Point-of-care nucleic acid testing with a one-step branched-DNA-based functional carbon biosensor

Nucleic acid biomarkers play important roles in early diagnosis, routine management, and prognosis of diseases. However, current nucleic acid testing (NAT) approaches either require cumbersome instruments or lack sensitivity for short detection time, making point-of-care (POC) NAT challenging. Here, we report an ultrasensitive carbon fiber paper (CFP)-based electrochemical biosensor with one-step branched DNA (bDNA)-based molecular signal amplification system for rapid, sensitive, and low-cost replication-free NAT. For nucleic acid quantification, the proposed biosensor exhibits a wide linear range of 10 aM–1 μM and a low limit of detection (LOD) of 1.4 aM. For fast semi-quantitative detection, the biosensor can evaluate the concentration of nucleic acids within 10 min with a threshold as low as 1 fM. Furthermore, the biosensor demonstrates negligible batch-to-batch variation with a relative standard deviation (RSD) of 4.25% at the cost of less than $1/device. The present one-step bDNA-based electrochemical biosensor serves as a promising and universal method for rapid, sensitive, and portable NAT.