Determination Of Homocysteine Research Articles

Colorimetric sensors with different reactivity for the quantitative determination of cysteine, homocysteine and glutathione in a mixture

We report a facile method for the quantitative detection of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in a mixture.

Selective electrochemical detection of thiol biomarkers in saliva using multiwalled carbon nanotube screen-printed electrodes

The selective electrochemical determination of homocysteine and glutathione was realized in spiked synthetic saliva using a two-part voltammetric method at a multiwalled carbon nanotube screen-printed electrode. This method involves first the use of the reaction of electro-oxidized catechol with a thiol via 1,4-Michael addition reaction; this results in an analytically useful adduct peak signal. Secondly, the procedure exploits the different rates of reaction of the targeted thiols with the ortho-quinone, coupled with variable voltage scan rates. At fast scan rate, homocysteine is only detected while at slower voltage scan rate, both homocysteine and glutathione detection is reflected in the adduct signal. Thus, the quantification of both homocysteine and glutathione can be achieved with a combination of both sets of data. Calibration curves were determined for both homocysteine and glutathione in synthetic saliva with sensitivities of ca. 13.2nAμM−1 and ca. 2.1nAμM−1 for homocysteine and glutathione respectively with limits of detection at ca. 0.9μM for homocysteine and ca. 2μM for glutathione within their corresponding linear ranges. Lastly, the use of commercially available multiwalled carbon nanotube screen-printed electrode was applied to the system for selective homocysteine and glutathione detection in different spiked synthetic saliva samples. Hitherto the method has been applied in vitro and to diluted blood plasma; the extension to saliva is attractive for diagnostic use because of the non-invasive nature of the sampling.

Liquid Chromatography-Tandem Mass Spectrometry Method for Determination of Homocysteine in Rat Plasma: Application to the Study of a Rat Model for Tauopathies.

Hyperhomocysteinemia is a common occurrence in many neurodegenerative diseases, including tauopathies. We developed and validated a simple and sensitive liquid chromatography-tandem mass spectrometry method for the analysis of homocysteine (Hcy) in rat plasma. Hcy was analyzed using ultra-performance liquid chromatography on a C8 column with detection by positive ESI tandem mass spectrometry. For optimal retention and separation, we used ion-pair reagent-heptafluorobutyric acid. The method utilizes heavy labeled internal standard and does not require any derivatization or extraction step. The procedure was validated in compliance with the European Medicines Agency guideline. The limit of detection was 0.15 µmol/L and the limit of quantification was 0.5 µmol/L. The method showed excellent linearity with regression coefficients higher than 0.99. The accuracy was in the range of 93-98%. The inter-day precision (n = 5 days), expressed as % relative standard deviation, was in the range 3-8%. Using this method, we analyzed plasma samples from two transgenic lines of the rat model for tauopathies.

Onsite naked eye determination of cysteine and homocysteine using quencher displacement-induced fluorescence recovery of the dual-emission hybrid probes with desired intensity ratio

Simple, inexpensive, portable sensing strategies for those clinically relevant molecules have attained a significant positive impact on the health care system. Herein, we have prepared a dual-emission ratiometric fluorescence probe with desired intensity ratio and demonstrated its efficiency for onsite naked eye determination of cysteine (Cys) and homocysteine (Hcy). The hybrid probe has been designed by hybridizing two differently sized CdTe quantum dots (QDs), in which the red-emitting CdTe QDs (rQDs) entrapped in the silica sphere acting as the reference signal, and the green-emitting CdTe QDs (gQDs) covalently attached on the silica surface serving as the response signal. When 1,10-phenanthroline with strong coordination ability to Cd atoms in gQDs was introduced, the fluorescence of the gQDs was effectively quenched, while the fluorescence of the rQDs stayed constant. Upon exposure to different contents of Cys or Hcy, the fluorescence of gQDs can be recovered gradually due to the displacement of the quencher. Based on the background signal of rQDs, the variations of the sensing system display continuous fluorescence color changes from red to green, which can be easily observed by the naked eye. The assay requires ∼20min and has a detection limit of 2.5 and 1.7μM for Cys and Hcy, respectively. Furthermore, we demonstrate that this sensing scheme can be fully integrated in a filter paper-based assay, thus enabling a potential point-of-care application featuring easy operation, low power consumption, and low fabrication costs.

Electrochemical Determination of Homocysteine at Disposable Graphite Electrodes

AbstractIn the case of disruption of Hcy metabolism, the blood level of Hcy increases and it causes particularly the cardiovascular diseases, cancer, dementia and Parkinson’s disease. Thus, the sensitive analysis of Hcy levels in biological fluids is very important. Hcy analysis was performed herein using very practical and cost‐effective protocol using differential pulse voltammetry and graphite electrode. Detection limit of Hcy was found to be 1.21 µM in the linear range from 2 µM to 20 µM. The electrochemical Hcy detection in artificial urine medium was also successfully performed even in the presence of L‐Cysteine, L‐Methionine and Glutathione.

