Sub-femtomolar drug monitoring via co-calibration mechanism with nanoconfined DNA probes

Synthetic drugs fundamentally reshape the illicit drug market due to their low cost, ease of production, and rapid manufacturing processes. However, current drug detection methods, which rely on complex instruments, have limited applicability and often neglect the influence of pH fluctuations, leading to potential bias and unreliable results. Herein, we propose co-calibration DNA probes on a nanoconfined biosensor (N_CB_S), covering the range of sweat pH 3-8 to achieve significantly enhanced target signal recognition. The N_CB_S exhibits a linear response range of 10³-10⁸ fM with a low limit of detection (LOD) of 3.58 fM in artificial sweat. Compared to the single-aptamer N_CB_S, the dual-aptamer N_CB_S offers a broader linear response range, primarily due to the synergistic effects of changes in surface wettability and the capture of hydrion, which together reduce signal interference in proton transport. The linear response range doubles, and its detection sensitivity improves by 4-5 orders of magnitude compared to existing drug detection methods. This sensing strategy expands the application scope of aptamer-based composite probes, offering an approach for ultra-sensitive drug detection and demonstrating significant potential in sweat sensing and drug monitoring fields.