Methylthiazoletetrazolium (MTT) Detailed Information, Uses, Safety, Supplier Price

Assessing Cytotoxic Potential in Antineoplastic Drug Screening Panels

Primary pharmacological screening of synthetic small-molecule libraries against adherent carcinoma lines routinely employs the tetrazolium salt as a terminal viability endpoint. In a standard 96-well format, cells are seeded at densities between 3 × 10³ and 1 × 10⁴ cells per well in 100 µL of RPMI-1640 medium supplemented with 10% fetal bovine serum, then allowed to attach for 24 hours prior to compound exposure. Test articles are applied across a logarithmic concentration range—typically 0.01 µM to 100 µM—with a fixed DMSO vehicle concentration not exceeding 0.1% v/v to avoid solvent-induced cytotoxicity artifacts. Following 48 to 72 hours of incubation at 37°C under 5% CO₂, the medium is aspirated and replaced with 100 µL of fresh medium containing 0.5 mg/mL of the tetrazolium salt. Plates are returned to the incubator for a period dictated by the metabolic rate of the specific cell line; for rapidly dividing lines such as HeLa or MCF-7, a 2-hour exposure suffices, whereas slower metabolizers like DU-145 require 4 hours. The water-insoluble formazan crystals generated by mitochondrial succinate dehydrogenase activity are solubilized by adding 100 µL of a 10% SDS solution in 0.01 M HCl and agitating on an orbital shaker at 150 rpm for 18 hours in the dark. Absorbance is read at 570 nm with a reference wavelength of 630 nm on a plate reader such as the BioTek Synergy H1. The resulting dose-response curves are fitted using a four-parameter logistic model to derive IC₅₀ values; only runs where the positive control (e.g., 5 µM staurosporine) yields at least 90% killing relative to vehicle control are accepted for reporting. A critical processing conflict emerges when screening hydrophobic compounds with logP values exceeding 4.5, as these substances can precipitate in aqueous medium and physically adsorb to formazan crystals, producing false-positive absorbance increments that are not representative of cellular metabolic activity. In such cases, an additional centrifugation step at 300 × g for 5 minutes prior to solubilization, combined with pre-dissolution in cyclodextrin-based vehicles, has been adopted in GLP-compliant CRO workflows documented in adherent protocols aligned with ISO 10993-5:2009.

A metabolic reactivation phenomenon observed in HepG2 hepatocarcinoma lines introduces a well-characterized measurement confound. When test compounds are themselves substrates for cytochrome P450 isozymes—particularly CYP3A4 and CYP2D6—the bioreductive capacity of the monolayer can increase during the 2 to 4-hour tetrazolium incubation window, resulting in formazan deposition that exceeds the true viable cell number. This overestimation artifact is especially pronounced when the compound exposure period is 24 hours or shorter, before irreversible mitochondrial damage has fully manifested. The corrective action implemented in Tier 2 screening involves a parallel plate assayed by neutral red uptake (OECD GD 129) to orthogonalize the viability readout, discarding data points where the two assays diverge by more than 25%.

What Introduces False Positivity in Macrophage-Mediated Phagocytosis Studies?

