Immunosensor Using Nanoparticle-based Signal Enhancement for Bacterial Pathogen Detection

Y. Wang, E.C. Alocilja
Michigan State University, US

Keywords: biosensor, nanoparticles, signal enhancement, detection, pathogen

Summary:

Biosensors for rapid and sensitive detection have involved the use of nanostructures, including nanoparticles, in various forms. We developed a tri-nano electrochemical immunosensor based on the assembly of 3 nanoparticles for the rapid detection of Escherichia coli O157:H7. The biosensor assay consists of magnetic separation using antibody-functionalized magnetic nanoparticles (MNPs) and electrochemical reporter using gold-conjugated lead sulfide (PbS) nanoparticles via oligonucleotide linkage (Figure 1). The AuNPs were firstly functionalized with polyclonal anti-E. coli O157:H7 antibodies to bind to the target bacterial cells which were captured and separated from the sample by antibody-functionalized MNPs. Because each AuNP was linked to multiple PbS nanoparticles, each binding event to the target resulted in substantial amplification. The signal of PbS was measured on screen-printed carbon electrode (SPCE) by square wave anodic stripping voltammetry (SWASV). Results show that the biosensor could detect E. coli O157:H7 in the range of 101 to 106 colony forming units per milliliter (cfu/ml) (Figure 2). Compared to conventional culture plating methods which take two to four days to obtain results, the immunosensor detected the target in 40 min from sample processing to final readout with comparable sensitivity. This immunosensor has potential applications in public health, biodefense, and food/water safety monitoring.