A Volumetric Absorptive Microsampling UPLC-MS/MS Method for Simultaneous Quantification of Tacrolimus, Mycophenolic Acid and Creatinine in Whole Blood of Renal Transplant Recipients

Electrochemical detection of creatinine at picomolar scale with an extended linear dynamic range in human body fluids for diagnosis of kidney dysfunction

BACKGROUND

Creatinine levels in different body fluids can serve as an important biomarker for kidney functioning relevant to prostate cancer and chronic kidney disease (CKD). Creatinine levels vary in concentration in different body fluids, such as blood, urine, and saliva. Unlike previously reported sensors, the developed creatinine sensor can be employed for all levels of creatinine in samples of real patients.

RESULTS

In this study, an efficient voltammetric sensor for creatinine is developed by modifying a glassy carbon electrode (GCE) with poly (ethyleneimine) (PEI) capped silver nanoparticles at titanium dioxide (PEI-AgNPs)/TiO2, i.e., titanium dioxide (TiO2)/graphene oxide (GO) nanocomposites (Ag@GO/TiO2-GCE). The Ag@GO/TiO2 nanocomposite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, Fourier transform infrared (FT-IR) spectroscopy, and UV-Vis spectrophotometry. Various voltammetric techniques namely cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed. The Ag@GO/TiO2-GCE demonstrated good selectivity, stability, and a quick response time of 1.0 s for creatinine. An extended linear dynamic range (LDR) of creatinine from 0.01 pM (DPV) to 1.0 M (CV) based on different voltammetric techniques is imperative for detecting diverse creatinine levels in various body fluids. The LOD and LOQ of the developed creatinine detection method were found to be 1.15 pM and 3.5 pM, respectively. The electrochemical sensor exhibited an exceptionally high sensitivity of 15.74 μApM-1cm-2.The body fluids from healthy volunteers were spiked with a known amount of creatinine to evaluate sensor efficiency in the context of recovery. Finally, blood serum, saliva, and urine samples of kidney patients were analyzed for creatinine levels.

SIGNIFICANCE

An important merit of the developed creatinine sensor is its ability for non-invasive point-of-care diagnosis in saliva with more than 90 % recovery. The comparison of the developed method with the standard Jaffes' colorimetric method endorsed its reliability and extended ability for the samples where Jaffes' method fails. The low LOD, high sensitivity, extended LDR, and low-cost render the possibility of adopting this method for point-of-care diagnosis.

Microsampling techniques and patient-centric therapeutic drug monitoring of immunosuppressants

Immunosuppressive pharmacotherapy after solid organ transplantation (SOT) requires therapeutic drug monitoring (TDM) for therapy individualization. The venous whole blood is still considered as routine matrix for monitoring immunosuppressive drug concentration. On the other hand, as an alternative, capillary blood collected using noninvasive sampling is convergent with a patient-centric approach. Despite their disadvantages regarding sample homogeneity and the hematocrit effect, well-known dried blood spot techniques have shown promising results. Volumetric absorptive microsampling (VAMS) and quantitative dried blood spot (qDBS) have successfully eliminated these unfavorable biased elements. Microsampling can be used in transplant recipients' care, mainly due to long-term therapy under control drug concentrations and the long distance between the place of the patient's residence and the diagnostic laboratory in the transplant center. The study aimed to discuss the clinical consequences of implementing microsampling techniques for TDM of immunosuppressants. Additionally, we have discussed the 'hot topics' in microsampling: home-based self-sampling, adherence to therapy monitoring, and drug concentration conversion to estimated traditional matrices. Finally, based on our experience and current practice, we propose best practices for microsampling implementation from bench to bedside. Microsampling techniques can potentially revolutionise immunosuppressive pharmacotherapy by enabling patient-centric individualisation in various subpopulations, significantly improving post-transplant care.