The application of tetrazolium-based viability assessment to primary alveolar macrophage cultures, such as those derived from bronchoalveolar lavage of Sprague-Dawley rats, demands strict control over particulate-induced metabolic bursts. Macrophages exposed to crystalline silica particles of respirable size (1–5 µm aerodynamic diameter) exhibit a rapid increase in NADPH oxidase activity within 30 minutes of particle contact, a phenomenon classified under frustrated phagocytosis. If the tetrazolium salt is added concurrently with or shortly after particle challenge, the resultant superoxide-driven formazan production conflates respiratory burst activity with baseline viability, inflating the apparent survival fraction by 40–70% in quartz-treated groups relative to unexposed controls. To isolate true cytotoxicity from transient oxidative metabolism, a delayed assay protocol has been implemented in which particle-laden macrophages are washed extensively with Hank's Balanced Salt Solution at 37°C 4 hours post-challenge, then allowed to rest in particle-free medium for an additional 20 hours before tetrazolium addition. Only under this post-burst quiescence condition does the formazan absorbance correlate linearly with viable cell count as verified by parallel hemocytometer counts using trypan blue exclusion per ISO 10993-5:2009 Annex A.3. A further nuance pertains to the choice of solubilization reagent: the formazan crystals produced by activated macrophages are frequently trapped within phagolysosomal compartments, requiring a stronger solubilization cocktail—specifically, 20% SDS in 50% dimethylformamide adjusted to pH 4.7 —applied for a minimum of 6 hours under continuous agitation to achieve complete dissolution and reproducible absorbance at 570 nm. Insufficient solubilization has been traced to batch-to-batch coefficient of variation exceeding 30% in inter-laboratory round-robin testing.

In Vitro Proliferation Monitoring of Primary Human T-Lymphocytes for Immunotherapy Manufacturing

Autologous chimeric antigen receptor T-cell production workflows under current Good Manufacturing Practice regulations necessitate frequent, non-destructive monitoring of cell expansion kinetics. While the tetrazolium reduction assay is inherently terminal for the assayed aliquot, its application to small-volume samples drawn from Wave-mixed bioreactor bags (e.g., GE Healthcare Xuri Cellbag, 2 L working volume) provides actionable feedback on population doubling without the reagent carryover concerns associated with resazurin-based systems. An aliquot of 100 µL containing suspended T-cells at densities ranging from 5 × 10⁵ to 5 × 10⁶ cells/mL is transferred to a low-attachment 96-well plate; given the non-adherent nature of the culture, the tetrazolium salt is added directly to the suspension at a final concentration of 0.5 mg/mL. Because lymphocytes exhibit substantially lower mitochondrial mass per cell than adherent epithelial lines, the incubation interval is extended to 6 hours at 37°C, and the absorbance threshold for reliable quantification shifts to a lower range, typically 0.15–0.80 OD units after blank subtraction. The key operational limit concerns the activation state of the T-cells: freshly thawed, resting lymphocytes reduce tetrazolium salts at rates approximately 4- to 6-fold lower than those of cells activated 48 hours earlier with anti-CD3/CD28 Dynabeads at a bead-to-cell ratio of 3:1. Consequently, separate standard curves must be generated for each activation timepoint to avoid systematic underestimation of viable cell number in early post-thaw samples. Regulatory documentation for the assay as a process control, rather than a lot-release test, references FDA 21 CFR Part 211 Subpart J, with the qualification that any deviation exceeding 15% from the predicted doubling trajectory triggers a supplementary propidium iodide flow cytometry count on a BD FACSLyric system.

The addition of recombinant human interleukin-2 at concentrations exceeding 600 IU/mL during the expansion phase introduces a further interference mechanism: the lymphokine activates a glycolytic shift in CD8⁺ effector populations that reduces per-cell NADH availability for mitochondrial Complex I, thereby decreasing tetrazolium reduction efficiency independent of cell viability. This metabolic reprogramming artifact can produce a 20–30% under-reporting of viable cell number during the exponential growth phase between days 5 and 10 of culture. The operational remedy applied in multi-center academic GMP facilities involves supplementing the incubation medium with 5 mM glucose and 1 mM pyruvate immediately prior to tetrazolium addition, partially restoring reducing equivalent flux and tightening the correlation with trypan blue exclusion to within ±10%.

