An aptasensor based on the microscopic enumeration of encoding gold nanoparticles for the detection of C-reactive protein.

C-reactive protein (CRP) is a crucial clinical biomarker for inflammatory and cardiovascular diseases. Therefore, the sensitive, selective and convenient detection of CRP is of great significance. Using gold nanoparticles (AuNPs) and combining the specific interaction between an aptamer and CRP, we developed a simple and convenient assay for CRP detection. The aptamer-based probe was fabricated through the hybridization of CRP-aptamer immobilized on magnetic beads (MBs) to a short complementary DNA (cDNA) chain attached to AuNPs to form a MB-Aptamer-AuNP sandwich structure. Upon the addition of CRP, aptamer-cDNA dehybridization occurred due to the strong interaction between CRP and the aptamer, resulting in the release of AuNPs, which were subjected to DFM imaging and subsequently counted using the MATLAB program. The number of AuNPs was therefore positively correlated to the concentration of CRP and a detection limit as low as 2.71 nM was achieved. The current approach could also exclude the disturbance of other proteins, including thrombin, IgG, Lys and BSA. In addition, the concentration of CRP detected was in good agreement with the amount cast in bovine and mouse serum, indicating that the proposed probe is robust and accurate, and it is very promising for practical applications where CRP detection is necessary. The current strategy is also promising for the detection of other proteins where a suitable aptamer is selected.