| Size | Price | Stock | Qty |
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| 5mg |
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| Other Sizes |
| Targets |
X-34 primarily targets amyloid fibrils, specifically binding to the cross-beta-sheet conformation characteristic of pathological protein aggregates in Alzheimer‘s disease (AD). The compound binds to amyloid-beta (Abeta) plaques and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein. X-34 binds at a distinct site compared to other amyloid-binding dyes such as Pittsburgh Compound B (PiB), binding specifically to the fibrillar structures rather than to prefibrillar oligomeric species. The binding interaction is non-covalent and relies on pi-pi stacking interactions and hydrogen bonding between the stilbene core of X-34 and the beta-sheet groove of amyloid fibrils. Upon binding, the fluorescence quantum yield of X-34 increases significantly due to the restricted rotation in the rigid environment of the fibril structure. This binding results in bright yellow-green fluorescence (excitation ~460 nm, emission ~520 nm), allowing for highly sensitive and specific histological staining and in vivo imaging. The binding affinity (Kd) for Abeta42 fibrils is reported to be in the nanomolar range.
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| ln Vitro |
X-34 exhibits potent in vitro binding activity to synthetic amyloid-beta (Abeta) fibrils. Using a standard fluorescence-based binding assay with pre-formed Abeta42 fibrils, X-34 demonstrates an apparent dissociation constant (Kd) in the low nanomolar range. The fluorescent signal intensity increases proportionally with increasing fibril concentration, making the compound a valuable quantitative tool. In competition binding studies, X-34 effectively competes with both Thioflavin T and Congo red for binding to Abeta fibrils, confirming its specificity for the cross-beta-sheet conformation of amyloid. Moreover, X-34 shows higher binding affinity for amyloid plaques compared to diffuse plaques, indicating preferential binding to dense, mature fibrils. The compound also binds efficiently to tau-derived filaments isolated from postmortem Alzheimer‘s disease brain tissue, showing comparable fluorescence intensity as with Abeta fibrils. The addition of lipophilic compounds such as lipids does not significantly interfere with the dye's binding affinity, maintaining robust signal detection under various in vitro conditions.
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| ln Vivo |
In vivo activity of X-34 has been demonstrated in transgenic mouse models of Alzheimer‘s disease, particularly in APP/PS1 double transgenic mice. After systemic administration, X-34 crosses the blood-brain barrier and binds to amyloid-beta plaques in the brain, producing bright fluorescence that can be detected by in vivo imaging techniques. In these models, a single intravenous administration of X-34 (5 mg/kg) results in rapid brain uptake within 30 minutes and selective retention in plaque-rich regions. Ex vivo fluorescence imaging of brain slices following X-34 injection confirms robust staining of both neuritic and diffuse plaques, as well as cerebrovascular amyloid deposits and neurofibrillary tangles. The compound's fast clearance from non-target tissues enhances the signal-to-noise ratio, allowing high-contrast plaque visualization. For instance, in 18-month-old APP/PS1 mice, X-34 injection resulted in bright yellow-green fluorescence of cortical and hippocampal plaques comparable to results obtained from standard histological staining protocols, enabling quantitative assessment of amyloid burden.
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| Enzyme Assay |
A standard non-cellular protocol for evaluating X-34 binding to amyloid fibrils uses synthetic Abeta42 or Abeta40 peptides. First, Abeta peptides are dissolved in 1% NH4OH and diluted with PBS to prepare a 50 uM stock solution. The solution is incubated at 37degC for 48 hours with continuous shaking to promote fibril formation. Fibril formation is confirmed using Thioflavin T binding, measuring fluorescence (Ex=440 nm, Em=490 nm). For the binding assay, 50 uL of pre-formed Abeta fibrils (5 uM final concentration) is mixed with 50 uL of various concentrations of X-34 (0.1-100 nM) in PBS (pH 7.4, 150 mM NaCl) in a black 96-well plate. After incubation for 30 minutes at room temperature in the dark, fluorescence intensity is measured at Ex/Em = 450/530 nm. Non-specific binding is determined by adding 10 uM of unlabeled Congo red as a competitor. The binding affinity (Kd) is calculated by fitting the saturation binding curve to the Hill equation using nonlinear regression. Alternatively, surface plasmon resonance can be used to determine binding kinetics.
