Here, we describe the radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-tryptophan, a positron emission tomography imaging agent for studying tryptophan metabolism, using a one-pot, two-step strategy in a radiochemistry synthesis system with good radiochemical yields, high enantiomeric excess, and high reliability.
The kynurenine pathway (KP) is a primary route for tryptophan metabolism. Evidence strongly suggests that metabolites of the KP play a vital role in tumor proliferation, epilepsy, neurodegenerative diseases, and psychiatric illnesses due to their immune-modulatory, neuro-modulatory, and neurotoxic effects. The most extensively used positron emission tomography (PET) agent for mapping tryptophan metabolism, α-[11C]methyl-L-tryptophan ([11C]AMT), has a short half-life of 20 min with laborious radiosynthesis procedures. An onsite cyclotron is required to radiosynthesize [11C]AMT. Only a limited number of centers produce [11C]AMT for preclinical studies and clinical investigations. Hence, the development of an alternative imaging agent that has a longer half-life, favorable in vivo kinetics, and is easy to automate is urgently needed. The utility and value of 1-(2-[18F]fluoroethyl)-L-tryptophan, a fluorine-18-labeled tryptophan analog, has been reported in preclinical applications in cell line-derived xenografts, patient-derived xenografts, and transgenic tumor models.
This paper presents a protocol for the radiosynthesis of 1-(2-[18F]fluoroethyl)-L-tryptophan using a one-pot, two-step strategy. Using this protocol, the radiotracer can be produced in a 20 ± 5% (decay corrected at the end of synthesis, n > 20) radiochemical yield, with both radiochemical purity and enantiomeric excess of over 95%. The protocol features a small precursor amount with no more than 0.5 mL of reaction solvent in each step, low loading of potentially toxic 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (K222), and an environmentally benign and injectable mobile phase for purification. The protocol can be easily configured to produce 1-(2-[18F]fluoroethyl)-L-tryptophan for clinical investigation in a commercially available module.
In humans, tryptophan is an essential component of the daily diet. Tryptophan is primarily metabolized via the kynurenine pathway (KP). The KP is catalyzed by two rate-limiting enzymes, indoleamine 2, 3-dioxygenase (IDO) and tryptophan 2, 3-dioxygenase (TDO). More than 95% of tryptophan is converted into kynurenine and its downstream metabolites, ultimately generating nicotinamide adenine dinucleotide, which is essential to cellular energy transduction. The KP is a key regulator of the immune system and an important regulator of neuroplasticity and neurotoxic effects1,2. Abnormal tryptophan metabolism is implicated in various neurologic, oncologic, psychiatric, and metabolic disorders; therefore, radiolabeled tryptophan analogs have been extensively used in clinical investigation. The two most common clinically investigated tryptophan radiotracers are 11C-α-methyl-L-tryptophan ([11C]AMT) and 11C-5-hydroxytryptophan (11C-5-HTP)3.
In the 1990s, 11C-5-HTP was used to visualize serotonin-secreting neuroendocrine tumors4 and to diagnose and monitor therapy of metastatic hormone-refractory prostatic adenocarcinoma5. Later, it was used as an imaging tool for the quantification of the serotonergic system in the endocrine pancreas6. 11C-5-HTP has also been a promising tracer for noninvasive detection of viable islets in intraportal islet transplantation and type 2 diabetes7,8. Over the past two decades, many radiolabeled amino acids have advanced to clinical investigation9,10. In particular, the carbon-11-labeled tryptophan analog [11C]AMT has received extensive attention for mapping brain serotonin synthesis11,12,13,14 and for localizing epileptic foci, epileptogenic tumors, tuberous sclerosis complex, gliomas, and breast cancers15,16,17,18,19,20,21,22,23,24,25,26. [11C]AMT also has high uptake in various low- and high-grade tumors in children27. Furthermore, kinetic tracer analysis of [11C]AMT in human subjects has been used to differentiate and grade various tumors and differentiate glioma from radiation-induced tissue injury15. [11C]AMT-guided imaging shows significant clinical benefits in brain disorders3,25. However, due to the short half-life of carbon-11 (20 min) and the laborious radiosynthesis procedures, [11C]AMT use is restricted to the few PET centers with an onsite cyclotron and a radiochemistry facility.
