Clinical applications of gas chromatography and gas chromatography-mass spectrometry of steroids

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.

Advancements in the gold standard: Measuring steroid sex hormones by mass spectrometry

Sex hormones, such as testosterone and estrogens, play an essential role in regulating physiological and reproductive development throughout the lifetime of the individual. Although variation in levels of these hormones are observed throughout the distinct stages in life, significant deviations from reference ranges can result in detrimental effects to the individual. Alterations, by either an increase or decrease, in hormone levels are associated with physiological changes, decreased reproductive capabilities, and increased risk for diseases. Hormone therapies (HTs) and assisted reproductive technologies (ARTs) are commonly used to address these factors. In addition to these treatments, gender-affirming therapies, an iteration of HTs, are also a prominent treatment for transgender individuals. Considering that the effectiveness of these treatments relies on achieving therapeutic hormone levels, monitoring of hormones has served as a way of assessing therapeutic efficay. The need for reliable methods to achieve this task has led to great advancements in methods for evaluating hormone concentrations in biological matrices. Although immunoassays are the more widely used method, mass spectrometry (MS)-based methods have proven to be more sensitive, specific, and reliable. Advances in MS technology and its applications for therapeutic hormone monitoring have been significant, hence integration of these methods in the clinical setting is desired. Here, we provide a general overview of HT and ART, and the immunoassay and MS-based methods currently utilized for monitoring sex hormones. Additionally, we highlight recent advances in MS-based methods and discuss future applications and considerations for MS-based hormone assays.

Determination of reference intervals for urinary steroid profiling using a newly validated GC-MS/MS method

Background:

Urinary steroid profiling (USP) is a powerful diagnostic tool to asses disorders of steroidogenesis. Pre-analytical factors such as age, sex and use of oral contraceptive pills (OCP) may affect steroid hormone synthesis and metabolism. In general, USP reference intervals are not adjusted for these variables. In this study we aimed to establish such reference intervals using a newly-developed and validated gas chromatography with tandem mass spectrometry detection method (GC-MS/MS).

Methods:

Two hundred and forty healthy subjects aged 20–79 years, stratified into six consecutive decade groups each containing 20 males and 20 females, were included. None of the subjects used medications. In addition, 40 women aged 20–39 years using OCP were selected. A GC-MS/MS assay, using hydrolysis, solid phase extraction and double derivatization, was extensively validated and applied for determining USP reference intervals.

Results:

Androgen metabolite excretion declined with age in both men and women. Cortisol metabolite excretion remained constant during life in both sexes but increased in women 70–79 years of age. Progesterone metabolite excretion peaked in 30–39-year-old women and declined afterwards. Women using OCP had lower excretions of androgen metabolites, progesterone metabolites and cortisol metabolites. Method validation results met prerequisites and revealed the robustness of the GC-MS/MS method.

Conclusions:

We developed a new GC-MS/MS method for USP which is applicable for high throughput analysis. Widely applicable age and sex specific reference intervals for 33 metabolites and their diagnostic ratios have been defined. In addition to age and gender, USP reference intervals should be adjusted for OCP use.

Aptatope mapping of the binding site of a progesterone aptamer on the steroid ring structure

In this work we report the mapping of the binding site of the only progesterone aptamer published to date, in an approach referred to as aptatope mapping. By linking the binding data obtained from microscale thermophoresis analysis to the structural differences on the ring structure of a range of steroids, we elucidated the moieties involved in aptamer-progesterone binding. This approach can be further exploited for the characterization of aptamer specificity and ultimately facilitate the development of aptamer-based assays depending on the desired specificity.

High-density lipoproteins and adrenal steroidogenesis: A population-based study

BACKGROUND

Cholesterol trafficked within plasma lipoproteins, in particular high-density lipoproteins (HDL), may represent an important source of cholesterol that is required for adrenal steroidogenesis. Based on a urinary gas chromatography method, compromised adrenal function has been suggested in men but not in women with (genetically determined) low plasma HDL-cholesterol (HDL-C).

OBJECTIVE

The objective of the article was to examine the extent to which glucocorticoid production relates to HDL-C in a population-based cohort.

