Immunoaffinity purification of peptide hormones prior to liquid chromatography–mass spectrometry in doping controls

Cationic exchange SPE combined with triple quadrupole UHPLC-MS/MS for detection of GHRHs in urine samples

The use of growth hormone-releasing hormones (GHRHs) is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA). Considering the complexity of urine samples and the low concentrations at which these analytes should be detected, analyzing GHRHs is a challenging task. In most of the studies, GHRHs are analyzed using UHPLC-HRMS with an orbitrap. The present developed and validated method for some GHRHs (tesamorelin, CJC-1295, sermorelin (GRF 1-29), sermorelin (3-29)-NH2, somatorelin) is based on the triple quadrupole UHPLC/MS-MS method with solid phase extraction (SPE) with weak cation exchange and is able to detect concentrations as low as 0.2 ng/mL (LOD), a limit of quantification (LOQ) at 0.6 ng/mL, and linearity across the range of 0.1 ng/mL to 1.2 ng/mL. The present method developed by our doping control laboratory was validated according to WADA technical documents for selectivity, limit of detection (LOD), carryover, reliability of detection, stability and recovery. The results show that the method has adequate recoveries and sensitivity, hence, it can be employed for routine screening in anti-doping laboratories.

Detection of synthetic analogues of insulin-like growth factor 1 in different biological fluids by liquid chromatography quadrupole time-of-flight mass spectrometry: comparison of different immunoaffinity protocols

Insulin-like growth factor 1 analogues are prohibited in sport for their ability to enhance athletic performance in several sport disciplines. Their detection presents several analytical challenges, mainly due to the minimum required performance limits fixed by the World Anti-Doping Agency. Here, we are presenting analytical workflows to detect IGF-1 and its analogues in different biological matrices. Several off-line immunocapture techniques and protocols were comparatively evaluated. Separation and detection were performed by using standard flow reverse-phase liquid chromatography coupled to a time-of-flight mass spectrometer. The best recoveries were obtained using magnetic beads or pipette tips functionalized with protein A. The analytical workflows were fully validated for qualitative determinations: all the target analytes were clearly distinguishable from the interference of the matrices, with limits of detection and identification in the range of 0.05-0.30 ng/mL in urine and 0.5-2.0 ng/mL in serum/plasma. The extraction efficiency proved to be repeatable (CV% < 10) with recoveries higher than 50%. Intra- and inter-day precision were found to be smaller than 10 and 15%, respectively. The method was successfully applied to the analysis of authentic matrix samples containing the target peptides at the minimum required performance limits, proving that the method developed can be successfully applied to detect and identify IGF-1 analogues for doping control purposes in all the matrices selected. The analytical workflow developed here to detect the target peptides in different matrices can be readily implemented in anti-doping laboratories and has the potential to be adapted for the simultaneous analysis of different similarly sized peptide hormones of doping relevance.

Online large volume sample staking preconcentration and separation of enantiomeric GHRH analogs by capillary electrophoresis

A capillary electrophoresis method is proposed to analyze the four most well-known growth hormone-releasing hormone (GHRH) analogs that are misused by athletes. Dimethyl-β-cyclodextrin used as a chiral selector allowed, for the first time, the separation of those basic peptide analogs, including enantiopeptides (sermorelin and CJC-1293) that differ by the chirality of only one amino acid. To increase the method sensitivity, electrokinetic preconcentration methods have been investigated. The large volume sample stacking with polarity switching (PS-LVSS) method with an injected sample volume corresponding to 80% of the capillary one was found superior to the sweeping in terms of signal enhancement factor (SEF). Acid and organic solvent addition to the sample (0.1 mM phosphoric acid with 30% methanol) led to a twofold signal improvement, when compared to water as a matrix. We increased capillary dimensions to provide a signal enhancement through the injection of a larger sample volume. Finally, using a combination of the optimized PS-LVSS preconcentration with the chiral capillary zone electrophoresis (CZE), the GHRH analogs were separated and limits of detection between 75 and 200 ng/mL were reached. This method was successfully applied to urine after a desalting step. An optimized C18 SPE was used for that purpose in order to provide low sample conductivity (<130 µS/cm) and preserve the efficiency of LVSS preconcentration. SEF of 640 was obtained with desalted urine spiked with sermorelin by comparison to the CZE (without preconcentration) method.

Synthetic Peptides in Doping Control: A Powerful Tool for an Analytical Challenge

Peptides are very diverse molecules that can participate in a wide variety of biological processes. In this way, peptides are attractive for doping, since these molecules can activate or trigger biological processes that can improve the sports performance of athletes. Peptide molecules are found in the official World Anti-Doping Agency lists, mainly in sections S2, S4, and S5. In most cases, these molecules have a very short half-life in the body and/or are identical to natural molecules in the body, making it difficult to analyze them as performance-enhancing drugs. This article reviews the role of peptides in doping, with special emphasis on the peptides used as reference materials, the pretreatment of samples in biological matrices, the instrumentation, and the validation of analytical methodologies for the analysis of peptides used in doping. The growing need to characterize and quantify these molecules, especially in complex biological matrices, has generated the need to search for robust strategies that allow for obtaining sensitive and conclusive results. In this sense, strategies such as solid phase peptide synthesis (SPPS), seeking to obtain specific peptides, metabolites, or isotopically labeled analogs, is a key tool for adequate quantification of different peptide molecules in biological matrices. This, together with the use of optimal methodologies for sample pretreatment (e.g., SPE or protein precipitation), and for subsequent analysis by high-resolution techniques (mainly hyphenated LC-HRMS techniques), have become the preferred instrumentation to meet the analytical challenge involved in the analysis of peptides in complex matrices.

