Magnetic Monitoring of Single-DNA Interaction Dynamics at Interfaces Using Diamond Quantum Sensors

Elucidating mechanisms of biomolecular interactions at interfaces is critical for understanding numerous physiological processes and optimizing various biomedical analysis technologies. However, inadequate sensitivity, stability, and specificity of existing detection techniques hinder interfacial biomolecular interaction studies, especially at the single-molecule level. Here, we introduce dynamic single-particle magnetic imaging (dSiPMI) leveraging nitrogen-vacancy centers in diamonds, enabling real-time magnetic detection of the dynamics of biomolecular interactions under physiological conditions. The dSiPMI visualized DNA hybridization occurring between functionalized surfaces of magnetic nanoparticle (MNP) and diamond, extracting characteristic kinetic parameters of single- and multiple-DNA interactions. Furthermore, capitalizing on the stable magnetic signature of MNPs and method robustness, we sustained monitoring of single-DNA hybridization events for 1 h through sequential measurements, revealing enhanced binding affinity correlated with increasing Na⁺ concentration (from 0 to 0.7 M). This study establishes a robust single-particle and single-molecule magnetic method for quantitatively analyzing the biomolecular interaction dynamics on chips and particles.