Label-free and highly-sensitive detection of calcium ions using a silicon-on-sapphire light-addressable potentiometric sensor

Background Ionic calcium (Ca 2+ ) plays a crucial role in maintaining normal physiological and biochemical functions within the human body. Detecting the concentration of Ca 2+ is of utmost significance for various purposes, including disease screening, cellular metabolism research, and evaluating drug effectiveness . However, current detection approaches such as fluorescence and colorimetry face limitations due to complex labeling techniques and the inability to track changes in Ca 2+ concentration. In recent years, extensive research has been conducted in this field to explore label-free and efficient approaches. Results In this study, a novel light-addressed potentiometric sensor (LAPS) using silicon-on-sapphire technology , has been successfully developed for Ca 2+ sensing. The Ca 2+ -sensitive LAPS achieved a wide-range detection of Ca 2+ , ranging from 10 −2  M to 10 −7  M, with an impressive detection limit of 100 nM. These advancements are attributed to the ultra-thin silicon layer, silicon dioxide layer, and solid-state silicon rubber sensitive membrane around 6 μm. Furthermore, the sensor demonstrated the ability to dynamically monitor fluctuations in Ca 2+ concentration ranging from 10 −9  M to 10 −2  M within a solution. Its remarkable selectivity , specificity, and long-term stability have facilitated its successful application in the detection of Ca 2+ in human serum and urine. Significance and novelty This work presents a Ca 2+ -sensitive sensor that combines a low detection limit and a wide detection range. The development represents the emergence of a label-free and rapid Ca 2+ detection tool with immense prospects in home-based health monitoring, community disease screening, as well as cellular metabolism, and drug screening evaluations.