Behavior of Regular Insulin in a Parenteral Nutrition Admixture: Validation of an LC/MS-MS Assay and the In Vitro Evaluation of Insulin Glycation

Parenteral-nutrition (PN)-induced hyperglycemia increases morbidity and mortality and must be treated with insulin. Unfortunately, the addition of insulin to a ternary PN admixture leads to a rapid decrease in insulin content. Our study’s objective was to determine the mechanistic basis of insulin’s disappearance. The literature data suggested the presence of a glycation reaction; we therefore validated an LC-MS/MS assay for insulin and glycated insulin. In a 24-h stability study, 20 IU/L of insulin was added to a binary PN admixture at pH 3.6 or 6.3. When the samples were diluted before analysis with a near-neutral diluent, insulin was fully stable at pH 3.6, while a loss of around 50% was observed at pH 6.3. Its disappearance was shown to be inversely correlated with the appearance of monoglycated insulin (probably a Schiff base adduct). Monoglycated insulin might also undergo a back-reaction to form insulin after acidic dilution. Furthermore, a second monoglycated insulin species appeared in the PN admixture after more than 24 h at high temperature (40 °C) and a high insulin concentration (1000 IU/L). It was stable at acidic pH and might be an Amadori product. The impact of insulin glycation under non-forced conditions on insulin’s bioactivity requires further investigation.

An antibody-free, ultrafiltration-based assay for the detection of growth hormone-releasing hormones in urine at low pg/mL concentrations using nanoLC-HRMS/MS

This work presents an ultrafiltration-based, validated method for the screening and confirmation of prohibited growth hormone-releasing hormone (GHRH) analogues (sermorelin/CJC-1293, sermorelin metabolite, CJC-1295 and tesamorelin) in urine by nanoLC-HRMS/MS. Sample preparation avoids the use of laborious antibody-based extraction approaches and consists solely of preconcentration by ultrafiltration. Even in the absence of immuno-affinity purification steps, high sensitivity was still ensured as limits of detection between 5 and 25 pg/mL and limits of identification between 25 and 50 pg/mL were established. The robustness of the miniaturized chromatographic setup was evaluated through the injection of 200 + preconcentrated urinary extracts. In a comparison with immuno-affinity purification, enhanced recoveries (59 - 115%) and similar sensitivity were achieved, yet at lower operational costs. Stability experiments showed the importance of the proper handling of urine samples to avoid degradation of these peptide hormones, especially for sermorelin and its metabolite which were found to rapidly degrade at temperatures > 4 °C and pH values < 7 in accordance with earlier studies. Without the need for specific antibodies, this method may be expanded to cover emerging peptide drugs (≥ ~3 kDa), as well as their metabolites in the future to facilitate coverage for this class of prohibited substances.

Detection of insulin analogues and large peptides > 2 kDa in urine

Insulin analogues and large bioactive peptides may be used by athletes to enhance performance and are banned by the World Anti-Doping Agency (WADA). In addition to insulin analogues, the large peptides include a structurally diverse set of peptides including analogues of growth hormone releasing hormone (GHRH), insulin-like growth factor-1 (IGF-1), and mechano-growth factor (MGF). Detection of this class of peptides is difficult due to their absorptive losses and presence at very low concentrations in urine. In this report, a high throughput method is described that allows sensitive detection of 4 classes of large peptides in one assay. Sample extraction is performed by ultrafiltration to concentrate the urine followed by solid phase extraction in a 96-well micro-elution plate. Peptides in the urine samples are detected on a triple quadrupole mass spectrometer coupled to standard flow liquid chromatography. The method was validated and evaluated for limit of detection, limit of identification, specificity, precision, carry-over, recovery, matrix interference, and post-extraction stability. The limit of detection for insulin analogues is between 5 - 25 pg/ml and between 5 - 50 pg/ml for the other peptide classes. Specificity was good with no detection of interfering peaks in blank urine samples. Carry-over from a high concentration sample was not observed and the post-extraction stability was between 77 - 107%. The method was able to detect insulin analogues in three diabetic urine samples. Increased screening for this class of peptides will improve detection and deterrence.