METHODS

A total of 240 subjects (120 men and 120 women, aged 20-79 years) without relevant comorbidities were recruited from the general population. Glucocorticoid metabolites were measured by gas chromatography with tandem mass spectrometric detection in 24-hour urine collections to estimate total glucocorticoid production (TGP). Fasting plasma (apo)lipoproteins were assayed by routine methods.

RESULTS

TGP was not decreased but tended to be increased in subjects with low HDL-C (NCEP-ATPIII criteria; P = .094). In univariate analysis, TPG was correlated inversely with HDL-C (r = -0.353, P < .001) and apoA-I (r = -0.263, P = .01). Multivariable linear regression analysis demonstrated that TGP was still inversely related to HDL-C (β = -0.145, P = .019) or alternatively to low HDL-C (β = -0.129, P = .013) taking age, sex, current smoking, and other metabolic syndrome components into account.

CONCLUSION

In this population-based study, urinary glucocorticoid metabolite excretion was inversely associated with HDL-C. We found no evidence for an attenuated adrenal function in men and women with low HDL-C.

A rapid and simple liquid chromatography-tandem mass spectrometry method for the measurement of testosterone, androstenedione, and dehydroepiandrosterone in human serum

BACKGROUND

The assay of androgens plays an important role for the differential diagnosis of androgen-related endocrine diseases. We developed a rapid and simple liquid chromatography tandem mass spectrometry (LC-MS/MS) method with small sample volume and simple sample preparation for simultaneous determination of serum testosterone, androstenedione and dehydroepiandrosterone (DHEA) in adults.

METHODS

We spiked 100 μL of serum with 200 μL of internal standard solution, which was prepared in methanol, for matrix effect relief and protein precipitation. The obtained supernatant was used directly for LC-MS/MS analysis.

RESULTS

The validated method exhibits excellent linearity for each analyte with linear correlation coefficient above 0.992. The total precisions at three concentrations were 15.66%, 8.81% and 4.34% for testosterone, 13.60%, 6.62% and 5.96% for androstenedione, 14.35%, 15.34% and 13.92% for DHEA, respectively. Recovery, carryover, matrix effect and analytical specificity were also performed for well validation of this LC-MS/MS method with satisfied results. Reference intervals (5th-95th centile) were also established for adult men and women.

DISCUSSION

This method offers simpler implement for quantification of steroids in clinical laboratories with minimal manual sample manipulation and minimized sample volume requirements.

CONCLUSION

It is demonstrated that a reliable, simple, sensitive and potential method for steroids assay in clinical laboratories had been successfully developed by LC-MS/MS.

Derivatization of steroids in biological samples for GC–MS and LC–MS analyses

The determination of steroids in biological samples is essential in different areas of knowledge. MS combined with either GC or LC is considered the best analytical technique for specific and sensitive determinations. However, due to the physicochemical properties of some steroids, and the low concentrations found in biological samples, the formation of a derivative prior to their analysis is required. In GC–MS determinations, derivatization is needed for generating volatile and thermally stable compounds. The improvement in terms of stability and chromatographic retention are the main reasons for selecting the derivatization agent. On the other hand, derivatization is not compulsory in LC–MS analyses and the derivatization is typically used for improving the ionization and therefore the overall sensitivity achieved.

Estradiol assays--The path ahead

Estradiol quantitation is useful in the clinical assessment of diseases like hypogonadism, hirsutism, polycystic ovary syndrome (PCOS), amenorrhea, ovarian tumors and for monitoring response in women receiving aromatase inhibitor therapy. Physiologically relevant serum estradiol concentration in women can span across four orders of magnitude. For example, in women undergoing ovulation induction serum estradiol concentration can range between 250-2000 pg/mL whereas aromatase inhibitor therapy can decrease serum estradiol concentration to <5 pg/mL. While high-through-put automated un-extracted (direct) immunoassays accommodate the growing clinical need for estradiol quantitation, are amenable to implementation by most hospital clinical laboratories, they display a significant loss of specificity and accuracy at low concentrations. Most clinical scenarios (example: estradiol monitoring in fertility treatments) place a modest demand on accuracy and precision of the assay in use but accurate quantitation of estradiol in certain clinical scenarios (pediatric and male patients and for monitoring aromatase inhibitor therapy) can be challenging using currently available immunoassays since the direct immunoassays are prone to issues with sub-optimal accuracy and specificity due to cross reactivity with estradiol conjugates and metabolites. In this review we discuss the bases for the evolution of estradiol assays from extracted (indirect) radio-immunoassays to direct immunoassays to liquid-chromatography tandem mass spectrometry (LC-MS/MS) based assays, discuss technical factors relevant for development and optimization of a LC-MS/MS assay for estradiol and present the details and performance characteristics of an ultra-sensitive LC-MS/MS estradiol assay with a limit of quantitation of 0.2 pg/mL.

