A visual cardiovascular biomarker detection strategy based on distance as readout by the coffee-ring effect on microfluidic paper

We first reported a novel visualized instrument-free signal conversion method on paper for cardiovascular biomarker detection based on the coffee-ring effect (CRE). Our strategy was based on the principle that cTnI was captured by DNA probe decorated detection antibody to form sandwich complex, which could hybridize with H1 probes to form G-quadruplex DNAzyme. As a peroxidase mimic, G-quadruplex DNAzyme could catalyze colorimetric reaction and generate colored products, which were converted to the end edge of the paper by evaporation-driven flow, forming a visible colored band. Hence, the resulted colored signals were converted to distance signal by CRE, so that the quantification of cTnI could be measured easily only by a ruler. Our results demonstrated that the length of the colored bands was proportional to the concentration of cTnI, with a limit of detection of 1.0 pg/mL. Furthermore, this strategy not only showed advanced performance to discriminate cTnI from complex samples but also exhibited high accuracy with standard method in real sample. Hence, these results demonstrated that this method established a promising equipment-free and visualized platform for detecting various kinds of genetic diseases and biomarkers, further promoting the development of point-of-care testing (POCT) in biomedicine. • A visual Cardiovascular Biomarker detection strategy was developed. • The resulted colored signals were converted to distance signal by CRE. • This method developed equipment-free and visualized platform.