Determination of homocysteine in cerebrospinal fluid as an indicator for surgery treatment in patients with hydrocefalus.

Increased homocysteine levels in serum are typical features of neurodegenerative brain diseases including hydrocephalus. The most frequent therapeutic approach consists of the insertion of a shunt, connecting the brain ventricles to an alternative drainage site. To decide whether the patient should undergo this, the lumbar drainage test is usually carried out to distinguish patients who can benefit from the shunt insertion. In searching for other potential biochemical markers for shunt indication we determined homocysteine levels in CSF during the lumbar drainage test. Homocysteine in CSF was measured during the 5-day lumbar drainage test in 27 patients with normal-pressure hydrocephalus (NPH) and in 25 patients with excluded hydrocephalus. A novelized gas chromatography method with flame ionization detection (GC-FID) was developed and evaluated. During the first two days of lumbar drainage, the levels of CSF homocysteine in NPH patients were significantly higher compared to the controls, while on the fifth day, the homocysteine levels in patients with hydrocephalus reached the level of controls. Determination of CSF homocysteine in patients with confirmed or suspected hydrocephalus may serve as an independent marker for deciding on their further treatment strategy.

Simultaneous determination of cystathionine, total homocysteine, and methionine in dried blood spots by liquid chromatography/tandem mass spectrometry and its utility for the management of patients with homocystinuria

BackgroundDisorders of homocysteine and B-vitamin metabolism represent a significant problem in clinical practice. Establishing the diagnosis requires specialized tests with demanding preanalytical requirements. To advance the detection of patients with these disorders, we developed a method for the simultaneous determination of cystathionine (Cysta), methionine (Met) and total homocysteine (tHcy) in dried blood spots (DBSs). MethodsA punch from a DBS sample was mixed with a solution of isotopically labeled internal standards, and analytes were extracted using methanol/0.1% formic acid/0.5mol/L dithiothreitol. The extract was injected into an LC–MS/MS system operating in MRM mode. ResultsThe analytical performance of the method employing DBS is adequate for its purpose and the type of sample. Compared with Cysta, tHcy and Met plasma levels, our method exhibited a negative bias between −3.8% and −42.2% due to the lower concentrations of these analytes in erythrocytes. The tHcy level and the Met/Cysta ratio in DBS enabled the clear detection of 12 patients with disorders of transsulfuration and with genetic and nutritional remethylation defects. ConclusionsThe ease of collecting and transporting DBS samples may advance diagnostic procedures in patients with neuropsychiatric disorders and thromboembolism. Consequently, this approach may facilitate detection and simplify the monitoring of patients with homocystinuria.

The use of screen-printed electrodes in a proof of concept electrochemical estimation of homocysteine and glutathione in the presence of cysteine using catechol.

Screen printed electrodes were employed in a proof of concept determination of homocysteine and glutathione using electrochemically oxidized catechol via a 1,4-Michael addition reaction in the absence and presence of cysteine, and each other. Using cyclic voltammetry, the Michael reaction introduces a new adduct peak which is analytically useful in detecting thiols. The proposed procedure relies on the different rates of reaction of glutathione and homocysteine with oxidized catechol so that at fast voltage scan rates only homocysteine is detected in cyclic voltammetry. At slower scan rates, both glutathione and homocysteine are detected. The combination of the two sets of data provides quantification for homocysteine and glutathione. The presence of cysteine is shown not to interfere provided sufficient high concentrations of catechol are used. Calibration curves were determined for each homocysteine and glutathione detection; where the sensitivities are 0.019 μA·μM−1 and 0.0019 μA·μM−1 and limit of detections are ca. 1.2 μM and 0.11 μM for homocysteine and glutathione, respectively, within the linear range. This work presents results with potential and beneficial use in re-useable and/or disposable point-of-use sensors for biological and medical applications.

Le degré de l’insuffisance rénale chronique est associé aux taux de cytokines pro-inflammatoires, à l’hyperhomocystéinémie et au stress oxydant

AimTo evaluate pro-inflammatory cytokines, homocysteinemia and markers of oxidative status in the course of chronic renal failure. Patients and methodsOne hundred and two patients (male/female: 38/64; age: 45±07 years) with chronic renal failure were divided into 4 groups according to the National Kidney Foundation classification. They included 28 primary stage renal failure patients, 28 moderate stage renal failure, 28 severe stage renal failure and 18 end stage renal failure. The inflammatory status was evaluated by the determination of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6) and total homocysteine. Pro-oxidant status was assessed by assaying thiobarbituric acid reactive substances, hydroperoxides, and protein carbonyls. Antioxidant defence was performed by analysis of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase. ResultsInflammatory markers were elevated in the end stage renal failure group compared to the other groups (P<0.001). Indeed, an increase in thiobarbituric acid reactive substances, hydroperoxides and protein carbonyls was noted in the end stage renal failure group in comparison with the other groups (P<0.001), while the levels of antioxidants enzymes activity were decreased in the study population (P<0.001). ConclusionImpaired renal function is closely associated with the elevation of inflammatory markers leading to both increased markers of oxidative stress and decreased antioxidant defense.