Diagnostic Value of Urinary Steroid Profiling in the Evaluation of Adrenal Tumors

Radiological examination may unexpectedly reveal an adrenal mass. Current algorithms for differentiating between benign and malignant lesions mainly rely on size and densitometry on unenhanced CT, which have limited specificity. We examined the diagnostic value of urinary steroid profiling by gas chromatography/mass-spectrometry (GC/MS) in differentiating between benign and malignant adrenal tumors. A retrospective study in two referral centers for patients with adrenal disease was performed. All urinary steroid profiles ordered for evaluation of an adrenal tumor between January 2000 and November 2011 were examined. Patients were diagnosed with adrenal cortical carcinoma (ACC), adrenal cortical adenoma (ACA), or other adrenal mass. Results of hormonal measurements, imaging studies, pathology reports, and clinical outcome were retrieved from medical records. The diagnostic value of individual urinary steroid metabolites was determined by receiver operating characteristics analysis. Cut-off values were compared to reference values from an age and gender-standardized population of healthy controls. Eighteen steroid metabolites were excreted in significantly higher concentrations in patients with ACC (n = 27) compared to patients with ACA (n = 107) or other adrenal conditions (n = 18). Tetrahydro-11-deoxycortisol (THS) at a cut-off value of 2.35 μmol/24 h differentiated ACC from other adrenal disorders with 100% sensitivity and 99% specificity. Elevated urinary excretion of THS was associated with a very high sensitivity and specificity to differentiate between an ACC and a benign adrenal mass. Urinary steroid profiling might be a useful diagnostic test for the evaluation of patients with an adrenal incidentaloma.

The pitfalls associated with urinary steroid metabolite ratios in children undergoing investigations for suspected disorders of steroid synthesis

Background

Urinary steroid metabolite ratios may improve the diagnostic yield of potential disorders of steroid hormone synthesis.

Objectives

To investigate the range of ratios and their predictive value in children with suspected disorders of steroid synthesis.

Design and methods

Twelve ratios were calculated on steroid metabolite data analysed by gas chromatography–mass spectrometry in urine samples collected between 2008–2010 from 93 children. Urine samples were also analysed in 252 children with no known endocrine concerns.

Results

Of the 252 controls, 115 (46%) were male with a median age of 10 yr (range 1 month,18.5 years). Of the 93 cases, 38 (41%) were male with a median age of 6.5 yr (1 day,18.5 yrs). Of these, 41 (44%) had at least one ratio greater than the 95% percentile for controls. The most frequently abnormal ratio, found in 18/93 (19%) cases was (THS/(THE + THF + 5αTHF)) suggestive of 11β-hydroxylase deficiency. Over this period, 8 (9%) children were subsequently diagnosed with a steroid hormone disorder; 4 with 21-hydroxylase deficiency, 2 with11β-hydroxylase deficiency and 2 with 5α-reductase deficiency. All except one of these children had at least 1 raised ratio.

Conclusions

Urinary steroid metabolite ratios in suspected disorders of hormone synthesis often exceed the reference range for normal children. The predictive value of steroid metabolite ratios in identifying a genetic abnormality may be condition specific and needs further study to improve its clinical utility.

