Dual Delivery of Cells and Bioactive Molecules for Wound Healing Applications.

Chronic wounds not only cause significant patient morbidity but also impose a substantial economic burden on the healthcare system. The primary barriers to wound healing include a deficiency of key modulatory factors needed to progress beyond the stalled inflammatory phase and an increased susceptibility to infections. While antimicrobial agents have traditionally been used to treat infections, stem cells have recently emerged as a promising therapy due to their regenerative properties, including the secretion of cytokines and immunomodulators that support wound healing. This study aims to develop an advanced dual-delivery system integrating stem cells and antibiotics. Stem cells have previously been delivered by encapsulation in gelatin methacrylate (GelMA) hydrogels. To explore a more effective delivery method, GelMA was processed into microparticles (MP). Compared to a bulk GelMA hydrogel (HG) encapsulation, GelMA MP supported greater cell growth and enhanced in vitro wound healing activity of human mesenchymal stem cells (hMSCs), likely due to a larger surface area for cell attachment and improved nutrient exchange. To incorporate antimicrobial properties, the broad-spectrum antibiotics penicillin/streptomycin (PS) were loaded into a bulk GelMA hydrogel, which was then cryo-milled into MPs to serve as carriers for hMSCs. To achieve a more sustained antibiotic release, gelatin nanoparticles (NP) were used as carriers for PS. PS was either incorporated during NP synthesis (NP+PS(S)) or absorbed into NP after synthesis (NP+PS(A)). MPs containing PS, NP+PS(S), or NP+PS(A) were tested for their cell carrier functions and antibacterial activities. The incorporation of PS did not compromise the cell-carrying function of MP configurations. The anti- activity was detected in conditioned media from MPs for up to eight days-four days longer than from bulk HG containing PS. Notably, the presence of hMSCs prolonged the antimicrobial activity of MPs, suggesting a synergistic effect between stem cells and antibiotics. PS loaded via synthesis (NP+PS(S)) exhibited a delayed initial release, whereas PS loaded via absorption (NP+PS(A)) provided a more immediate release, with potential for sustained delivery. This study demonstrates the feasibility of a dual-delivery system integrating thera.