Name: quantification of the immunosuppressant tacrolimus on dried blood spots using lc-ms/ms
Uploaded: 2015-11-08T14:00:00
Description: Watch this Scientific Journal Video about Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS at JoVE.com

This work was supported by the United States Federal Drug Administration (FDA) contract HHSF223201310224C and the United States National Institutes of Health/FDA grant 1U01FD004573-01.

De-identified blood samples from healthy individuals were from the University of Colorado Hospital (Aurora, Colorado). The use of de-identified blood bank samples for validation studies as well as for the preparation of calibrators and quality control samples was considered &#8220;exempt&#8221; by the Colorado Multi-institutional Review Board (COMIRB, Aurora, Colorado).
1. Preparation of References and Solutions
<ol>
	<li>Purchase tacrolimus and the internal standard D2,13</s...

Although, as aforementioned, the concept of therapeutic drug and adherence monitoring of tacrolimus based on dried blood spots is attractive, there are analytical challenges that go beyond those typically associated with the LC-MS/MS analysis of tacrolimus in venous EDTA whole blood samples. These include, but are not limited to, the fact that the matrix is capillary whole blood soaked into the cotton linters material of the filter card material used here and the low blood volume (20 &#181;l). Nevertheless, high-throughp...

Tacrolimus is a potent immonosuppressant1-7 that has a macrolide structure8 (Figure 1). Due to cis-trans isomerism of the C-N bonds it forms two rotamers in solution9 that can be separated by reversed phase high-performance liquid chromatography (HPLC) Tacrolimus is lipophilic and soluble in alcohols (methanol: 653 g/L, ethanol: 355 g/L), halogenated hydrocarbons (chloroform: 573 g/L) and ether. It is sparingly soluble in aliphatic hydrocarbons (hexane: 0.1 g/L and water (pH 3: 0.0047 g/L)9. The molecule does not contain any chromophore and its UV-absorption maximum is 192 nm. Tacrolimus acts via inhibition of calcineurin. Its mechanism of action has been reviewed in references10,11. It is currently used in more than 80% of solid-organ transplant patients in the United States12.
The therapeutic index of tacrolimus is considered to be narrow13. In addition, the correlation between tacrolimus doses and blood concentrations is poor and pharmacokinetics is variable14,15. Therapeutic drug monitoring to guide tacrolimus dosing in transplant patients is therefore general clinical practice16-20. The goal is to keep the tacrolimus blood concentrations within a pre-defined therapeutic range. Tacrolimus blood concentrations below the therapeutic range may result in increased activity of chronic or acute allo-immune reactions, while concentrations above the therapeutic window increase the risk for over-immunosuppression, cancer and toxicities, such as nephrotoxicity, neurotoxicity, hypertension, and diabetes. High pharmacokinetic intra-individual variability of tacrolimus may be detrimental to both transplant organ and patient survival21,22. While inter-individual variability of tacrolimus pharmacokinetics is mainly caused by CYP3A5 polymorphisms, reasons for intra-individual variability include, but are not limited to, drug-drug, disease-drug and food-drug interactions14,15. Also lack of adherence to the immunosuppressive therapeutic drug regimen is a contributing factor and a major reason for graft loss23,24.
These considerations suggest that frequent home therapeutic drug and adherence monitoring of tacrolimus whole blood concentrations may be beneficial to ensure that patients have tacrolimus exposure within the desired therapeutic window at all times. However, the logistics and cost of more frequent therapeutic drug monitoring as it is current clinical practice15 is prohibitive. One of the reasons is that the patient has to see a phlebotomist to have the required venous blood sample drawn. Dried blood spots have recently emerged as an attractive concept25-28. After a simple finger stick the patient collects a blood drop on a special filter paper card and after the blood spot has dried, it can be mailed to a central laboratory for analysis of tacrolimus and any other immunosuppressant that the patient may currently be taking. This has become possible due to the development of highly sensitive and specific LC-MS/MS assays for the quantification of tacrolimus and other immunosuppressants in very small blood volumes such as dried blood spots (typically 20 &#181;l of blood)25,29-43. Another advantage is that minimally invasive, low volume sample collection strategies such as dried blood spots greatly facilitate therapeutic drug monitoring and pharmacokinetic studies in small children28.
Tacrolimus is usually measured in venous EDTA whole blood15. Reasons are that tacrolimus extensively distributes into blood cells and that clinical studies have reported better correlation between tacrolimus trough concentrations in blood than in plasma with clinical events15,18. In comparison, the analysis of tacrolimus in dried blood spots is based on capillary blood that is mixed with the filter paper matrix. This presents challenges in terms of solubilization of tacrolimus and potential interferences with the LC-MS/MS analysis. Here we present an established and validated assay based on homogenization of the dried blood spot using a bullet blender in combination with a high-flow online column sample clean up procedure and LC-MS/MS analysis. As of today, this assay has successfully been used for the quantification of more than five thousand tacrolimus dried blood spot samples for adherence monitoring in clinical trials.