Introduction of a PEGylated EPO conjugate as internal standard for EPO analysis in doping controls

Immunopurification of doping control samples is a mandatory necessity in erythropoietin (EPO) analysis during a confirmation procedure; moreover, it has become common practice to also immunopurify samples for the initial testing procedure. Typically used materials (e.g., Stemcell purification plate and MAIIA purification kit) rely on anti-EPO antibodies for purification. Also, the detection of EPO after electrophoretic separation and western blotting is based on a monoclonal anti-EPO antibody, clone AE7A5, directed against a 26 amino acid sequence of the N-terminal region of human EPO. While the electrophoretic separation and blot transfer efficiency can be monitored with reference standards and quality control samples, it is presently not possible to monitor the functionality of the entire sample preparation procedure. The reliance on antibodies for both purification and detection has complicated the implementation of an internal standard (ISTD). In this study, customized EPO-polyethylene glycol (PEG) conjugates were synthesized as potential ISTDs and assessed as to their compatibility with existing sample preparation procedures for urine and blood sample analysis using the most common immunopurification techniques. Moreover, probing for the impact of the ISTD on sodium N-lauroylsarcosinate ("sarcosyl") polyacrylamide gel electrophoresis (SAR-PAGE)-based EPO analysis concerning potential interference with target analytes was conducted. The presented data demonstrate that a 12-kDa PEG residue attached to human EPO represents a particularly useful construct to serve as ISTD for erythropoietin-receptor agonist (ERA) analysis. The conjugate is applicable to both urine and blood testing using the commonly employed purification techniques, supporting and improving result interpretations especially concerning specimens where the natural abundance of human EPO is low.

Facilitated Qualitative Determination of Insulin, Its Synthetic Analogs, and C-Peptide in Human Urine by Means of LC-HRMS

The increasing importance to determine bioactive peptide hormones such as insulin, its synthetic analogs, and C-peptide in urine samples represents an analytical challenge. The physiological concentrations of insulin in urine are commonly found at sub-ng/mL levels and thus represent a complex analytical task. C-peptide concentrations, on the other hand, tend to be in the moderate ng/mL range and are hence much easier to determine. Insulin and C-peptide are important in the diagnostics and management of metabolic disorders such as diabetes mellitus and are also particularly relevant target analytes in professional sports and forensics. All insulins are classified on the World Anti-Doping Agency's (WADA) list of prohibited substances and methods in sports with a minimum required performance level (MRPL) of 50 pg/mL. Until now, methods combining immunoextraction and subsequent mass spectrometric detection have mostly been used for this purpose. With the method developed here, sample preparation has been simplified considerably and does not require an antibody-based sample purification. This was achieved by a sophisticated mixed-mode solid-phase extraction and subsequent separation with liquid chromatography coupled to high-resolution mass spectrometry. Included target insulins were human, lispro, glulisine, aspart, glargine metabolite, degludec, and additionally, human C-peptide. The method was validated for the synthetic insulin analogs considering WADA requirements including specificity, limit of detection (10-25 pg/mL), limit of identification, recovery (25-100%), robustness, carry over (<2%), and matrix effects. All sample preparation steps were controlled by two stable isotope-labeled internal standards, namely, [[2H10] LeuB6, B11, B15, B17]-insulin and [[13C6] Leu26, 30] C-peptide. Finally, the method was applied to samples from patients with diabetes mellitus treated with synthetic insulins.

Detection of LongR3 -IGF-I, Des(1-3)-IGF-I, and R3 -IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes

Insulin-like growth factor-I (IGF-I) and its analogs LongR³ -IGF-I, Des(1-3)-IGF-I, and R³ -IGF-I are prohibited substances in sport. Although they were never approved for use in humans, they are readily available as black market products for bodybuilding and can be used to enhance physical performance. This study's aims were to validate a fast and sensitive detection method for IGF-I analogs and to evaluate their detectability after intramuscular administration in rats. The sample preparation consisted of an immunopurification on MSIA™ microcolumns using a polyclonal anti-human-IGF-I antibody. The target substances were then directly analyzed by nano-liquid chromatography coupled with high-resolution mass spectrometry. Abundant signs of lower quality, oxidized peptide forms were found in black market products, justifying the need to monitor at least both the native and mono-oxidized forms. The analytical performance of this method (linearity, carry over, detection limits, precision, specificity, recovery, and matrix effect) was studied by spiking the analogs into human serum. Following a single intramuscular administration (100 μg/kg) in rats, detection was evaluated up to 36 h after injection. While unchanged Des(1-3)-IGF-I and R³ -IGF-I were detected until 24 h after administration, LongR³ -IGF-I disappeared rapidly after 4 h. Des(1)-LongR³ -IGF-I, a new N-terminal Long-R³ -IGF-I degradation product, was detected in addition to Des(1-10)-LongR³ -IGF-I and Des(1-11)-LongR^3- IGF-I: the latter was detected up to 16 h. The same products were found after in vitro incubation of the analogs in human whole blood, suggesting that observations in rats may be extrapolated to humans and that the validated method may be applicable to antidoping testing.

