Collection, storage, and filtration of in vivo study samples using 96-well filter plates to facilitate automated sample preparation and LC/MS/MS analysis

Lectin and Liquid Chromatography-Based Methods for Immunoglobulin (G) Glycosylation Analysis

Immunoglobulin (Ig) glycosylation has been shown to dramatically affect its structure and effector functions. Ig glycosylation changes have been associated with different diseases and show a promising biomarker potential for diagnosis and prognosis of disease advancement. On the other hand, therapeutic biomolecules based on structural and functional features of Igs demand stringent quality control during the production process to ensure their safety and efficacy. Liquid chromatography (LC) and lectin-based methods are routinely used in Ig glycosylation analysis complementary to other analytical methods, e.g., mass spectrometry and capillary electrophoresis. This chapter covers analytical approaches based on LC and lectins used in low- and high-throughput N- and O-glycosylation analysis of Igs, with the focus on immunoglobulin G (IgG) applications. General principles and practical examples of the most often used LC methods for Ig purification are described, together with typical workflows for N- and O-glycan analysis on the level of free glycans, glycopeptides, subunits, or intact Igs. Lectin chromatography is a historical approach for the analysis of lectin-carbohydrate interactions and glycoprotein purification but is still being used as a valuable tool in Igs purification and glycan analysis. On the other hand, lectin microarrays have found their application in the rapid screening of glycan profiles on intact proteins.

Semi-Automated Sample Preparation for Plasma Proteomics

The discovery of new biomarkers will be an essential step to enhance our ability to better diagnose and treat human disease. The proteomics research community has recently increased its use of human blood (plasma/serum) as a sample source for these discoveries. However, while blood is fairly non-invasive and readily available as a specimen, it is not easily analyzed by liquid chromatography (LC)/mass spectrometry (MS), because of its complexity. Therefore, sample preparation is a crucial step prior to the analysis of blood. This sample preparation must also be standardized in order to gain the most information from these valuable samples and to ensure reproducibility. We have designed a semi-automated and highly parallel procedure for the preparation of human plasma samples. Our process takes the samples through eight successive steps before analysis by LC/MS: (1) receipt, (2) reformatting, (3) filtration, (4) depletion, (5) concentration determination and normalization, (6) digestion, (7) extraction, and (8) randomization, triplication, and lyophilization. These steps utilize a number of different liquid handlers and liquid chromatography (LC) systems. This process enhances our ability to discover new biomarkers from human plasma.

Bioanalysis in oncology drug discovery

Bioanalysis is an important aspect of drug discovery process regardless of the chosen therapeutic area. There is a general misconception that bioanalysis is seldom important during the drug discovery process because there is no scrutiny of the data from a regulatory perspective. However, bioanalytical data gathered during the discovery stage enable several key decision(s) inclusive of termination of the program and/or creating adequate differentiation from the lead competitive molecules. The review covers various stage gate screens and experimental designs where bioanalytical data are extensively used for making an informed decision during the process of drug discovery.

Development and full validation of six inhibition assays for five major cytochrome P450 enzymes in human liver microsomes using an automated 96-well microplate incubation format and LC–MS/MS analysis

Substrate inhibition assays for five of the major CYP enzymes (phenacetin for CYP1A2, diclofenac for CYP2C9, (S)-mephenytoin for CYP2C19, dextromethorphan for CYP2D6 and midazolam and testosterone for CYP3A4) in human liver microsomes were developed. Fully automated incubations were conducted in a 96-well format under optimized enzyme kinetic conditions. Metabolites of probe substrates were analyzed with rapid LC-MS/MS methods. The assays were fully validated following the procedure for validating bioanalytical methods recommended by regulatory agencies. Quality control samples and a positive control CYP inhibitor were included in each assay. The IC(50) values determined for typical CYP inhibitors were reproducible and consistent with those reported in the literature. The high quality and throughput of these assays make them ideally suited for providing information for decision making in late drug discovery and early development and for providing labeling input for new drug registrations.

