Competitive Aptasensor for Ultrasensitive Multiplexed Detection of Cancer Biomarkers by Fluorescent Nanoparticle Counting
Cancer biomarker quantifications in human serum are of great importance for accurate patient diagnosis and informed clinical management. To this end, ultrasensitive multiplexed detection of the proteins without amplification is still a major challenge. Herein, we proposed a competitive aptasensor strategy for ultrasensitive multiplex cancer biomarker detection by fluorescent nanoparticle (FNP) counting. The sequences are designed such that the binding abilities of linker DNA (L-DNA) with DNA-functionalized FNP (DNA-FNP) and aptamer are comparable. As long as one target binds with one molecule of aptamer, a signaling FNP will form sandwich-structured nanocomposite, and subsequently observed and enumerated with the fluorescence microscope. This 1:1 target-to-signal FNP production assured an improved sensitivity, benefiting from the reasonably good brightness and photostability of FNPs. For both singleplexed and multiplexed detection, this proposed strategy achieved approximately 1000-fold improved limit of detection than the conventional with the 3.2 μL detection volume. Notably, results for carcinoembryonic antigen (CEA) detection directly from 9 human serum samples (colorectal/lung/healthy individuals) were consistent with that by ELISA, showing promising potential application in clinical diagnosis.