Shop All Cellular Sensors & Indicators

Premo™ Halide Sensor (Invitrogen™)

The Premo™ Halide Sensor is based on a yellow fluorescent protein (YFP) molecule sensitive to halide ions. The combination of the YFP (Venus) biosensor with efficient and non-cytopathic BacMam delivery and expression gives researchers a highly sensitive, robust and easy-to-use tool to efficiently screen halide ion channels and transporter modulators in their cellular models of choice. No specialized instruments are needed, as the sensor works on standard HTS platforms. - Cl– channel–specific—measure halide ion flux in voltage- and ligand-gated chloride channels and transporters - Fast—measure chloride flux in high-throughput mode with highly reproducible results - Robust—reliably high expression of the bright and fast maturating Venus sensor gives an excellent signal window - Convenient—study chloride flux in your cellular model by efficient and non-cytopathic delivery of Premo™ Halide Sensor by BacMam technology - Pharmacologically relevant—known modulators show dose-dependent quenching and BacMam delivery enables assays in primary cells The assay combines the YFP Venus halide sensor with a surrogate ion for chloride (iodide); upon stimulation of the chloride channel or transporter, iodide ions flow down the concentration gradient into the cells and quench YFP fluorescence upon binding; the amount of quench is directly proportional to the ion flux (chloride channel or transporter activity). Due to the bright Venus fluorescence, the Premo™ Halide Sensor signal window is excellent. We have demonstrated the utility and efficiency of the Premo™ Halide Sensor as a robust and true “no wash" HTS chloride assay. Premo™ Halide Sensor is pre-packaged and ready for immediate use. It contains all components required for cellular delivery and expression. Screening can be conducted in complete medium and without any wash steps. To uncouple cell maintenance and preparation from screening, simply freeze transduced cells and bring out as little as 4 h before the screen. Both stable cell lines and human primary cells can be prepared frozen and “assay-ready".

RedoxSensor™ Red CC-1 - Special Packaging (Invitrogen™)

RedoxSensor Red CC-1 is a unique probe whose fluorescence localization appears to be based on a cell's cytosolic redox potential. Upon passively entering live cells, the stain is either oxidized in the cytosol to a red-fluorescent product (excitation/emission maxima ~540/600 nm), which then accumulates in mitochondria, or the probe is transported to lysosomes, where it is subsequently oxidized. The differential distribution of the oxidized product appears to depend on the redox potential of the cytosol.

SPQ (6-Methoxy-N-(3-Sulfopropyl)Quinolinium, Inner Salt) (Invitrogen™)

The chloride indicator SPQ has absorption/emission maxima ~344/443 and detects Cl- via diffusion-limited collisional quenching.

Fluo-4 NW Calcium Assay Kit (Invitrogen™)

Fluo-4 NW (No-Wash) Calcium Assay Kitsoffer a proprietary calcium assay formulation that requires neither a washstep nor a quencher dye. The fluo-4 NW assay achieves largerincreases in fluorescence intensity than standard fluo-3 and fluo-4assays with a wash step. Eliminating the wash step results inlower variability and higher Z´ values than the standard fluo-4 assay,while providing an easier and faster assay as well.

The fluo-4NW indicator is nonfluorescent and stable in pH 7–7.5 buffer forseveral hours, so spontaneous conversion to the Ca2+-sensitive formis not a significant source of background fluorescence. Contributionsto baseline fluorescence by the growth medium (e.g., esteraseactivity, proteins interacting with receptors of interest, or phenolred) are eliminated by removing the medium prior to adding theindicator dye to the wells.

Another source of potential fluorescenceoutside the cells is extrusion of the indicator out of the cell by organicanion transporters. Probenecid is commonly used to inhibitthis transport and reduce the baseline signal. We have synthesizeda proprietary water-soluble probenecid, which is supplied with theFluo-4 NW Calcium Assay Kits. This form of probenecid has theadvantages of being easy to dissolve in buffer and safer to use thanthe free acid, which requires caustic 1 M NaOH to dissolve. TheFluo-4 NW Calcium Assay Kits are designed for microplates andHTS, and the assay can be performed on adherent as well as nonadherentcells.

