<i>In Situ</i> Electrospun Thermochromic Menthol-Loaded Fibrous Membranes for Monitoring Body Temperature Indicator

This study aimed to develop a smart body temperature indicator membrane using poly(vinyl butyral) (PVB) nanofibers to evaluate individuals with fever higher than 38 °C. Skin surface temperatures above 38 °C were visibly monitored as the color of the nanofibers changed from blue to white, facilitated by the integration of thermochromic microcapsules into the polymer. The reversible color change in the membrane was verified to be rapid and perceivable during the three-cycle tests. The optimal polymeric spinning solution was prepared by mixing 12% PVB (w/w), 4% poly(vinylpyrrolidone) (PVP, w/w), 2% thermochromic powder (w/w), and 2% menthol (w/w). The release rate of menthol from the fibers was accelerated in response to the wettability of the skin surface caused by sweating at higher body temperatures, providing a cooling effect for patients with fever. To address the complexity and inconvenience of traditional electrospinning, a portable handheld device was used to develop multifunctional nanofibers via an in situ electrospinning process. The morphology and properties of the as-spun fibers were characterized. In vitro and in vivo experiments demonstrated remarkable antibacterial effects against Escherichia coli and Staphylococcus aureus and excellent biocompatibility. Western blot experiments, immunofluorescence labeling assays, and molecular docking algorithms confirmed the cooling and anti-inflammatory effects of menthol by comparing the expression of TRPM8 and TNF-α. Overall, the obtained nanofibrous membranes have potential for future clinical treatments.