QCM immunosensor for the determination of Staphylococcus aureus antigen

Abstract

Staphylococcus aureus is a causative agent of infectious diseases and a producer of a group of highly toxic proteins called Staphylococcal enterotoxins. Currently, the presence of S. aureus in a sample can be determined by a wide spectrum of genetic, immunochemical and microbiological techniques. Despite availability of standard methods and devices, they are not fully suitable for a simple, label-free mode of use by an unskilled worker. In this paper, a biosensor based on quartz crystal microbalance (QCM) sensor is performed as a tool for a simple and reliable determination of S. aureus. The biosensor contained an antibody specific to S. aureus immobilized through protein A on 10 MHz QCM sensors and the interdigitated layer was stabilized by iron nanoparticles. The assay was performed as label free and sample was applied without any pretreatment. Limit of detection 145 µg/ml (5.18 × 108 CFU/ml) was achieved. When considered standard size of a sample 50 μl, the limit of detection was equal to 7.25 μg (2.59 × 107 CFU). The biosensors kept more than 90% sensitivity to the analyte after storage in laboratory conditions for 90 days. Good correlation to standard enzyme-linked immunosorbent assay was also proved. The biosensor appears as a simple but reliable tool for S. aureus assay and the QCM platform would provide further applications in microbial analyses.