Purpose: The purpose of this study is to further validate our DNA-based biosensor detection system by testing its ability to detect specific bacterial DNAt within solid food matrices such as egg yolks and spinach.
Methods: Non-PCR amplified genomic DNAt samples were extracted from food matrices spiked with Salmonella Enteritidis, E. coli, Salmonella Enteritidis and E. coli, or LB broth (control). DNA targets (50 ng/ml) were then hybridized into a sandwich-like structure consisting of MNPs/DNAt/AuNPs, of which both MNPs and AuNPs contained probes specific for the insertional element (Iel) of Salmonella Enteritidis. The sandwich structures were then placed onto screen-printed carbon electrodes to detect the voltammetric peaks of gold using differential pulse voltammetry (DPV). All samples were run in triplicate.
Results: The biosensor was able to detect non-PCR amplified Salmonella Enteritidis genomic DNAt from all food matrices that had been spiked with Salmonella Enteritidis compared to those spiked with another pathogen or control. For example, gold voltammetric peaks were higher (P ≤ 0.05) in DNAt samples isolated from yolks spiked with Salmonella Enteritidis (4.4 x 10-5 A) or Salmonella Enteritidis and E. coli (3.2 x 10-5 A) compared to samples spiked with E. coli (1.6 x 10-5 A) or LB broth (6.5 x 10-6A).
Significance: These findings suggest that our DNA-based biosensor can serve as a means to detect bacterial food pathogens from solid food matrices. Future work will determine if it can be used in a field non-laboratory setting.