Abstract: A system for analyzing a wound fluid. The system includes a transparent layer, a membrane layer, and an indicator layer that contains a colorimetric or fluorescent indicator reagent for detecting pH, a nitrite, an enzyme, a reactive oxygen species, a reactive nitrogen species, a nucleic acid, or a combination thereof. The membrane layer is impermeable to blood clots and cellular debris and is permeable to wound fluid. Also provided are methods for analyzing a wound fluid and for detecting biological fluid on biomedical instruments and waste materials using the system.