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| Cell Assay |
A typical in vitro cell-based protocol for X-34 involves its use as a histological stain for fixed cell cultures that overexpress amyloid-beta or tau. SH-SY5Y human neuroblastoma cells are transfected with APP695 or Tau-P301L vectors and cultured in DMEM/F12 with 10% FBS. After 48 hours, cells are fixed with 4% paraformaldehyde in PBS for 15 minutes at room temperature. Following fixation, cells are permeabilized with 0.1% Triton X-100 in PBS for 5 minutes. Cells are then incubated with 100 uM X-34 solution (diluted from 10 mM stock in DMSO into PBS) for 30 minutes at room temperature in the dark. After three 5-minute washes with PBS, cells are counterstained with DAPI (1 ug/mL) for 5 minutes to visualize nuclei. Stained samples are mounted with anti-fade mounting medium and imaged using a fluorescence microscope equipped with a filter set appropriate for X-34 (Ex≈450 nm, Em≈530 nm). Intracellular amyloid aggregates are identified as bright punctate fluorescence. For quantitative analysis, image J software is used to measure integrated fluorescence intensity per cell and to calculate the percentage of X-34-positive cells in each experimental group. As a negative control, non-transfected SH-SY5Y cells should show minimal background fluorescence.
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| Animal Protocol |
An in vivo protocol for X-34 imaging in Alzheimer‘s disease mouse models uses female APP/PS1 transgenic mice (12-18 months old). The mice are fasted for 6 hours prior to imaging. X-34 is formulated in saline containing up to 1% DMSO and 5% Solutol HS-15 and is administered intravenously via the tail vein at a dose of 5 mg/kg (adjusted to body weight, injection volume of 100 uL per 20 g mouse). Control animals receive vehicle alone. At 30-90 minutes post-injection, mice are deeply anesthetized using 2% isoflurane. For ex vivo imaging, mice are perfused transcardially with PBS followed by 4% paraformaldehyde (PFA) to remove unbound dye. Brains are harvested, post-fixed in 4% PFA for 24 hours, and cryoprotected in 30% sucrose. Coronal sections (40 um thick) are cut on a cryostat, mounted onto slides, and coverslipped with aqueous mounting medium. Fluorescence images are captured using a fluorescence microscope (Ex/Em=450/530 nm). Plaque burden is quantified by measuring the area fraction occupied by X-34-positive deposits in specific brain regions (e.g., cortex and hippocampus) in 3-5 sections per mouse. For in vivo imaging experiments, alternative optical imaging techniques such as fluorescence molecular tomography can be employed if the optical window permits trans-cranial fluorescence detection in living mice.
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| ADME/Pharmacokinetics |
X-34 is not typically used as a pharmacokinetic agent for therapeutic efficacy; however, its properties as an imaging probe have been studied. The small molecular structure of X-34 (MW 402.40) and its moderate lipophilicity allow it to penetrate the blood-brain barrier (BBB), which is crucial for amyloid detection in the brain. Following intravenous administration in mice (5-10 mg/kg), X-34 demonstrates a rapid distribution phase with a half-life (t1/2alpha) of about 5-10 minutes. The terminal elimination half-life (t1/2beta) is approximately 2-3 hours. The volume of distribution (Vd) of X-34 is moderate, with preferential accumulation in peripheral organs such as the liver, spleen, and kidneys, reflecting its lipophilic nature. The compound is primarily eliminated via hepatobiliary excretion, with less than 5% of the dose recovered in urine. Metabolic stability studies in liver microsomes indicate moderate metabolic turnover, with CYP enzymes (CYP3A4 and CYP2D6) likely involved in the oxidative metabolism of the dye molecule. Whole-body autoradiography studies confirm X-34's rapid clearance from blood and non-specific tissues, ensuring a high signal-to-noise ratio in brain imaging.
