Commensal Engineered Living Materials for Sustained Secretome Delivery and Wound Healing
Using living cells as dynamic biological factories offers immense potential for the continuous, localized production of therapeutic proteins within compromised tissues. This strategy is particularly compelling for treating chronic non-healing wounds, which lack therapeutics that are able to function effectively in the inflammatory microenvironment. Commensal bacteria have been shown to promote healing in these hostile microenvironments, yet applying live microbes directly onto compromised tissue is clinically unfeasible due off-target safety risks and engraftment challenges. Herein, we establish a well-defined commensal Engineered Living Material (cELM) that allows encapsulation, retention, function, and delivery of native beneficial bacteria for localized production and release of a pro-healing secretome over weeks. We specifically encapsulated a pro-healing human wound bacterial isolate, Alcaligenes faecalis, using biocompatible, click-reactive hydrogel building blocks (thiol- or vinyl-sulfone-functionalized multi-arm poly(ethylene glycol)) and systematically varied the density of the polymer network and of the encapsulated bacteria to establish design rules for creating pro-healing cELMs. Physical confinement in the hydrogel network ensured bacterial biocontainment, while the hydrogel mesh size still permitted diffusion of the therapeutic secretome. Notably, controlling encapsulation density revealed an inverse relationship wherein lower cell densities yielded significantly enhanced per-cell metabolic activity and provided sustained production of pro-healing secreted factors. In a murine diabetic wound model, these A. faecalis cELMs shielded the encapsulated bacteria from host clearance, maintained biocontainment, accelerated re-epithelialization, and improved wound bed maturity. Together, these findings establish design principles for cELMs that couple bacterial biocontainment with sustained secretome delivery, providing a promising platform for localized treatment of chronic wounds.