Dental caries caused by oral microbiome dysbiosis with the elevation of acidogenic bacteria is the most prevalent non-communicable disease worldwide. Early prevention and timely fluoride treatment are crucial for caries lesion management. Herein, to address the challenges of in situ sensing and topical drug delivery within the oral cavity, a miniaturized, battery-free, and wearable dental patch system was developed for microenvironment monitoring and controlled fluoride treatment. With the integration of near-field communication, the dental patch realizes wireless energy harvesting and data transmission with mobile terminals like smartphones when attached conformally to the tooth surface. The acidic microenvironment caused by bacterial metabolism are electrochemically detected, while fluorides can be delivered locally from the electric-responsive drug delivery electrode for on-demand treatment. As flexible electronics armed to the teeth, this intraoral theranostic wearable system provides an inspiring platform for point-of-care monitoring and treatment of dental caries and oral diseases.

Cortisol is commonly used as a significant biomarker of psychological or physical stress. With the accelerated pace of life, non-invasive cortisol detection at the point of care (POC) is in high demand for personal health monitoring. In this paper, an ultrasensitive immunosensor using gold nanoparticles/molybdenum disulfide/gold nanoparticles (AuNPs/MoS₂/AuNPs) as transducer was explored for non-invasive salivary cortisol monitoring at POC with the miniaturized differential pulse voltammetry (DPV) system based on a smartphone. Covalent binding of cortisol antibody (CORT-Ab) onto the AuNPs/MoS₂/AuNPs transducer was achieved through the self-assembled monolayer of specially designed polyethylene glycol (PEG, SH-PEG-COOH). Non-specific binding was avoided by passivating the surface with ethanolamine. The miniaturized portable DPV system was utilized for human salivary cortisol detection. A series current response of different cortisol concentrations decreased and exhibited a linear range of 0.5–200 nM, the detection limit of 0.11 nM, and high sensitivity of 30 μA M⁻¹ with a regression coefficient of 0.9947. Cortisol was also distinguished successfully from the other substances in saliva. The recovery ratio of spiked human salivary cortisol and the variation of salivary cortisol level during one day indicated the practicability of the immunosensor based on the portable system. The results demonstrated the excellent performance of the smartphone-based immunosensor system and its great potential application for non-invasive human salivary cortisol detection at POC.