Aptamer based high throughput colorimetric biosensor for detection of staphylococcus aureus.

To develop a high throughput colorimetric biosensor for detection of Staphylococcus aureus (SA) based on specific aptamer and catalysis of dsDNA-SYBR Green I (SG I) complex. SA specific aptamer was immobilized on a 96-well plate by hybridization with the capture probe anchored on the plate surface through streptavidin-biotin binding. In presence of SA, the aptamer was dissociated from the capture probe-aptamer duplex due to the stronger interaction between the aptamer and SA. The consequent single-strand capture probe could be hybridized with a three-way junction (TWJ) probe. With the presence of SG I, the dsDNA-SG I complex catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) under photo-irradiation, producing sensitive photo-catalyzed colorimetric response to SA. Under the optimal conditions, the proposed method could directly detect SA with the limit of detection (LOD) at 81 CFU mL-1 in PBS buffer in 5.5 hours, which demonstrated the sensitive and fast quantification of target pathogenic bacteria. The method showed weak colorimetric signal to Escherichia coli and Pseudomonas aeruginosa, indicating the high specificity for SA. In addition, the method can simultaneously detect 96 samples which can be used for high throughput analysis. The designed method may become a powerful tool for pathogenic microorganisms screening in clinical diagnostics, food safety and environmental monitoring.