Calcein AM is a hydrophobic compound that easily permeates intact live cells. It is widely used in cell viability assays. The hydrolysis of the non-fluorescent Calcein AM by intracellular esterases generates the strongly fluorescent hydrophilic Calcein that is well-retained in the cell cytoplasm. The esterase activity is proportional to the number of vial cells, and thus directly related to the fluorescence intensity of Calcein generated from the esterase-catalyzed hydrolysis of Calcein AM. Calcein AM is one of the most popular fluorescent probes used for labeling and monitoring cellular functions of live cells. However, the single color of Calcein AM makes it impossible to use this valuable reagent in the multicolor applications. For example, it is impossible to use Calcein AM in combination of GFP-tranfacted cells due to the fact that Calcein AM has the same color as GFP.
Spectral Properties of Calcein Dyes
To address the above-mentioned color limitation of Calcein AM, we have developed
Calcein Orange™ and
Calcein Red™. These two new Calcein AM analogs enable the multicolor labeling and functional analysis of live cells in combination with Calcein AM. In addition, we have also developed
CytoCalcein™ Violet 450,
CytoCalcein™ Violet 500, CytoCalcein™ Blue 550 and CytoCalcein™ Blue 600 for flow cytometric applications. CytoCalcein™ dyes exhibit similar biological properties to Calcein, AM. They are optimized for the excitation wavelengths of a variety of flow cytometers, providing additional colors for flow cytometric analysis of live cells. CytoCalcein™ Violet 450 and CytoCalcein™ Violet 500 are well excited by violet laser (405 nm) and emit fluorescence at 450 nm and 500 nm respectively. CytoCalcein™ Blue 550 and CytoCalcein™ Blue 550 are well excited by blue laser (488 nm) and emit fluorescence at 550 nm and 600 nm respectively.
Use of Cell Viability Indicator AM Esters
AM esters are the non-polar esters that readily cross live cell membranes, and rapidly hydrolyzed by cellular esterases inside live cells. AM esters are widely used for loading a variety of polar fluorescent probes into live cell non-invasively. However, cautions must be excised when AM esters are used since they are susceptible to hydrolysis, particularly in solution. They should be reconstituted just before use in high-quality, anhydrous dimethylsulfoxide (DMSO). DMSO stock solutions may be stored desiccated at -20 °C and protected from light. Under these conditions, AM esters should be stable for several months.
Following is our recommended protocol for loading AM esters into live cells. This protocol only provides a guideline, and should be modified according to your specific needs.
Store at –20 °C, protected from light. Expiration date is 6 months from the date of receipt.