Rapid colorimetric gene-sensing of food pathogenic bacteria using biomodification-free gold nanoparticle

Foodborne pathogens have been recognised as the major cause for infection of people worldwide with vital health damage. Thus the development of rapid food pathogen detection method has become an urgent task. It is described here, a simple, rapid gold nanoparticle (GNP) colorimetric assay for Listeria monocytogenes and Salmonella enterica detection. The method is based on polymerase chain reaction (PCR) using thiol-labelled primers. PCR is applied to amplify hly gene of L. monocytogenes and hut gene of S. enterica, and the products with thiol-label at one end were acquired. After mixing PCR products and GNPs, the sulphur-gold linkage resulted in the formation of GNP-PCR products. Due to the GNP-PCR products are more salt-tolerant than primers linked GNPs, detection of the bacteria can be achieved by a facilitated GNP based colorimetric testing using naked eyes. Further, more accurate analysis could be executed by spectrum measurement. The limit of detection of analyzing genome DNA of L. monocytogenes and S. enterica are 0.015 ng mL−1 and 0.013 ng mL−1, respectively. The specificity is evaluated by distinguishing target pathogenic bacteria from other bacterias. The artificial contaminated food samples were also detected for its potential applications in real food samples.