Detection of inv A gene of Salmonella by DNA-gold nanoparticles biosensor and its comparison with PCR

The genus of Salmonella are very important pathogenic bacteria and their detection in medicine and food industry is of high priority. The presence of these bacteria in food is a causative agent of food poisoning. In addition to human, these organisms are infective in most animals. Salmonellosis is the most common disease caused by the organisms. Thyphoid fever occurs when some of the Salmonella organisms are not killed by the normal human immune defences after they enter the gastrointestinal tract. In this study oligonucleotide-capped gold nanoparticles (GNPs) were used in a colorimetric assay in order to detect the inv A gene of Salmonella. A 60 nucleotides sequence of inv A gene was selected, then specific primers and probes were designed. GNPs with 20 nm diameter were modified with (alkanethiol)-31 nucleotide probes. This method relies on the hybridisation of amplified or unamplified target sequence with this probes and GNPs aggregation. Aggregation of Au-nanoparticles caused a colour change in solution and a shift in the surface plasmon absorbance. Sensitivity of this method was compared with polymerase chain reaction (PCR) method. When target DNA was amplified with PCR, this method demonstrated a greater sensitivity in comparison with agarose gel electrophoresis but its sensitivity was lower when target DNA was unamplified.

Salmonella; inv A; gold nanoparticle; nanosensor; PCR