An extraction free modified o-phthalaldehyde assay for quantifying residual protein and microbial biofilms on...

Biological contamination of surfaces in industry and healthcare is an important vector of disease transmission. Current assays for detecting surface-adherent contamination require extraction of biological soil. However, physical inaccessibility or poor solubility may limit recovery. Here, how the o-phthalaldehyde (OPA) protein assay can be modified to measure residual protein (modeled with bovine serum albumin) or biofilm on a surface without extraction is described. The assay limit of detection (LOD) for protein was 1.6 µg cm^-2. The detection threshold for Staphylococcus epidermis biofilm was 117 µg cm^-2. The clinical utility of the method was demonstrated for measurements taken from clinically used endoscopes. Since this method is more sensitive than extraction-based testing, clinical results should not be compared with conventional benchmarks. By enabling direct detection and quantification of soils in complex or hard-to-reach areas, this method has potential to improve the margin of safety in medical and industrial cleaning processes.