Fluorine-18 has a favorable half-life of 109.8 min, compared with the 20 min half-life of carbon-11. Increasingly, efforts have been focused on the development of fluorine-18-labeled radiotracers for tryptophan metabolism3,28. A total of 15 unique fluorine-18 radiolabeled tryptophan radiotracers have been reported in terms of radiolabeling, transport mechanisms, in vitro and in vivo stability, biodistribution, and tumor uptake in xenografts. However, rapid in vivo defluorination was observed for several tracers, including 4-, 5-, and 6-[18F]fluorotryptophan, precluding further clinical translation29. 5-[18F]Fluoro-α-methyltryptophan (5-[18F]FAMT) and 1-(2-[18F]fluoroethyl)-L-tryptophan (L-[18F]FETrp, also known as (S)-2-amino-3-(1-(2-[18F]fluoroethyl)-1H-indol-3-yl)propanoic acid, molecular weight 249.28 g/mole), are the two most promising radiotracers with favorable in vivo kinetics in animal models and great potential to surpass [11C]AMT for the evaluation of clinical conditions with deregulated tryptophan metabolism28. 5-[18F]FAMT showed high uptake in IDO1-positive tumor xenografts of immunocompromised mice and is more specific to imaging the KP than [11C]AMT28,30. However, the in vivo stability of 5-[18F]FAMT remains a potential concern as no in vivo defluorination data have been reported beyond 30 min post injection of the tracer30.
A preclinical study in a genetically engineered medulloblastoma mouse model showed that when compared with 18F-fluorodeoxyglucose (18F-FDG), L-[18F]FETrp had high accumulation in brain tumors, negligible in vivo defluorination, and low background uptake, demonstrating a superior target-to-nontarget ratio31,32. Radiation dosimetry studies in mice indicated that L-[18F]FETrp had an approximately 20% lower favorable dosimetry exposure than the clinical 18F-FDG PET tracer33. In agreement with other researchers' findings, preclinical study data provide substantial evidence to support the clinical translation of L-[18F]FETrp for the investigation of abnormal tryptophan metabolism in humans with brain disorders such as epilepsy, neuro-oncology, autism, and tuberous sclerosis28,31,32,33,34,35,36. An overall comparison between the three most widely investigated tracers for tryptophan metabolism, 11C-5-HTP, [11C]AMT, and L-[18F]FETrp, is shown in Table 1. Both 11C-5-HTP and [11C]AMT have a short half-life and laborious radiolabeling procedures. A protocol for the radiosynthesis of L-[18F]FETrp using a one-pot, two-step approach is described here. The protocol features the use of a small amount of radiolabeling precursor, a small volume of reaction solvents, low loading of toxic K222, and an environmentally benign and injectable mobile phase for purification and easy formulation.
CAUTION: The protocol involves radioactive materials. Any additional dose of radioactive materials could lead to a proportional increase in the chance of adverse health effects such as cancer. Researchers must follow the 'as low as reasonably achievable' (ALARA) dose practices to guide the radiosynthesis protocol with adequate protection in the hot cell or lead hood. Minimizing direct contact time, using a lead shield, and keeping maximum distance for any radiation exposure step in the radiosynthesis process are essential. Wear a radiation dosimetry badge and hand monitoring rings throughout the entire experiment, and frequently monitor potentially contaminated surfaces such as gloves, sleeves, and feet. Nuclear Regulatory Commission (NRC), local, and institutional regulations must be followed for the usage, shipping, and disposal of any radioactive materials.
1. Initial preparations
2. Assemble the radiolabeling supplies and radiosynthesize L-[18F]FETrp
3. Post-run system clean
The reaction scheme is shown in Figure 1. The radiolabeling includes the following two steps: 1) reaction of the tosylate radiolabeling precursor with [18F]fluoride provides the 18F-labeled intermediate, and 2) deprotection of the tert-butyloxycarbonyl and tert-butyl-protecting groups in the intermediate affords the final product L-[18F]FETrp. Both reaction steps continue at 100 °C for 10 min.