An antibody-free LC-MS/MS method for the quantification of intact insulin-like growth factors 1 and 2 in human plasma

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) are important biomarkers in research and diagnosis of growth disorders. Quantitative analysis is performed using various ligand-binding assays or enzymatic digestion LC-MS/MS methods, whose widespread adoption is hampered by time-consuming sample preparation procedures. We present a simple and fast antibody-free LC-MS/MS method for the quantification of intact IGF-1 and IGF-2 in human plasma. The method requires 50 μL of plasma and uses fully ¹⁵N-labelled IGF-1 as internal standard. It features trifluoroethanol (TFE)-based IGF/IGF-binding protein complex dissociation and a two-step selective protein precipitation workflow, using 5% acetic acid in 80/20 acetone/acetonitrile (precipitation 1) and ice-cold ethanol (precipitation 2). Detection of intact IGF-1 and IGF-2 is performed by means of a Waters XEVO TQ-S triple quadrupole mass spectrometer in positive electrospray ionisation (ESI+) mode. Lower limits of quantification were 5.9 ng/mL for IGF-1 and 8.4 ng/mL for IGF-2. Intra-assay imprecision was below 4.5% and inter-assay imprecision was below 5.8% for both analytes. An excellent correlation was found between nominal and measured concentrations of the WHO reference standard for IGF-1. Comparison with the IDS-iSYS IGF-1 immunoassay showed good correlation (R² > 0.97), although a significant bias was observed with the immunoassay giving substantially higher concentrations. The LC-MS/MS method described here allows for reliable and simultaneous quantification of IGF-1 and IGF-2 in plasma, without the need for enzymatic digestion. The method can be readily implemented in clinical mass spectrometry laboratories and has the potential to be adapted for the analysis of different similarly sized peptide hormones.

Comparison of magnetic bead surface functionalities for the immunopurification of growth hormone-releasing hormones prior to liquid chromatography-high resolution mass spectrometry

Growth hormone-releasing hormone and its analogues sermorelin, tesamorelin and CJC-1295 are included in the prohibited list of the World Antidoping Agency. These target peptides are found at very low concentrations in urine (at the pg/mL level). For this reason, hyphenated enrichment and purification steps prior to mass spectrometric detection are required. Among different strategies, immunopurification based on magnetic beads is an excellent alternative, as it offers improved selectivity when the immunoreactivity and orientation of the antibody are optimum and non-specific adsorption is minimized. However, choosing the magnetic bead surface functionalities that provide the best recoveries is not so straightforward. In this work, we have evaluated the suitability of magnetic beads with different supports, binding capacities and affinity chemistries prior analysis of human urine samples by liquid chromatography coupled to high resolution mass spectrometry using a Quadrupole-Orbitrap instrument. After optimization of the immunopurification protocol with the magnetic beads that provided better recoveries, the method was fully validated and found to be adequate considering the parameters specificity, intra- and inter-day precision (lower than 15 and 25%, respectively), matrix effect, limit of detection (0.2 ng/mL) and limit of identification (0.5 ng/mL).

Identification of metabolites of peptide-derived drugs using an isotope-labeled reporter ion screening strategy

Background

Peptide-derived drugs represent an emerging class of prohibited substances in professional sports and, thus, in modern doping controls. After parental administration (e.g. subcutaneous, intravenous), these drugs undergo various metabolic processes, which degrade them to biologically active or inactive peptides. Knowledge about these metabolic processes and the hereby produced metabolites plays a key role in successful doping controls due to the effective design of analytical assays under consideration of optimal analytical targets. Unfortunately, the complexity of biological matrix (e.g. blood or urine) complicates the immediate identification of relevant metabolites due to the enormous excess of naturally occurring peptides and their degradation products.

Methods

In this study, a strategy employing in-vitro metabolism of stable isotope-labeled peptides producing characteristic reporter ions derived from labeled immonium ions is shown. The in-vitro experiments were performed with human skin tissue microsomes (S9), and model drugs representing prohibited peptide hormones were synacthen, insulin, and corticorelin (respectively, their stable isotope-labeled analogs). After generic sample preparation, the metabolites were identified by means of liquid chromatography (LC) coupled to high-resolution mass spectrometry (MS) in an untargeted approach.

Results and conclusions

For all three model peptides, several metabolic products were readily identified. While insulin and corticorelin were found to be comparably stable, synacthen was fully degraded, yielding a plethora of metabolic products. A proof of concept concerning the transferability of the obtained data was accomplished by analyzing plasma samples collected post-administration of recombinant human insulin, corroborating the presence of a skin protease-indicative insulin metabolite in vivo.

An Intact ACTH LC-MS/MS Assay as an Arbiter of Clinically Discordant Immunoassay Results

BACKGROUND

Measurement of plasma adrenocorticotropic hormone (ACTH) is key in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. Two-site sandwich immunoassays dominate clinical testing of ACTH in North America; however, discordant results between manufacturers have been repeatedly reported. To resolve the discrepancy, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) assay for the intended measurand, biologically active intact ACTH (iACTH).