Direct analysis of anabolic steroids in urine using Leidenfrost phenomenon assisted thermal desorption-dielectric barrier discharge ionization mass spectrometry

Rapid detection of trace level anabolic steroids in urine is highly desirable to monitor the consumption of performance enhancing anabolic steroids by athletes. The present article describes a novel strategy for identifying the trace anabolic steroids in urine using Leidenfrost phenomenon assisted thermal desorption (LPTD) coupled to dielectric barrier discharge (DBD) ionization mass spectrometry. Using this method the steroid molecules are enriched within a liquid droplet during the thermal desorption process and desorbed all-together at the last moment of droplet evaporation in a short time domain. The desorbed molecules were ionized using a dielectric barrier discharge ion-source in front of the mass spectrometer inlet at open atmosphere. This process facilitates the sensitivity enhancement with several orders of magnitude compared to the thermal desorption at a lower temperature. The limits of detection (LODs) of various steroid molecules were found to be in the range of 0.05-0.1 ng mL(-1) for standard solutions and around two orders of magnitude higher for synthetic urine samples. The detection limits of urinary anabolic steroids could be lowered by using a simple and rapid dichloromethane extraction technique. The analytical figures of merit of this technique were evaluated at open atmosphere using suitable internal standards. The technique is simple and rapid for high sensitivity and high throughput screening of anabolic steroids in urine.

Chemometric evaluation of urinary steroid hormone levels as potential biomarkers of neuroendocrine tumors

Neuroendocrine tumors (NETs) are uncommon tumors which can secrete specific hormone products such as peptides, biogenic amines and hormones. So far, the diagnosis of NETs has been difficult because most NET markers are not specific for a given tumor and none of the NET markers can be used to fulfil the criteria of high specificity and high sensitivity for the screening procedure. However, by combining the measurements of different NET markers, they become highly sensitive and specific diagnostic tests. The aim of the work was to identify whether urinary steroid hormones can be identified as potential new biomarkers of NETs, which could be used as prognostic and clinical course monitoring factors. Thus, a rapid and sensitive reversed-phase high-performance liquid chromatographic method (RP-HPLC) with UV detection has been developed for the determination of cortisol, cortisone, corticosterone, testosterone, epitestosterone and progesterone in human urine. The method has been validated for accuracy, precision, selectivity, linearity, recovery and stability. The limits of detection and quantification were 0.5 and 1 ng mL⁻¹ for each steroid hormone, respectively. Linearity was confirmed within a range of 1–300 ng mL⁻¹ with a correlation coefficient greater than 0.9995 for all analytes. The described method was successfully applied for the quantification of six endogenous steroid levels in human urine. Studies were performed on 20 healthy volunteers and 19 patients with NETs. Next, for better understanding of tumor biology in NETs and for checking whether steroid hormones can be used as potential biomarkers of NETs, a chemometric analysis of urinary steroid hormone levels in both data sets was performed.

Androgen glucuronides analysis by liquid chromatography tandem-mass spectrometry: could it raise new perspectives in the diagnostic field of hormone-dependent malignancies?

Breast and prostate constitute organs of intense steroidogenic activity. Clinical and epidemiologic data provide strong evidence on the influence of androgens and estrogens on the risk of typical hormone-dependent malignancies, like breast and prostate cancer. Recent studies have focused on the role of androgen metabolites in regulating androgen concentrations in hormone-sensitive tissues. Steroid glucuronidation has been suggested to have a prominent role in controlling the levels and the biological activity of unconjugated androgens. It is well-established that serum levels of androgen glucuronides reflect androgen metabolism in androgen-sensitive tissues. Quantitative analysis of androgen metabolites in blood specimens is the only minimally invasive approach permitting an accurate estimate of the total pool of androgens. During the past years, androgen glucuronides analysis most often involved radioimmunoassays (RIA) or direct immunoassays, both methods bearing serious limitations. However, recent impressive technical advances in mass spectrometry, and particularly in high performance liquid chromatography coupled with mass spectrometry (LC-MS/MS), have overcome these drawbacks enabling the simultaneous, quantitative analysis of multiple steroids even at low concentrations. Blood androgen profiling by LC-MS/MS, a robust and reliable technique of high selectivity, sensitivity, specificity, precision and accuracy emerges as a promising new approach in the study of human pathology. The present review offers a contemporary insight in androgen glucuronides profiling through the application of LC-MS/MS, highlighting new perspectives in the study of steroids and their implication in hormone-dependent malignancies.