Before receiving [18F]fluoride from the commercial vendor, assemble the reagent vials, formulation vials, and cartridges; equilibrate the semi-preparative, QC systems; and run a QC system suitability test. The detailed workflow for the radiosynthesis of L-[18F]FETrp is outlined in Figure 2. In brief, the radioactivity is surveyed and transferred to the radiochemistry synthesis system, and the [18F]fluoride is azeotropically dried in the reaction vessel after the trapping/releasing steps. After the [18F]fluoride incorporation in the first step, acid is added to deprotect the two functional groups, followed by base neutralization. The reaction mixture is transferred to an intermediate vial, and the reaction vessel is rinsed with a mixed solution. The combined mixture is loaded onto the HPLC loop for purification. A combination of chiral and C18 HPLC columns is used to remove the chemical impurities. The target fraction is collected into a formulation vial prefilled with sodium chloride to adjust the dose concentration and tonicity. The final product is sterile-filtered into a final-dose vial, assayed, and aliquoted for QC before the doses are released.
The schematic diagram of the system setup is shown in Figure 3. The module consists of the following major components: 1) input MVP for reagent addition, 2) output MVP for reactor venting and rinse, 3) formulation MVP for HPLC fraction collection and dose formulation, 4) [18F]fluoride trapping and releasing MVP, and 5) HPLC purification system. The trends for radioactivity, reaction temperature, and pressure can be monitored in real time through the control panel. A typical semipreparative HPLC chromatogram is shown in Figure 4. The target fraction containing UV impurities is diverted to a short C18 column (the black trace overlapped with the red UV trace, Figure 4). The impurities in the target component can be removed by passing the fraction through a C18 column. The purified HPLC fraction eluted from the C18 column is collected in the formulation vial. The dose is assayed and aliquoted for QC.
The representative HPLC chromatograms for QC are shown in Figure 5. The chromatogram of the blank sample shows insignificant peaks between the void volume and 10 min of the program. The nonradiolabeled standard reference L-FETrp shows a single isomer, separated well from the standard reference of its D-counterpart. The final dose of L-[18F]FETrp shows high chemical purity and radiochemical purity. Stability testing of the final product at the highest dose concentration for up to 8 h shows that L-[18F]FETrp is stable in terms of chemical purity, radiochemical purity, enantiomeric excess, and pH value (Table 2)37. This protocol for the one-pot, two-step radiosynthesis of L-[18F]FET takes approximately 100 min. The decay-corrected yield is 20 ± 5%, with chemical and radiochemical purities greater than 95%. Starting from 12-18 GBq of [18F]fluoride, the molar activity of L-[18F]FET is 88-118 GBq/µmol. The mass concentration is typically less than 0.5 µg/mL, with the dose concentration in the range of 37-185 MBq/mL.
Figure 1: Reaction scheme for one-pot, two-step radiosynthesis of L-[18F]FETrp. Abbreviations: MeCN = acetonitrile; L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan; K222 = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane. Please click here to view a larger version of this figure.
Figure 2: Overview of the L-[18F]FETrp radiosynthesis workflow. *A complete quality control according to USP823, USP797 will be followed for human use of L-[18F]FETrp. Abbreviations: QC = quality control; MeCN = acetonitrile; L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan. Please click here to view a larger version of this figure.
Figure 3: Production of L-[18F]FETrp. Schematic diagram of setup (left) and the photograph of the radiosynthesis platform (right). The setup includes the following major components: 1. Input MVP; 2. Output MVP; 3. Formulation MVP; 4. [18F]Fluoride-trapping/releasing MVP; 5. QMA cartridge; 6. Intermediate vial; 7. Alumina/C8 cartridges; 8. Reactor; 9. Chiral HPLC column; 10, C18 column; 11. HPLC waste bottle to the chiral column; 12. Diversion MVP; 13. HPLC waste bottle to the chiral and C18 columns; 14. Formulation vial; 15. Back up vial. Abbreviations: L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan; MVP = modular vial positioner; QMA = quaternary methylammonium. Please click here to view a larger version of this figure.
Figure 4: Typical semipreparative chromatogram for purification of L-[18F]FETrp. Red trace, UV channel at 254 nm. Black trace, radioactivity channel. Arrows 1, 2 indicate the start and end of diverting the radioactive fraction containing L-[18F]FETrp to the C18 column, respectively. Arrows 3, 4 indicate the start and end of collecting the purified target fraction L-[18F]FETrp eluted from the C18 column, respectively. Abbreviation: L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan. Please click here to view a larger version of this figure.
Figure 5: Typical analytical HPLC chromatogram for quality control of L-[18F]FETrp. 1) Blank solution, 2) standard solution of L-FETrp, 3) standard solution of L-FETrp and D-FETrp mixtures, 4) UV trace of L-FETrp at 230 nm, 4) radioactivity trace of L-[18F]FETrp formulation. Abbreviation: L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan; L-FETrp = 1-(2-Fluoroethyl)-L-tryptophan; D-FETrp = 1-(2-Fluoroethyl)-D-tryptophan. Please click here to view a larger version of this figure.
Tracer | Clinical Investigation | Major Indications | Pros | Cons | |||
11C-5-HTP | Yes | Imaging serotonin-producing neuroendocrine tumors, neuropsychiatric diseases | Sensitive in detecting small neuroendocrine tumors | Need an onsite cyclotron, short half-life, laborious procedures, multi-enzymatic radiosynthesis, sensitive to precursor concentration and solution pH, unspecific uptake in dopaminergic and noradrenergic areas | |||
[11C]AMT | Yes | Localization of epileptogenic tissue and brain tumors based on strong kynurenine pathway activations | cGMP production available, not incorporated into protein synthesis | Need an onsite cyclotron, short half-life, laborious procedures, complicated quantification under pathological conditions | |||
L-[18F]FETrp | No | Imaging kynurenine pathway including epileptic foci, brain tumors, and detecting epilepsy-associated neuroinflammatory abnormalities | Favorable half-life, available for satellite delivery, cGMP radiosynthesis, high stability towards defluorination and favorable radiation dosimetry | Uptake facilitated by both L-amino acid transporter and alanine-serine-cysteine transporter, no human investigations yet |
Table 1: Comparison of 11C-5-HTP, [11C]AMT, and L-[18F]FETrp. Abbreviations: cGMP = current good manufacturing practices; α-[11C]methyl-L-tryptophan; L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan; 11C-5-HTP = 11C-5-hydroxytryptophan.
Hours After End of Synthesis of Assay | Radiochemical Purity by HPLC (%) | Chemical Purity (%) | Enantiomeric Excess (%) | pH Value |
0 | 99 | >95 | 98 | 5.5 |
1 | 99 | >95 | 99 | 5.5 |
2 | 99 | >95 | 99 | 5.5 |
4 | 99 | >95 | 98 | 5.5 |
6 | 98 | >95 | 98 | 5.5 |
8 | 97 | >95 | 97 | 5.5 |
Table 2: Stability test of L-[18F]FETrp in a typical batch at the highest dose concentration. Abbreviation: L-[18F]FETrp = 1-(2-[18F]Fluoroethyl)-L-tryptophan.
Tryptophan is an essential amino acid for humans. It plays an important role in the regulation of mood, cognitive function, and behavior. Radiolabeled tryptophan derivatives, particularly the carbon-11-labeled [11C]AMT, have been extensively studied due to their unique role in mapping serotonin synthesis38,39, detecting and grading tumors40, guiding epilepsy surgery41,42, and evaluating treatment response in diabetes43. However, the short half-life and laborious radiolabeling procedures limit the widespread application of [11C]AMT. Efforts are underway to develop fluorine-18-labeled agents for tryptophan metabolism. Two recent review articles summarize the development and imaging properties of fluorine-18-labeled tryptophan imaging agents3,28.
Compared with its 11C-labeled predecessor, L-[18F]FETrp demonstrates favorable in vivo imaging properties, good metabolic stability, and resistance to defluorination33. Additionally, L-[18F]FETrp demonstrates a favorable dosimetry profile compared to 18F-FDG and has been proposed as a promising tryptophan imaging agent for clinical translation32,33. The methodology described here utilizes a one-pot, two-step strategy for the radiosynthesis of L-[18F]FETrp in a radiochemistry synthesis system. L-[18F]FETrp was produced with high chemical purity, radiochemical purity, and enantiomeric excess. The total nonradiolabeled L-FETrp mass in the final dose is no more than 5 µg, and the ethanol content is no more than 10%. L-[18F]FETrp is routinely produced in the PET center for the imaging of tryptophan metabolism in a transgenic medulloblastoma mouse brain tumor model and has shown favorable imaging results32. When compared with the reported method for L-[18F]FETrp, the current protocol includes the benefits detailed below.
First, a small reaction vessel and less precursor and reaction solvents are used for the radiolabeling when compared with other reported radiolabeling modules and methods (in which 9 mg of precursor in 1.1 mL of solvent was used)35, and only 1-2 mg of radiolabeling precursor in 0.5 mL of solvent is added to the reaction but with a much higher yield of the enantiomer. Less than 1% yield has been reported for a two-pot, three-step radiosynthesis of L-[18F]FETrp without any report of the enantiomeric excess value44.
Second, the lowest amount of toxic K222, compared with reported procedures for L-[18F]FETrp or racemic [18F]FETrp, is used. Typically 4-5 mg of K222 is used compared with 37.5 mg used by others35. K222 is a phase transfer catalyst frequently used in the radiosynthesis of 18F-labeled PET tracers. The limit specified in the USP for K222 is less than 50 µg/mL. A color spot test for the detection of the residual K222 concentration must be performed to meet the criteria before releasing the final dose for clinical use45.
Third, only 1% water is introduced to the K2CO3/K222 solution for [18F]fluoride elution, which expedites the drying process of aqueous [18F]fluoride. [18F]fluoride anions are heavily hydrated and become chemically inert in aqueous media46. Therefore, enhancing the nucleophilicity by desolvating [18F]fluoride and azeotropic drying of the aqueous solution is required for [18F]fluoride incorporation. Water will also compete with [18F]fluoride to hydrolyze instead of the desired [18F]fluoride nucleophilic substitution of the radiolabeling precursor.
Fourth, an injectable mobile phase is used for the purification of L-[18F]FETrp. Ten percent ethanol in 50 mM sodium acetate/acetic acid, pH 5.5, is used as the mobile phase to purify the radiotracer, readily bringing the ethanol content to less than 10% in the final dose for clinical use. While 90% ethanol in water has been reported to resolve the enantiomers, it takes more time to evaporate the ethanol content to less than 10% at 78 °C34.
The preclinical study of L-[18F]FETrp in a transgenic medulloblastoma mouse model shows 1-L-[18F]FETrp had high brain tumor accumulation with favorable kinetics, negligible in vivo defluorination, and low background uptake32. 1-L-[18F]FETrp also shows a superior target-to-nontarget ratio to 18F-FDG31. Furthermore, the protocol is easy to set up for the production of L-[18F]FETrp for clinical investigation37. Additional, comprehensive QC tests, including filter integrity, radionuclidic purity, residual solvent levels, K222 concentration, bacterial endotoxin level, and sterility tests, can be readily performed for the final dose of the radiopharmaceutical. The process of regulatory approval for the clinical utilization of L-[18F]FETrp in human subjects is actively ongoing.
The method has some limitations. Two HPLC columns are used to obtain adequate chemical purity and enantiomeric excess of L-[18F]FETrp. A flow rate of the mobile phase at 3 mL/min is used for the purification. A higher flow rate results in high backpressure, while a lower flow rate leads to extended time for purification and poor baseline resolution of the peaks. Alternative HPLC columns that are compatible with the mobile phase and show better selectivity towards enantiomers and good resolution over the impurities may simplify the purification steps.
The radiochemistry synthesis module is a noncommercial system. The fully automated radiosynthesis of racemic [18F]FETrp has been reported in a commercial GE FASTlab synthesizer. Chiral separation of the enantiomers is performed with a chiral analytical HPLC column; the final L- and D-isomers are formulated on a second FASTLab cassette35. Xin and Cai34 reported the automatic radiosynthesis of optically pure L-[18F]FETrp using a GE FX-N system. While the two enantiomers can be readily separated with the semipreparative chiral HPLC column, the mobile phase with a high ethanol content (90% ethanol in water) is not suitable for direct human injection34. The use of a commercial radiosynthesizer and an injectable mobile phase for L-[18F]FETrp with high enantiomeric excess is highly desirable for easy clinical investigation.
In conclusion, a fluorine-18-labeled tryptophan analog L-[18F]FETrp was synthesized in a radiochemistry synthesis system using a one-pot, two-step approach with high reliability and reproducibility. The radiosynthesis features small amounts of radiolabeling precursor and solvents, an injectable mobile phase, and easy implementation for clinical production of L-[18F]FETrp for human use. The protocol will facilitate more widespread utilization of this radiotracer for neurological disorders and cancers implicated with tryptophan metabolism.
The authors have nothing to disclose.