Reliable on-line sample preparation of basic compounds from plasma using a reversed phase restricted access media in column-switching LC

We investigated on-line sample preparation of basic compounds from plasma using a methylcellulose-immobilized reversed-phase restricted-access media in column-switching liquid chromatography (LC). Dilution of the plasma sample with phosphate buffered saline prevented or delayed the formation of fibrin clots at 4 degrees C and resulted in reproducible on-line sample preparation over a 30-h period. The use of an ion-pair reagent in the extraction LC enhanced recoveries of hydrophilic basic compounds. The ability of the methods to quantify compounds in plasma were validated and the method was successfully applied to the pharmacokinetic study of a hydrophilic basic compound injected into the bloodstream of rats.

High throughput screening of protein formulation stability: practical considerations

The formulation of protein drugs is a difficult and time-consuming process, mainly due to the complexity of protein structure and the very specific physical and chemical properties involved. Understanding protein degradation pathways is essential for the success of a biopharmaceutical drug. The present review concerns the application of high throughput screening techniques in protein formulation development. A protein high throughput formulation (HTF) platform is based on the use of microplates. Basically, the HTF platform consists of two parts: (i) sample preparation and (ii) sample analysis. Sample preparation involves automated systems for dispensing the drug and the formulation ingredients in both liquid and powder form. The sample analysis involves specific methods developed for each protein to investigate physical and chemical properties of the formulations in microplates. Examples are presented of the use of protein intrinsic fluorescence for the analysis of protein aqueous properties (e.g., conformation and aggregation). Different techniques suitable for HTF analysis are discussed and some of the issues concerning implementation are presented with reference to the use of microplates.

High throughput therapeutic drug monitoring of clozapine and metabolites in serum by on-line coupling of solid phase extraction with liquid chromatography–mass spectrometry

The characteristics of automated on-line solid phase extraction with liquid chromatography-mass spectrometry (SPE-LC-MS) are very amenable for flexibility and throughput in therapeutic drug monitoring (TDM). We demonstrate this concept of automated, on-line SPE-LC-MS for the analysis of clozapine and metabolites (desmethylclozapine and clozapine-N-oxide) in serum. Method development, optimisation and validation are described and a comparison with previously published methods for the determination of clozapine and metabolites in serum and plasma is made. Optimisation of chromatographic and SPE conditions for increased throughput resulted in SPE-LC-MS cycle times of only about 2.2 min, demonstrating the great potential of automated on-line SPE-LC-MS for TDM. The new method is shown to be clearly favourable, in particular in terms of ease of sample handling, throughput and detection limits. Recovery is essentially quantitative. Detection limits are at about 0.15-0.3 ng ml(-1), depending on the ionisation source used. Calibration follows a quadratic model for clozapine and its N-oxide and a linear model for the desmethyl metabolite (all cases: R > 0.99). Accuracy, evaluated at three concentration levels spanning the whole therapeutic range, shows that bias is less than 10%. Precision (intra - and inter assay) ranges from about 5% R.S.D. at the high end of the therapeutic range (700-1,000 ng ml(-1)) to about 20% R.S.D. (OECD defined limit) at the lower limit of quantitation ( approximately 50 ng ml(-1)). The lower limit of quantitation is well below the low end of the therapeutic range at 350 ng ml(-1).

Rapid and direct measurement of free concentrations of highly protein-bound fluoxetine and its metabolite norfluoxetine in plasma

Fluoxetine (F) and its active N-demethylated metabolite, norfluoxetine (NF), are selective serotonin re-uptake inhibitors that bind extensively to plasma proteins. Development and validation of a novel method for measuring free concentrations of F and NF in plasma are reported here. The plasma filtrate was prepared by a high-speed short-duration ultrafiltration (UF) and then submitted directly to a short-column liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay. There was no significant matrix effect on the analysis, and non-specific binding of the analytes to the UF devices was negligible. For validation of the method, the recovery of the free analytes was compared to that from an optimized equilibrium dialysis method, and analyte stability was examined under conditions mimicking the sample storage, handling, and analysis procedures. The linearity range was 0.37-12 ng/mL for F and NF; the within-run and between-run relative standard deviations were less than 11.9%, and accuracies across the assay range were 100 +/- 10.3%. This new method was then further validated in a pharmacokinetic (PK) study in beagle dogs receiving a single oral dose of fluoxetine hydrochloride. The integrity of the resulting PK data of free F and NF was absolute. The PK data indicate that the novel method is accurate and reliable. To our knowledge this is the first report describing a rapid and reliable method for direct measurement of free concentrations of F and NF in plasma, which will be useful for clinical pharmacokinetic/pharmacodynamic studies of F. Furthermore, the strategies described herein may be applied to the development and validation of methods for measuring the free concentrations of other drugs in plasma.