METHODS

The multiple reaction monitoring LC-MS/MS assay was designed to selectively measure full-length iACTH, as well as ACTH analogs and fragments (i.e., ACTH1–24 and ACTH18–39). Epitope assignment of the Roche Elecsys antibodies was performed by MALDI-TOF mass spectrometry. A method comparison between Roche Elecsys and Siemens Immulite ACTH immunoassays was performed and clinically concordant/discordant results identified. In a subset of these samples, the iACTH concentration was determined using the LC-MS/MS method.

RESULTS

The lower limit of the measuring interval of the iACTH LC-MS/MS assay was 9 pg/mL (2 pmol/L). The assay was linear from 9 to 1938 pg/mL (2 to 427 pmol/L). Epitope mapping revealed that the Roche capture and detection antibodies bound residues 9–12 and 36–39 of ACTH, respectively. The iACTH LC-MS/MS analysis demonstrated that for discordant results between 2 immunoassays studied, only the Roche results were highly positively correlated with the iACTH concentration.

CONCLUSIONS

Immunoprecipitation of biologically active ACTH molecules followed by LC-MS/MS analysis enabled selective detection of iACTH and relevant biologically active fragments in plasma. Applied to the investigation of clinically discrepant results, this method can act as an arbiter of the concentration of iACTH present.

Recent advances in the determination of insulins from biological fluids

The qualitative and quantitative determination of insulin and its related substances (e. g., C-peptide) is of great importance in many different areas of analytical chemistry. In particular, due to the steadily increasing prevalence of metabolic disorders such as diabetes mellitus, an adequate control of the circulating amount of insulin is desirable. In addition, also in forensics and doping control analysis, the determination of insulin in blood, urine or other biological matrices plays a major role. However, in order to establish general reference values for insulin and C-peptide for diabetology, the comparability of measured concentrations is indispensable. This has not yet been fully implemented, although enormous progress has been made in recent years, and the search for a "gold standard" method is still ongoing. In addition to established ligand-binding assays, an increasing number of mass-spectrometric methods have been developed and employed as the to-date available systems (for example, high-resolution/high accuracy mass spectrometers) provide the sensitivity required to determine analyte concentrations in the sub-ng/mL (sub-100pmol/L) level. Meanwhile, also high-throughput measurements have been realized to meet the requirement of testing a high number of samples in a short period of time. Further developments aim at enabling the online measurement of insulin in the blood with the help of an insulin sensor and, in the following, in addition to a brief review, today's state of the art testing developments are summarized.

A quantitative LC-MS/MS method for insulin-like growth factor 1 in human plasma

BACKGROUND

Insulin-like growth factor 1 (IGF1) is a biomarker with various applications in medicine and also in doping control.

METHODS

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed that employs 15N-IGF1 as an internal standard. The method features urea-based IGF1/IGFBP-complex dissociation which is directly followed by tryptic digestion. Following solid-phase extraction (SPE) sample clean-up of the digest, IGF1 is detected by means of two signature peptides that enable quantification of total IGF1 as well as discrimination between IGF1 proteoforms with 'native' and modified or extended N-terminal sequences.

RESULTS

Our method is capable of measuring plasma IGF1 concentrations over the clinically relevant range of 10-1000 ng/mL and was validated according to regulatory guidelines. Comparison with the IDS-iSYS IGF1 immunoassay revealed good correlation (R2>0.97) and no proportional bias between both assays was observed after normalizing the results against the WHO reference standard for IGF1 (02/254). Evaluation of several commercially available IGF1 preparations showed varying responses which were due to inconsistencies in purity and absolute amount of IGF1 present in these products.

CONCLUSIONS

Our LC-MS/MS method introduces urea-based dissociation of IGF1/IGFBP-complexes to enable reliable quantification of IGF1 in plasma. Furthermore, the method is able to detect clinically relevant IGF1 levels without an enrichment procedure at the protein-level and thereby minimizes the risk of losing IGF1 proteoforms during sample preparation.

A method for confirming CJC-1295 abuse in equine plasma samples by LC-MS/MS

CJC-1295 is a peptide-based drug that stimulates the production of growth hormone (GH) from the pituitary gland. It incorporates a functional maleimido group at the C-terminus that allows it to covalently bind plasma proteins such as serum albumin. These CJC-1295-protein conjugates have a much greater half-life compared to the unconjugated peptide and are capable of stimulating GH production for more than six days in humans after a single administration. Conjugated CJC-1295 is difficult to detect in blood by mass spectrometry due to its low abundance, high molecular weight, and conjugation to a range of different protein substrates. Previously we described a screening procedure for the detection of CJC-1295 in equine plasma using an immuno-PCR assay. Here we demonstrate the confirmation of CJC-1295 in equine plasma by LC-MS/MS after immuno-affinity capture and tryptic digestion. Using this method, CJC-1295 was identified down to concentrations as low as 180 pg/mL in 1 mL of equine plasma.