Implementation of Volumetric Finger-Prick Self-Sampling for Therapeutic Drug Monitoring of Immunosuppressants After Kidney Transplantation: Lessons Learned From the Practice

BACKGROUND

Home-based hospital services are becoming increasingly popular, and the addition of remote outpatient appointments after kidney transplantation facilitates more practical and closer follow-up. In this context, finger-prick self-sampling is an important aspect of monitoring of immunosuppressants and biomarkers. Nevertheless, several issues must be addressed to ensure the feasibility and quality when implementing microsampling in clinical practice. We summarize our experiences and opinions in this field.

METHODS

This article is based on the authors' experience regarding the laboratory and clinical implementation of finger-prick self-sampling in kidney transplant recipients. The referenced literature is related to the authors' knowledge in this field.

RESULTS

We present considerations for the selection of relevant analytes, key characteristics of selected volumetric sampling tools (Mitra and Capitainer), and the associated sampling pitfalls. In addition, we address the requirements for patients performing finger-prick sampling, appropriate design of methods and workflow, critical points for validation, and aspects related to logistics and digital solutions.

CONCLUSIONS

Volumetric finger-prick self-sampling is suitable for monitoring immunosuppressants and certain biomarkers that are relevant to outpatient follow-up after kidney transplantation. We believe that a carefully designed system for the entire workflow, including patient training, will be beneficial in enabling a safe experience for transplant recipients, as well as ensuring overall efficiency and adequate quality. In the future, a combination of immunosuppressants with a wide range of biomarkers has significant potential for use in at-home self-sampling after kidney transplantation.

Clinical validation of two volumetric absorptive microsampling devices to support home-based therapeutic drug monitoring of immunosuppression

AIMS

Dried blood volumetric absorptive microsamples (VAMS) may facilitate home-based sampling to enhance therapeutic drug monitoring after transplantation. This study aimed to clinically validate a liquid chromatography-tandem mass spectrometry assay using 2 VAMS devices with different sampling locations (Tasso-M20 for the upper arm and Mitra for the finger). Patient preferences were also evaluated.

METHODS

Clinical validation was performed for tacrolimus and mycophenolic acid by comparison of paired VAMS and venipuncture samples using Passing-Bablok regression and Bland-Altman analysis. Conversion of mycophenolic acid VAMS to serum concentrations was evaluated using haematocrit-dependent formulas and fixed correction factors defined a priori. Patients' perspectives, including useability, acceptability and feasibility, were also investigated using established questionnaires.

RESULTS

Paired samples (n = 50) were collected from 25 kidney transplant recipients. Differences for tacrolimus whole-blood concentration were within ±20% for 86 and 88% of samples from the upper arm and fingerstick, respectively. Using correction factors of 1.3 for the upper-arm and 1.47 for finger-prick samples, 84 and 76% of the paired samples, respectively, were within ±20% for mycophenolic acid serum concentration. Patient experience surveys demonstrated limited pain and acceptable useability of the upper-arm device.

CONCLUSIONS

Tacrolimus and mycophenolic acid can be measured using 2 common VAMS devices with similar analytical performance. Patients are supportive of home-based monitoring with a preference for the Tasso-M20 device.

Targeted and untargeted metabolomics and lipidomics in dried blood microsampling: Recent applications and perspectives

Blood microsampling (BµS) offers an alternative to conventional methods that use plasma or serum for profiling human health, being minimally invasive and cost effective, especially beneficial for vulnerable populations. We present a non-systematic review that offers a synopsis of the analytical methods, applications and perspectives related to dry blood microsampling in targeted and untargeted metabolomics and lipidomics research in the years 2022 and 2023. BµS shows potential in neonatal and paediatric studies, therapeutic drug monitoring, metabolite screening, biomarker research, sports supervision, clinical disorders studies and forensic toxicology. Notably, dried blood spots and volumetric absorptive microsampling options have been more extensively studied than other volumetric technologies. Therefore, we suggest that a further investigation and application of the volumetric technologies will contribute to the use of BµS as an alternative to conventional methods. Conversely, we support the idea that harmonisation of the analytical methods when using BµS would have a positive impact on its implementation.

