Nanocatalysis of silver-nanobioprobe based supersensitive electrochemical detection of Salmonella serotypes targeting virulence protein

Abstract

Herein, we report a supersensitive and specific detection of Salmonella employing nanocatalysis of silver nanoparticle (AgNp). A nanobioprobe was developed employing specific antibody (Ab) that binds to a peptide present in transmembrane protein of Salmonella. We have studied 7 surface-exposed peptide hits from conserved virulence proteins (PagC, ST50, PagN, CdtB and FliC). These peptides were experimentally evaluated by BLI (Bio layer interferometry) for their reactivity towards antisera raised against an admix of major Salmonella serogroups. The most promising peptide was used to generate Ab with binding affinity Kd of 5.6 x 10-9 M. The Ab exhibited high specificity towards entire Salmonella serotypes prevalent in foods, as illustrated by the FACS (Fluorescence-activated cell sorting) study. The Ab-AgNp probe was blocked with a dual layer to prevent non-specific interactions, confirmed by employing BLI and TEM (Transmission electron microscopy). For the electrochemical detection, the autonanocatalysis of AgNp in presence of H2O2 was used to generate numerous Ag+ resulting in an amplified signal that could detect 10 cells/mL. The relative standard deviation (RSD) was observed to be 4.5%. The platform achieved recovery of 100-112% calculated for 102 cells/mL. The performance was validated in milk, buffer peptone water (BPW) and tap water by spiking studies. The study highlights the effectiveness of efficiently blocked AgNp-mediated probes for the highly selective and sensitive detection of Salmonella, representing a significant advancement in bacterial sensing.