Validation of a Fully Automated Immunoaffinity Workflow for the Detection and Quantification of Insulin Analogs by LC–MS-MS in Postmortem Vitreous Humor

The analysis of biological specimens collected at autopsy for the presence of exogenous insulin(s) is of special interest in select death investigations as they may be suspected in the cause of a death. Technical challenges include the limited stability of insulin, and the forensic requirement of differentiating endogenous insulin from pharmaceutical analogs. A novel method was developed for the detection and quantification of human insulin, Glulisine, Lispro, Aspart, Glargine and Detemir in vitreous fluid. An immunoaffinity extraction procedure is performed followed by separation of the insulin α- and β-chains. Liquid chromatography tandem mass spectrometry analysis of the β-chain allows for the unequivocal identification of each insulin analog. The analytical measurement range for each insulin was 0.5–25 ng/mL. The method was evaluated for accuracy, precision, carryover, interferences and stability. Eight vitreous fluid samples collected from cases where untoward insulin use was suspected were subjected to analysis. Positive results were obtained from three samples, and a detailed case history is provided for one of these cases. Even though insulin instability in postmortem biological fluid remains a challenge, this method allows for a reliable forensic-level analysis in vitreous fluid.

Immunoaffinity techniques coupled to mass spectrometry for the analysis of human peptide hormones: advances and applications

INTRODUCTION

The accurate and comprehensive determination of peptide hormones from biological fluids has represented a considerable challenge to analytical chemists for decades. Besides long-established bioanalytical ligand binding assays (or ELISA, RIA, etc.), more and more mass spectrometry-based methods have been developed recently for purposes commonly referred to as targeted proteomics. Eventually the combination of both, analyte extraction by immunoaffinity and subsequent detection by mass spectrometry, has shown to synergistically enhance the test methods' performance characteristics. Areas covered: The review provides an overview about the actual state of existing methods and applications concerning the analysis of endogenous peptide hormones. Here, special focus is on recent developments considering the extraction procedures with immobilized antibodies, the subsequent separation of target analytes, and their detection by mass spectrometry. Expert commentary: Key aspects of procedures aiming at the detection and/or quantification of peptidic analytes in biological matrices have experienced considerable improvements in the last decade, particularly in terms of the assays' sensitivity, the option of multiplexing target compounds, automatization, and high throughput operation. Despite these advances and progress as expected to be seen in the near future, immunoaffinity purification coupled to mass spectrometry is not yet a standard procedure in routine analysis compared to ELISA/RIA.

Peptide Antibodies in Clinical Laboratory Diagnostics

Peptide antibodies, with their high specificities and affinities, are invaluable reagents for peptide and protein recognition in biological specimens. Depending on the application and the assay, in which the peptide antibody is to used, several factors influence successful antibody production, including peptide selection and antibody screening. Peptide antibodies have been used in clinical laboratory diagnostics with great success for decades, primarily because they can be produced to multiple targets, recognizing native wildtype proteins, denatured proteins, and newly generated epitopes. Especially mutation-specific peptide antibodies have become important as diagnostic tools in the detection of various cancers. In addition to their use as diagnostic tools in malignant and premalignant conditions, peptide antibodies are applied in all other areas of clinical laboratory diagnostics, including endocrinology, hematology, neurodegenerative diseases, cardiovascular diseases, infectious diseases, and amyloidoses.

Exploiting Nanobodies in the Detection and Quantification of Human Growth Hormone via Phage-Sandwich Enzyme-Linked Immunosorbent Assay

BACKGROUND

Monitoring blood levels of human growth hormone (hGH) in most children with short stature deficiencies is crucial for taking a decision of treatment with extended course of daily and expensive doses of recombinant hGH (rhGH or Somatropin^®). Besides, misusing of rhGH by sportsmen is banned by the World Anti-Doping Agency and thus sensitive GH-detecting methods are highly welcome in this field. Nanobodies are the tiniest antigen-binding entity derived from camel heavy chain antibodies. They were successfully generated against numerous antigens including hormones.

METHODS

A fully nanobody-based sandwich ELISA method was developed in this work for direct measurement of GH in biological samples.

RESULTS

Two major characteristics of nanobody were exploited for this goal: the robust and stable structure of the nanobody (NbGH04) used to capture hGH from tested samples, and the great ability of tailoring, enabling the display of the anti-GH detector nanobody (NbGH07) on the tip of M13-phage. Such huge, stable, and easy-to-prepare phage-Nb was used in ELISA to provide an amplified signal. Previously, NbGH04 was retrieved on immobilized hGH by phage display from a wide "immune" cDNA library prepared from a hGH-immunized camel. Here, and in order to assure epitope heterogeneity, NbGH07 was isolated from the same library using NbGH04-captured hGH as bait. Interaction of both nanobodies with hGH was characterized and compared with different anti-GH nanobodies and antibodies. The sensitivity (~0.5 ng/ml) and stability of the nanobody-base sandwich ELISA were assessed using rhGH before testing in the quantification of hGH in blood sera and cell culture supernatants.

CONCLUSION

In regard to all advantages of nanobodies; stability, solubility, production affordability in Escherichia coli, and gene tailoring, nanobody-based phage sandwich ELISA developed here would provide a valuable method for hGH detection and quantification.

