Simultaneous Single-Cell Analysis of Na⁺, K⁺, Ca²⁺, and Mg²⁺ in Neuron-Like PC-12 Cells in a Microfluidic System

Various intracellular metal ions have closely related functional roles in the nervous system. An excess or deficiency of essential metal ions can contribute to neurodegenerative diseases. Thus, the detection of various metal ions in neurons is important for diagnosing and monitoring these diseases. In particular, single-cell analysis of multiple metal ions allows us to not only understand the cellular heterogeneity and differentiation but also determine the actual relationships among multiple metal ions in each individual cell. Aiming at the low efficient single-cell manipulation and interference of complex biological matrices within cells in the existing method for single-cell metal ion detection, in this manuscript, we present a convenient, sensitive, and reliable method to simultaneously identify and quantify multiple metal ions at the single-cell level using a microfluidic system. Using the combination of on-chip electrophoresis separation and multicolor fluorescence detection, we achieved the simultaneous analysis of Na⁺, K⁺, Ca²⁺, and Mg²⁺ in single PC-12 cells and studied changes in these four metal ions in Aβ_25-35-treated PC-12 cells, which is a model of Alzheimer's disease (AD). The data showed that metal ions imbalances in neuron-like cells may be associated with AD induced by Aβ_25-35. This method paves the way for multiple metal ion detection in single neuron-like cells, and the results provide insights regarding synergistic function of multiple metal ions in regulation of neurological diseases at the single-cell level.