Fingerprick volumetric absorptive microsampling for therapeutic drug monitoring of antiseizure medications: Reliability and real-life feasibility in epilepsy patients

Volumetric absorptive microsampling (VAMS) is increasingly proposed as a clinically reliable therapeutic drug monitoring (TDM) sampling methodology. The study aimed to establish the reliability and real-life feasibility of patient self-collected capillary VAMS for TDM of antiseizure medication (ASMs), using plasma ASMs concentrations from venous blood as a reference standard. Nurses collected venous and capillary blood samples using VAMS. Afterward, persons with epilepsy (PWE) performed VAMS sampling by themselves. All samples were analyzed by UHPLC-MS/MS. We performed a cross-validation study, comparing ASMs concentrations obtained by VAMS nurses and patients' self-collected versus plasma through Bland-Altman analysis and Passing-Bablok regression. We enrolled 301 PWE (M: F 42.5%:57.5%; mean age 44±16 years), treated with 13 ASMs, providing a total of 464 measurements. Statistical analysis comparing VAMS self-collected versus plasma ASMs concentrations showed a bias close to zero and slope and intercept values indicating a good agreement for CBZ, LCS, LEV, LTG, OXC, PB, and PHT, while a systematic difference between the two methods was found for VPA, PMP, TPM and ZNS. This is the first study showing the reliability and feasibility of the real-world application of PWE self-collected VAMS for most of the ASMs considered, giving a promising basis for at-home VAMS applications.

Tacrolimus and Cyclosporin Pharmacotherapy, Detection Methods, Cytochrome P450 Enzymes after Heart Transplantation

BACKGROUND

Advances in organ transplantation were made after the discovery of the pure form of cyclosporine by Dr Jean Borel in the 1970s. In fact, in clinical practice achieving a delicate balance in circulating immunosuppressive necessitate focus on the difficult task of posttransplant therapeutic drug monitoring.

OBJECTIVE

The purpose of this study was to determine the pharmacologic properties of cyclosporine- tacrolimus, detection methods, and the effects on the activity of cytochrome P450 enzymes when prescribing the most efficient treatments in forms of polypharmacy for the recipients of heart transplantation.

METHODS

Scientific literature on the interactions of tacrolimus and cyclosporine with human cytochrome P450 enzymes was searched using PUBMED.Gov (https://pubmed.ncbi.nlm.nih.gov/), Web of Science, and Scopus.

RESULTS

Prescription immunosuppressive drugs based on polypharmacy accompanied by induction agents could result in hidden neurotoxicity and nephrotoxicity. A literature search shows that cyclosporine prescription with antihypertensives drugs needs close monitoring. Co-administration of tacrolimus and diltiazem or verapamil needs a decrease in the tacrolimus dose by 20-50%. Vigilant attention to the lowest possible statin dose is needed when coadministered with fluvastatin or pravastatin. Polypharmacy based on ticlopidine, clopidogrel, and cyclosporine or tacrolimus needs monitoring of immunosuppressive drug levels for several months. A prescription with clotrimazole or fluconazole needs close monitoring, and itraconazole or ketoconazole needs to reduce the initial dose by 50%. Combination with nefazodone needs to be avoided, and alternative drugs such as sertraline or citalopram could be prescribed in addition to further monitoring consideration. In prescription with phenytoin, the bound and free phenytoin levels need close monitoring.

CONCLUSION

Polypharmacy based on tacrolimus or cyclosporine needs vigilant therapeutic drug monitoring due to the cytochrome P450 enzymes associated with biochemical variables in metabolic pathways. Further attention to polypharmacy should be given to circulate drugs that could hide pharmacokinetics interactions associated with infections, malignancies, chronic kidney disease, and rejection after organ transplantation.