A 96-Well Screen Filter Plate for High-Throughput Biological Sample Preparation and LC−MS/MS Analysis

A novel 96-well screen filter plate (patent pending) has been invented to eliminate a time-consuming and labor-intensive step in preparation of in vivo study samples--to remove blood or plasma clots. These clots plug the pipet tips during a manual or automated sample-transfer step causing inaccurate pipetting or total pipetting failure. Traditionally, these blood and plasma clots are removed by picking them out manually one by one from each sample tube before any sample transfer can be made. This has significantly slowed the sample preparation process and has become a bottleneck for automated high-throughput sample preparation using robotic liquid handlers. Our novel screen filter plate was developed to solve this problem. The 96-well screen filter plate consists of 96 stainless steel wire-mesh screen tubes connected to the 96 openings of a top plate so that the screen filter plate can be readily inserted into a 96-well sample storage plate. Upon insertion, the blood and plasma clots are excluded from entering the screen tube while clear sample solutions flow freely into it. In this way, sample transfer can be easily completed by either manual or automated pipetting methods. In this report, three structurally diverse compounds were selected to evaluate and validate the use of the screen filter plate. The plasma samples of these compounds were transferred and processed in the presence and absence of the screen filter plate and then analyzed by LC-MS/MS methods. Our results showed a good agreement between the samples prepared with and without the screen filter plate, demonstrating the utility and efficiency of this novel device for preparation of blood and plasma samples. The device is simple, easy to use, and reusable. It can be employed for sample preparation of other biological fluids that contain floating particulates or aggregates.

Self-Contained On-Chip Cell Culture and Pretreatment System

In this study, we describe a simple on-chip cell culture and pretreatment system that requires no external machines. Conventional cell culture utilizes culture dishes or microtiter plates, where pipetting and centrifugation are indispensable for washing cells and changing media. However, our microdevice requires no external centrifugation or pump. Utilizing this microdevice, we attained dramatically shorter total analytical time with a high-throughput screening system for proteomic analysis (1 min per 12 samples; one eightieth of the conventional time). Protein expression of Jurkat cells during stress-shock induced apoptosis was readily analyzed using this system. We found that a seaweed extraction effectively induced apoptosis of Jurkat cells.

Quantitative high-throughput analysis of drugs in biological matrices by mass spectrometry

To support pharmacokinetic and drug metabolism studies, LC-MS/MS plays more and more an essential role for the quantitation of drugs and their metabolites in biological matrices. With the new challenges encountered in drug discovery and drug development, new strategies are put in place to achieve high-throughput analysis, using serial and parallel approaches. To speed-up method development and validation, generic approaches with the direct injection of biological fluids is highly desirable. Column-switching, using various packing materials for the extraction columns, is widely applied. Improvement of mass spectrometers performance, and in particular triple quadrupoles, also strongly influences sample preparation strategies, which remain a key element in the bioanalytical process.

Investigation of EDTA anticoagulant in plasma to improve the throughput of liquid chromatography/tandem mass spectrometric assays

In this study, EDTA and heparin are compared as anticoagulants with respect to their efficiency in preventing clot formation in plasma samples that were subsequently analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS). A pilot in vivo pharmacokinetic study for the drug chlorpheniramine was conducted in which both EDTA and heparin plasma samples were collected simultaneously. All conditions except the anticoagulant were held constant during the pharmacokinetic study. Bioanalytical results were compared from samples transferred by manual pipette and by an automated liquid handler workstation. The concentration of chlorpheniramine in samples was determined by LC/MS/MS. Results from the analysis of variances (ANOVA) of log-transformed plasma chlorpheniramine concentrations were used to calculate 90% confidence intervals for the ratio least-squares mean values for anticoagulants and for transfer methods. Analytical concentrations of the drug chlorpheniramine were equivalent in heparin- and EDTA-containing plasma. Results suggest that the failure rate for transfer of EDTA plasma (50 micro L by automated workstation or manually) is less than that for heparinized plasma. As a consequence of these results, the vast majority of plasma samples in our laboratories are now collected in EDTA, which allows for use of automated sample transfer resulting in a three-fold timesaving over manual transfer using a single-channel pipette. The ability to use automation has resulted in improved efficiency and cost savings.