Ultrahigh-sensitivity label-free single mode-tapered multimode-single mode fiber U-shaped biosensor for Staphylococcus aureus detection

The rapid detection of Staphylococcus aureus (S. aureus), particularly in the case of very low levels of S. aureus, is very important in food safety and medical diagnostics. In this paper, a fast (<20 mins), label-free biosensor using a U-shaped single mode-tapered multimode-single mode (STMS) fiber structure is presented. The average wavelength shift of the sensor (modified with the IgG from porcine serum with a concentration 200 ??g/mL) is as high as 1.552 nm when it is immersed into an S. aureus sample with a concentration of 4 cells/mL. By further diluting the S. aureus to 0.4 cells/mL for a sample volume of 1.5 mL, it is found that a dip wavelength shift of 0.348 nm is observed on occasion which confirms that the biosensor can detect a single colony (cell) of S. aureus. Results for the detection of S. aureus in milk and lettuce samples are also presented and are compared with the wavelength shift results in phosphate buffered saline (PBS), and it is found that the variation in the average wavelength shift is -21% for S. aureus concentrations from 4 to 4 ?? 103 cells/mL.

Automated summary

This paper presents a fast (<20 mins), label-free biosensor using a U-shaped single mode-tapered multimode-single mode (STMS) fiber structure for rapid detection of Staphylococcus aureus (S. aureus) at very low concentrations. The biosensor showed an average wavelength shift of 1.552 nm when immersed in an S. aureus sample with a concentration of 4 cells/mL, and a dip wavelength shift of 0.348 nm when the S. aureus concentration was further diluted to 0.4 cells/mL, confirming its ability to detect single colonies of S. aureus. The variation in the average wavelength shift for S. aureus concentrations from 4 to 4 × 103 cells/mL was found to be -21% in milk and lettuce samples.