**Background**
Calcium ions ($\text{Ca}^{2+}$) play a pivotal role in various physiological processes within the human body. While the majority of calcium is sequestered in bones and teeth, small but critical concentrations are maintained in the blood and tissues to regulate cellular signaling. Intracellular calcium homeostasis is essential for numerous biological functions, including muscle contraction, neurotransmitter release, and gene expression. Dysregulation of calcium levels is often associated with various pathological conditions, making the precise monitoring of intracellular $\text{Ca}^{2+}$ a cornerstone of biomedical research. To facilitate these studies, high-sensitivity fluorescent probes are required to visualize and quantify ion fluctuations in real-time. In this context, we will introduce a high-sensitivity calcium ion detection probe – Indo-1 AM.
**Definition**
Indo-1 AM is a cell-permeant fluorescent indicator used for the specific identification and measurement of intracellular calcium ions. According to the Indo-1 AM Description, it is an acetylmethyl ester derivative designed to efficiently enter cells and bind to $\text{Ca}^{2+}$ to produce strong fluorescence.
**In Vitro Studies**
The Indo-1 AM biological activity is characterized by its ability to cross the cell membrane due to the AM ester group. Once inside the cell, intracellular esterases cleave the ester group, trapping the probe within the cytoplasm where it can bind to calcium ions. For researchers seeking detailed Indo-1 AM technical information, the probe exhibits an excitation wavelength of 364 nm and an emission wavelength of 410 nm.
In vitro applications typically follow a specific Indo-1 AM protocol. For suspension cells (density $1 \times 10^6/\text{mL}$), cells are incubated with a working solution of 1-10 $\mu\text{M}$ for 5-30 minutes at room temperature before observation via fluorescence microscopy or flow cytometry. For adherent cells, a similar incubation period of 5-30 minutes with the working solution is employed on sterile coverslips. Beyond calcium, it has been noted that at specific concentrations (usually 5 mM), this probe can also effectively identify intracellular magnesium ions. In conclusion, Indo-1 AM is a highly sensitive and low-cytotoxicity tool for the real-time monitoring of intracellular calcium and magnesium ions.
Keywords
Indo-1 AM, 112926-02-0, Indo-1 Acetoxymethyl ester, Fluorescent Dye, Inhibitor, inhibitor, inhibit
References
[1] Andrienko T, et al. Real-Time Fluorescence Measurements of ROS and [Ca2+] in Ischemic / Reperfused Rat Hearts: Detectable Increases Occur only after Mitochondrial Pore Opening and Are Attenuated by Ischemic Preconditioning. PLoS One. 2016 Dec 1;11(12):e0167300.
[2] Blatter LA, et al. Intracellular diffusion, binding, and compartmentalization of the fluorescent calcium indicators indo-1 and fura-2. Biophys J. 1990 Dec;58(6):1491-9.
[3] Andrienko T, et al. Real-Time Fluorescence Measurements of ROS and [Ca2+] in Ischemic / Reperfused Rat Hearts: Detectable Increases Occur only after Mitochondrial Pore Opening and Are Attenuated by Ischemic Preconditioning. PLoS One. 2016 Dec 1;11(12):e01