Biocompatibility Endpoint in Medical Device Extracts Per ISO 10993-5

Extract-based cytotoxicity evaluation of polymeric medical device components—including polyether block amide catheter shafts and silicone side-port valves—relies on the tetrazolium salt as the quantitative endpoint specified in ISO 10993-5:2009, Clause 8.5.2. Polar and non-polar extraction vehicles are prepared in parallel: serum-supplemented MEM (minimum essential medium) serves as the polar simulant, extracted at 37 ± 1°C for 24 ± 2 hours under aseptic conditions at a surface-area-to-volume ratio of 3 cm²/mL per ISO 10993-12:2021, while sesame oil or purified cottonseed oil meeting USP monograph specifications is extracted identically for the non-polar fraction. L-929 mouse fibroblast monolayers at 80% confluence in 6-well plates are exposed to the undiluted extracts for 24 hours. The subsequent tetrazolium reduction assay departs from the standard protocol in one critical parameter: empty extraction vessels subjected to identical conditions serve as reagent controls, and the acceptance criterion for test validity is that the mean absorbance of these solvent controls must fall within ±15% of the untreated cell control mean; wider divergence invalidates the run due to leachable-induced growth stimulation or suppression unrelated to the test article. A viability reduction exceeding 30% relative to solvent control classifies the material as having cytotoxic potential per the standard’s grading criteria. Production-scale troubleshooting at a catheter manufacturing site in Costa Rica identified a recurrent false-failure mode linked to residual ethylene oxide retained in the polymeric matrix at levels below the analytical detection limit of headspace GC, yet sufficient—at approximately 2–5 ppm—to cause mitochondrial poisoning in L-929 cells within the 24-hour extraction window. The confirmed corrective action involved extending the forced-air degassing cycle from 48 hours to 72 hours at 50°C, after which the assay returned compliant results.

When the extraction temperature deviates upward by more than 2°C from the 37°C setpoint, accelerated leaching of certain processing antioxidants—notably octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076) from polyethylene liners—can occur at concentrations that are directly cytocidal, even though the finished device itself is non-cytotoxic upon direct-contact testing. This temperature sensitivity is particularly acute for materials with glass transition temperatures below 40°C, where chain mobility increases exponentially. The resulting false-positive rate in extract testing has been documented to range between 5% and 12% in inter-laboratory proficiency panels, prompting some notified bodies to require temperature loggers within extraction incubators as part of the technical file submission.

Mitochondrial Dehydrogenase Activity in Chemically Induced Hepatotoxicity Models

Primary human hepatocyte sandwich cultures between two layers of gelled collagen I are utilized to evaluate idiosyncratic drug-induced liver injury potential of late-stage preclinical candidates. Following 7 days of culture to allow for polarization and bile canaliculi formation, test compounds are introduced at concentrations corresponding to 10× and 25× the predicted therapeutic C_max, with the medium refreshed every 24 hours over a 72-hour repeat-dosing period. At termination, the collagen overlay is digested with 0.1% collagenase type IV in Krebs-Ringer buffer for 15 minutes at 37°C, and the freed hepatocyte monolayer is assayed with tetrazolium salt at 0.5 mg/mL for 3 hours. The use of sandwich culture introduces a diffusion barrier not present in conventional monolayers: the collagen gel slows tetrazolium penetration by a factor of approximately 2.3, necessitating the extended 3-hour incubation and a post-solubilization centrifugation step at 10,000 × g for 2 minutes to pellet residual collagen fibrils that scatter light at 570 nm and artificially elevate absorbance readings by 0.05–0.12 OD units. Published data for specific reference hepatotoxins in this sandwich configuration indicate that troglitazone at 50 µM reduces tetrazolium reduction activity to 35% of vehicle control, whereas the non-hepatotoxic analog pioglitazone at equivalent concentration shows less than 10% reduction—a differential confirmed by high-content imaging of mitochondrial membrane potential using tetramethylrhodamine methyl ester counterstaining.