Urinary steroid profiling

Urinary steroid profiling is a long-established technique which has wide application in the study of disorders of human steroid biosynthesis and catabolism. The method divides into extraction of free and conjugated steroids, steroid conjugate hydrolysis, free steroid re-extraction, derivatization and analysis by GC or GC-MS. Several developments have led to better understanding of these processes and of ways to simplify and speed them up. The core method is described, together with some alternative options.

Steroid profiles as potential biomarkers in patients with urogenital tract cancer for diagnostic investigations analyzed by liquid chromatography coupled to mass spectrometry

Large discrepancy remains for the hormone-responsible cancers with regards to the conditions generating the optimal opportunity for cancerogenesis. In the research, altered steroid profiles were observed in patients with urogenital tract cancer diseases, namely bladder, kidney, prostate and testis ones. The presented steroid profiles from 154 subjects, including 77 urogenital tract cancer patient and 77 healthy controls were determined by liquid chromatography coupled to mass spectrometry method. Because the original experimental data obtained as a result of analytical experiment in order to interpret them in better way required the appropriate pre-treatment, the data were standardized by scaling and centering. In order to determine which samples form a collection for a high-capacity predictive model, Kennard-Stone's algorithm was used. A principal component analysis of preprocessed data provided better consistency of the steroid profiles with health status of subjects than PCA profiles without data preprocessing and showed a tendency to separate clusters of cancer patients from healthy subjects. The discriminant analysis was also performed and the percent of correct classification of cancer patients and control group was calculated. Finally, detailed studies examined the role of steroid profiles measured in urine, and considered as potential biomarkers related to urogenital cancer and associated renal dysfunctions.

LC-MS/MS fast analysis of androgenic steroids in urine

The liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated to detect androgenic steroids: trenbolone, nortestosterone, boldenone, methylboldenone, testosterone, methyltestosterone, 17β-1-testosterone and their metabolites in bovine urine. Sample preparation before LC-MS/MS analysis involved an enzymatic hydrolysis with glucuronidase AS-HP, isolation of free hormones from urine on C(18) SPE column and purification of the extract using liquid-liquid extraction with n-pentane and SPE NH(2) column. For the chromatographic separation of steroids, the Poroshell 120-EC C18 column (150 × 2.1 mm, 2.7 μm) was used. Mass spectrometric measurement was achieved using the API 4000 triple quadrupole (QqQ) instrument with a TurboIon-Spray source operating in positive electrospray ionization mode. The procedure was validated according to the Decision 2002/657/EC. Recovery ranged from 76.5% to 118.9% for all examined compounds. The repeatability was below 20% and reproducibility did not exceed the 25%. The linearity was good for all analytes in the whole range of tested concentrations, as proved by the correlation coefficients greater than 0.99. The decision limit (CCα) ranged from 0.10 to 0.17 μg L(-1) for all analytes, whereas the detection capability (CCβ) ranged from 0.17 to 0.29 μg L(-1). The application of an innovative Poroshell column allowed for very good chromatographic separation of steroids with a much shorter time of analysis.

Metabolic studies with promagnon, methylclostebol and methasterone in the uPA+/+-SCID chimeric mice

The chimeric uPA(+/+)-SCID mouse model, transplanted with human hepatocytes, was previously validated as an alternative tool to study in vivo the human steroid metabolism. This humanized mouse model was now applied, in the framework of anti-doping research, to test different nutritional supplements containing steroids. These steroids, intentionally or accidentally added to a nutritional supplement, usually are derivatives of testosterone. Information about the metabolism of these derivatives, which is important to assure their detection, is quite limited. However, due to ethical constraints, human volunteers cannot be used to perform experimental excretion studies. Therefore the chimeric mice were selected to perform three separated excretion studies with superdrol (methasterone), promagnon and also methylclostebol. The urine of the humanized mice was collected 24h after a single dose administration and analyzed by gas chromatography-mass spectrometry (GC-MS). The results indicated the presence of several metabolites including a 3-keto reduced metabolite and numerous hydroxylated metabolites. Also phase 2 metabolism was investigated to update the complete picture of their metabolism.

