A simple aptamer-based colorimetric assay for rapid detection of C-reactive protein using gold nanoparticles


C-reactive protein (CRP) is a clinical biomarker for inflammatory diseases. In this work, we present a simple and fast colorimetric method for CRP detection that employs citrate-capped gold nanoparticles (AuNPs) and a CRP-binding aptamer as sensing elements. The aptamer consisted in a guanine rich single-stranded DNA (ssDNA) that adsorbs onto the surface of the AuNPs. In the presence of the CRP, the ssDNA releases from the AuNPs surface to interact preferentially with the protein to form guanine-quadruplexes. The exposure of the unprotected AuNPs to buffer salts leads to aggregation and subsequent color change from red-wine to blue-purple that was readily seen by the naked eye. The AuNPs aggregation was monitored using UV-Vis spectroscopy and the CRP concentration in the samples could be correlated with the aggregation ratio (A(670nm)/A(520nm)). A linear sensing range of 0.889-20.7 mu g/mL was found. The detection limit (LOD) was 1.2 mu g/mL which is comparable to the typical clinical cutoff concentration in high-sensitivity CRP assays (1 mu g/mL) and lower than the detection limit of nephelometric methods used in clinical practice. This method can provide a fast (5 min analysis time), simple, and sensitive way for CRP detection, with negligible interference of bovine serum albumin (BSA) up to concentrations of 100 nM.



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Antonio, M; Ferreira, R; Vitorino, R; Daniel-da-Silva, AL

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This work was developed within the scope of the project IF/00405/2014/CP1222/CT007, the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, the project iBiMED (UIDB/04501/2020, POCI-01-0145-FEDER-007628) and the project LAQVREQUIMTE (UIDB/50006/2020), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. A.L.D.-d.-S. acknowledges FCT (Fundacao para a Ciencia e a Tecnologia) for the contract (IF/00405/2014). R.V. thanks the FCT for the Investigator Grant (IF/00286/2015). M.A. thanks FCT for the PhD grant SFRH/BD/13688/2018.

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