Rapid and sensitive SERS detection of the cytokine tumor necrosis factor alpha (tnf-α) in a magnetic bead pull-down assay with purified and highly Raman-active gold nanoparticle clusters
Tumor necrosis factor alpha (TNF-α) is a cytokine with significance in early diagnosis of cardiovascular diseases, obesity and insulin resistance. We demonstrate the proof of concept for a rapid and sensitive detection of TNF-α using a magnetic bead pull-down assay in combination with surface-enhanced Raman scattering (SERS). The use of purified and highly SERS-active small clusters of gold nanoparticles (AuNP) provides the high sensitivity of the assay with a limit of detection of ca. 1 pg/mL. Continuous density gradient centrifugation was employed for separating the very bright silica-encapsulated AuNP dimers and trimers from the significantly weaker AuNP monomers. Negative control experiments with other cytokines (IL-6, IL-8) and bovine serum albumin (BSA) confirm the high specificity of the assay, but indicate also space for future improvements by further reducing non-specific binding between proteins and the SERS nanotags. The multiplexing potential of this SERS-based detection scheme is exemplarily demonstrated by using a set of three spectrally distinct and highly SERS-active AuNP clusters with unique spectral barcodes.
KeywordsSilica encapsulation Gold nanoparticles Surface-enhanced Raman scattering TNF-α Multiplexing
Y.M.L. thanks the China Scholarship Council (CSC) for the financial support of her research visit at the University of Duisburg-Essen. YML also thanks the Fundamental Research Funds from the Central Universities (FRF-TP-15-012A2) for the financial support. SS and YW acknowledge financial support from the German Research Foundation (DFG, WA 3369/1-1).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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