Bacterial infection and poor cell recruitment are among the main factors that prolong wound healing. To address this, a strategy is required that can prevent infection while promoting tissue repair. Here, we have created a silver nanoparticle-based hydrogel composite that is antibacterial and provides nutrients for cell growth, while filling cavities of various geometries in wounds that are difficult to reach with other dressings. Silver nanoparticles (AgNPs) were synthesized by chemical reduction and characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and inductively coupled plasma-mass spectroscopy (ICP-MS). Using varying concentrations of AgNPs (200, 400, and 600 ppm), several collagen-based silver–hydrogel nanocomposite candidates were generated. The impact of these candidates on wound healing was assessed in a rat splinted wound model, while their ability to prevent wound infection from a contaminated surface was assessed using a rat subcutaneous infection model. Biocompatibility was assessed using the standard MTT assay and in vivo histological analyses. Synthesized AgNPs were spherical and stable, and while hydrogel alone did not have any antibacterial effect, AgNP–hydrogel composites showed significant antibacterial activity both in vitro and in vivo. Wound healing was found to be accelerated with AgNP–hydrogel composite treatment, and no negative effects were observed compared to the control group. The formulations were non-cytotoxic and did not differ significantly in hematological and biochemical factors from the control group in the in vivo study. By presenting promising antibacterial and wound healing activities, silver–hydrogel nanocomposite offers a safe therapeutic option that can be used as a functional scaffold for an acceleration of wound healing.

Introduction Burn wound infections are a serious complication of thermal injury. Among the many factors that may limit effective wound healing in patients with burn, bacterial infection and poor cell recruitment appear as the leading causes for prolonged healing. Thus, a novel strategy that aims to prevent bacterial infection within the wound, while at the same time providing structural scaffolding that promotes endogenous tissue repair, would be of great interest. As a nutritional protective barrier for the wound, we developed a thermosensitive collagen-based matrix called MeshFill (MF) that contains all nutrition required for cell growth with the ability to fill up all the cavities and void areas in wounds regardless of their geometry. In a previous study, MF was successfully combined with partial-thickness mesh grafted skin in a porcine model and improved healing and aesthetic outcomes. In the present work, we report on the development, and in vitro and in vivo testing of a new formulation of MF containing silver nanoparticles (AgNPs), which simultaneously prevent bacterial infection and promote skin regeneration. Methods We fabricated MF/Ag formulation by loading different concentrations of AgNPs in MF hydrogel. The antibacterial activity of MF/Ag formulation against Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA) was examined in vitro. The wound healing efficacy of the formulation was evaluated in a silicon ring splinted delayed wound healing model in rats. The splinted full-thickness wounds were generated on the back of rats and treated with either MF or MF/Ag with different concentrations of AgNPs or were bandaged with no treatment (NT) as a control. The healing process was monitored for 18 days. Clinical wound measurements and histological assessments were performed to compare different treatment regimens Results The results of in vitro antibacterial study showed MF/Ag released a sufficient concentration of silver which caused a marked reduction in colony forming units (CFU) of MRSA and PA as compared to MF alone. MF/Ag did not show any cytotoxicity to human fibroblast. Moreover, the result of the animal study confirmed the safety and efficacy of applying different concentrations of AgNPs loaded in MF without compromising the healing outcome in our rat model. Conclusions These findings suggest that AgNPs loaded MF would be a safe, nutritional, flowable hydrogel that provides an ideal moisture environment for healing while protecting the wound from bacteria and can potentially be used as a functional scaffold in partial-thickness mesh grafted skin in burn patients.

Introduction: Among the many factors that may limit effective wound healing in patients with chronic ulcers, bacterial infection and poor cell recruitment are primary causes that contribute to prolonged healing. Thus, a novel strategy that aims to prevent bacterial infection within the wound, while at the same time providing structural scaffolding that promotes endogenous tissue repair, would be of great interest. Here, we developed a thermo-sensitive silver nanoparticle hydrogel composite as an antibacterial nutritional scaffold for the wound that contains all nutrients required for cell growth while preventing bacterial infection with the ability to fill up all the cavities and void areas in wounds regardless of their geometry. Methods: Silver nanoparticles (AgNPs) were synthesized by chemical reduction. After characterization, silver hydrogel nanocomposite was developed by reconstitution of collagen-based hydrogel powder in a nanoparticle suspension of varying AgNPs concentrations (200, 400, and 600 ppm). The antibacterial activity of the formulations was examined in vitro and in vivo in subcutaneous implant infected model. The wound healing efficacy of the hydrogel nanocomposite was also evaluated using a splinted wound model in rats through comparison of clinical wound measurements and histological assessments. Cytocompatibility assay and biochemical analysis of blood at the end of in vivo wound healing study were performed to evaluate the safety of formulations. Results: The synthesized nanoparticles were spherical and stable. While hydrogel alone did not show any bacterial reduction in vitro, the inhibition of bacterial growth was significant in all silver hydrogel nanocomposites compared to controls (p <0.05) and was dose-dependent, with maximum reduction observed in the 600 ppm group (4.56±0.26 LOG CFU/mL, P<0.001). All concentrations of AgNPs hydrogel composites showed significant antibacterial activity in vivo as well (P<0.0001). Treatment of splinted wounds with AgNPs hydrogel composite resulted in faster wound closure and accelerated wound re-epithelialization. The formulations were non-cytotoxic and did not differ significantly in hematological and biochemical factors from the control group in in vivo study. Conclusions: By presenting promising antibacterial and wound healing activity, silver hydrogel nanocomposite offers a safe therapeutic option that can be used as a functional scaffold for an acceleration of wound healing.

Introduction In full-thickness wounds, high levels of inflammation, lack of matrix deposition and paucity of progenitor cells delays normal healing processes. One major problem with commercially available solid (sheet) scaffolds is their inability to conform to wounds of varying shapes and sizes. To overcome this, we previously generated a liquid, injectable skin substitute which can fill wounds of any shape and depth from bottom up and has all the necessary ingredients for skin cells to be nourished, proliferate, and migrate in. In combination with adipose micro fragments as a viable source of progenitor cells, a composite, in situ forming skin substitute was tested for treatment of silicon ring splinted wounds in rats. Methods The in vitro survival and migratory capacity of adipocytes derived from rat micro-fragmented fat when cultured in our 3D nutritional scaffold was examined with a Live/Dead assay. The efficacy of our combined liquid scaffold alone (MF) or with adipose micro fragments (MFA) in treating full thickness splinted wounds in rats was compared to a standard dressing protocol (NT). The healing process was monitored for 10 days. Following wound measurements, histological and immunofluorescent analyses were performed and compared. Results Adipose-derived cells migrated within the 3D nutritional liquid scaffold after 7 and 14 days. The number of red (dead) cells was negligent, indicating cell viability. In vivo, both MFA and MF showed both accelerated and ameliorated wound healing, including complete epithelialization and less immune cell infiltration, compared to the NT control. No significant differences were observed between the MF and MFA groups for any outcome. Conclusions Our findings show that a 3D nutritional liquid skin scaffold is a rich environment for adipocyte viability and migration and that addition of adipose micro fragments to this scaffold can be used as a rich source of cells.