Programmable DNA nanotube-based dual-mode electrochemical and fluorescence biosensor for real-time evaluation of...

Monitoring therapeutic response is essential for improving the precision and efficacy of photodynamic therapy (PDT), yet quantitative and real-time evaluation remain challenging. Herein, we report a programmable DNA nanotube-based dual-mode biosensing platform for monitoring PDT-induced apoptosis through complementary fluorescence and electrochemical signals. In this system, methylene blue (MB) functions as a multifunctional component, simultaneously acting as a photosensitizer, near-infrared imaging probe, and electrochemical reporter. A caspase-3-responsive peptide is integrated into the DNA nanotube scaffold, enabling apoptosis-triggered fluorescence activation. Caspase-3 activation triggers peptide cleavage, resulting in fluorescence recovery and enhanced electrochemical signals, with limits of detection (LOD) of 0.786 ng/mL for the fluorescence method and 0.622 ng/mL for square-wave voltammetry (SWV). Gold nanoparticles incorporated into the DNA nanotube further catalyze endogenous H₂O₂ decomposition to generate oxygen, alleviating tumor hypoxia and enhancing PDT efficacy. The platform demonstrated accurate dual-mode detection capability in complex biological samples. These results demonstrate that the programmable DNA nanotube-based platform enables synchronized electrochemical and fluorescence biosensing through a shared caspase-3-responsive mechanism, thereby allowing real-time therapeutic feedback during photodynamic therapy.