Volumetric Absorptive Microsampling in the Analysis of Endogenous Metabolites

Volumetric absorptive microsampling (VAMS) has arisen as a relevant tool in biological analysis, offering simplified sampling procedures and enhanced stability. Most of the attention VAMS has received in the past decade has been from pharmaceutical research, with most of the published work employing VAMS targeting drugs or other exogenous compounds, such as toxins and pollutants. However, biomarker analysis by employing blood microsampling has high promise. Herein, a comprehensive review on the applicability of VAMS devices for the analysis of endogenous metabolites/biomarkers was performed. The study presents a full overview of the analysis process, incorporating all the steps in sample treatment and validation parameters. Overall, VAMS devices have proven to be reliable tools for the analysis of endogenous analytes with biological importance, often offering improved analyte stability in comparison with blood under ambient conditions as well as a convenient and straightforward sample acquisition model.

In-situ preparation of norepinephrine-functionalized silver nanoparticles and application for colorimetric detection of tacrolimus in plasma samples

Tacrolimus (Tac) is a well-documented immunosuppressive agent for the prevention of graft-vs-host diseases in several types of organ transplants. The narrow therapeutic window and the individual-variable pharmacokinetics of Tac demonstrate the importance of regular therapeutic drug monitoring (TDM) as an imperative concept for its oral medication regimens. A simple, one-step, selective, and sensitive colorimetric platform is fabricated for the determination of Tac by surface modification of the silver nanoparticles (AgNPs) via norepinephrine (NE) molecules. The attachment of NE and Tac induces the aggregation of the AgNPs, which is observed by color distinction (yellow to brown) and a noteworthy shifting of the absorption peak in the visible region. The fabricated nanoprobe can detect Tac concentrations in plasma samples in two linear ranges from 2 ng/mL to 70 ng/mL and 70 ng/mL to 1000 ng/mL with R2 > 0.99. The limit of detection (LOD) was calculated as low as 0.1 ng/mL. The developed method was applied for the determination of Tac in patient's plasma samples under Tac medication therapy.

Therapeutic drug monitoring of mycophenolic acid (MPA) using volumetric absorptive microsampling (VAMS) in pediatric renal transplant recipients: ultra-high-performance liquid chromatography-tandem mass spectrometry analytical method development, cross-validation, and clinical application

BACKGROUND

Mycophenolic acid (MPA) is widely used in posttransplant pharmacotherapy for pediatric patients after renal transplantation. Volumetric absorptive microsampling (VAMS) is a recent approach for sample collection, particularly during therapeutic drug monitoring (TDM). The recommended matrix for MPA determination is plasma (PL), and conversion between capillary-blood VAMS samples and PL concentrations is required for the appropriate interpretation of the results.

METHODS

This study aimed to validate and develop a UHPLC-MS/MS method for MPA quantification in whole blood (WB), PL, and VAMS samples, with cross and clinical validation based on regression calculations. Methods were validated in the 0.10-15 µg/mL range for trough MPA concentration measurement according to the European Medicines Agency (EMA) guidelines. Fifty pediatric patients treated with MPA after renal transplantation were included in this study. PL and WB samples were obtained via venipuncture, whereas VAMS samples were collected after the fingerstick. The conversion from VAMS_MPA to PL_MPA concentration was performed using formulas based on hematocrit values and a regression model.

RESULTS

LC-MS/MS methods were successfully developed and validated according to EMA guidelines. The cross-correlation between the methods was evaluated using Passing-Bablok regression, Bland-Altman bias plots, and predictive performance calculations. Clinical validation of the developed method was successfully performed, and the formula based on regression was successfully validated for VAMS_MPA to PL_MPA concentration and confirmed on an independent group of samples.

CONCLUSIONS

This study is the first development of a triple matrix-based LC-MS/MS method for MPA determination in the pediatric population after renal transplantation. For the first time, the developed methods were cross-validated with routinely used HPLC-DAD protocol.