Serum steroid profiling by isotopic dilution-liquid chromatography-mass spectrometry: comparison with current immunoassays and reference intervals in healthy adults

BACKGROUND

The simultaneous, rapid and reliable measurement of a wide steroid panel is a powerful tool to unravel physiological and pathological hormone status. Clinical laboratories are currently dominated by high-throughput immunoassays, but these methods lack specificity due to cross-reactivity and matrix interferences. We developed and validated an isotopic dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method for the simultaneous measurement of cortisol, corticosterone, 11deoxycortisol, androstenedione, deoxycorticosterone (DOC), testosterone, 17OHprogesterone, dehydroepiandrosterone (DHEA) and progesterone in serum, and compared it to routine immunoassays employed in our laboratory. We also established adult reference intervals in 416 healthy subjects.

METHODS

0.9 ml of serum were spiked with labelled internal standards (IS) and extracted on C18 cartridges. Eluate was injected into a two-dimensional LC-system, purified in a perfusion column and separated on a C8 column during a 21 min gradient run. Analytes were revealed by atmospheric pressure chemical ionization (APCI) followed by multiple reaction monitoring (MRM) analysis.

RESULTS

Of the four immunoassays compared with the ID-LC-MS/MS method, only the results of ElecsysE170 for cortisol, testosterone in males and progesterone>1 ng/ml were in agreement with ID-LC-MS/MS. ElecsysE170 for testosterone in females and progesterone<1 ng/ml, Immulite2000 for androstenedione, DSL-9000 for DHEA and 17OHP Bridge for 17OHprogesterone, respectively, showed poor agreement. Reference intervals and steroid age and fertility related fluctuations were established.

CONCLUSION

Our ID-LC-MS/MS method proved to be reliable and sensitive in revealing steroid circulating concentrations in adults and in highlighting the limits of routine immunoassays at low concentrations.

Beyond the HPA Axis: Progesterone-Derived Neuroactive Steroids in Human Stress and Emotion

Stress and social isolation are well-known risk factors for psychopathology. However, more research is needed as to the physiological mechanisms by which social support buffers the impacts of stress. Research in animal models suggests important roles for progesterone (P) and its product, the neuroactive steroid allopregnanolone (ALLO), in stress and psychopathology. These hormones are produced in brain and periphery during stress in rodents, and down-regulate anxiety behavior and hypothalamic-pituitary-adrenal axis activity. Human clinical populations, including depressed patients, have alterations in ALLO levels, but it is unclear whether these basal hormone level differences have clinical import. To begin to address this question, this review examines the role of P and ALLO in stress physiology, and the impact of these hormones on mood, in healthy humans. Evidence largely supports that P and ALLO increase during stress in humans. However, P/ALLO administration appears to cause only mild effects on mood and subjective anxiety, while exerting effects consistent with gamma-aminobutyric acid receptor modulation. Additionally, P is linked to motivation for affiliation/social contact; P (and ALLO) release may be especially responsive to social rejection. These observations lead to the novel hypothesis that stress-related P/ALLO production functions not only to down-regulate stress and anxiety, but also to promote social contact as a long-term coping strategy. Malfunctioning of the P/ALLO system could therefore underlie depression partly by decreasing propensity to affiliate with others.

Detection of carbohydrates and steroids by cation-enhanced nanostructure-initiator mass spectrometry (NIMS) for biofluid analysis and tissue imaging