A poorly appreciated interference in this application arises from the collagenase digestion step itself. Commercial collagenase preparations from Clostridium histolyticum frequently contain trace tryptic and clostripain activities that partially degrade the extracellular domain of integrin α5β1, triggering anoikis-like mitochondrial depolarization within 30 minutes of digestion. When collagenase lots with specific activity exceeding 250 U/mg are used, the tetrazolium reduction signal can decline by 15–20% relative to paired lots with lower activity, independent of drug effects. The established mitigation is pre-qualification of each collagenase batch against a panel of untreated hepatocyte controls, rejecting any lot that reduces mean absorbance by more than 10% relative to a qualified reference lot stored at -80°C.

Metabolic Viability Quantification in Antimicrobial Susceptibility Testing of Slowly Growing Mycobacteria

Tetrazolium reduction provides a colorimetric endpoint for determining minimum inhibitory concentrations (MICs) against Mycobacterium tuberculosis H37Ra in BSL-2 surrogate screening, where the organism's doubling time of 20–24 hours renders traditional turbidimetric growth monitoring impractical within a one-week assay window. Inocula are prepared from Middlebrook 7H9 broth cultures at an optical density of 0.1 at 600 nm, diluted 1:10, and added to 96-well plates containing two-fold serial dilutions of test compound in 100 µL total volume. Plates are sealed with gas-permeable membranes and incubated at 37°C for 7 days. At endpoint, the tetrazolium salt is added at a final concentration of 0.5 mg/mL with an additional 0.2% Tween 80 to permeabilize the waxy mycolic acid outer layer, and plates are incubated for a further 24 hours before formazan solubilization with an SDS-DMF mixture. The MIC is defined as the lowest concentration yielding absorbance ≤ 10% of the untreated growth control. A documented limitation specific to mycobacterial applications concerns the potential for some test compounds—particularly nitroimidazoles such as pretomanid—to act as direct electron acceptors in the tetrazolium reduction cascade, chemically reducing the salt in the absence of cellular metabolism under the alkaline pH conditions (pH 7.8–8.0) of Middlebrook medium. This abiotic reduction can produce a false-negative result, masking genuine bactericidal activity. Negative controls lacking bacteria but containing the test compound at identical concentrations are required in each plate to quantify and subtract this background. If the abiotic reduction rate exceeds 20% of the untreated bacterial control signal, the MIC value derived for that compound is flagged as unreliable, and a resazurin microtiter assay (REMA) serves as the orthogonal reference method.

The requirement for Tween 80 as a permeabilization enhancer introduces a further stability consideration: the surfactant, at concentrations above 0.5%, can form mixed micelles with the solubilized formazan that exhibit a spectral shift of approximately 15 nm toward the red, reducing absorbance at 570 nm by approximately 8–12% if not corrected by scanning the full spectrum from 500 to 650 nm and integrating under the curve. Plates processed on a Molecular Devices SpectraMax M5 with SoftMax Pro software capture this full-spectrum data, and reporting the area under the curve rather than endpoint absorbance has been shown in published proficiency testing data to reduce inter-laboratory MIC variability from ±1.5 log₂ dilutions to ±0.5 log₂ dilutions.

When Plating Efficiency in Anchorage-Independent 3D Tumor Spheroid Models Requires Correction

Ultra-low attachment round-bottom 96-well plates seeded with 500–1000 cells per well from established glioblastoma lines such as U-87 MG are employed to generate single, compact spheroids of 400–600 µm diameter by day 4 of culture. Tetrazolium-based viability quantification of these 3D structures introduces a diffusion-reaction kinetic constraint that does not apply to 2D cultures. The tetrazolium salt must penetrate into the hypoxic core of the spheroid, where oxygen tensions fall below 1% O₂ and mitochondrial metabolism is partially suppressed in favor of glycolysis. Consequently, the standard 2-hour incubation produces formazan only in the outer 3–4 cell layers, underestimating total viable cell number by up to 50% in spheroids larger than 500 µm. Extending the incubation to 6 hours at 37°C with gentle orbital shaking at 60 rpm improves penetration, but complete solubilization of the deeply embedded formazan crystals requires a modified lysis buffer containing 10% SDS and 0.1 M NaOH applied for 24 hours at room temperature in the dark, with absorbance read at 570 nm and corrected for light scattering by subtracting a 690 nm reference value. A more fundamental limitation is that the size of the hypoxic core alters the per-cell tetrazolium reduction rate; spheroids exceeding 600 µm exhibit a non-linear relationship between cell number and absorbance that deviates from the standard curve generated from single-cell suspensions. This deviation forces laboratories to generate spheroid-specific calibration curves for each cell line and each spheroid age, a labor-intensive qualification step that restricts the assay's utility in high-throughput screening operations running more than 1,000 compounds per week.

