A stretchable PVA–agar hydrogel patch embedded with metal-doped carbon dots (MCD) for monitoring the Ca2+ biomarker†

Abstract

Calcium ions play a vital role in skeletal growth, muscle action and neural signalling. Thus, the level of calcium in the body is a crucial parameter in the diagnosis of muscle weakness and osteoporosis. Fluorescence conductive hydrogels are widely employed in electronic devices as they are able to monitor single or multiple parameters in synergistic optical and electrical modes. However, integrating optical and conductive modalities and synergizing their various functions to develop a wearable sensor is challenging. In this regard, a PVA–agar hydrogel (PAGH) cross-linked with copper-doped carbon dot (MCD) was fabricated. The developed MCD@PAGH addressed Ca²⁺ recognition through a change in ionic conductance and fluorescence. The hydrogel patch sensor was not cytotoxic, exhibited bactericidal activity, and monitored Ca²⁺ level in sweat in both the fluorescence and electrical modes. This work provides a strategy to design multifunctional materials to address prospective applications in wearable biosensors.