An Electrochemical DNA Sensing System Using Modified Nanoparticle Probes for Detecting Methicillin-Resistant Staphylococcus aureus.

We have developed a novel, highly sensitive, biosensing system for detecting methicillin-resistant Staphylococcus aureus (MRSA). The system employs gold nanoparticles (AuNPs), magnetic nanoparticles (mNPs), and an electrochemical detection method. We have designed and synthesized ferrocene- and single-stranded DNA-conjugated nanoparticles that hybridize to MRSA DNA. Hybridized complexes are easily separated by taking advantage of mNPs. A current response could be obtained through the oxidation of ferrocene on the AuNP surface when a constant potential of +250 mV vs. Ag/AgCl is applied. The enzymatic reaction of L-proline dehydrogenase provides high signal amplification. This sensing system, using a nanoparticle-modified probe, has the ability to detect 10 pM of genomic DNA from MRSA without amplification by the polymerase chain reaction. Current responses are linearly related to the amount of genomic DNA in the range of 10-166 pM. Selectivity is confirmed by demonstrating that this sensing system could distinguish MRSA from Staphylococcus aureus (SA) DNA.

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 10-166pM, and this sensing system could also distinguish MRSA from S. aureus.

Detection of influenza virus: traditional approaches and development of biosensors.

Influenza is an acute respiratory disease caused by the influenza virus. The disease occurs annually, causing fatality in the elderly and children and billions of dollars loss in business and productivity. Traditional viral detection methods include MDCK cell culture, complement fixation, hemagglutinin-inhibition, and recently RT-PCR. Although effective, these methods generally involve labor-intensive laboratory procedures and often require trained personnel to carry them out. The development of biosensor technologies will enable rapid and specific disease diagnosis on-site so that a clinician can quickly determine whether treatment is needed. This paper reviews traditional viral assays and progress in the biosensor development for influenza virus. Recent advances in single-step direct detection using non-labeling techniques such as surface plasmon resonance, quartz-crystal microbalance, and colorimetric functional polymers are discussed.