Nanostructure-initiator mass spectrometry (NIMS) is a highly sensitive, matrix-free technique that is well suited for biofluid analysis and imaging of biological tissues. Here we provide a new technical variation of NIMS to analyze carbohydrates and steroids, molecules that are challenging to detect with traditional mass spectrometric approaches. Analysis of carbohydrates and steroids was accomplished by spray depositing NaCl or AgNO(3) on the NIMS porous silicon surface to provide a uniform environment rich with cationization agents prior to desorption of the fluorinated polymer initiator. Laser desorption/ionization of the ion-coated NIMS surface allowed for Na(+) cationization of carbohydrates and Ag(+) cationization of steroids. The reliability of the approach is quantitatively demonstrated with a calibration curve over the physiological range of glucose and cholesterol concentrations in human serum (1-200 microM). Additionally, we illustrate the sensitivity of the method by showing its ability to detect carbohydrates and steroids down to the 800-amol and 100-fmol levels, respectively. The technique developed is well suited for tissue imaging of biologically significant metabolites such as sucrose and cholesterol. To highlight its applicability, we used cation-enhanced NIMS to image the distribution of sucrose in a Gerbera jamesonii flower stem and the distribution of cholesterol in a mouse brain. The flower stem and brain sections were placed directly on the ion-coated NIMS surface without further preparation and analyzed directly. The overall results reported underscore the potential of NIMS to analyze and image chemically diverse compounds that have been traditionally challenging to observe with mass spectrometry-based techniques.

Hydropyrolysis over a platinum catalyst as a preparative technique for the compound-specific carbon isotope ratio measurement of C27 steroids

Compound-specific stable carbon isotope analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is an important method for the determination of the (13)C/(12)C ratios of biomolecules such as steroids, for a wide range of applications. However, steroids in their natural form exhibit poor chromatographic resolution, while derivatisation adds carbon thereby corrupting the stable isotopic composition. Hydropyrolysis with a sulphided molybdenum catalyst has been shown to defunctionalise the steroids, while leaving their carbon skeleton intact, allowing for the accurate measurement of carbon isotope ratios. The presence of double bonds in unsaturated steroids such as cholesterol resulted in significant rearrangement of the products, but replacing the original catalyst system with one of platinum results in higher conversions and far greater selectivity. The improved chromatographic performance of the products should allow GC/C/IRMS to be applied to more structurally complex steroid hormones and their metabolites.

Interlaboratory comparison study of serum total testosterone [corrected] measurements performed by mass spectrometry methods

BACKGROUND

Though mass spectrometry (MS) assays are increasingly used for routine clinical measurements of serum total testosterone (TT), information about the variability of results is limited. This study assessed the variability of TT measurement results from routine MS assays.

METHODS

Twenty serum samples (12 females, 8 males) were analyzed on 2 days by seven high performance liquid chromatography (HPLC), and one gas chromatography (GC)-tandem mass spectrometry (HPLC-MS/MS, GC-MS/MS) assays. Two samples (male and female) were provided in five replicates to assess the within-run variability. Results were compared against those obtained at National Institute of Standards and Technology (NIST). The within- and between-laboratory variability was assessed for each sample. Comparisons to the NIST results were performed using bias plot and Deming regression analysis.

RESULTS

The overall coefficient of variation of the results obtained with MS assays was <15%CV at >1.53 nmol/L and <34%CV at 0.3 nmol/L. The between-assay variability was the major contributor to the overall variability. The assay precision was the highest (<3%CV) with assays using liquid-liquid extraction for sample preparation or GC-MS/MS. The mean percent difference to the reference assay was 11%. The slopes of Deming regression analysis of the MS assays were between 0.903 and 1.138 (correlation coefficient: >0.996). TT concentrations for one assay were above the measurement range.

CONCLUSIONS

The variability of TT measurement results among MS assays is substantially smaller than that reported for immunoassays. The type of sample preparation may affect assay precision. Standardizing assays can further reduce the variability of measurement results.

Steroid hormone analysis by tandem mass spectrometry

BACKGROUND

New high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) methods are among the most successful approaches to improve specificity problems inherent in many immunoassays.

CONTENT

We emphasize problems with immunoassays for the measurement of steroids and review the emerging role of LC-MS/MS in the measurement of clinically relevant steroids. The latest generation of tandem mass spectrometers has superior limits of quantification, permitting omission of previously employed derivatization steps. The measurement of steroid profiles in the diagnosis and treatment of congenital adrenal hyperplasia, adrenal insufficiency, chronic pelvic pain and prostatitis, oncology (breast cancer), and athletes has important new applications.

CONCLUSIONS

LC-MS/MS now affords the specificity, imprecision, and limits of quantification necessary for the reliable measurement of steroids in human fluids, enhancing diagnostic capabilities, particularly when steroid profiles are available.