Fluo-4 AM is a fluorescent Ca+2 indicator that is widely usedfor in-cell measurement of agonist-stimulated and antagonist inhibitedcalcium signaling in high-throughput screening (HTS)applications. Its visible wavelength excitation (compatible withargon-ion laser sources), high sensitivity, and large fluorescenceincrease upon binding Ca2+ has made it the indicator of choicefor characterizing G-protein–coupled receptor (GPCR) pharmacologyand function. These properties have made fluo-4 AMattractive not only for microplate screening applications but formicroscopy and flow cytometry as well.

PBFI, Tetraammonium Salt, cell impermeant (Invitrogen™)

PBFI is a potassium-sensitive molecule used measure intracellular K+ fluxes in animal cells and in plant cells and vacuoles. Although the selectivity of PBFI for K+ is less than that of calcium indicators such as fura-2, it is sufficient for the detection of physiological concentrations of K+ in the presence of other monovalent cations. The spectral response of PBFI upon ion binding permit excitation ratio measurements, and this indicator can be used with the same optical filters and equipment used for fura-2.

Fluorescent Ion Indicators Specifications:
• Label (Ex/Em): PBFI (~340,380/500 nm)
• Lyophilized product may be dissolved in distilled water or aqueous buffer for use
• Product is typically loaded into cells by diffusion from a patch pipette for correlated fluorescence imaging and electrophysiological recording


Selectivity Considerations and Cell Loading Strategies
The Kd of PBFI for K+ is strongly dependent on whether Na+ is present, with a value of 5.1 mM in the absence of Na+ and 44 mM in solutions with a combined Na+ and K+ concentration of 135 mM (which approximates physiological ionic strength). In buffers in which the Na+ is replaced by tetramethylammonium chloride, the Kd of PBFI for K+ is 11 mM; choline chloride and N-methylglucamine are two other possible replacements for Na+ in the medium. Although PBFI is only 1.5-fold more selective for K+ than for Na+, this selectivity is often sufficient because intracellular K+ concentrations are normally about 10 times higher than Na+ concentrations.

PBFI is available as both cell-impermeant acid salt (P1265MP) and as cell-permeant acetoxymethyl (AM) esters (P1267MP). The anionic acid forms can be loaded into cells using our Influx™ pinocytic cell-loading reagent (I14402, Chelators, Calibration Buffers, Ionophores and Cell-Loading Reagents—Section 19.8), or by microinjection, patch-pipette infusion or electroporation. For AM ester loading (Loading and Calibration of Intracellular Ion Indicators—Note 19.1), addition of the Pluronic® F-127 (P3000MP, P6866, P6867) or PowerLoad™ (P10020) dispersing agents as well as relatively long incubation times—up to four hours—are typically necessary.

Find Fluorescent Indicators for Na+ and K+
We offer a number of fluorescent indicators for measuring Na+ and K+. Review Fluorescent Na+ and K+ Indicators—Section 21.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.

APF (Hydroxyl Radical, Hypochlorite or Peroxynitrite Sensor) (Invitrogen™)

Aminophenyl fluorescein (APF) and hydroxyphenyl fluorescein (HPF, H36004), two reactive oxygen species (ROS) indicators developed by T. Nagano, offer greater specificity and stability than dichlorodihydrofluorescein diacetate (H2DCFDA, D399). APF and HPF show limited non-selective reactivity and relatively high resistance to light-induced oxidation. Both of these new fluorescein derivatives are nonfluorescent until they react with the hydroxyl radical or peroxynitrite anion; APF will also react with the hypochlorite anion. Together, these two ROS indicators can selectively detect hypochlorite anion. Upon oxidation, both APF and HPF exhibit bright green fluorescence (excitation/ emission maxima ~490/515 nm), making them compatible with any instrument that can detect fluorescein.

