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Fluo-8H™, AM

U2OS cells were seeded overnight at 40,000 cells per 100 uL per well in a 96-well black all/clear bottom costar plate.  The growth medium was removed, and the cells were incubated with 100 uL of 4 uM Fluo-3 AM, Fluo-4 AM or Fluo-8® AM in HHBS at 37 °C for 1 hour. The cells were washed twice with 200 uL HHBS, then imaged with a fluorescence microscope using FITC channel.
U2OS cells were seeded overnight at 40,000 cells per 100 uL per well in a 96-well black all/clear bottom costar plate.  The growth medium was removed, and the cells were incubated with 100 uL of 4 uM Fluo-3 AM, Fluo-4 AM or Fluo-8® AM in HHBS at 37 °C for 1 hour. The cells were washed twice with 200 uL HHBS, then imaged with a fluorescence microscope using FITC channel.
Ordering information
Price ()
Catalog Number21090
Unit Size
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Additional ordering information
InternationalSee distributors
ShippingStandard overnight for United States, inquire for international
Physical properties
Dissociation constant (Kd, nM)232
Molecular weight1074.98
Spectral properties
Correction Factor (260 nm)1.076
Correction Factor (280 nm)0.769
Extinction coefficient (cm -1 M -1)23430
Excitation (nm)495
Emission (nm)516
Quantum yield0.161
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure
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Molecular weight
Dissociation constant (Kd, nM)
Correction Factor (260 nm)
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Quantum yield
Calcium measurements are critical for numerous biological investigations. Fluorescent probes that show spectral responses upon binding Ca2+ have enabled researchers to investigate changes in intracellular free Ca2+ concentrations by using fluorescence microscopy, flow cytometry, fluorescence spectroscopy, and fluorescence microplate readers. Fluo-3 AM and Fluo-4 AM are most commonly used among the visible light-excitable calcium indicators for live-cell calcium imaging. However, Fluo-3 AM and Fluo-4 AM are only moderately fluorescent in live cells upon esterase hydrolysis and require harsh cell loading conditions to maximize their cellular calcium responses. Fluo-8® dyes are developed to improve cell loading and calcium response while maintaining the convenient Fluo-3 and Fluo-4 spectral wavelengths of Ex/Em = ∼490/∼520 nm. Fluo-8® AM can be loaded into cells at room temperature, while Fluo-3 AM and Fluo-4 AM require 37°C for cell loading. In addition, Fluo-8® AM is two times brighter than Fluo-4 AM and four times brighter than Fluo-3 AM. AAT Bioquest offers a set of our outstanding Fluo-8® reagents with different calcium-binding affinities (Fluo-8® Kd = 389 nM; Fluo-8H™ Kd = 232 nM; Fluo-8L™ Kd = 1.86 µM; Fluo-8FF™ Kd = 10 µM). We also offer versatile packing sizes to meet your special needs (e.g., 1 mg, 10x50 µg, 20x50 µg, and HTS packages) with no additional packaging charge.


Fluorescence microscope

Recommended plateBlack wall/clear bottom

Fluorescence microplate reader

Recommended plateBlack wall/clear bottom
Instrument specification(s)Bottom read mode/Programmable liquid handling

Example protocol


Unless otherwise noted, all unused stock solutions should be divided into single-use aliquots and stored at -20 °C after preparation. Avoid repeated freeze-thaw cycles.

Fluo-8H™ AM Stock Solution
Prepare a 2 to 5 mM stock solution of Fluo-8H™ AM in high-quality, anhydrous DMSO.


Fluo-8H™ AM Working Solution
On the day of the experiment, either dissolve Fluo-8H™ AM in DMSO or thaw an aliquot of the indicator stock solution to room temperature. Prepare a dye working solution of 2 to 20 µM in a buffer of your choice (e.g., Hanks and Hepes buffer) with 0.04% Pluronic® F-127. For most cell lines, Fluo-8H™ AM at a final concentration of 4-5 μM is recommended. The exact concentration of indicators required for cell loading must be determined empirically.
Note     The nonionic detergent Pluronic® F-127 is sometimes used to increase the aqueous solubility of Fluo-8H™ AM. A variety of Pluronic® F-127 solutions can be purchased from AAT Bioquest.
Note     If your cells contain organic anion-transporters, probenecid (1-2 mM) may be added to the dye working solution (final in well concentration will be 0.5-1 mM) to reduce leakage of the de-esterified indicators. A variety of ReadiUse™ probenecid products, including water-soluble, sodium salt, and stabilized solution, can be purchased from AAT Bioquest.


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.
  1. Prepare cells in growth medium overnight.
  2. On the next day, add 1X Fluo-8H™ AM working solution into your cell plate.
    Note     If your compound(s) interfere with the serum, replace the growth medium with fresh HHBS buffer before dye-loading.
  3. Incubate the dye-loaded plate in a cell incubator at 37 °C for 30 to 60 minutes.
    Note     Incubating the dye for longer than 2 hours can improve signal intensities in certain cell lines.
  4. Replace the dye working solution with HHBS or buffer of your choice (containing an anion transporter inhibitor, such as 1 mM probenecid, if applicable) to remove any excess probes.
  5. Add the stimulant as desired and simultaneously measure fluorescence using either a fluorescence microscope equipped with a FITC filter set or a fluorescence plate reader containing a programmable liquid handling system such as an FDSS, FLIPR, or FlexStation, at 490/525 nm cutoff 515 nm. 


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Fluo-8H™, AM to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM93.025 µL465.125 µL930.25 µL4.651 mL9.302 mL
5 mM18.605 µL93.025 µL186.05 µL930.25 µL1.86 mL
10 mM9.302 µL46.512 µL93.025 µL465.125 µL930.25 µL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)Molecular weightVolume (Calculate)Concentration (Calculate)Moles


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Spectral properties

Correction Factor (260 nm)1.076
Correction Factor (280 nm)0.769
Extinction coefficient (cm -1 M -1)23430
Excitation (nm)495
Emission (nm)516
Quantum yield0.161


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