Reference intervals of urinary steroid metabolites using gas chromatography-mass spectrometry in Chinese adults

BACKGROUND

Urinary steroid profiling by GC or GC-MS are established clinical tools to complement other biochemical tests in the diagnosis and investigation of a wide range of adrenocortical disorders, but normative data on adults using the more specific GC-MS are lacking. Our objective was to set up the reference intervals of commonly detected urinary steroid metabolites as well as marker metabolites seen in disease states.

METHOD

Apparently healthy adult Chinese males and females were recruited by completing health questionnaires. A 24-h urine specimen was collected from all the participants for urinary steroid profiling by GC-MS in cyclic scan mode. The analyzer was calibrated by using authentic steroid standards. Statistical methods recommended by the National Committee for Clinical Laboratory Standards were followed for setting up the reference intervals of various steroid metabolites. After outliers were excluded, the data were tested for the necessity to partition into sex-, menopausal status- and age-specific reference intervals.

RESULTS

83 males and 89 females were recruited for the study. Necessity to partition into sex-specific reference intervals was demonstrated for almost all steroid metabolites. Menopausal status and age also had a significant impact on steroid metabolite excretion, making separate reference intervals necessary.

CONCLUSIONS

We have set up the normative data on the levels of urinary steroid metabolite excretion in Chinese adults for future reference in patient management and research in steroid metabolism.

Simultaneous determination of prednisolone, prednisone, cortisol, and cortisone in plasma by GC-MS: estimating unbound prednisolone concentration in patients with nephrotic syndrome during oral prednisolone therapy

Individual variability of the pharmacokinetics of prednisolone based on the unbound concentration in plasma is of significant clinical consideration. The unbound concentrations of prednisolone were measured in 10 patients with nephrotic syndrome, two patients with systemic lupus erythematosus, and one patient with dermatomyositis by examining protein bindings of prednisolone on one or more occasions during prednisolone treatment. In this study, plasma concentrations of prednisolone, prednisone, cortisol, and cortisone were simultaneously analyzed by GC-MS by using stable isotope-labeled internal standards. Equilibrium dialysis was employed to accurately estimate the unbound fractions of prednisolone in plasma. The unbound fraction of prednisolone changed depending on plasma total prednisolone concentration and plasma albumin concentration. The unbound fraction of prednisolone (Y) is calculated: Y=(-0.0101x' + 0.0736) x + 10.23, where x' is the plasma albumin concentration and x is the total prednisolone concentration. The estimated concentrations of unbound prednisolone by using the above equation were in good agreement with the measured concentrations of unbound prednisolone. Since the protein binding of prednisolone did not change in the presence of prednisone (114.0 ng/ml), it appeared that prednisone produced from the therapeutic dose of prednisolone did not affect the unbound fraction of prednisolone.

A possibility of detection of the non-charge based analytes using ultra-thin body field-effect transistors

Ultra-thin body of p-type field-effect transistors were developed as transducer for biosensors. Changes of conductance resulted from the changes of the surface potentials of ultra-thin body field-effect transistors (UTB-FETs) due to surface chemical modifications were demonstrated. The channel surface of UTB-FETs were modified with N-[3-(trimethoxysilyl)propyl]ethylenediamine (AEAPTMS) and then gold nanoparticles (AuNPs) to immobilize the bio-component, the genetically engineered Delta(5)-3-ketosteroid isomerase (Art_KSI) or the Art_KSI conjugated with charged reporter (Art_KSI_mA51). The binding of charge-based molecules or nanoparticles has been demonstrated to strongly affect the conductivity of UTB-FETs; the increase or decrease of the conductance depends on the polarity of the immobilized molecules or nanoparticles. A new protocol involving the detection of a non-charged analyte relied on the competitive binding of analyte (19-norandrostendione) and a charged reporter (mA51) with KSI. When exposed to a 19-norandrostendione solution (10 microM), the conductance of Art_KSI_mA51-modified UTB-FET increased by 265 nS ( approximately 12%). On the other hand, conductance of Art_KSI-modified UTB-FET showed no distinct change under the same detection conditions.