Development of an immunopredictor for the evaluation of the risk of cardiovascular diseases based on the level of soluble P-selectin.

Due to its physiologic role in modulating adhesive interactions between blood cells and the endothelium during inflammatory processes or at injury sites, the adhesion molecule P-selectin is of great interest. The level of soluble P-selectin in plasma or serum can be detected and used as a clinical predictor for adverse cardiovascular events, leading to the presumption that it is secreted, shed or cleaved from the cell membrane during the process of diseases. Increased levels of soluble P-selectin in the plasma have been shown to be associated with a range of cardiovascular disorders, including coronary artery disease, hypertension and atrial fibrillation. Therefore, it is of huge significance to develop simple, rapid and sensitive methods for the detection of such pathological predictors, not only for facilitating the surveillance of cardiovascular mortality/sudden cardiac death, but also for effectively monitoring the drug potency on platelets based on measurement of P-selectin performed on fixed blood samples following platelet stimulation in whole blood in a remote setting. We herein developed a simple, yet novel and sensitive electrochemical sandwich immunosensor for the detection of P-selectin; it operates through covalent linkage of anti-P-selectin antibody on CNT@GNB nanocomposites-modified disposable screen-printed electrode as the detection platform, with the potassium ferrocyanide-encapsulated, anti-P-selectin-tagged liposomal biolabels as the electrochemical signal probes. The immunorecognition of the sample P-selectin by the liposomal biolabels occurred on the surface of the electrodes; the release of potassium ferrocyanide from the bound liposomal biolabels extensively contributed to the increase in electrochemical signal, which was acquired in HCl solution at +0.32V in square wave voltammetry mode. The resulting sigmoidally shaped dose-response curves possessed a linear dynamic working range from 1×10(-13) to 1×10(-5)g/mL. This liposome-based electrochemical immunoassay provides an amplification approach for detecting P-selectin at trace levels, leading to a detection limit as low as 4.3fg (equivalent to 5μL of 0.85pg/mL solution). A commercially available ELISA kit was used as a reference method to validate the newly-developed assay through the analysis of mouse serum samples. A strong correlation was observed between the two data sets as the R-squared value of 0.997 from the linear regression line. This electrochemical immunosensor will be useful for the detection of P-selectin in biological fluids and tissue extracts.