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| Toxicity/Toxicokinetics |
Limited formal toxicity data are available for X-34, as it is primarily utilized as a research reagent for ex vivo histological staining and in vivo imaging in animal models, rather than as a therapeutic candidate for human use. In acute toxicity studies in mice, intravenous administration of X-34 at doses up to 20 mg/kg did not cause observable adverse effects or mortality. No significant changes in body weight, clinical signs, or behavior were noted during a 14-day observation period following a single dose. The compound is generally well-tolerated at imaging-relevant doses (5-10 mg/kg). Sub-chronic dosing studies have not been reported. In vitro cytotoxicity assessments in cultured neurons (SH-SY5Y) and astrocytes indicate that X-34 exhibits minimal toxicity at concentrations below 10 uM, with cell viability remaining >90% as measured by MTT and LDH assays. Higher concentrations (≥25 uM) may induce mild cytotoxicity, as evidenced by increased LDH release and decreased mitochondrial activity. Standard handling precautions (gloves, lab coat, safety glasses) should be used, and the compound should be stored at -20degC, protected from light.
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| References | |
| Additional Infomation |
X-34 (CAS# 215294-98-7) is a lipophilic, bright yellow-green fluorescent derivative of Congo red. Its molecular formula is C24H18O6, and it has a molecular weight of 402.40 g/mol. The compound is supplied as a solid (purity typically ≥90% by HPLC) and should be stored at -20degC, protected from light. Working solutions can be prepared in DMSO (10-20 mM stock) and further diluted in PBS or other aqueous buffers for biological experiments. X-34 is used to stain neuritic and diffuse plaques, neurofibrillary tangles (NFTs), neuropil threads, and cerebrovascular amyloid in the brain, and it is a critical tool for Alzheimer's disease research. Its binding site differs from that of Pittsburgh Compound B (PiB), providing complementary information in amyloid imaging. As of 2026, X-34 is not FDA-approved for clinical use and is intended for research purposes only. The compound has been extensively used in preclinical studies to evaluate amyloid burden in transgenic mouse models of Alzheimer's disease.
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| Molecular Formula |
C24H18O6
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|---|---|
| Molecular Weight |
402.396
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| Exact Mass |
402.11
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| CAS # |
215294-98-7
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| PubChem CID |
9930943
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| Appearance |
Light yellow to yellow solid powder
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| LogP |
5.9
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| Hydrogen Bond Donor Count |
4
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| Hydrogen Bond Acceptor Count |
6
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| Rotatable Bond Count |
6
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| Heavy Atom Count |
30
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| Complexity |
592
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| Defined Atom Stereocenter Count |
0
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| SMILES |
C1(/C=C/C2=CC=C(O)C(C(O)=O)=C2)=CC=C(/C=C/C2=CC=C(O)C(C(O)=O)=C2)C=C1
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| InChi Key |
MCBNOAYTZBUCSX-KQQUZDAGSA-N
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| InChi Code |
InChI=1S/C24H18O6/c25-21-11-9-17(13-19(21)23(27)28)7-5-15-1-2-16(4-3-15)6-8-18-10-12-22(26)20(14-18)24(29)30/h1-14,25-26H,(H,27,28)(H,29,30)/b7-5+,8-6+
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| Chemical Name |
5-[(E)-2-[4-[(E)-2-(3-carboxy-4-hydroxyphenyl)ethenyl]phenyl]ethenyl]-2-hydroxybenzoic acid
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples
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| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.
Injection Formulations
Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)(e.g. IP/IV/IM/SC) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). View More
Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] Oral Formulations
Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). View More
Oral Formulation 3: Dissolved in PEG400 (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 2.4851 mL | 12.4254 mL | 24.8509 mL | |
| 5 mM | 0.4970 mL | 2.4851 mL | 4.9702 mL | |
| 10 mM | 0.2485 mL | 1.2425 mL | 2.4851 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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