Rhod-5N, Tripotassium Salt, cell impermeant (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. They have uses in many calcium signaling investigations, including measuring Ca2+ in cells and tissues that have high levels of autofluorescence and also for detecting Ca2+ release generated by photoreceptors and photoactivatable chelators. Cells may be physically loaded with the cell-impermeant salt forms of these indicators using patch pipette, microinjection, or our Influx™ pinocytotic cell-loading reagent. The fluorescence signal from these cells is generally measured using fluorescence microscopy.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Rhod-5N (551/576 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in the absence of Mg2+, in buffer: ~320 µM
• Exhibit fluorescence increase upon binding Ca2+ with little shift in wavelength


Using TPEN to Control Heavy Metal Cations
In addition, BAPTA-based indicators such as these bind various heavy metal cations (e.g., Mn2+, Zn2+, Pb2+) with substantially higher affinity than Ca2+. Perturbations to calcium measurements caused by presence of these ions can be controlled using the heavy metal-selective chelator TPEN.

More Choices for Fluorescent Calcium Indicators
We offer a large selection of Molecular Probes® calcium indicators for use in various experimental scenarios. For more information, review Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3 in the Molecular Probes® Handbook.

For UV-excitable Ca2+ indicators, protein-based Ca2+ indicators, conjugates of Ca2+ indicators, and for fluorescence-based indicators of other metal ions (i.e., Mg2+, Zn2+) review Indicators for Ca2+, Mg2+, Zn2+ and Other Metal Ions—Chapter 19 in the Molecular Probes® Handbook.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

PBFI, AM, cell permeant - Special Packaging (Invitrogen™)

PBFI is a potassium-sensitive molecule used measure intracellular K+ fluxes in animal cells and in plant cells and vacuoles. Although the selectivity of PBFI for K+ is less than that of calcium indicators such as fura-2, it is sufficient for the detection of physiological concentrations of K+ in the presence of other monovalent cations. The spectral response of PBFI upon ion binding permit excitation ratio measurements, and this indicator can be used with the same optical filters and equipment used for fura-2.

Fluorescent Ion Indicators Specifications:
• Label (Ex/Em): PBFI (~340,380/500 nm)
• Lyophilized product may be dissolved in DMSO for use
• Product is typically loaded into cells by adding the dissolved indicator to medium containing cells


Selectivity Considerations and Cell Loading Strategies
The Kd of PBFI for K+ is strongly dependent on whether Na+ is present, with a value of 5.1 mM in the absence of Na+ and 44 mM in solutions with a combined Na+ and K+ concentration of 135 mM (which approximates physiological ionic strength). In buffers in which the Na+ is replaced by tetramethylammonium chloride, the Kd of PBFI for K+ is 11 mM; choline chloride and N-methylglucamine are two other possible replacements for Na+ in the medium. Although PBFI is only 1.5-fold more selective for K+ than for Na+, this selectivity is often sufficient because intracellular K+ concentrations are normally about 10 times higher than Na+ concentrations.

PBFI is available as both cell-impermeant acid salt (P1265MP) and as cell-permeant acetoxymethyl (AM) esters (P1267MP). The anionic acid forms can be loaded into cells using our Influx™ pinocytic cell-loading reagent (I14402, Chelators, Calibration Buffers, Ionophores and Cell-Loading Reagents—Section 19.8), or by microinjection, patch-pipette infusion or electroporation. For AM ester loading (Loading and Calibration of Intracellular Ion Indicators—Note 19.1), addition of the Pluronic® F-127 (P3000MP, P6866, P6867) or PowerLoad™ (P10020) dispersing agents as well as relatively long incubation times—up to four hours—are typically necessary.

Find Fluorescent Indicators for Na+ and K+
We offer a number of fluorescent indicators for measuring Na+ and K+. Review Fluorescent Na+ and K+ Indicators—Section 21.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.

Calcium Green™-1 dextran, Potassium Salt, 10,000 MW, Anionic (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. They have uses in many calcium signaling investigations, including measuring intracellular Ca2+, following Ca2+ influx and release, and multiphoton excitation imaging of Ca2+ in living tissues. Cells may be physically loaded with the cell-impermeant salt forms of these dextran-conjugated indicators using patch pipette, microinjection, or our Influx pinocyte-loading reagent. The fluorescence signal from these cells is measured using fluorescence microscopy. The dextran forms of our calcium indicators show a dramatic reduction in both leakage and compartmentalization compared to the AM ester forms.

