Buffer-free integrative nanofluidic device for real-time continuous flow bioassays by ion concentration polarization.

To perform precision medicine in real-time, a sensor capable of continuously monitoring target biomolecules secreted from a patient under dynamic situations is essential. In this study, a novel portable device combining an aptamer probe and a nanofluidic component was developed, enabling the buffer-free continuous monitoring of small molecules in biological fluids. This integration is synergistic: the aptamer sensor is used to bind target biomolecules, triggering a fluorescence signal change, while the nanofluidic component is applied to achieve ion concentration polarization and convert serum into a clean buffer for aptamer signal regeneration. To demonstrate the system's versatility, we measured various adenosine triphosphate concentrations in human serum for hours with high sensitivity and specificity at minute temporal resolution. Our results demonstrate that this integrative device can be applied for the continuous measurement of target biomolecules and online signal regeneration in patient samples without the use of bulky clean buffer solutions for dynamic real-time healthcare.