Cryogenically Induced Highly Ordered Single-Strand DNA-Modified Magnetic Nanoprobes for Rapid and Ultrasensitive Bioanalysis

The development of highly sensitive detection methods for bioanalysis is crucial for early disease diagnosis. Electrochemical biosensing technology offers unique advantages in this area due to its rapid response, high sensitivity, and low cost. However, achieving efficient and rapid transfer of signaling molecules to the electrode interface to facilitate effective interaction between signal molecules and the sensing surface remains a critical challenge for ultrasensitive electrochemical detection. In this study, we discovered that single-stranded DNA-modified magnetic nanoprobes (signal probe A) subjected to cryogenic treatment can rapidly form an orderly monolayer at the electrode interface under an external magnetic field, while this phenomenon was not observed with double-stranded DNA-modified magnetic nanoprobes (signal probe B). Building on this finding, we developed a signal probe with a protective complementary strand (signal probe B) that, upon interaction with target molecules, is converted into signal probe A. This transformation, combined with cryogenic treatment, enables the ultrasensitive detection of target molecules. Using miRNA-21 and a carcinoembryonic antigen (CEA) as model targets, we optimized the detection conditions, achieving a detection limit as low as 3.4 aM for miRNA-21 and 0.28 fg/mL for CEA with excellent versatility. In summary, this study introduces a highly efficient, rapid, enzyme-free, and environmentally friendly electrochemical signal amplification strategy. This approach not only provides an innovative solution for the ultrasensitive bioanalysis but also offers new insights into enhancing signal molecule-sensor interface interactions in electrochemical biosensors.