Real time label-free monitoring of plasmonic polymerase chain reaction products

摘要

The high mortality rate in developing countries stemming from poverty and diseases, and the pressure on healthcarebudgets in developed countries have evoked a major concern in healthcare delivery. The need for less costly and patientcenteredhealthcare delivery brings point-of-care (POC) testing to the fore. POC devices help to eliminate the overheadassociated with centralized bench-top laboratory instruments. Although handheld devices such as glucose biosensor stripexist, POC devices for molecular techniques such as Polymerase Chain Reaction (PCR) are new and emerging. PCR makesit possible to replicate DNA and generate millions of copies from a single strand. This finds applications in the medicalfield to identify and detect infectious diseases. Conventional PCR equipment is expensive and requires a significant amountof personnel time and space to setup and run in the laboratory. We have recently demonstrated a rapid and low-cost PCRthermocycler based on laser heating of gold nanoparticles suspended in the PCR tube. A critical aspect of PCR systems isthe need to detect amplified products in real time. Here we show that by measuring the optical absorption of the suspendedgold nanoparticles at a single wavelength during thermocycling, it is possible to detect amplified PCR products in realtime. We investigate several different signal processing approaches in order to determine the most sensitive monitoringtechnique. This method makes it possible to distinguish between negative and positive PCRs with starting copy numbersas low as 10,000 genome copies per microliter.