Electrochemical immunosensor for simultaneous detection of dual cardiac markers based on a poly(dimethylsiloxane)-gold nanoparticles composite microfluidic chip: a proof of principle.

BACKGROUND The emergence of microfluidic immunosensors has provided a promising tool for improving clinical diagnoses. We developed an electrochemical immunoassay for the simultaneous detection of cardiac troponin I (cTnI) and C-reactive protein (CRP), based on microfluidic chips. METHODS The quantitative methodology was based on ELISA in poly(dimethylsiloxane)-gold nanoparticle composite microreactors. CdTe and ZnSe quantum dots were bioconjugated with antibodies for sandwich immunoassay. After the CdTe and ZnSe quantum dots were dissolved, Cd(2+) and Zn(2+) were detected by square-wave anodic stripping voltammetry to enable the quantification of the 2 biomarkers. The 2 biomarkers were measured in 20 human serum samples by using the proposed method and commercially available methods. RESULTS This immunosensor allowed simultaneous detection of serum cTnI and CRP. The linear range of this assay was between 0.01 and 50 μg/L and 0.5 and 200 μg/L, with the detection limits of approximately 5 amol and approximately 307 amol in 30-μL samples corresponding to cTnI and CRP, respectively. Slopes close to 1 and the correlation coefficient over 0.99 were obtained for both analytes. CONCLUSIONS This strategy demonstrates a proof of principle for the successful integration of microfluidics with electrochemistry that can potentially provide an alternative to protein detection in the clinical laboratory.