Electrochemical determination of homocysteine using carbon nanotubes modified paste electrode and isoprenaline as a mediator

Homocysteine (HCy) is an important amino acid containing thiol group and is known as a risk factor in relation to ischemic heart disease and stroke. In this study the electrochemical determination of homocysteine (HCy) has been described using isoprenaline hydrochloride (ISP) as a mediator on multiwall carbon nanotubes modified paste electrode (MWCNTPE). Electrochemical behavior of homocysteine was investigated by cyclic voltarrtmetry and chronoamperometry. The cyclic voltammograms showed that the electrocatalytic oxidation of homocysteine occurs in the presence of ISP on the surface of MWCNTPE at a potential about 640 mV. Also, results showed that the oxidatation peak current of HCy at the modified carbon nanotubes electrode was more than unmodified electrode. The diffusion coefficient and the kinetic parameters including electron transfer coefficient and rate constant of electrocatalytic reaction were determined using electrochemical approaches. Linear sweep voltammetry results showed that electrocatalytic oxidation peak current of HCy had linear dynamic range in the range of 5.0 to 800 μmol L−1 with a detection limit of 3.3 μmol L−1 in pH 3.5 (universal buffer).

Nanostructured base electrochemical sensor for voltammetric determination of homocysteine using a modified single-walled carbon nanotubes paste electrode

A carbon paste electrode modified with benzoylferrocene (BF) and carbon nanotubes (CNTs) have been applied to the electrocatalytic oxidation of homocysteine which reduced the overpotential by about 165 mV with an obvious increase in the current response. The transfer coefficient (α) for the electrocatalytic oxidation of homocysteine and diffusion coefficient of this substance under the experimental conditions were also investigated. In a phosphate buffer solution (PBS) of pH 7.0, the oxidation current increased linearly with two concentration intervals of homocysteine; one is 0.1 to 10.0 μM, and the other is 10.0 to 80.0 μM. The detection limit (3σ) obtained by square wave voltammetry (SWV) was 50.0 nM. The proposed method was successfully applied to the determination of homocysteine in real samples.

Selective electrochemical determination of homocysteine in the presence of cysteine and glutathione

The electrochemical oxidation of 3,5-di-tert-buthylcatechol in the presence of homocysteine was used for the selective electrochemical determination of homocysteine in the presence of cysteine and glutathione at a glassy carbon and a glassy carbon electrode modified with carbon nanotube. The results revealed that the electrochemically generated 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione exhibits high catalytic activity toward homocysteine oxidation at reduced over-potential and low catalytic activity for oxidation of cysteine. The catalytic activity 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione toward cysteine was suppressed in the presence of 4-N,N-dimethylaminocinnamaldehyde. Contrary to homocysteine and cysteine, the reaction of glutathione with 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione is a substituation reaction. This method exhibits three dynamic linear ranges of 2.5 to 10μmolL−1, 10 to 100μmolL−1 and 100 to 1000μmolL−1, and a lower detection limit (3σ) of 0.89±3.53% μmol L−1 for homocysteine.

Simultaneous determination of total homocysteine and cysteine in human plasma by capillary zone electrophoresis with pH-mediated sample stacking

An accurate, simple and sensitive method for simultaneous determination of total homocysteine (Hcy) and total cysteine (Cys) in human plasma has been developed and validated. Hcy and Cys play a major role in metabolism and cellular homeostasis. An elevated level of plasma Hcy is considered an important risk factor or marker for several diseases, in particular cardiovascular disease, while Cys is involved in a variety of important cellular functions such as protein synthesis, detoxification and metabolism. The proposed analytical procedure consists of reduction of title thiol dimers and unsymmetrical disulfides with tris(2-carboxyethyl)phosphine, and derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) followed by pH-mediated stacking capillary electrophoresis separation and ultraviolet-absorbance detection of Hcy-CMQT and Cys-CMQT derivatives at 355 nm. Effective baseline electrophoretic separation was achieved using a standard fused-silica capillary (effective length 91.5 cm, 75 μm id) and 0.1 mol L−1, lithium acetate buffer adjusted to pH 4.75. The limit of quantification (signal to noise ratio of 9) for derivatized Hcy and Cys in plasma was 2 μmol L−1. The calibration curves obtained for Hcy and Cys in plasma showed linearity in the range 2–20 μmol L−1, with R2 = 0.9986 and 20–300 μmol L−1, with R2 = 0.9998, respectively. The relative standard deviation of the points of the calibration curve was lower than 7%. The method can be used for a routine monitoring of total Hcy and total Cys levels in plasma of human subjects.