<table border="0" cellpadding="0" cellspacing="0">
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			<td>Reference Materials</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tacrolimus</td>
			<td>U.S. Pharmacopeial Convention</td>
			<td>1642802</td>
		</tr>
		<tr>
			<td>D2,13C-Tacrolimus</td>
			<td>Toronto Research Chemicals Inc.</td>
			<td>F370002</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Test Materials</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Red blood cells</td>
			<td>University of Colorado Hospital</td>
			<td>W20091305500 V</td>
		</tr>
		<tr>
			<td>Plasma</td>
			<td>University of Colorado Hospital</td>
			<td>W2017130556300Q</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
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			<td>Solvents</td>
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			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone CHROMASOLV, HPLC, &#8805; 99,9 %</td>
			<td>Sigma-Aldrich</td>
			<td>439126-4 L</td>
		</tr>
		<tr>
			<td>Acetonitrile Optima LC/ MS, UHPLC- UV</td>
			<td>Thermo Fisher Scientific</td>
			<td>A955-4</td>
		</tr>
		<tr>
			<td>Isopropanol 99.9 %, HPLC</td>
			<td>Fisher Scientific</td>
			<td>BP2632-4</td>
		</tr>
		<tr>
			<td>Methanol Optima LC/ MS</td>
			<td>Thermo Fisher Scientific</td>
			<td>A452-4</td>
		</tr>
		<tr>
			<td>Water Optima LC/ MS, UHPLC- UV</td>
			<td>Thermo Fisher Scientific</td>
			<td>W6-4</td>
		</tr>
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			<td></td>
			<td></td>
			<td></td>
		</tr>
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			<td>Other Chemicals</td>
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			<td></td>
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			<td>Formic acid</td>
			<td>Thermo Fisher Scientific</td>
			<td>A118P-500</td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline (PBS)</td>
			<td>Sigma-Aldrich</td>
			<td>D8537</td>
		</tr>
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			<td>Zinc sulfate</td>
			<td>Thermo Fisher Scientific</td>
			<td>Z68-500</td>
		</tr>
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			<td></td>
			<td></td>
			<td></td>
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			<td>Laboratory Instruments and Consumables</td>
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		<tr>
			<td>0.5 &#8211; 10 &#181;l pipet, VoluMate LIQUISYSTEMS</td>
			<td>Mettler Toledo</td>
			<td>17008649</td>
		</tr>
		<tr>
			<td>1,5 mL- Eppendorf tube</td>
			<td>Thermo Fisher Scientific</td>
			<td>02-682-550</td>
		</tr>
		<tr>
			<td>10 &#8211; 100 &#181;L pipet, VoluMate LIQUISYSTEMS</td>
			<td>Mettler Toledo</td>
			<td>17008651</td>
		</tr>
		<tr>
			<td>10 &#956;L- pipet tips with filter, sterile</td>
			<td>Neptune</td>
			<td>BT 10XLS3</td>
		</tr>
		<tr>
			<td>100 &#8211; 1000 &#181;l pipet, VoluMate LIQUISYSTEMS</td>
			<td>Mettler Toledo</td>
			<td>17008653</td>
		</tr>
		<tr>
			<td>100 &#956;L- pipet tips with filter, sterile</td>
			<td>Neptune</td>
			<td>BT 100</td>
		</tr>
		<tr>
			<td>1000 &#956;L- pipet tips with filter, sterile</td>
			<td>Multimax</td>
			<td>2940</td>
		</tr>
		<tr>
			<td>2 &#8211; 20 &#181;L pipet, VoluMate LIQUISYSTEMS</td>
			<td>Mettler Toledo</td>
			<td>17008650</td>
		</tr>
		<tr>
			<td>2 mL- Eppendorf tube</td>
			<td>Thermo Fisher Scientific</td>
			<td>02-681-258</td>
		</tr>
		<tr>
			<td>20 &#8211; 200 &#181;L pipet, VoluMate LIQUISYSTEMS</td>
			<td>Mettler Toledo</td>
			<td>17008652</td>
		</tr>
		<tr>
			<td>20 &#956;L- pipet tips with filter, sterile</td>
			<td>GeneMate</td>
			<td>P-1237-20</td>
		</tr>
		<tr>
			<td>200 &#956;L- pipet tips with filter</td>
			<td>Multimax</td>
			<td>2938T</td>
		</tr>
		<tr>
			<td>200 &#956;L- pipet tips with filter, sterile</td>
			<td>Multimax</td>
			<td>2936J</td>
		</tr>
		<tr>
			<td>50 mL- Falcon tube</td>
			<td>BD Falcon</td>
			<td>352070</td>
		</tr>
		<tr>
			<td>300 &#956;L inserts for&#160; HPLC vials</td>
			<td>Phenomenex</td>
			<td>ARO-9973-13</td>
		</tr>
		<tr>
			<td>Balance PR2002</td>
			<td>Mettler Toledo</td>
			<td>1117050723</td>
		</tr>
		<tr>
			<td>Balances AX205 Delta Range</td>
			<td>Mettler Toledo</td>
			<td>1119343379</td>
		</tr>
		<tr>
			<td>Bullet Blender Homogenizer</td>
			<td>Next Advance</td>
			<td>BBX24</td>
		</tr>
		<tr>
			<td>Centrifuge Biofuge Fresco</td>
			<td>Heraeus</td>
			<td>290395</td>
		</tr>
		<tr>
			<td>Disposable Wipes</td>
			<td>PDI</td>
			<td>Q55172</td>
		</tr>
		<tr>
			<td>Glass v ials, 4 mL</td>
			<td>Thermo Fisher Scientific</td>
			<td>14-955-334</td>
		</tr>
		<tr>
			<td>Glass vials, 20 mL</td>
			<td>Thermo Fisher Scientific</td>
			<td>B7800-20</td>
		</tr>
		<tr>
			<td>Gloves, nitrile</td>
			<td>Titan Brand Gloves</td>
			<td>44-100S</td>
		</tr>
		<tr>
			<td>HPLC vials, 9 mm, 2 mL, clear</td>
			<td>Phenomenex</td>
			<td>ARO- 9921-13</td>
		</tr>
		<tr>
			<td>Lids for HPLC vials</td>
			<td>Phenomenex</td>
			<td>ARO- 8952-13-B</td>
		</tr>
		<tr>
			<td>Needle, 18G 1.5</td>
			<td>Precision Glide</td>
			<td>305196</td>
		</tr>
		<tr>
			<td>Rack for Eppendorf tubes</td>
			<td>Thermo Fisher Scientific</td>
			<td>03-448-11</td>
		</tr>
		<tr>
			<td>Rack for HPLC Vials</td>
			<td>Thermo Fisher Scientific</td>
			<td>05-541-29</td>
		</tr>
		<tr>
			<td>Steel beads 0.9 &#8211; 2 mm</td>
			<td>Next Advance</td>
			<td>SSB14B</td>
		</tr>
		<tr>
			<td>Storage boxes for freezers / refrigerators</td>
			<td>Thermo Fisher Scientific</td>
			<td>03-395-464</td>
		</tr>
		<tr>
			<td>Standard multi-tube vortexer</td>
			<td>VWR Scientific Products</td>
			<td>658816-115</td>
		</tr>
		<tr>
			<td>Whatman Paper, 903 Protein Saver US 100/PK</td>
			<td>GE Whatman&#160;</td>
			<td>2016-05</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC Equipment and Columns</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Autosampler</td>
			<td>CTC PAL&#160;</td>
			<td>PAL.HTCABIx1</td>
		</tr>
		<tr>
			<td>Binary pump, Agilent 1260 Infinity</td>
			<td>Agilent Technologies</td>
			<td>1260 G1312B</td>
		</tr>
		<tr>
			<td>Binary pump, Agilent 1290 Infinity</td>
			<td>Agilent Technologies</td>
			<td>1290 G4220A</td>
		</tr>
		<tr>
			<td>Micro vacuum degasser, Agilent 1260</td>
			<td>Agilent Technologies</td>
			<td>1260 G13798</td>
		</tr>
		<tr>
			<td>Column oven,&#160; Agilent 1290 with 2 position&#160;</td>
			<td>Agilent Technologies</td>
			<td>1290 G1216C</td>
		</tr>
		<tr>
			<td>Thermostated column compartment with integrated 6 port switching valve</td>
			<td>Agilent Technologies</td>
			<td>1290 G1316C</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC pre-column cartridge, Zorbax XDB C8 (5 &#181;m particle size), 4.6 &#183; 12.5 mm</td>
			<td>Phenomenex</td>
			<td>820950-926</td>
		</tr>
		<tr>
			<td>HPLC analytical column, Zorbax Eclipse-XDB-C8 (5 &#181;m particle size), 4.6 &#183; 150 mm</td>
			<td>Phenomenex</td>
			<td>993967-906</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tandem Mass Spectrometer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>API5000 MS/MS with TurboIonspray source</td>
			<td>AB Sciex</td>
			<td>4364257</td>
		</tr>
		<tr>
			<td>Mass spectrometry software</td>
			<td>AB Sciex</td>
			<td>Analyst 1.5.1</td>
		</tr>
	</tbody>
</table>

quantification of the immunosuppressant tacrolimus on dried blood spots using lc-ms/ms

The calcineurin inhibitor tacrolimus is the cornerstone of most immunosuppressive treatment protocols after solid organ transplantation in the United States. Tacrolimus is a narrow therapeutic index drug and as such requires therapeutic drug monitoring and dose adjustment based on its whole blood trough concentrations. To facilitate home therapeutic drug and adherence monitoring, the collection of dried blood spots is an attractive concept. After a finger stick, the patient collects a blood drop on filter paper at home. After the blood is dried, it is mailed to the analytical laboratory where tacrolimus is quantified using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in combination with a simple manual protein precipitation step and online column extraction.
For tacrolimus analysis, a 6-mm disc is punched from the saturated center of the blood spot. The blood spot is homogenized using a bullet blender and then proteins are precipitated with methanol/0.2 M ZnSO4 containing the internal standard D2,13C-tacrolimus. After vortexing and centrifugation, 100 &#181;l of supernatant is injected into an online extraction column and washed with 5 ml/min of 0.1 formic acid/acetonitrile (7:3, v:v) for 1 min. Hereafter, the switching valve is activated and the analytes are back-flushed onto the analytical column (and separated using a 0.1% formic acid/acetonitrile gradient). Tacrolimus is quantified in the positive multi reaction mode (MRM) using a tandem mass spectrometer.
The assay is linear from 1 to 50 ng/ml. Inter-assay variability (3.6%-6.1%) and accuracy (91.7%-101.6%) as assessed over 20 days meet acceptance criteria. Average extraction recovery is 95.5%. There are no relevant carry-over, matrix interferences and matrix effects. Tacrolimus is stable in dried blood spots at RT and at +4 &#176;C for 1 week. Extracted samples in the autosampler are stable at +4 &#176;C for at least 72 hr.

Representative ion chromatograms of a blank sample, a sample spiked at the lower limit of quantification and a patient sample are shown in Figure 3.
Calibration Curves
The lower limit of detection was 0.5 ng/ml and the lower limit of quantification was 1.0 ng/ml. Fifty ng/ml was chosen as the highest calibrator as higher concentrations are unlikely to be reached in the clinic under normal circumstances.
Calibration curves...

Watch this Scientific Journal Video about Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS at JoVE.com

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS

Here we describe a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay to quantify the immunosuppressant tacrolimus in dried blood spots using a simple manual protein precipitation step and online column extraction.

The calcineurin inhibitor tacrolimus is the cornerstone of most immunosuppressive treatment protocols after solid organ transplantation in the United ...

quantification-immunosuppressant-tacrolimus-on-dried-blood-spots

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Medicine

A Contusive Model of Unilateral Cervical Spinal Cord Injury Using the Infinite Horizon Impactor

While the majority of human spinal cord injuries occur in the cervical spinal cord, the vast majority of laboratory research employs animal models of spinal cord injury (SCI) in which the thoracic spinal cord is injured. Additionally, because most human cord injuries occur as the result of blunt, non-penetrating trauma (e.g. motor vehicle accident, sporting injury) where the spinal cord is violently struck by displaced bone or soft tissues, the majority of SCI researchers are of the opinion that the most clinically relevant injury models are those in which the spinal cord is rapidly contused.1 Therefore, an important step in the preclinical evaluation of novel treatments on their way to human translation is an assessment of their efficacy in a model of contusion SCI within the cervical spinal cord. Here, we describe the technical aspects and resultant anatomical and behavioral outcomes of an unilateral contusive model of cervical SCI that employs the Infinite Horizon spinal cord injury impactor.
Sprague Dawley rats underwent a left-sided unilateral laminectomy at C5. To optimize the reproducibility of the biomechanical, functional, and histological outcomes of the injury model, we contused the spinal cords using an impact force of 150 kdyn, an impact trajectory of 22.5&deg; (animals rotated at 22.5&deg;), and an impact location off of midline of 1.4 mm. Functional recovery was assessed using the cylinder rearing test, horizontal ladder test, grooming test and modified Montoya's staircase test for up to 6 weeks, after which the spinal cords were evaluated histologically for white and grey matter sparing.
The injury model presented here imparts consistent and reproducible biomechanical forces to the spinal cord, an important feature of any experimental SCI model. This results in discrete histological damage to the lateral half of the spinal cord which is largely contained to the ipsilateral side of injury. The injury is well tolerated by the animals, but does result in functional deficits of the forelimb that are significant and sustained in the weeks following injury. The cervical unilateral injury model presented here may be a resource to researchers who wish to evaluate potentially promising therapies prior to human translation.

A reliable and repeatable way to produce a cervical unilateral spinal cord injury using the Infinite Horizon impactor is described. The method takes advantage of a custom designed frame and clamp to stabilize the spine. The standardized procedure and biomechanical injury parameters result in sufficient and sustained injuries.

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Formation of Human Prostate Epithelium Using Tissue Recombination of Rodent Urogenital Sinus Mesenchyme and Human Stem Cells

Progress in prostate cancer research is severely limited by the availability of human-derived and hormone-na&iuml;ve model systems, which limit our ability to understand genetic and molecular events underlying prostate disease initiation. Toward developing better model systems for studying human prostate carcinogenesis, we and others have taken advantage of the unique pro-prostatic inductive potential of embryonic rodent prostate stroma, termed urogenital sinus mesenchyme (UGSM). When recombined with certain pluripotent cell populations such as embryonic stem cells, UGSM induces the formation of normal human prostate epithelia in a testosterone-dependent manner. Such a human model system can be used to investigate and experimentally test the ability of candidate prostate cancer susceptibility genes at an accelerated pace compared to typical rodent transgenic studies. Since Human embryonic stem cells (hESCs) can be genetically modified in culture using inducible gene expression or siRNA knock-down vectors prior to tissue recombination, such a model facilitates testing the functional consequences of genes, or combinations of genes, which are thought to promote or prevent carcinogenesis.
The technique of isolating pure populations of UGSM cells, however, is challenging and learning often requires someone with previous expertise to personally teach. Moreover, inoculation of cell mixtures under the renal capsule of an immunocompromised host can be technically challenging. Here we outline and illustrate proper isolation of UGSM from rodent embryos and renal capsule implantation of tissue mixtures to form human prostate epithelium. Such an approach, at its current stage, requires in vivo xenografting of embryonic stem cells; future applications could potentially include in vitro gland formation or the use of induced pluripotent stem cell populations (iPSCs).

To unravel the earliest molecular mechanisms underlying prostate cancer initiation, novel and innovative human model systems and approaches are desperately needed. The potential of pre-prostatic urogenital sinus mesenchyme (UGSM) to induce pluripotent stem cell populations to form human prostate epithelium is a powerful experimental tool in prostate research.

Progress in prostate cancer research is severely  limited by the availability of human-derived and hormone-na&iuml;ve model systems,  which limit our ...

Dried Blood Spot Collection of Health Biomarkers to Maximize Participation in Population Studies

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Biomarkers are directly-measured biological indicators of disease or health. In population and social sciences, biomarkers need to be easy to obtain, transport, and analyze. Dried Blood Spot (DBS) collection meets this need, can be collected in the field with high response rates&#160;and analyzed for a variety of biomarkers.

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An antibody-independent Reference Measurement Procedure (RMP) was developed based on solid-phase extraction (SPE) and liquid chromatography (LC)-tandem mass spectrometry (MS/MS), where stable, isotope-labeled A&#946; peptides were used as internal standards, enabling absolute quantification. A high-resolution quadrupole-orbitrap hybrid instrument was used for the measurements. The method allows for the quantification of CSF A&#946;1-42 between 150-4,000 pg/mL.

Absolute Quantification of A&amp;#946;&lt;sub&gt;1-42&lt;/sub&gt; in CSF Using a Mass Spectrometric Reference Measurement Procedure

A reference measurement procedure for the absolute quantification of A&#946;1-42 in human CSF based on solid-phase extraction and liquid chromatography tandem mass spectrometry is described.

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly and accounts for 60-80% of all cases of dementia. Currently, the ...

Optimized LC-MS/MS Method for the High-throughput Analysis of Clinical Samples of Ivacaftor, Its Major Metabolites, and Lumacaftor in Biological Fluids of Cystic Fibrosis Patients

Defects in the cystic fibrosis trans-membrane conductance regulator (CFTR) are the cause of cystic fibrosis (CF), a disease with life-threatening pulmonary manifestations. Ivacaftor (IVA) and ivacaftor-lumacaftor (LUMA) combination are two new breakthrough CF drugs that directly modulate the activity and trafficking of the defective CFTR-protein. However, there is still a dearth of understanding on pharmacokinetic/pharmacodynamic parameters and the pharmacology of ivacaftor and lumacaftor. The HPLC-MS technique for the simultaneous analysis of the concentrations of ivacaftor, hydroxymethyl-ivacaftor, ivacaftor-carboxylate, and lumacaftor in biological fluids in patients receiving standard ivacaftor or ivacaftor-lumacaftor combination therapy has previously been developed by our group and partially validated to FDA standards. However, to allow the high-throughput analysis of a larger number of patient samples, our group has optimized the reported method through the use of a smaller pore size reverse-phase chromatography column (2.6 &#181;m, C8 100 &#197;; 50 x 2.1 mm) and a gradient solvent system (0-1 min: 40% B; 1-2 min: 40-70% B; 2-2.7 min: held at 70% B; 2.7-2.8 min: 70-90% B; 2.8-4.0 min: 90% B washing; 4.0-4.1 min: 90-40% B; 4.1-6.0 min: held at 40% B) instead of an isocratic elution. The goal of this study was to reduce the HPLC-MS analysis time per sample dramatically from ~15 min to only 6 min per sample, which is essential for the analysis of a large amount of patient samples. This expedient method will be of considerable utility for studies into the exposure-response relationships of these breakthrough CF drugs.

Ivacaftor and ivacaftor-lumacaftor combination are two new CF drugs. However, there is still a dearth of understanding on their PK/PD and pharmacology. We present an optimized HPLC-MS technique for the simultaneous analysis of ivacaftor and its major metabolites, and lumacaftor.

Defects in the cystic fibrosis trans-membrane conductance regulator (CFTR) are the cause of cystic fibrosis (CF), a disease with life-threatening ...

A Chronic Cardiac Ischemia Model in Swine Using an Ameroid Constrictor

Cardiovascular disease remains the number one cause of mortality in the United States. There are numerous approaches to treating these diseases, but regardless of the approach, an in vivo model is needed to test each treatment. The pig is one of the most used large animal models for cardiovascular disease. Its heart is very similar in anatomy and function to that of a human. The ameroid placement technique creates an ischemic area of the heart, which has many useful applications in studying myocardial infarction. This model has been used for surgical research, pharmaceutical studies, imaging techniques, and cell therapies.
There are several ways of inducing an ischemic area in the heart. Each has its advantages and disadvantages, but the placement of an ameroid constrictor remains the most widely used technique. The main advantages to using the ameroid are its prevalence in existing research, its availability in various sizes to accommodate the anatomy and size of the vessel to be constricted, the surgery is a relatively simple procedure, and the post-operative monitoring is minimal, since there are no external devices to maintain. This paper provides a detailed overview of the proper technique for the placement of the ameroid constrictor.

The purpose of this protocol is to demonstrate the placement of a delayed constricting device (an ameroid constrictor) around a coronary artery in a swine model. This device creates an ischemic area of the heart that is useful for studying new diagnostic imaging techniques and new methods of treatment.

Cardiovascular disease remains the number one cause of mortality in the United States. There are numerous approaches to treating these diseases, but ...

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) models based on pBECs in mono-culture (MC), MC with astrocyte-conditioned medium (ACM), and non-contact co-culture (NCC) with astrocytes of porcine or rat origin. pBECs were isolated and cultured from fragments of capillaries from the brain cortices of domestic pigs 5-6 months old. These fragments were purified by careful removal of meninges, isolation and homogenization of grey matter, filtration, enzymatic digestion, and centrifugation. To further eliminate contaminating cells, the capillary fragments were cultured with puromycin-containing medium. When 60-95% confluent, pBECs growing from the capillary fragments were passaged to permeable membrane filter inserts and established in the models. To increase barrier tightness and BBB characteristic phenotype of pBECs, the cells were treated with the following differentiation factors: membrane permeant 8-CPT-cAMP (here abbreviated cAMP), hydrocortisone, and a phosphodiesterase inhibitor, RO-20-1724 (RO). The procedure was carried out over a period of 9-11 days, and when establishing the NCC model, the astrocytes were cultured 2-8 weeks in advance. Adherence to the described procedures in the protocol has allowed the establishment of endothelial layers with highly restricted paracellular permeability, with the NCC model showing an average transendothelial electrical resistance (TEER) of 1249 &#177; 80 &#937; cm2, and paracellular permeability (Papp) for Lucifer Yellow of 0.90 10-6 &#177; 0.13 10-6 cm sec-1 (mean &#177; SEM, n=55). Further evaluation of this pBEC phenotype showed good expression of the tight junctional proteins claudin 5, ZO-1, occludin and adherens junction protein p120 catenin. The model presented can be used for a range of studies of the BBB in health and disease and, with the highly restrictive paracellular permeability, this model is suitable for studies of transport and intracellular trafficking.

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of the protocol is to present an optimized procedure for the establishment of an in vitro blood-brain barrier (BBB) model based on primary porcine brain endothelial cells (pBECs). The model shows high reproducibility, high tightness, and is suitable for studies of transport and intracellular trafficking in drug discovery.

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) ...

Blood Collection Through Subclavian Vein Puncture in Mice

The mouse is the foremost mammalian model for studying human disease and human health. However, blood sample collection from mice is challenging in research work. Tail blood collection is a popular method when a small amount of blood sample is needed. Orbital artery could be considered if a large amount of blood is needed but this blood collection method has ethical issues. Formerly, we demonstrated the feasibility and safety of blood sample collection through subclavian vein puncture in rats, and here we investigate whether this method could be used in mice. We report that this method is safe and practical for blood collection in mice. Blood collection through the subclavian vein puncture in mice can be a convenient method in daily research works.

Here, we present a protocol to take blood samples from the subclavian vein of mice.

The mouse is the foremost mammalian model for studying human disease and human health. However, blood sample collection from mice is challenging in ...

Evaluation of Cerebral Blood Flow Autoregulation in the Rat Using Laser Doppler Flowmetry

When investigating the body&#39;s mechanisms for regulating cerebral blood flow, a relative measurement of microcirculatory blood flow can be obtained using laser Doppler flowmetry (LDF). This paper demonstrates a closed skull preparation that allows cerebral blood flow to be assessed without penetrating the skull or installing a chamber or cerebral window. To evaluate autoregulatory mechanisms, a model of controlled blood pressure reduction via graded hemorrhage can be utilized while simultaneously employing LDF. This enables the real time tracking of the relative changes in the blood flow in response to reductions in arterial blood pressure produced by the withdrawal of circulating blood volume. This paradigm is a valuable approach to study cerebral blood flow autoregulation during reductions in arterial blood pressure and, with minor modifications in the protocol, is also valuable as an experimental model of hemorrhagic shock. In addition to evaluating autoregulatory responses, LDF can be used to monitor the cortical blood flow when investigating metabolic, myogenic, endothelial, humoral, or neural mechanisms that regulate cerebral blood flow and the impact of various experimental interventions and pathological conditions on cerebral blood flow.

This article demonstrates the use of laser Doppler flowmetry to evaluate the ability of the cerebral circulation to autoregulate its blood flow during reductions in arterial blood pressure.

When investigating the body&#39;s mechanisms for regulating cerebral blood flow, a relative measurement of microcirculatory blood flow can be obtained ...

Validated LC-MS/MS Panel for Quantifying 11 Drug-Resistant TB Medications in Small Hair Samples

Drug resistant-tuberculosis (DR-TB) is a growing public health threat, and assessment of therapeutic drug levels may have important clinical benefits. Plasma drug levels are the current gold standard assessment, but require phlebotomy and a cold chain, and capture only very recent adherence. Our method uses hair, a matrix that is easily collected and reflective of long-term adherence, to test for 11 anti-TB medications. Previous work by our group shows that antiretroviral drug levels in hair are associated with HIV outcomes. Our method for DR-TB drugs uses 2 mg of hair (3 cm proximal to the root), which is pulverized and extracted in methanol. Samples are analyzed with a single LC-MS/MS method, quantifying 11 drugs in a 16 min run. Lower limits of quantification (LLOQs) for the 11 drugs range from 0.01 ng/mg to 1 ng/mg. Drug presence is confirmed by comparing ratios of two mass spectrometry transitions. Samples are quantified using the area ratio of the drug to the deuterated, 15N-, or 13C-labeled drug isotopologue. We used a calibration curve ranging from 0.001-100 ng/mg. Application of the method to a convenience sample of hair samples collected from DR-TB patients on directly observed therapy (DOT) indicated drug levels in hair within the linear dynamic range of nine of the eleven drugs (isoniazid, pyrazinamide, ethambutol, linezolid, levofloxacin, moxifloxacin, clofazimine, bedaquiline, pretomanid). No patient was on prothionamide, and the measured levels for ethionamide were close to its LLOQ (with further work instead examining the suitability of ethionamide&#8217;s metabolite for monitoring exposure). In summary, we describe the development of a multi-analyte panel for DR-TB drugs in hair as a technique for therapeutic drug monitoring during drug-resistant TB treatment.

Current methods of analyzing patients&#8217; adherence to complex drug resistant-tuberculosis (DR-TB) regimens can be inaccurate and resource-intensive. Our method analyzes hair, an easily collected and stored matrix, for concentrations of 11 DR-TB medications. Using LC-MS/MS, we can determine sub-nanogram drug levels that can be utilized to better understand drug adherence.

Drug resistant-tuberculosis (DR-TB) is a growing public health threat, and assessment of therapeutic drug levels may have important clinical benefits. ...