Abstract
Shear horizontal surface acoustic wave (SH-SAW) biosensors measure the reaction of capture antibodies immobilized on the sensing surface to capture test molecules (antigens) by using the change in SH-SAW propagation characteristics. SH-SAW displacement exists not only on the SH-SAW propagating surface, but also partially penetrates the specimen liquid to a certain depth, which is determined by the liquid properties of the specimen and the operating frequency of the SH-SAW. This phenomenon is called viscosity penetration. In previous studies, the effect of viscosity penetration was not considered in the measurement of SH-SAW biosensors, and the mass or viscosity change caused by the specific binding of capture antibodies to the target antigen was mainly used for the measurement. However, by considering the effect of viscosity penetration, it was found that the antigen–antibody reaction could be measured and the detection characteristics of the biosensor could be improved. Therefore, this study aims to evaluate the detection properties of SH-SAW biosensors in the surface height direction by investigating the relationship between molecular dimensions and SH-SAW propagation characteristics, which are pseudo-changed by varying the diameter of gold nanoparticles. For the evaluation, we introduced a layer parameter defined by the ratio of the SH-SAW amplitude change to the SH-SAW velocity change caused by the antigen–antibody reaction. We found a correlation between the layer parameter and pseudo-varied molecular dimensions. The results suggest that SH-SAW does not only measure the mass and viscosity but can also measure the size of the molecule to be detected. This shows that SH-SAW biosensors can be used for advanced functionality.
Highlights
Introduction published maps and institutional affilThe global outbreak of COVID-19 in 2020 has reminded everyone of the enormous impact of infectious diseases on industrial activities, social life, and people’s lives
We characterized Shear-horizontal surface acoustic wave (SH-SAW) biosensors through an antigen–antibody reaction to detect C-reactive protein (CRP) using secondary antibodies conjugated with gold nanoparticles of various diameters
The layer parameter calculated using simulated results demonstrated the same trends as that of the layer parameter obtained after measuring the CRP antigen–antibody reaction with various gold nanoparticle diameters
Summary
Introduction published maps and institutional affilThe global outbreak of COVID-19 in 2020 has reminded everyone of the enormous impact of infectious diseases on industrial activities, social life, and people’s lives. Effective measures to prevent the spread of COVID-19 include testing and isolation. The difference is that the former test detects the infection at the time of testing, while the latter test detects the presence of antibodies in the body that developed as a result of past infection with the virus or vaccination. Despite this difference, the requirements for these tests are common, that is, simplicity of the test procedure, low workload for medical personnel, rapid results, and capability to perform the test on-site. Shear-horizontal surface acoustic wave (SH-SAW) technology-based [1,2,3,4,5,6] biosensors are considered promising candidates for the iations
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