{
  "abstract": "Introduction Infection control is an essential aspect of wound healing in an austere environment. Exposed open wounds are typically more susceptible to colonization by pathogens, which may prolong or complicate the wound-healing process. Here, we present an infection monitoring sensor in the form of a ‘smart bio-patch’ with a closed-loop mechanism for enhanced treatment of wound-related complications. The patch is designed in the form of transdermal microneedles capable of penetrating the skin barrier facilitating the detection of infection-associated biomarkers and delivering active biochemicals directly to the wound bed, enhancing antimicrobial efficacy and potentially accelerating wound healing ( figure 1).Abstract A23 Figure 1Microneedle bio-patch loaded with probiotic bacteria that sense infection biomarker (lactate) in wound space and release antimicrobial compounds (peptides) to stop infection at the point of injuryMethods A probiotic strain of E. coliNissle 1917 was engineered to detect lactate, a suitable biomarker for infection, and respond by synthesizing and secreting antimicrobial compounds to mitigate the infection. The sensing mechanism utilizes an optimized LldPRD promoter, controlled by the LldR regulator, in response to L-lactate.1 A hydrogel microneedle bio-patch was prepared by casting polymer solutions containing engineered cells from negative molds, using a biocompatible and naturally derived polymer, hyaluronic acid. The patch was assessed during in vitro and ex vivo stimulations with lactate to produce a fluorescence output signal, which was later replaced with an antimicrobial peptide-producing response in the final product. This evaluation was performed using synthetic and animal skin tissue grafts.Results We demonstrated a successful response of the bio-patch during in vitro and ex vivo studies. The crosslinking degree and composition of the biopolymer hydrogel were optimized to produce porous hydrogel microneedles with optimal permeability and swelling parameters. Optimal cell loading, metabolic state during incorporation into the hydrogel patch, and cell-hydrogel matrix ratio were optimized to improve critical parameters of bio-patch function. The engineered E. coli cells retained their functionality, operating in the range of physiological and elevated lactate concentrations (1–20 mM). Several recombinant antimicrobial peptides were expressed and accumulated in the culture medium in the presence of lactate. The microneedle bio-patch was tested on skin surrogates, demonstrating the ability to sense and release mitigation compounds in a controlled manner.Conclusions We present a microneedle transdermal bio-patch with a sense-and-release mechanism for application to wounded skin. To facilitate wound repair and accelerate skin healing, the hydrogel bio-patch was prepared from hyaluronic acid, a polymer with anti-inflammatory and antioxidant properties widely used in the medical field. 2 The patch was developed to detect early stages of bacterial infection and, as a countermeasure, release mitigation compounds to reduce the severity of the condition. We envision this type of smart bio-patch to be applied in military operations when medical help might be delayed due to combat activities.Disclaimer The views expressed are those of the authors and do not reflect the official guidance or position of the United States Government, the Department of Defense or of the United States Air Force. Imagery in this document is property of the U.S. Air Force.References Zúñiga A, Camacho M, Chang H.-J, et al. Engineered L-lactate responding promoter system operating in glucose-rich and anoxic environments. ACS Synth. Biol. 2021;10:3527–3536.Parmal S, Subbappa P, Nikam V, et al. Hyaluronic acid based approaches for wound healing: A comprehensive review. Int. J. Biol. Macromol. 2025;306:141625.",
  "authors": [
    {
      "affiliations": [
        "711 HPW, 2510 Fifth St., WPAFB, OH, USA"
      ],
      "name": "Svetlana V Harbaugh"
    },
    {
      "affiliations": [
        "711 HPW, 2510 Fifth St., WPAFB, OH, USA"
      ],
      "name": "Irina V Drachuk"
    },
    {
      "affiliations": [
        "711 HPW, 2510 Fifth St., WPAFB, OH, USA"
      ],
      "name": "Jorge L Chávez"
    }
  ],
  "title": "A23 Microneedle bio-patch for detection and treatment of wound infections in austere environment",
  "uid": "2e05a2fe-d0d7-5550-b9c0-9fc394761cb9"
}