Abstract
Suspension microsphere immunoassays are rapidly gaining attention in multiplex bioassays. Accurate detection of multiple analytes from a single measurement is critical in modern bioanalysis, which always requires complex encoding systems. In this study, a novel bioassay with Raman-coded antibody supports (polymer microbeads with different Raman signatures) and surface-enhanced Raman scattering (SERS)-coded nanotags (organic thiols on a gold nanoparticle surface with different SERS signatures) was developed as a model fluorescent, label-free, bead-based multiplex immunoassay system. The developed homogeneous immunoassays included two surface-functionalized monodisperse Raman-coded microbeads of polystyrene and poly(4-tert-butylstyrene) as the immune solid supports, and two epitope modified nanotags (self-assembled 4-mercaptobenzoic acid or 3-mercaptopropionic acid on gold nanoparticles) as the SERS-coded reporters. Such multiplex Raman/SERS-based microsphere immunoassays could selectively identify specific paratope–epitope interactions from one mixture sample solution under a single laser illumination, and thus hold great promise in future suspension multiplex analysis for diverse biomedical applications.
Highlights
Nowadays, accurate diagnosis of human malignant diseases at the earliest stage is vital to curtail the side effects of surgical procedures and radio- and/or chemotherapies, subsequently followed by costly treatment
Raman-coded polymeric microbeads were used as the immune solid supports in bead-based immunoassays [45,46,47]
Dispersion polymerization was used for the synthesis of monodisperse polymer microbeads with average sizes of ~1.5 μm (Figure 2a,b) and narrow size distributions (CV < 1%), where a small amount of attained acid (AA) was introduced as the comonomer to generate functional carboxylic acid groups on the surfaces of microbeads [41]
Summary
Accurate diagnosis of human malignant diseases at the earliest stage is vital to curtail the side effects of surgical procedures and radio- and/or chemotherapies, subsequently followed by costly treatment. Infectious or immune-system-related diseases generate various antigens as the first sign of abnormality in organisms. The most representative method for analysis of such disease biomarkers is immunoassays, realized by the immune recognition between antigens and relevant specific antibodies. High sensitivity and high throughput are the desired features in developing novel multiplex immunoassays. Traditional biological detection strategies such as ELISA and fluorescence are widely used in various clinical applications, but suffer from various shortcomings, such as high background noise, high spectral overlap, low sensitivity, and photobleaching. Among these readout technologies, SERS-based immunoassays have realized significant application in multiplex analyses
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