Nanostructured biochip for label-free and real-time optical detection of polymerase chain reaction

In this report, Au-coated nanostructured biochip with functionalized thiolated primers on its surface is developed for label-free and real-time optical detection of polymerase chain reaction (PCR). A PCR chamber of 150 μm in thickness containing Au-coated nanostructured substrate in the bottom layer was bordered with SU-8 100 walls. After immobilization of 5′-thiolated primers on the surface, simultaneous DNA amplification and detection were performed without any labeled molecules via the relative reflected intensity (RRI) of Au-coated nanostructured substrate. When human genomic DNA at several concentrations of 0.2, 0.5 and 1 ng μL⁻¹ was included in the initial DNA samples, the increases in the RRI peak values were clearly observed with the increasing PCR cycle numbers. We found that the starting point of the optical signal, which was divergent from the background in our PCR biochip, was around 3-4 cycles, much lower than that of the fluorescent real-time PCR analysis (around 23-25 cycles). Our proposed PCR device using Au-coated nanostructured substrate holds noteworthy promise for rapid, label-free and real-time DNA detection for point-of-care testing (POCT) applications.