(WHS-P45) BACTERIAL PROTEASE-RESPONSIVE SHAPE MEMORY POLYMERS FOR INFECTION SURVEILLANCE & TREATMENT OF CHRONIC WOUNDS
Friday, May 17, 2024
7:30 AM – 5:00 PM East Coast USA Time
The purpose of this study was to determine the sensitivity and specificity of a polyurethane shape memory polymer with bacterial protease-sensitive peptides (PUR-PEP) towards bacteria. Additionally, we explore the incorporation of molecular force sensors known as spiropyrans (SP) into the polymer to improve visible surveillance of infected wounds. Strained PUR-PEP samples (n=3) were incubated in mammalian enzymes (matrix metalloproteinase-1, trypsin, and lysozyme), and in bacterial enzymes (S. aureus V8 and beta-lactamase) at 37°C for 10 days. Sample dimensions were measured using digital calipers every 24hr, and recovery ratios were determined based on differences in length. Strained PUR-PEP samples (n=3) were also incubated in serial dilutions of S. aureus (107 to 109 colony forming units (CFUs)) in stasis buffer for 7 days at 37°C. Samples were imaged daily with a camera, and dimensions were quantified using ImageJ software. To enable color change with shape change, 2.5 g of polymer was dissolved in chloroform, and 1.25 mg of photochromic SP was added. The mixture was poured into a Teflon dish until solvent evaporated, and the resultant films were dried in a vacuum oven. Samples were cut from the films, heated to 100°C, strained lengthwise, and then cooled. Samples were then imaged on a fluorescence microscope using the green channel or irradiated using a UV lamp (λmax= 365 nm) and imaged with a camera to assess color changes before and after straining. Strained PUR-PEP samples underwent significant shape recovery (~55%) (p < 0.05) in both mammalian and bacterial enzymes. The material also recovered in all tested concentrations of bacteria, and a one-way ANOVA showed no association between bacteria concentration and shape recovery (F (1,5) = 0.68, ns). The strained PUR with SP exhibited increased fluorescence and luminiscence when irradiated with a UV lamp. PUR-PEP recovery in mammalian enzymes indicates that the material chemistry requires tuning to improve its specificity towards bacterial proteases. However, the material recovery in all concentrations indicated high sensitivity and the potential to be utilized in detecting low grade or early infections. The photochromic response visible by fluorescence microscopy was due to increased absorbance by SP upon straining the PUR films. These are promising results as SPs could be used as a sensor to visually indicate changes in the shape of our PUR wound dressings, providing easily detectable color-based surveillance of infection in wounds.