Sensitive Escherichia coli detection using porous Si immunosensor coupled with rapid catalytic signal amplification

Rapid, facile and sensitive detection of water-borne pollutants is crucial to safeguarding public health. Herein, a miniaturized biosensing platform based on a porous silicon (p-Si) interferometer was designed to detect Escherichia coli (E. coli) contamination in a rapid and reliable manner. An indirect immunoassay followed by simple syringe filtration was adapted to exclude the unreacted antibodies tagged with horseradish peroxidase (HRP) from the bacterial suspension, while the optical transducer assessed the residual immuno-entities. Quantification of minute E. coli concentrations was achieved by the HRP moieties' biochemical activation and real-time monitoring of the reaction products' infiltration into the porous nanostructure by alternating reflectance spectra. The developed bioassay depicted high sensitivity against target microorganism detection, as low as 2 CFU mL(-1), with a linear response of 10(1) - 10(5) CFU mL(-1). Furthermore, the selectivity was tested using the common interfering pathogens, Listeria monocytogenes, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Staphylococcus epidermidis and Bacillus cereus, resulting in satisfactory output. Finally, the potential applicability of the developed platform for real-life scenarios was interpreted with respect to the standard culture plate approach while depicting recovery values of 92 - 107 % in ground, irrigation and river water, as well as in staple food samples (raw and pasteurized milk). Overall, the miniaturized p-Si scaffold can be utilized for various emerging applications with pathogenesis-relevant assessments conducted under on-site conditions.