Phage-modified dual-peak long-period fiber grating biosensor for ultrasensitive, rapid and specific detection of pathogen strains

Abstract

Herein, we present an ultrasensitive, rapid and specific phage-modified dual-peak long-period fiber grating (Phage-DP-LPFG) biosensor for detecting foodborne pathogens. Compared to the single-peak resonance LPFG with a grating period of 360 μm, the DP-LPFG with a grating period of 163 μm offers enhanced sensitivity to refractive index changes caused by bacterial adsorption. By directionally immobilising phages on the DP-LPFG, the sensor achieves high specificity for target bacterial strains. Upon capturing the target strain, the short-wavelength near-infrared transmission loss peak undergoes a blue shift, whereas the long-wavelength transmission loss peak exhibits a red shift. The shift in spacing between the two peaks (Δλ) increases with higher bacterial capture, enabling the quantification of target strains based on Δλ changes. Using Escherichia coli O157:H7 (E. coli O157:H7) as a model, the Phage-DP-LPFG biosensor demonstrates a linear detection range of 25–108 CFU/mL with a low limit of detection of 8 CFU/mL in 10 min under optimal conditions. The biosensor was also tested on food samples such as fish and milk, showing no notable differences from standard methods but with reduced detection time. It was further extended to the detection of another foodborne pathogen strain Hafnia paralvei (MCCC 1K06097) (H. paralvei (MCCC 1K06097)) with satisfactory results. This study offers a novel approach for the rapid, sensitive and specific detection of trace pathogenic strains in foods.