Sensing Intra‐ and Extra‐Cellular Ca 2+ in the Islet of Langerhans

Calcium ions (Ca 2+ ) take part in intra‐ and inter‐cellular signaling to mediate cellular functions. Sensing this ubiquitous messenger is instrumental in disentangling the specific functions of cellular sub‐compartments and/or intercellular communications. In this review, the authors first describe intra‐ and inter‐cellular Ca 2+ signaling in relation to insulin secretion from the pancreatic islets, and then outline the development of diverse sensors, for example, chemically synthesized indicators, genetically encoded proteins, and ion‐selective microelectrodes, for intra‐ and extra‐cellular sensing of Ca 2+ . Particular emphasis is placed on emerging approaches in this field, such as low‐affinity Ca 2+ indicators and unique Ca 2+ ‐responsive composite materials. The authors conclude by remarking on the challenges and opportunities for further developments in this field, which may facilitate a more comprehensive understanding of Ca 2+ signaling within and outside the islets, and its relevance in health and disease.