Cascade Amplification Powers a High-sensitivity Electrochemical Biosensor for Accurate Cordyceps Sinensis Identification

The internal transcribed spacer (ITS) sequence has become a key molecular marker for the identification of valuable Chinese medicinal herbs. In this study, a specific DNA sequence (TDNA) was designed to selectively recognize and bind to the ITS region of Cordyceps sinensis. The interaction between TDNA-modified gold nanorods (Au NRs) and the acetaminophen substrate generated a catalytic current signal. The capture DNA probe (CapDNA), amplified by polymerase chain reaction (PCR) and functionalized with amino groups (–NH2), was covalently immobilized onto the organic-modified carbon (OMC) electrode surface through an amide-bonding reaction with carboxyl groups (–COOH). Electrochemical measurements demonstrated that the proposed method exhibited a wide linear range (0.005–27 ng·μL-1), high sensitivity (1.96 μA·ng·μL-1), and a low limit of detection (LOD) of 0.01 ng·μL-1. This sensor was therefore suitable for the identification of Cordyceps sinensis. Moreover, practical application results showed that the sensor could successfully distinguish Cordyceps sinensis from five counterfeit products at the DNA level, highlighting its strong potential for reliable herbal medicine authentication.