Skin repair and infection control in diabetic, obese mice using bioactive laser-activated sealants

Conventional wound approximation devices, including sutures, staples, and glues, are widely used but risk of wound dehiscence, local infection, and scarring can be exacerbated in these approaches, including in diabetic and obese individuals. This study reports the efficacy and quality of tissue repair upon photothermal sealing of full-thickness incisional skin wounds using silk fibroin-based laser-activated sealants (LASEs) containing copper chloride salt (Cu-LASE) or silver nanoprisms (AgNPr-LASE), which absorb and convert near-infrared (NIR) laser energy to heat. LASE application results in rapid and effective skin sealing in healthy, immunodeficient, as well as diabetic and obese mice. Although lower recovery of epidermal structure and function was seen with AgNPr-LASE sealing, likely because of the hyperthermia induced by laser and presence of this material in the wound space, this approach resulted in higher enhancement in recovery of skin biomechanical strength compared to sutures and Cu-LASEs in diabetic, obese mice. Histological and immunohistochemical analyses revealed that AgNPr-LASEs resulted in significantly lower neutrophil migration to the wound compared to Cu-LASEs and sutures, indicating a more muted inflammatory response. Cu-LASEs resulted in local tissue toxicity likely because of effects of copper ions as manifested in the form of a significant epidermal gap and a 'depletion zone', which was a region devoid of viable cells proximal to the wound. Compared to sutures, LASE-mediated sealing, in later stages of healing, resulted in increased angiogenesis and diminished myofibroblast activation, which can be indicative of lower scarring. AgNPr-LASE loaded with vancomycin, an antibiotic drug, significantly lowered methicillin-resistant Staphylococcus aureus (MRSA) load in a pathogen challenge model in diabetic and obese mice and also reduced post-infection inflammation of tissue compared to antibacterial sutures. Taken together, these attributes indicate that AgNPr-LASE demonstrated a more balanced quality of tissue sealing and repair in diabetic and obese mice and can be used for combating local infections, that can result in poor healing in these individuals.