Abstract
Point-of-care facile and economical detection ofStaphylococcus aureus(S. aureus), one of the main causes of food-borne illness, is highly demanded for the early diagnosis and control of infections. Herein, inspired by the proteolytic activity ofS. aureusprotease on a specific peptide substrate, we developed a rapid, simple and cost-effective biosensor forS. aureususing dual colorimetric and electrochemical detection on the same platform. In this approach, gold screen printed electrodes were used on which specific peptide sequences coupled to magnetic nanoparticles were immobilized giving the black color of the sensor surface. The addition of theS. aureusprotease solution on the electrode surface causes cleavage of the peptide sequence and the release of the magnetic nanoparticles revealing the golden colour of the electrode which can be easily seen by the naked eye. Furthermore, square wave voltammetric signals can be detected on the same electrode in the ferro/ferricyanide redox couple. The change in the peak current after peptide cleavage was directly proportional to the concentration ofS. aureus. The detection limit of the electrochemical assay was 3 CFU ml(-1)after 1 min. Moreover, the biosensor was capable of specifically distinguishingS. aureusfrom other food- and water-borne bacteria such asE. coliandListeriausing the dual mode colorimetric and electrochemical detection. The biosensor was also tested in spiked milk and water samples showing very good recovery percentages. Thus, we believe that this dual mode biosensing platform enables the easy and accurate determination ofS. aureusand holds great promise for point-of-care diagnosis.