The Determination of Insulin Overdose in Postmortem Investigations

The analysis of biological specimens for the presence of exogenous insulin is of special interest in select postmortem investigations. Insulin analogues are primarily used to mediate the regulation of blood glucose concentrations; however, their use has also been implicated or suspected as a cause of death in suicides, accidents, and homicides. Toxicological analysis for these compounds is challenging due to the large molecular weight, the limited stability of insulin in whole blood, and complexities associated with sample preparation and instrumental testing. As a consequence, determination of insulin in postmortem specimens is not routinely offered by most forensic toxicology laboratories. Forensic death investigation is further complicated by interpretative difficulties such as the frequent absence of anatomical findings, concentration interpretation in known insulin users, and addressing the impact of chemical instability and postmortem redistribution. There are ongoing efforts, however, to develop and validate robust methods that may be used for this analysis on these challenging samples and that are capable of withstanding scientific and legal scrutiny for forensic use. In this regard, in recent years, methods for the detection of exogenous insulin in postmortem samples have been reported and results of this testing has been published in a handful of cases. The purpose of this article is to review the primary functions of insulin, the disease states associated with the therapeutic use of exogenous insulin, the current state of laboratory testing, and to provide case summaries that summarize the timeline of advancements and underscore the importance of this work.

Evaluation of water-soluble DBS for small proteins: a conceptual study using insulin as a model analyte

Aim: Water-soluble sampling materials for DBS have been introduced to solve some of the common challenges of DBS. Methodology: Carboxymethyl cellulose (CMC) as water-soluble material was evaluated for small proteins using insulin as model analyte. 15 µl of whole blood was deposited and dried on a sheet of CMC prior to dissolvation of the whole spot, matrix precipitation with acetonitrile and LC–MS/MS analysis. Results: CMC was shown to promote matrix precipitation resulting in cleaner extracts than precipitation without CMC present. The recovery of insulin from the spot was 68 ± 4%, and the spotted samples were stable for at least 1 week in room temperature. Conclusion: Water-soluble DBS showed promising performance also in analysis of small proteins.

Qualitative identification of growth hormone-releasing hormones in human plasma by means of immunoaffinity purification and LC-HRMS/MS

The use of growth hormone-releasing hormones (GHRHs) is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA). The aim of the present study was to develop a method for the simultaneous detection of four different GHRHs and respective metabolites from human plasma by means of immunoaffinity purification and subsequent nano-ultrahigh performance liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry. The target analytes included Geref (Sermorelin), CJC-1293, CJC-1295, and Egrifta (Tesamorelin) as well as two metabolites of Geref and CJC-1293, which were captured from plasma samples using a polyclonal GHRH antibody in concert with protein A/G monolithic MSIA™ D.A.R.T.'S® (Disposable Automation Research Tips) prior to separation and detection. The method was fully validated and found to be fit for purpose considering the parameters specificity, linearity, recovery (19-37%), lower limit of detection (<50 pg/mL), imprecision (<20%), and ion suppression/enhancement effects. The analytes' stability and metabolism were elucidated using in vitro and in vivo approaches. EDTA blood samples were collected from rats 2, 4, and 8 h after intravenous administration of GHRH (one compound per test animal). All intact substances were detected for at least 4 h but no anticipated metabolite was confirmed in laboratory rodents' samples; conversely, a Geref metabolite (GHRH3-29) was found in a human plasma sample collected after subcutaneous injection of the drug to a healthy male volunteer. The obtained results demonstrate that GHRHs are successfully detected in plasma using an immunoaffinity-mass spectrometry-based method, which can be applied to sports drug testing samples. Further studies are however required and warranted to account for potential species-related differences in metabolism and elimination of the target analytes.

Netnography of Female Use of the Synthetic Growth Hormone CJC-1295: Pulses and Potions

BACKGROUND

Communal online folk pharmacology fuels the drive for short cuts in attaining muscle enhancement, fat loss, and youthful skin.

OBJECTIVES

The study used "netnography" to explore female use of CJC-1295, a synthetic growth hormone analogue from the perspectives contained in Internet forum activity.

METHODS

A systematic Internet search was conducted using variation of the term "CJC-1295"; and combined with "forum." Ninety-six hits related to bodybuilding websites where CJC-1295 was mentioned. Following application of exclusion criteria to confine to female use and evidence of forum activity, 9 sites remained. These were searched internally for reference to CJC-1295. Twenty-three discussion threads relating to female use of CJC-1295 formed the end data set, and analyzed using the Empirical Phenomenological Psychological method.

RESULTS

Forum users appeared well versed and experienced in the poly use of performance and image drug supplementation. Choice to use CJC-1295 centered on weight loss, muscle enhancement, youthful skin, improved sleep, and injury healing. Concerns were described relating to female consequences of use given gender variations in growth hormone pulses affecting estimation of dosage, cycling, and long-term consequences.

