A piezoelectric immunosensor for specific capture and enrichment of viable pathogens by quartz crystal microbalance sensor, followed by detection with antibody-functionalized gold nanoparticles

A sensitive bacteria enrichment and detection system for viable Escherichia coli O157:H7 was developed using a piezoelectric biosensor-quartz crystal microbalance (QCM) with antibody-functionalized gold nanoparticles (AuNPs) used as detection verifiers and amplifiers. In the circulating-flow QCM system, capture antibodies for E. coli O157:H7 were first immobilized onto the QCM chip. The sample containing E. coli O157:H7 was circulated through the system in the presence of 10ml of brain heart infusion (BHI) broth for 18h. The cells of E. coli O157:H7 specifically captured and enriched on the chip surface of the QCM were identified by QCM frequency changes. Listeria monocytogenes and Salmonella Typhimurium were used as negative controls. After bacterial enrichment, detection antibody-functionalized AuNPs were added to enhance the changes in detection signal. The use of BHI enrichment further enhanced the sensitivity of the developed system, achieving a detection limit of 0–1log CFU/ml or g. The real-time monitoring method for viable E. coli O157:H7 developed in this study can be used to enrich and detect viable cells simultaneously within 24h. The unique advantages of the system developed offer great potential in the microbial analysis of food samples in routine settings. ► Simultaneously enrich and detect pathogens in QCM has never been reported. ► Our system can detect concentrations as low as one single viable target cell. ► We used antibody-functionalized AuNPs as detection verifiers and amplifiers. ► BHI broth was first used to enrich and confirm the viability of bacteria in QCM. ► Sample size was scaled up to 10ml, an improvement over many other biosensors.