Citrate-Based Hydrogels Promote Closure of Infected Diabetic Wounds

Diabetic foot ulcers (DFUs) are a significant threat to the quality of life for individuals with diabetes, affecting approximately 1.6 million patients in the US, as of 2023. When these wounds do not heal and become chronic wounds, they can become infected and increase the risk of digit and/or lower limb amputation. Therefore, there is a critical need for therapies that promote wound closure in the presence and absence of infection. We have previously reported the potential benefits of the thermoresponsive citrate-based macromolecule poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) in diabetic rodent and swine models of non-infected full thickness dermal wounds. In this study, we compared four PPCN formulations (PPCN, PPCN-CMOF, A5G81-PPCN, and A5G81-PPCN-CMOF), which are functionalized with the laminin-derived cell adhesion peptide A5G81 and/or contain entrapped copper metal-organic framework nanoparticles (CMOF) designed to release Cu2+ slowly, in diabetic mice with wounds infected with S. aureus. In infected wounds, all four formulations significantly improved cumulative closure relative to saline (adjusted p = 0.002-0.021). In non-infected wounds, only PPCN-CMOF significantly improved cumulative closure relative to saline (p = 0.046), although all four formulations reached ≥95% closure earlier than saline (adjusted p = 0.009-0.045). In vitro, the CMOF-containing formulations produced the highest bacterial killing (90% for A5G81-PPCN-CMOF and 84% for PPCN-CMOF), whereas A5G81-PPCN and PPCN reduced bacterial colonies by 76% and 59%. PPCN modification with A5G81 and/or CMOF increased endothelial mesh formation in vitro. In vivo, PPCN-based formulations increased granulation tissue thickness and, depending on formulation and infection status, vascular marker expression. These results suggest that PPCN and PPCN formulations containing CMOF and/or A5G81 are a potentially viable technology that can be added to the wound care toolbox to accelerate healing of diabetic foot ulcers in the presence of infection. These findings support further investigation of PPCN as an instructive pro-regenerative biomaterial in a preclinical large animal model.