CONCLUSIONS

Public health interventions should consider female self-medicating use of synthetic growth hormone within a repertoire of product supplementation, and related adverse health consequences.

Current trends in mass spectrometry of peptides and proteins: Application to veterinary and sports-doping control

Detection of misuse of peptides and proteins as growth promoters is a major issue for sport and food regulatory agencies. The limitations of current analytical detection strategies for this class of compounds, in combination with their efficacy in growth-promoting effects, make peptide and protein drugs highly susceptible to abuse by either athletes or farmers who seek for products to illicitly enhance muscle growth. Mass spectrometry (MS) for qualitative analysis of peptides and proteins is well-established, particularly due to tremendous efforts in the proteomics community. Similarly, due to advancements in targeted proteomic strategies and the rapid growth of protein-based biopharmaceuticals, MS for quantitative analysis of peptides and proteins is becoming more widely accepted. These continuous advances in MS instrumentation and MS-based methodologies offer enormous opportunities for detection and confirmation of peptides and proteins. Therefore, MS seems to be the method of choice to improve the qualitative and quantitative analysis of peptide and proteins with growth-promoting properties. This review aims to address the opportunities of MS for peptide and protein analysis in veterinary control and sports-doping control with a particular focus on detection of illicit growth promotion. An overview of potential peptide and protein targets, including their amino acid sequence characteristics and current MS-based detection strategies is, therefore, provided. Furthermore, improvements of current and new detection strategies with state-of-the-art MS instrumentation are discussed for qualitative and quantitative approaches.

Is isolation of comprehensive human plasma peptidomes an achievable quest?

The low molecular weight (LMW; <10kDa)* plasma peptidome has been considered a source of useful diagnostic biomarkers and potentially therapeutic molecules, as it contains many cytokines, peptide hormones, endogenous peptide products and potentially bioactive fragments derived from the parent proteome. The small size of the peptides allows them almost unrestricted vascular and interstitial access, and hence distribution across blood-brain barriers, tumour and other vascular permeability barriers. Therefore, the peptidome may carry specific signatures or fingerprints of an individual's health, wellbeing or disease status. This occurs primarily because of the advantage the peptidome has in being readily accessible in human blood and/or other biofluids. However, the co-expression of highly abundant proteins (>10kDa) and other factors present inherently in human plasma make direct analysis of the blood peptidome one of the most challenging tasks faced in contemporary analytical biochemistry. A comprehensive compendium of extraction and fractionation tools has been collected concerning the isolation and micromanipulation of peptides. However, the search for a reliable, accurate and reproducible single or combinatorial separation process for capturing and analysing the plasma peptidome remains a challenge. This review outlines current techniques used for the separation and detection of plasma peptides and suggests potential avenues for future investigation. This article is part of a Special Issue entitled: HUPO 2014.

Mass spectrometric characterization of a biotechnologically produced full-length mechano growth factor (MGF) relevant for doping controls

OBJECTIVE

Since Goldspink and colleagues identified the expression of the mRNA of an insulin-like growth factor 1 (IGF-1) isoform in response to mechanical stress in 1996, substantial research into the so-called mechano growth factor and its modus operandi followed until today. Promising preclinical results were obtained by using the synthetic, 24-amino acid residues spanning peptide translated from the exons 4-6 of IGF-1Ec (which was later referred to as the mechano growth factor (MGF) peptide), particularly with regard to increased muscle myoblast proliferation. Consequently, the MGF peptide represented a promising drug candidate for the treatment of neuromuscular disorders; however, its misuse potential in sport was also identified shortly thereafter, and the substance (or class of substances) has been considered prohibited according to the regulations of the World Anti-Doping Agency (WADA) since 2005. While various MGF peptide versions have been known to sports drug testing authorities, the occurrence of a 'full-length MGF' as offered via illicit channels to athletes or athletes' managers was reported in 2014, arguably being undetectable in doping controls.

METHODS

An aliquot of the product was obtained and the content characterized by state-of-the-art analytical approaches including gel electrophoretic and mass spectrometric (top-down and bottom-up) sequencing approaches. Upon full characterization, its implementation into modified routine doping controls using ultrafiltration, immunoaffinity-based isolation, and nanoliquid chromatography-high resolution/high accuracy mass spectrometry was established.

RESULTS

A protein with a monoisotopic molecular mass of 12264.9 Da and a sequence closely related to IGF-1Ec (lacking the signal- and propeptide moiety) was identified. The C-terminus was found to be modified by the elimination of the terminal lysine and a R109H substitution. With the knowledge of the compound's composition, existing doping control assays targeting peptide hormones such as IGF-1 and related substances were assessed as to their capability to detect the full-length MGF. The analyte was detectable at concentrations of 0.25 ng/mL using adapted routine test methods employing immunoaffinity purification followed by nanoscale liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry.

CONCLUSIONS

A potentially performance enhancing 'full-length' MGF derivative was identified and successfully implemented into sports drug testing protocols. Future tests are indicated probing for optimized/dedicated detection methods and assessment of efficacy and elimination kinetics of the substance.