Real-time and sensitive detection of Salmonella Typhimurium using an automated quartz crystal microbalance (QCM) instrument with nanoparticles amplification

The accidental contamination of Salmonella in raw and processed foods is a major problem for the food industry worldwide. At present many of the currently used methods for Salmonella detection are time and labour intensive. Therefore, rapid detection is a key to the prevention and identification of problems related to health and safety. This paper describes the application of a new quartz crystal microbalance (QCM) instrument with a microfluidic system for the rapid and real time detection of Salmonella Typhimurim. The QCMA-1 bare gold sensor chip which contain two sensing array was modified by covalently immobilising the monoclonal capture antibody on the active spot and a mouse IgG antibody on the control spot using a conventional amine coupling chemistry (EDC-NHS). The binding of the Salmonella cells onto the immobilised anti-Salmonella antibody alters the sensor frequency which was correlated to cells concentration in the buffer samples. Salmonella cells were detected using direct, sandwich, and sandwich assay with antibody conjugated gold-nanoparticles. The performance of the QCM immunosensor developed with gold-nanoparticles gave the highest sensitivity with a limit of detection (LOD) ~10–20 colony forming unit (CFU) ml−1 compared to direct and sandwich assay (1.83×102CFUml−1 and 1.01×102CFUml−1, respectively). The sensor showed good sensitivity and selectivity for Salmonella in the presence of other bacteria in real food samples and helped in reducing the pre-enrichment step, hence, demonstrating the potential of this technology for the rapid and sensitive microbial analysis. Quartz crystal microbalance immunosensor for Salmonella Typhimurium [Display omitted] •Immobilisation of biomolecules to sensor surface is a crucial step for biosensors sensitivity.•Development of a fully automated immunosensor based on QCM sensor chip for Salmonella detection enabled rapid analysis.•Use of gold nanoparticles enhanced the sensitivity of the QCM sensor.•Cross reactivity and specificity of the sensor signal in real food samples.