Calcium Indicator (Cell-Impermeant Salts, Dextran Conjugates) Specifications:
• Label (Ex/Em): Calcium Green™ -1 (506/531 nm)
• Fluorescence intensity increase upon binding Ca2+: ~14 fold
• Dextran size: 10,000 MW
• Exhibit fluorescence increase upon binding Ca2+ with little shift in wavelength


Spectral Characteristics of Molecular Probes® Calcium Indicators
These probes are excited by visible light, and because the energy required for excitation is low, the potential for cellular photodamage is reduced. Commonly used laser-based instruments (i.e., confocal laser scanning microscopes) are able to efficiently excite these indicators, and their emissions are in regions of the spectrum where cellular autofluorescence and scattering backgrounds are often less of a problem.

More Choices for Fluorescent Calcium Indicators
We offer a large selection of Molecular Probes® calcium indicators for use in various experimental scenarios, for example dextran versions for reduced leakage and compartmentalization and BAPTA conjugates for detecting high-amplitude calcium transients. For more information, review Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3 in the Molecular Probes® Handbook.

For UV-excitable Ca2+ indicators, protein-based Ca2+ indicators, conjugates of Ca2+ indicators, and for fluorescence-based indicators of other metal ions (i.e., Mg2+, Zn2+) review Indicators for Ca2+, Mg2+, Zn2+ and Other Metal Ions—Chapter 19 in the Molecular Probes® Handbook.

For Research Use Only. Not intended for animal or human therapeutic or diagnostic use.

Rhod-2, Tripotassium Salt, cell impermeant (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. They have uses in many calcium signaling investigations, including measuring Ca2+ in cells and tissues that have high levels of autofluorescence and also for detecting Ca2+ release generated by photoreceptors and photoactivatable chelators. Cells may be physically loaded with the cell-impermeant salt forms of these indicators using patch pipette, microinjection, or our Influx™ pinocytotic cell-loading reagent. The fluorescence signal from these cells is generally measured using fluorescence microscopy.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Rhod-2 (552/581 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in the absence of Mg2+, in buffer: ~570 nM
• Exhibit fluorescence increase upon binding Ca2+ with little shift in wavelength


Using TPEN to Control Heavy Metal Cations
In addition, BAPTA-based indicators such as these bind various heavy metal cations (e.g., Mn2+, Zn2+, Pb2+) with substantially higher affinity than Ca2+. Perturbations to calcium measurements caused by presence of these ions can be controlled using the heavy metal-selective chelator TPEN.

More Choices for Fluorescent Calcium Indicators
We offer a large selection of Molecular Probes® calcium indicators for use in various experimental scenarios. For more information, review Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3 in the Molecular Probes® Handbook.

For UV-excitable Ca2+ indicators, protein-based Ca2+ indicators, conjugates of Ca2+ indicators, and for fluorescence-based indicators of other metal ions (i.e., Mg2+, Zn2+) review Indicators for Ca2+, Mg2+, Zn2+ and Other Metal Ions—Chapter 19 in the Molecular Probes® Handbook.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Fluo-4, Pentapotassium Salt, cell impermeant (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. Fluo-3 has been used to image the spatial dynamics of Ca2+ signaling, in flow cytometry experiments involving photoactivation of caged chelators, second messengers, and neurotransmitters, and for cell-based pharmacological screening. Fluo-4 is an analog of fluo-3 with the two chlorine substituents replaced by fluorines, which results in increased fluorescence excitation at 488 nm and consequently higher fluorescence signal levels. Cells may be physically loaded with the cell-impermeant salt forms of these indicators using patch pipette, microinjection, or our Influx™ pinocytotic cell-loading reagent. These indicators are useful for fluorescence and confocal microscopy, flow cytometry, and microplate screening applications.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Fluo-4 (494/516 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in buffer: ~335 nM
• Exhibit fluorescence increase upon binding Ca2+ with little shift in wavelength


Using TPEN to Control Heavy Metal Cations
In addition, BAPTA-based indicators such as these bind various heavy metal cations (e.g., Mn2+, Zn2+, Pb2+) with substantially higher affinity than Ca2+. Perturbations to calcium measurements caused by presence of these ions can be controlled using the heavy metal-selective chelator TPEN.

