Detection of biomolecules using retroreflective optical signal from Janus particle probes

Abstract Recent reports regarding sensing of biomolecules using retroreflective optical signal from Janus particle probes provided great possibility for on-site, easy, and fast signaling of target biomolecules. Here, we describe the effect of Janus probe’s size on signaling retroreflective light. Firstly, we modified silica particles of different sizes (1 μm, 1.5 μm, 2 μm, 3 μm) to introduce azide groups and then used the solvent volatilization method to uniformly disperse them on a glass surface before depositing metal layers (Al: 40 nm, Au: 20 nm). These particles were utilized as optical probes in combination with a microfluidic channel chip for target DNA detection. We investigated the signal intensities of retroreflective Janus particles (RJPs) of varying diameters (1.0 μm, 1.5 μm, 2.0 μm, and 3.0 μm) following the capture of target DNA molecules and evaluated the influence of reaction time on detection performance. Notably, reliable sensitivity was maintained even with a reaction time of 5 min. Further detection of target DNA at varying concentrations using 1.0 μm and 2.0 μm RJPs showed that the limits of detection were approximately 13.1 pM and 17.2 pM, respectively. Furthermore, by employing our designed “vortex vibration method”, background noise signals were reduced by approximately threefold, significantly enhancing detection accuracy and enabling more precise signal readout.