This work was supported by the Diagnostic & Research PET/MRI Center, and by the Departments of Biomedical Research and Radiology at Nemours/Alfred I. duPont Hospital for Children.
[18F]Fluoride in [18O]H2O | PETNET Solutions Inc. | N/A | |
4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane | ACROS | 291950010 | Kryptofix 222 or K222, 98% |
Acetic acid | ACROS | 222142500 | 99.8% |
Acetonitrile | Sigma-Aldrich | 271004 | anhydrous, 99.8% |
Agilent 1260 HPLC system | Agilent Technologies | Agilent 1260 | Agilent 1260 series |
Analytcial chiral HPLC column | Sigma-Aldrich | 12024AST | Astec CHIROBIOTIC T, 25 cm × 4.6 mm |
Carbon dioxide, 60 LBS | Airgas | REFR744R200S | 99.99% |
D-FETrp standard reference | Affinity Research Chemicals Inc | N/A | Custom synthesis |
Empty sterile vial | Jubilant HollisterStier | 7515 | 20 mm closure, 10 mL |
Ethanol | Decon Labs | 2716 | 200 proof, USP grade. ≥99.9% |
Fisherbrand 13 mm Syringe Filter, 0.22 µm, PVDF, sterile | Fisher Scientific | 09-720-3 | |
Hydrochloric acid | Sigma-Aldrich | 30721 | ≥37% |
Isopropanol | Decon Labs | 8316 | 70%, sterile |
L-[18F]FETrp radiolabeling precursor | Affinity Research Chemicals Inc | N/A | Custom synthesis |
L-FETrp standard reference | Affinity Research Chemicals Inc | N/A | Custom synthesis |
Light C8 cartridge | Waters | WAT036770 | Sep-Pak C8 plus light cartridge |
Needle, 20 G x 1 | Becton-Dickinson & Co. | 305175 | |
Needle, 20 G x 1 ½ | Becton-Dickinson & Co. | 305176 | |
Needle, 21 G x 2 | Becton-Dickinson & Co. | 305129 | |
Neutral aluminum oxide | Waters | WAT023561 | Sep-Pak alumina N plus light |
Nylon membrane (0.20 µm ) | MilliPore | GNWP04700 | 47 mm |
Pall Acrodisc 25 mm syringe sterile filter | Pall Corporation | 4907 | |
PETCHEM radiochemistry synthesis system | PETCHEM Solutions Inc. Pinckney, MI | N/A | Radiosynthesizer |
pH strips 2.0 – 9.0 | EMD Millipore | 1.09584.0001 | |
Potassium carbonate | Sigma-Aldrich | 367877 | 99.995% |
Quaternary methylammonium light cartridge | Waters | 186004051 | Sep-Pak QMA light |
Semi-preparative C18 HPLC column | Phenomenex | 00D-4253-N0 | 100 × 10 mm |
Semi-preparative chiral HPLC column | Sigma-Aldrich | 12034AST | Astec CHIROBIOTIC T, 25 cm × 10 mm |
Sodium chloride injection 23.4% | APP Pharmaceutical, LLC | 18730 | USP grade |
Sodium chloridei injection 0.9% | Hospira | NDC 0409-4888-10 | USP grade |
Sodium hydroxide | Honeywell | 306576 | 99.99% |
Spinal needle, 20 G x 3 ½ | Becton-Dickinson & Co. | 405182 | |
Sterile alcohol prep pads | BioMed Resource Inc. | PC661 | |
Sterile empty vials, 2 mL | Hollister Stier | 7505ZA | 13 mm closure |
Sterile empty vials, 30 mL | Jubilant HollisterStier | 7520ZA | 20 mm closure |
Syringe PP/PE, 3 mL, Luer Lock | Air-Tite | 4020-X00V0 | |
Syringe PP/PE, 5 mL, Luer Lock | Becton-Dickinson & Co. | 309646 | |
Syringe, PP/PE, 10 mL, NORM-JECT | Air-Tite | 4100-000V0 | |
Syringe, 1 mL, Luer Slip | Becton-Dickinson & Co. | 309659 | |
Syringe, 3 mL, Luer-Lock | Becton-Dickinson & Co. | 309657 | |
Ultra high purity argon | Airgas | AR UHP300 | 99.999% |
Ultrapure water | MilliporeSigma | ZRQSVP300 | Direct-Q 3 tap to pure and ultrapure water purification system |