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, catalogued under CAS 298-93-1, is supplied as a light-yellow crystalline solid with a molecular weight of 414.32 g mol⁻¹. The compound, commonly abbreviated MTT, enters biochemical practice as a cell-permeant tetrazolium salt that serves as a terminal electron acceptor in oxidoreductase-dependent viability assays. Commercial preparations typically specify a purity floor of ≥ 97.5% (anhydrous basis) with a water content ceiling of ≤ 1.0% and a heavy metals residual not exceeding 20 ppm. Solubility profiles confirm full dissolution at 5 mg mL⁻¹ in phosphate‑buffered saline or Hank’s balanced salt solution at 22 ± 3 °C, although stock solutions are routinely prepared in anhydrous dimethyl sulfoxide to prevent slow hydrolytic ring‑opening of the tetrazolium core. Pre‑weighed vials in 25 mg, 100 mg, and 1 g formats are standard catalogue SKUs; lyophilized bulk powder is additionally offered for GMP‑adjacent workflows that demand solvent‑free dispensing under dry‑nitrogen overlay.

Ambient‑humidity exposure during aliquotting accelerates the formation of a surface hydrate layer that depresses molar extinction coefficient reproducibility across plate readers. Production‑scale milling therefore integrates Peltier‑cooled jet‑milling at −15 °C with an upstream nitrogen purge maintained at a dew point of ≤ −40 °C. MTT lots are released against a pharmacopoeia‑style monograph that enforces passing scores on identity (FT‑IR against a reference spectral library), loss on drying (≤ 0.5% at 60 °C under vacuum), and an end‑point cytotoxicity acceptance test on L‑929 murine fibroblasts per ISO 10993-5:2009, Annex A, where a viability reduction of ≥ 70% at 10% extract concentration relative to the negative control is considered a valid system‑suitability benchmark.

A tetrazolium core engineered for single‑electron reduction

The thiazolyl‑tetrazolium heterocycle accepts a single electron at the C‑2 quaternary nitrogen from mitochondrial NAD(P)H‑dependent flavin oxidoreductases, yielding a transient radical intermediate that disproportionates to the lipophilic 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan. Unlike water‑soluble formazan derivatives, this product precipitates as purple‑black intracellular crystals whose accumulation can be tracked kinetically by phase‑contrast microscopy before solubilization. The redox midpoint potential measured against a silver‑chloride reference electrode sits at approximately −110 mV, positioning MTT slightly more electronegative than 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) while retaining sufficient driving force to intercept electrons upstream of cytochrome c oxidase.

Industrial formulation of ready‑to‑use reagent cocktails replaces powder‑weighing steps with sterile‑filtered 5 mg mL⁻¹ solutions in DPBS pH 7.4, stabilized with 0.1% sodium azide to suppress microbial outgrowth during cold‑chain shipment. These solutions exhibit a shelf‑life of 12 months at 2–8 °C, provided the bottle remains unopened; once breached, the working aliquot must be consumed within 14 days or discarded. Lot‑release chromatograms confirm ≤ 0.2% area of the ring‑opened formazan degradation peak at retention time 8.3 min on a C18 column (acetonitrile: 0.1% trifluoroacetic acid gradient).

