An electrophoresis approach with online thermal lens detection to monitoring DNA surface coatings on gold nanoparticles

The coverage density of oligonucleotides on the surface of gold nanoparticles (AuNPs) is crucial for optimizing the sensitivity of AuNPs-based biosensors and evaluating the interactions between thiol-functionalized oligonucleotides and AuNPs. In this study, we report a novel approach based on a miniaturized gel electrophoresis chip (MGEC) integrated with online thermal lens detection for monitoring the amount of DNA on the surface of AuNPs. The microcontroller-based digitization board platform enables simultaneous measurement and recording of data. AuNPs were functionalized with a mixed thiol-terminated monolayer containing single stranded DNA at variable density, which is able to load binders for high sensitivity biorecognition. Due to high spatial and temporal resolution of the thermal lens detection system, our approach enables extremely small differences in the electrophoretic mobility of the particles to be resolved. Hence, small differences in the DNA surface density (55-275 nM) on the particles can be easily distinguished in short time (<6 min), not otherwise detectable using conventional UV-Vis spectrophotometers. In addition, the analytical capability of the proposed MGEC was validated measuring the low detection limit for standard AuNPs solutions using a 80 mu L buffer, 100 mu L gel, and a 37.5 V/cm electrical field. The result showed that the thermal lens signal linearly increased with the concentration of AuNPs over the range of 0.1-10 nM. The detection limit and relative standard deviation were 23 pM and 4%, respectively. We envisage that the system has potential as an advanced instrumental platform for designing biosensors in nanotechnology.