More Choices for Fluorescent Calcium Indicators
We offer a large selection of Molecular Probes® calcium indicators for use in various experimental scenarios. For more information, review Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3 in the Molecular Probes® Handbook.

For UV-excitable Ca2+ indicators, protein-based Ca2+ indicators, conjugates of Ca2+ indicators, and for fluorescence-based indicators of other metal ions (i.e., Mg2+, Zn2+) review Indicators for Ca2+, Mg2+, Zn2+ and Other Metal Ions—Chapter 19 in the Molecular Probes® Handbook.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Oregon Green™ 488 BAPTA-2, Octapotassium Salt, cell impermeant (Invitrogen™)

The cell-impermeant visible light—excitable, high affinity Ca2+ indicator, Oregon Green® 488 BAPTA-2, octapotassium salt has a Kd for Ca2+ ~580 nM in the absence of Mg2+ and absorption/emission maxima ~494/523 nm.

A-23187 Free Acid (Calcimycin) (Invitrogen™)

The Ca2+ ionophore A-23187 is commonly used for in situ calibrations of fluorescent Ca2+ indicators, to equilibrate intracellular and extracellular Ca2+ concentrations and to permit Mn2+ to enter the cell to quench intracellular dye fluorescence. Although the intrinsic fluorescence of A-23197 is too high for use with UV-excitable calcium indicators like fura-2, indo-1 and quin-2 it is suitable for use with the visible light-excitable indicators, including fluo-4, fluo-3, Calcium Green and rhod-2. A-23187 can also be used to equilibrate extracelular and intrcellular Mg2+ concentrations, making it useful for calibrating Mg2+ indicators.

MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) (Invitrogen™)

MTT is used to assess cell viability as a function of redox potential. Actively respiring cells convert the water-soluble MTT to an insoluble purple formazan. The formazan is then solubilized and its concentration determined by optical density.

Premo™ Cellular Redox Sensor (Invitrogen™)

Premo™ Cellular Redox Sensor is a genetically encoded sensor that is transduced/transfected into cells, enabling dynamic measurement of glutathione redox potential or oxidative stress in live cells. This detection system responds to stimuli quickly and is reversible, and can be readily combined with other dyes for multiplexed measurement of other relevant markers. Premo™ Cellular Redox Sensor can be used as an alternative method of detecting redox potential or oxidative stress, in concert with organic-based fluorescent dyes such as CellROX®, 2',7'-dichlorodihydrofluorescein diacetate (H2-DCFDA), or ThiolTrackers™ dyes. With the incorporated BacMam technology, this sensor is ready to use—simply add to cells in growth media and incubate overnight.

The roGFP-Grx1 Chimera
Premo™ Cellular Redox Sensor combines the selectivity of a roGFP-Grx1 chimera with the transduction efficiency of BacMam 2.0 technology. Redox-senstive green fluorescent protein (roGFP) detects reactive oxygen through two cysteines introduced into the β-barrel structure of the GFP protein. Dilsulfide formation between the cysteines leads to protonation of GFP and increases the 400 nm excitation spectra at the expense of the 488 nm excitation spectra. The fluorescence at the two different excitation wavelengths can be quantitated using the same emission wavelength of 515 nm. roGFP responds to levels of GSH/GSSG through electron exchange with glutaredoxin (GRX1). The availability of GRX1 to this dynamic reaction is ensured through the linking of GRX1 to roGFP, enabling roGFP to respond faster to stimulus and be more sensitive to GSH/GSSG with reversible functionality.

BacMam Technology
The incorporated BacMam technology is based on the use of an insect cell virus (baculovirus) to efficiently deliver and express genes in mammalian cells. Because mammalian cells do not support replication of baculoviruses, transduction is extremely well tolerated and generally lacking in cytopathic effects, even at high virus levels. Learn more about BacMam technology.