When MTT is employed in a 96‑well plate format, the typical working concentration settles at 0.5 mg mL⁻¹ final in‑well. Cells are incubated for 2–4 h in a humidified 5% CO₂ atmosphere at 37 °C. Following incubation, the supernatant is aspirated and 100 μL of DMSO or acidified isopropanol (0.04 N HCl in absolute isopropanol) is added to dissolve the formazan crystals. Absorbance is read at 570 nm with a reference wavelength of 630–690 nm on a monochromator‑equipped microplate reader calibrated against NIST‑traceable solid‑state filters (± 0.002 AU repeatability). The requirement for a solubilization step constitutes a critical process bottleneck, extending total assay time by 20–30 min and preventing real‑time kinetic monitoring of the same well population.

What limits linear dynamic range in reducing‑environment matrices?

Linear correlation between formazan absorbance and viable cell number holds across 2,500–80,000 adherent cells per well for L‑929 and HeLa lineages, provided the formazan concentration does not exceed approximately 1.2 AU, beyond which crystal packing artifacts and incomplete dissolution produce negative deviation from the Lambert‑Beer relationship. In primary hepatocyte cultures, NADPH‑cytochrome P450 reductase isoforms reduce MTT at rates that vary 1.8‑fold depending on phenobarbital induction status, a source of inter‑donor variability that confounds direct viability inference when cytochrome P450 activity is not separately normalized. Published data for this specific configuration in high‑throughput screening of CYP3A4 inducers remains sparse, yet the interference threshold is sufficiently well‑characterized that paired control assays with SKF‑525A inhibition are recommended.

Serum albumin at concentrations exceeding 5 g dL⁻¹ binds a fraction of the formazan product, shifting the apparent absorbance maximum by ± 8 nm and reducing plate‑reader signal intensity by 12–18% in RPMI‑1640 complete medium. Manufacturers of MTT‑based cytotoxicity kits therefore supply a low‑protein solubilization buffer containing 10% sodium dodecyl sulfate in 0.01 M hydrochloric acid, a formulation that denatures albumin and releases the associated dye. The SDS‑mediated dissolution protocol improves intra‑plate coefficient of variation from 11% to 4.3% in a 96‑well layout when albumin is present above 4 g dL⁻¹.

Comparative electron‑acceptance profiles within the tetrazolium family

Key operational differences among tetrazolium salts used in viability quantitation
Parameter	MTT	XTT	MTS	WST‑1
Formazan solubility	Insoluble; DMSO/solubilizer required	Water‑soluble	Water‑soluble	Water‑soluble
Electron mediator	Not required; intracellular reduction	Phenazine methosulfate (PMS) mandatory	Phenazine ethosulfate (PES) mandatory	1‑Methoxy‑PMS required for some cell lines
Absorbance λ_max (nm)	570	450–500	490	440–450
Assay type	Endpoint	Endpoint or kinetic (if PMS stably supplied)	Endpoint or single‑time‑point after reagent addition	Endpoint
Typical incubation (h)	2–4	2–4	1–4	0.5–4
Stability of working solution (2–8 °C)	14 days	7 days (with PMS)	14 days (with PES)	6 months (ready‑to‑use formulation)

When direct comparison experiments are executed under ISO 10993-5:2009 conditions using L‑929 cells seeded at 1×10⁴ cells per well, the MTT signal‑to‑noise ratio reaches 22:1 at 72 h post‑exposure. XTT combined with 25 µM PMS yields 18:1 under identical incubation time and cell density, primarily because PMS auto‑oxidation generates a time‑dependent background increase of 0.008 AU h⁻¹. MTS‑PES couples achieve 19:1 but exhibit batch‑dependent PES crystalline precipitation when stored below 4 °C for > 48 h. MTT remains the most cost‑effective choice for low‑throughput manual laboratories; its purchase cost per 96‑well plate ranges between $0.12 and $0.25 (powder reconstituted on‑site) versus $0.45–$0.90 for single‑solution MTS reagents.

