A low-cost optical transducer utilizing common electronics components for the gold nanoparticle-based immunosensing application

Abstract

We developed a cost-effective and convenient optical transducing platform for use in gold nanoparticle-based immunosensing applications. Two types of gold nanoparticles were prepared and used as optical signaling probes: spherical gold nanoparticles (GNPs) exhibiting maximal absorbance at 519nm and gold nanorods (GNRs) exhibiting maximal absorbance at 620nm. Common components used in electronics, including two types of laser diodes (λmax=532- and 635-nm), solar cells, and a multimeter, were reassembled to construct the optical transducing platform. Under the condition in which the emission spectra of lasers and the absorption spectra of gold nanoparticles are matched, laser intensity is decreased. In the designed transducing system, these changes in light intensity are directly indicated as alterations in the DC voltage signal. Based on this principle, we demonstrated the immunosensing applicability of the optical transducing platform. As model immunoreaction pairs, we used anti-mouse IgG/mouse IgG and anti-human IgG/human IgG; superparamagnetic microparticles (MPs) were conjugated with capture antibodies (anti-mouse IgG and anti-human IgG) and the GNPs and GNRs were conjugated with the target mouse IgG and human IgG (model antigens). When the capture antibody-modified MPs and the optical probes mixed in the platform's reaction channel, the optical probes bound to the MPs through an affinity-based reaction. Under a magnetic field, the biospecifically conjugated MP/GNP and MP/GNR complexes could be localized in the reaction channel. Consequently, the amounts of the GNPs and GNRs remaining in the solution were inversely proportional to the rate of the MP/GNP and MP/GNR reactions, and could be registered as DC voltage signals. Based on these results, we expect the novel transducing system and immunosensing strategy presented herein to be applied in practical optical immunosensing performed using key disease markers and their antibodies.