logo
Products
Services
Resources
Selection Guides
About
Cal-520® Calcium Indicators
Cal-520® provides the most robust homogeneous fluorescence-based assay tool for detecting intracellular calcium mobilization. Cal-520® AM is a new fluorogenic calcium-sensitive dye with a significantly improved signal to background ratio and intracellular retention compared to the existing green calcium indicators (such as Fluo-3 AM and Fluo-4 AM). The higher signal/background ratio and better intracellular retention make the Cal-520® calcium assay a robust tool for evaluating GPCR and calcium channel targets as well as for screening their agonists and antagonists. Our preliminary in-house research indicated that Cal-520® AM can be readily loaded to a guinea pig heart and stays there for a few hours in the absence of probenecid. The calcium signal can be readily monitored with Cal-520® AM while it is difficult to observe the calcium signal under the same conditions with other green calcium dyes, such as Fluo-3 AM and Fluo-4 AM.
Key Features of Cal-520® AM:
  • Better Intracellular Retention, Cal-520® AM is better retained in live cells than Fluo-3 AM and Fluo-4 AM.
  • Higher Sensitivity, Cal-520® AM has much higher signal/background ratio than Fluo-3 AM and Fluo-4 AM in cells.
  • Convenient, Cal-520® AM has almost identical spectra to those of Fluo-4 AM.
Fig. 1
with probenecid;without probenecid
Left: ATP-stimulated calcium responses of endogenous P2Y receptor in CHO-K1 cells incubated with Cal-520™ AM (red curve, Catalog Number 21131), or Fluo-4 AM (blue curve) respectively with probenecid under the same conditions. CHO-K1 cells were seeded overnight at 50,000 cells/100 µL/well in a Costar 96-well black wall/clear bottom plate. 100 µL of 5 µM Fluo-4 AM or Cal-520™ AM in HHBS with 2.5 mm probenecid was added into the cells, and the cells were incubated at 37 °C for 2 hours. ATP (50 µL/well) was added using FlexSation® to achieve the final indicated concentrations. Right: ATP-stimulated calcium responses of endogenous P2Y receptors in CHO-K1 cells incubated with Cal-520™ AM (red curve, Catalog Number 21131), or Fluo-4 AM (blue curve) respectively, without probenecid under the same conditions. CHO-K1 cells were seeded overnight at 50,000 cells/100 µL/well in a Costar 96-well black wall/clear bottom plate. 100 µL of 5 µM Fluo-4 AM or Cal-520™ AM in HHBS was added into the cells, and the cells were incubated at 37 °C for 2 hours. ATP (50 µL/well) was added using FlexSation® to achieve the final indicated concentrations.
This document (03.0071.150501r1) was last updated on Mon Oct 13 2025. All trademarks and registered trademarks mentioned herein are the property of their respective owners.
Cal-520® Calcium Indicators
Key Features of Cal-520® AM: