Real-Time Monitoring of DNA Adsorption on Silica Surfaces without Pretreatment Based on Quantum Weak Measurement

Real-time, label-free DNA sensing is essential for elucidating the mechanisms of biomolecular interactions at interfaces. In particular, monitoring DNA binding at silica surfaces is crucial for advancing biophysical research and developing diagnostic technologies. However, conventional methods are often limited by labeling interference and complex surface processing, which impede the accurate detection of DNA in its native state. We introduce a quantum weak measurement technique based on total internal reflection and develop a biosensor with an intrinsic phase sensitivity of 70.48 nm/rad. There is no need for DNA markers and prism pretreatment; this system enables real-time monitoring of DNA adsorption on silica surfaces by detecting the differential phase changes between s-polarized and p-polarized light. Real-time adsorption analysis reveals that DNA adsorption reaches equilibrium within 20 min at an initial DNA concentration of 200 μmol/L, with a measured saturation uptake of 14.92 μmol/L. Moreover, the adsorption process is effectively regulated by the Na⁺ concentration and pH value. Experimental results indicate that optimal DNA adsorption on silica surfaces occurs at a 0.1 mol/L sodium ion concentration under acidic conditions. This study not only provides insights into the development of novel optical biosensors but also offers new technical support for investigating interfacial molecular processes.