(586c) Highly Elastic, Antimicrobial, and Sprayable Hydrogel for Wound Healing
Devyesh Rana1, Ehsan Shirzaei Sani2, Roberto Portillo Lara2, Suzanne Mithieux3, Anthony Weiss3, Nasim Annabi2,4,5
1 Department of Bioengineering, Northeastern University, Boston, MA, 02115-5000, USA
2 Department of Chemical Engineering, Northeastern University, Boston, MA, 02115-5000, USA
3School of Life and Environmental Sciences, Charles Perkins Centre, University of Sydney, Sydney, 2006, Australia
4Biomaterials Innovation Research Center, Brigham and Womenâ??s Hospital, Harvard Medical School, Boston, MA, USA.
5Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
The skin is the largest functional organ in the human body. Its primary function is to serve as a protective barrier against foreign agents, both micro- (e.g. bacteria, viruses, etc.) and macroscopic (e.g. dirt, debris, etc.) (1). Hence, the risk of developing infections is amplified upon impaired skin integrity. Chronic wounds are estimated to affect 6.5 million patients. The annual health care cost associated with chronic wounds are estimated to exceed $25 billion (2). Burn wounds alone account for $11.3 billion (3). Patients suffering from severe burns and skin injuries still exhibit high mortality rates due to complications during the early stages of trauma. The first line of care in managing burn and trauma patients is to cover the wound properly to avoid excessive transdermal fluid loss, and to protect the wound area from environmental exposure to pathogens, in particular bacteria. The next step is to promote healing to restore the integrity of the skin and its barrier function (4, 5). However, large burns and chronic wounds often do not heal in a timely and orderly fashion, and bacterial infection remains a life threatening condition for these patients (6). In this project, we engineered a multifunctional hydrogel that can be sprayed on wounds to prevent bacterial growth and facilitate wound healing. This visible light-activated hybrid hydrogel is comprised of methacrylated tropoelastin (MeTro) and gelatin methacrylate (GelMA), which are conjugated with an antibacterial peptide (AMP). We hypothesize that the engineered hybrid gel will mimic the mechanical properties of the native skin and will adhere to the skin tissue upon photopolymerization to form an antibacterial and regenerative barrier on the wound area.
Materials and methods
All chemicals were purchased from Sigma Aldrich and used without further purification. GelMA and MeTro were prepared according to procedures described in our previous works [7, 8]. Different ratios of MeTro/GelMA prepolymer solutions (100/0, 70/30, 50/50, 30/70, 0/100) were interspersed in a solution of trimethanolamine (1.8% w/v) as a co-initiator, vinylcaprolactam (1.25% w/v) as a catalyst, and Eosin-Y (20% v/v) as a photoinitiator. An antimicrobial peptide (CPS Scientific) in the range of 0.01-0.03 % (w/v) was then incorporated into the MeTro/GelMA solution prior to polymerization via visible light (400-500 nm) for 120s. Mechanical properties such as tensile and compression moduli were tested using an Instron 5944 machine. Antimicrobial properties were also evaluated using colony forming and live/dead assays. In vitro biocompatibility of the engineered hydrogels was assessed by 2D and 3D culture of NIH 3T3 fibroblast cells.
Results and Discussion
The tensile modulus of the hybrid hydrogel was found to be tunable in the range of 5 - 35 kPa based on MeTro/GelMA ratios and final polymer concentrations. Similarly, the compressive modulus ranged from 4 - 65 kPa by varying polymer composition and concentration. The resulting hydrogels were sprayed onto porcine skin and were shown to adhere well to the tissue after photopolymerization based on wound closure tests. In vitro bacterial studies indicate that incorporation of 0.01% v/v antimicrobial peptide into a MeTro/GelMA hydrogel with the ratio of 70/30 was effective at killing both gram positive (Methicillin-resistant Staphylococcus aureus (MRSA)) and gram negative (Escherichia coli) bacteria. The number of colony forming units (CFUs) decreased from 38 to 15 for MRSA and from 13 to 2 for E.coli. In addition, in vitro tests on the engineered hydrogels containing antimicrobial peptide showed more than 90% mammalian cell viability at days 1, 3, and 5 post-seeding. This result confirmed that the engineered hybrid hydrogels exhibit no apparent cytotoxic effect on 3T3 fibroblasts. The engineered sprayable and antimicrobial hydrogel has a remarkable potential to be used as a novel biomaterial for wound healing.
In this study, we developed a novel regenerative sprayable hydrogel with antimicrobial properties for wound treatment. In particular, the hydrogel formulation consisting of 70/30 MeTro/GelMA with a 15% final polymer concentration and 0.01% antimicrobial peptide, attained optimal mechanical, antimicrobial and biocompatible properties.
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