A smart DNA sensing system for detecting methicillin-resistant Staphylococcus aureus using modified nanoparticle probes

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of hospital-acquired infections. To prevent epidemics, a quick and simple detection method is required. In this study, we developed a novel electrochemical DNA detection method that does not rely upon polymerase chain reaction (PCR) and may be used in point-of-care facilities. The electrochemical DNA sensing system presented here is based on the chronoamperometric detection of ferrocene-labeled probes that were conjugated to gold nanoparticles (AuNPs). This DNA sensor system employed magnetic nanoparticle (MNP)-modified probes allowing easy sample DNA recovery. AuNP nanoparticles with ferrocene-labeled probes enabled the generation of an electric signal, and MNP/DNA/AuNP conjugates were formed by hybridization. Following hybridization, the MNP/DNA/AuNP hybridization complex is magnetically separated, and electrochemical current responses could be obtained because of the AuNP-ferrocene complexes. To construct a highly sensitive system, dye-linked l-proline dehydrogenase (l-proDH) was employed to amplify current responses following a catalytic reaction with l-proline. Rapid catalytic reaction of l-proDH and substrate was able to amplify the oxidation of ferrocene. Target DNA from MRSA could be quantified over a range of 10-166 pM, and this sensing system could also distinguish MRSA from S. aureus.