Lysozyme-responsive polymer systems for detection of infection

There is a strong need for new point-of-care systems for the detection of wound infection. Overseen infections in chronic wounds induce severe complications, such as delayed healing and high risks for the patients, while time-consuming common gold and silver standard methods for infection assessment cannot be implemented in home care units. This study demonstrates for the first time the between correlation of lysozyme activity and silver-standard microbiological evaluation of wounds. Significantly higher (eightfold increase; p < 0.001) lysozyme activity in infected wounds was in accordance with increasing bacterial burden of infected wound fluids. Moreover, a two-layer membrane-based test system was developed providing visible results on infection in a short time (30 min) while avoiding any intermediate steps such as centrifugation. In the first layer of the system, a size exclusion membrane (1.2-8 μm cut-off) retained labeled peptidoglycane while allowing only smaller fragments resulting from lysozyme hydrolysis to pass through. These fragments were then captured in a second layer, an anion-exchanging diethylaminoethyl cellulose membrane, resulting in clearly visible color changes. Colorimetric measurements demonstrated significant differences (p < 0.001) and sixfold higher delta E values between infected and noninfected wound fluids. This system allows a quick and straightforward determination of the status of a wound. The colorimetric readout indicates the increased lysozyme activity in infected wound fluid.