A Dual‐Modal Single‐Antibody Plasmonic Spectro‐Immunoassay for Detection of Small Molecules

Abstract

Small molecules play a pivotal role in regulating physiological processes and serve as biomarkers to uncover pathological conditions and the effects of therapeutic treatments. However, it remains a significant challenge to detect small molecules given the size as compared to macromolecules. Recently, the newly emerging plasmonic immunoassays based on surface‐enhanced Raman scattering (SERS) offer great promise to deliver extraordinary sensitivity. Nevertheless, they are limited by the intrinsic SERS intensity fluctuations associated with the SERS uncertainty principle. The single transducer that relies on the intensity change is also prone to false signals. Additionally, the prevailing sandwich immunoassay format proves less effective towards detecting small molecules. To circumvent these critical issues, a dual‐modal single‐antibody approach that synergizes both the intensity and shift of the peak‐based immunoassay with Raman enhancement, coined as the INSPIRE assay, is developed for small molecules detection. With two independent transduction mechanisms, it allows better prediction of analyte concentration and attenuation of signal artifacts, providing a new and robust strategy for molecular analysis. With a proof‐of‐concept demonstration for detection of free T4 and testosterone in serum matrix, the authors envision that the INSPIRE assay could be expanded for a wide spectrum of applications in biomedical diagnosis, discovery of new biopharmaceuticals, food safety, and environmental monitoring.

Leveraging Nanomechanical Perturbations in Raman Spectro‐Immunoassays to Design a Versatile Serum Biomarker Detection Platform

“…As established in our previous study, it can be readily fabricated using nanosphere lithography (Figure S3, Supporting Information) while possessing superior SERS performance. [ 37 ] Representative scanning electron micrscope images and reflection spectrum of the fabricated gold nanopyramid arrays are respectively shown in Figure a and Figure S4, Supporting Information. The pyramidal geometry featured sharp edges and vertices that are desired for SERS enhancement.…”

“…[34,36] We have recently leveraged the SERS frequency shift combined with the intensity change to create a dual-modal spectro-immunoassay for detecting small molecules. [37] Notably, it relied on a two-step reaction with its sensing performance augmented by the synergistic plasmonic coupling between gold star nanoprobes and the underlying plasmonic substrate.…”

Application of SERS in In‐Vitro Biomedical Detection

“…Zheng et al. designed the process of capturing the target molecules as shown in Figure 3b (i) [63] . First, drop thyroxine (T4) of different concentrations on the substrate, and incubate it at 37 °C for 20 minutes to allow antibody‐antigen interaction.…”

“…Zheng et al designed the process of capturing the target molecules as shown in Figure 3b (i). [63] First, drop thyroxine (T4) of different concentrations on the substrate, and incubate it at 37 °C for 20 minutes to allow antibodyantigen interaction. After washing off the unconjugated antigen, drop the Raman reporters on the substrate, incubate at 37 °C for another 20 minutes, then wash off the unconjugated Raman reporters, and finally conduct SERS detection.…”

Deep Learning Image Analysis of Nanoplasmonic Sensors: Toward Medical Breath Monitoring

“…Nanoplasmonics is a research area of growing importance that has increasingly contributed to enabling capabilities for developing cost-effective biomedical diagnostics. Much of the success has been in solution-phase detection, where lock-and-key binding creates readily detectable changes in interfacial optical properties. − Gas-phase plasmonic studies are much less common. − However, the advantages of plasmonic devices ,− ,− such as rapid response speed, high sensitivity, miniature size, and the capability for remote measurement by using an optical spectrometer/camera/photodetector outside the sampling chamber offer enormous possibilities for a broader range of gas-phase applications, one of which is the expanding need for noninvasive medical breath analysis and monitoring. ,− …”