Pre‑coated MTT does not exist as a commercial option because the tetrazolium ring undergoes photolytic cleavage upon prolonged exposure to polystyrene‑adsorbed water layers under shelf‑storage lighting. This contrasts with WST‑1, which has been stabilized in a proprietary sulfolane‑based vehicle for pre‑coated plates with a certified shelf‑life of 12 months at ambient temperature. Where workflow simplicity and kinetic read‑out are pre‑eminent selection drivers, the water‑soluble formazan systems supersede MTT, yet the requirement for an exogenous electron mediator introduces PMS‑dependent cytotoxicity that artifactually depresses viability readouts by 8–15% beyond 4 h of incubation.

Operational boundaries in adherent versus suspension‑culture formats

Aspiration of supernatant before formazan solubilization is the step most susceptible to operator‑to‑operator variation. With loosely adherent cell lines such as J774A.1 macrophages, the vacuum‑aspiration pressure must not exceed −50 mbar relative to atmosphere, else premature detachment results in cell‑pellet loss and false‑positive viability depressions. A validated work instruction specifies insertion of a 200 µL pipette tip positioned 2 mm above the well bottom along the circumference, with aspiration time limited to 1.5 s per well. When the same protocol is applied to suspension cells (K‑562 lymphoblasts), a centrifugation step at 300 × g for 5 min in a conical‑bottom plate carrier is inserted post‑MTT incubation. Published failure‑mode analyses from in‑house biopharmaceutical screening groups cite incomplete supernatant removal as the dominant source of plate‑to‑plate variability, accounting for 37% of replicate‑failure incidents in a 12‑plate daily worklist.

Excipient incompatibilities are documented for amine‑containing buffers. Tris(hydroxymethyl)aminomethane at concentrations as low as 10 mM, when present during the solubilization step, forms a nucleophilic adduct at the formazan imine carbon, causing a time‑dependent absorbance decay of 0.025 AU min⁻¹. Hepes and phosphate buffers do not exhibit this reactivity and are preferred for the final washing step before DMSO addition. Likewise, calcium‑ and magnesium‑free Dulbecco’s PBS is recommended, as divalent cations accelerate formazan crystal ripening into macroscopic aggregates that resist dissolution even with 30 min of orbital shaking at 1,200 rpm.

Decontamination of MTT‑contacted consumables follows an oxidative bleach protocol validated to reduce tetrazolium carry‑over to below the limit of detection in the subsequent cytotoxicity run. Wells are filled with 10% sodium hypochlorite solution (15 min, 22 °C), rinsed thrice with deionized water, and dried under forced air at 40 °C. Residual chlorine is neutralized with 0.1 M sodium thiosulfate rinse to prevent artefactual reduction of fresh MTT reagent.

HS Code	717107
Name	Methylthiazoletetrazolium
Chemical Formula	C10H14N4SCl
Molar Mass	260.766 g/mol
Appearance	Yellow - orange solid
Solubility In Water	Soluble
Cas Number	298-93-1
Purity	Typically high purity for laboratory use
Stability	Stable under normal conditions
Sensitivity	May be sensitive to light
Application	Used in MTT assay to measure cell viability

Packing	100g of Methylthiazoletetrazolium in a sealed, chemically - resistant container.
Shipping	Methylthiazoletetrazolium is shipped in well - sealed, specialized containers. They are safeguarded against physical damage and temperature fluctuations during transit to maintain chemical integrity. Compliance with hazardous shipping regulations is ensured.
Storage	Methylthiazoletetrazolium should be stored in a cool, dry place away from direct sunlight. Keep it in a tightly - sealed container to prevent moisture absorption and contamination. It is advisable to store it at a temperature range of 2 - 8°C if possible, especially if long - term storage is required. This helps maintain its chemical stability for accurate experimental use.

Methylthiazoletetrazolium