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Negative-pressure-wound-therapy is commonly used in clinical routine for wound management. Aim of the present study was to assess the feasibility and safety of using an additional container to collect wound fluid during ongoing negative-pressure-wound-therapy. In this present prospective observational study, patients with negative-pressure-wound-therapy were included. An additional container was inserted in the connecting tube between the wound and the vacuum generating device. The following 3 days, the container was changed daily and replaced by a new one. Further safety outcome parameters were assessed. A questionnaire was answered by the responsible surgeon. Twenty-two patients with negative-pressure-wound-therapy with a median (IQR) age of 58.5 (53.0-70.0) years were included in the present study. In median, the duration of negative-pressure-wound-therapy was 5.0 (4.6-5.5) days. In mean ± SD the collected volume of the wound fluid in millilitres (mL) was on day one 7 ± 4 on day two 8 ± 7 and 10 ± 11 on day three. In one patient, there was0.1 mL of clear water in the additional container. No safety concerns due to the additional container were observed. This study demonstrates that collecting wound fluid during ongoing negative-pressure-wound-therapy over a time period of 3 days is feasible and safe. No safety concerns were observed.

There is a strong need for simple and fast methods for wound infection determination. Myeloperoxidase, an immune system-derived enzyme was found to be a suitable biomarker for wound infection. Hence, alkoxysilane-derivatized Fast Blue RR was immobilized via simple hydrolytic polymerization. The resulting enzyme-responsive siloxane layers were incubated with myeloperoxidase, wound fluid or hemoglobin. The reaction was monitored via HPLC measurements and the color development quantified spectrophotometrically. Myeloperoxidase was indeed able to oxidize immobilized Fast Blue RR leading to a blue colored product. No conversion was detected in non-infected wound fluids. The visible color changes of these novel materials towards blue enable an easy distinction between infected and non-infected wound fluids.

There is a pressing need for point-of-care diagnostics indicating early stages of infection. Polymers can respond to enzymes secreted by microorganisms or released by the human immune system. This provokes either a direct color reaction or release of dyes, allowing early-stage detection of wound infections and contamination of medical devices. Conventional methods for the detection of infection indicators are based on slow, laboratory-based procedures and, consequently, do not allow a timely assessment. In contrast, polymer-based materials offer real-time responses in point-of-care devices that, in turn, allow therapists to amend treatment before the infection has become firmly established. The use of protein, polysaccharide and mixed polymer systems provides a sensitive means to detect the low levels of proteases and glycosyl hydrolases produced on initiation of infection in the clinical setting. These polymers can be easily fabricated into various forms that can be directly applied in diagnostic devices.

Bacterial contamination of platelet concentrates (PCs) can lead to fatal transfusion transmitted diseases and is the most abundant infectious risk in transfusion medicine. The storage conditions of PCs provide a good environment for bacterial growth. The detection of these contaminations at an early stage is therefore important to avoid the transfusion of contaminated samples. In this study, bioresponsive polymer (BRP) systems were used for the detection of microorganisms in PCs. The backbone of the polymer consisted of labelled protein (casein), which was demonstrated to be degraded by pure proteases as models and by extracellular enzymes released by contaminating microorganisms. The concomitant colour change was easily visible to the naked eye. To enhance stability, the protein was cross-linked with glycidyl methacrylate (GMA). The cross-linked polymer was easier to handle but was less sensitive than the non-cross-linked material. A contamination of a PC with 10CFU/mL S. aureus was detectable after 24 hours. The visible colour reaction was quantified as a ΔE value according to the CIELab concept. A ΔE value of 21.8 was already reached after 24 hours. Hence, this simple but effective system could prevent transfusion of a contaminated PC.

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.

Bioresponsive polymers (BRPs) allow the detection of potentially pathogenic microorganisms. Here, peptidoglycan and cellulose based hydrogels were constructed with potential for diagnosis of wound infection or, for example, Aspergillosis, respectively. These systems respond to extracellular enzymes from microbes or enzymes secreted from the human immune system in case of infection. Laccases as ‘enhanzymes’ were incorporated into these devices for signal and stability enhancement when compared to simple dye release based systems. To retain the enhanzymes within the BRPs, they were either PEGylated laccase (Laccase_PEG) to increase size or methacrylated laccase (Laccase_MA) to allow covalent attachment to the polysaccharide matrices. PEGylation of Trametes hirsuta laccase led to a fivefold increase in size to 270 kDa according to size exclusion chromatography (SEC). Likewise, successful methacrylation of the laccase was demonstrated by using reversed phase chromatography while SEC analysis proved covalent attachment of the enzyme to the methacrylated polysaccharide matrix. Upon incubation of peptidoglycan based BRPs with fluid from infected wounds, the difference to controls was four times higher for Laccase_PEG based signalling when compared to simple dye release. Similarly, the control signals (i.e. leaching) were considerably reduced in case of Laccase_MA incorporated in crosslinked peptidoglycan (PG) and carboxymethylcellulose (CMC) hydrogels for signalling. In addition, Laccase_MA catalysed colour formation enhanced the signal dramatically with factors between 100- and 600-fold. Laccase_MA was demonstrated to oxidise silica gel immobilised ferulic acid incorporated into the BRP with clearly visible colour changes of 4.5 Δ E units according the CIELab concept upon incubation by trigger enzymes as well as infected wound fluids.