Target-responsive DNA hydrogel with microfluidic chip smart readout for quantitative point-of-care testing of...

Swift and effective diagnosis of acute myocardial infarction (AMI) is critical to patient survival due to its serious life-threatening effects and increasing incidence. Creatine kinase MB (CK-MB) is one of the markers of AMI. In this work, we enabled a portable visual quantitative assay of CK-MB by incorporating target-responsive DNA hydrogel with a microfluidic chip. The CK-MB aptamer and the complementary short DNA strand were grafted onto the polyacrylamide strand separately and formed the hydrogel by base-paired linkage. Upon introduction of CK-MB, the aptamer bound to CK-MB. This led to hydrogel dissociation and subsequent release of pre-trapped gold nanoparticles (AuNPs), which is proportional to the concentration of CK-MB. To achieve portable on-site detection, we further combined the hydrogel with a microfluidic chip and utilized the color change caused by the released AuNPs to take picture and analyze the average gray value. Then, as low as 0.027 nM CK-MB could be detected by cell phone. With good portability, visualization, and simple sample handling, this method has great potential for quantitative point-of-care testing (POCT) of targets in resource-constrained settings.