Determination of homocysteine by lc-ms-ms with atmospheric pressure chemical ionization

Homocysteine (Hcy) is an intermediate of methionine metabolism. High plasma Hcy concentrations are an independent risk factor for stroke, peripheral vascular disease, deep venous thrombosis, coronary disease, and cognitive deficiency. Apparently, it is a great importance to measure Hcy levels in human blood. A new method for the quantification of Hcy by means of reversed-phase LC/atmospheric pressure chemical ionization mass spectrometry has been developed. The MRM ion transition, m/z 136.0 ® 90.0 was used for Hcy quantification. The limit of detection was 0.4 mM, quantification was performed from 1 mM to 40 mM with coefficient of determination of R2=0,997. The method was applied successfully to Hcy determination in human blood.

Homocysteine: validation and comparison of two methods using samples from patients with pulmonary hypertension

Introduction and objective: The determination of homocysteine plasma levels has been reported as a risk marker of interest in severe diseases involving endothelial injury and associated with the development or progression of atherosclerotic lesions and thrombus formation. The aims of this study were to validate method for quantification of plasma homocysteine by high performance liquid chromatography (HPLC) with fluorimetric detection, and to compare the results obtained from patients with pulmonary hypertension by HPLC with those obtained by spectrophotometric enzymatic cycling (S-Ec) method. Materials and methods: The validation parameters, such as linearity, matrix effect, precision, accuracy, detection and quantitation limits, and robustness of the method were evaluated aiming to demonstrate that it is suitable for the intended use. The data obtained in the quantification of homocysteine using the validated method (HPLC) and the spectrophotometric enzymatic cycling (S-Ec) method, were compared. Results: The method was precise, accurate, and robust; it also had good recovery and showed no matrix effect. The linearity covered a range of 5.0-85.0 µmol/l and the limits of detection and quantification were 1.0 µmol/l and 3.4 µmol/l, respectively. The results obtained for homocysteine determination by HPLC and S-Ec methods were comparable. Conclusion: The validated HPLC method showed good performance for quantification of plasma homocysteine levels, while S-Ec method provided results for homocysteine comparable with those obtained by the validated method; therefore, this methodology is a potential alternative of automated method for clinical laboratories.

Determination of cysteine, homocysteine, cystine, and homocystine in biological fluids by HPLC using fluorosurfactant-capped gold nanoparticles as postcolumn colorimetric reagents

We have demonstrated for the first time the suitability of fluorosurfactant-capped spherical gold nanoparticles as HPLC postcolumn colorimetric reagents for the direct assay of cysteine, homocysteine, cystine, and homocystine. The success of this work was based on the use of an on-line tris(2-carboxyethyl)phosphine reduction column for cystine and homocystine. Several parameters affecting the separation efficiency and the postcolumn colorimetric detection were thoroughly investigated. Under the optimized conditions, cysteine, homocysteine, cystine, and homocystine in human urine and plasma samples were determined. Detection limits for cysteine, homocysteine, cystine, and homocystine ranged from 0.16-0.49 μM. The accuracy in terms of recoveries ranged between 94.0-102.1%. This proposed method was rapid, inexpensive, and simple.

Determination of Homocysteine in Human Saliva by Liquid Chromatography and Electrospray Ionization Quadrupole Time-of-flight Mass Spectrometry: Profiles in Healthy Adults

Homocysteine (Hcys) is a non-essential amino acid associated with a range of diseased and abnormal metabolic conditions. Hcys concentration in saliva is routinely determined by enzyme assays, which are broadly specific, but can be expensive and suffer from cross-reactivity. Total Hcys (tHcys) concentrations in eight healthy adults were determined to establish the inter-day variation during resting, normal and intensive physical activity, using the more sensitive analytical techniques of liquid chromatography and tandem mass spectrometry without prior derivatization. Saliva (~ 1.5 mL) was collected over four days; early morning (EA), normal activity (NA) and during physical activity (PA). Samples were processed by disulphide reduction, acetonitrile precipitation and then centrifugation-filtration. Extracts were chromatographically resolved and analysed on a quadrupole time- of-flight (QToF) mass spectrometer. The protonated [M+H]+, m/z 136.101 and product ([M+H]+- HCOOH) m/z 90.103 ions were then monitored against an internal standard (13CHcys) and external set of calibration standards. