, indicating a potential for a multiphase controlled release platform. RAW 264.7 cells showed a polarization switch from M1 to M2 in line with hypothesized rates of release from the particle-laden sponge.

This study demonstrated the tunability of a dual-component silk fibroin sponge, while also establishing its potential as a multiphase controlled release platform to modulate immune interactions in future in vivo studies.