Optically-induced immunoassay detects coronavirus spike proteins in 5 min

24 Sep 2024

Osaka Met University develops sensitive method using the “weak light” of a laser pointer.

Optical condensation of protein-modified biological nanoparticles.

Like moths to a flame, microbes can also be moved by light. Using this knowledge, researchers from Osaka Metropolitan University’s Research Institute for Light-induced Acceleration System (RILACS) have demonstrated a method to detect the presence of viruses quickly and using only a small sample.

The research team led by OMU Professor Takuya Iida, the director of RILACS, and Associate Professor Shiho Tokonami, the deputy director, report their achievement in npj Biosensing.

How it works

Using laser irradiation for less than 1 minute, a nanoparticle-imprinted plasmonic substrate with a series of nanobowl structures (500 nm in diameter for each) could be coated with antibodies for the spike proteins of the novel coronavirus.

A 5 mW laser, as low power as commercial laser pointers, could then form bubbles on the biochip that drew virus-mimicking nanoparticles, thereby accelerating the selective detection of the particles.

Because light-induced convection helps move the nanoparticles around so that they end up assembling at the stagnant region between the substrate surface and the bottom of the bubble, a high concentration of the particles was not required. In under five minutes, the entire process, from substrate coating to detection, could be completed.

“This study shows that we can shorten the cumbersome antibody coating process and perform rapid and highly sensitive protein detection,” said Professor Iida. “We believe our findings can contribute to the early diagnosis of not only the novel coronavirus, but possibly also various infectious diseases, cancer, even dementia.”

Nature paper abstract

The Abstract in the npj Biosensing paper states, “The efficient detection of protein biomarkers is critical for public health. However, the sensitivity of conventional antigen test kits is relatively low for early diagnosis, and laboratory immunoassays require complex pretreatment processes overnight. If target nanomaterials could be remotely guided to the detection site, simpler and faster methods would be developed.

“We reveal here the mechanism of light-induced immunoassay that anti-spike-protein antibodies for SARS-CoV-2 were coated on our developed nanoparticle-imprinted plasmonic substrate (NPI-PS) over the sub-millimeter area within one minute and nanoparticles modified with spike proteins can be selectively detected within a few minutes at one or two orders of higher sensitivity via a two-step optical condensation using NPI-PS.

“NPI-PS exhibits high-performance optical condensation with high photothermal properties even under milliwatt-class nonresonant laser irradiation, enabling a wide range of quantitative measurements. These findings support an innovative strategy to mitigate pandemic threats and various diseases through the high-throughput detection of protein biomarkers.”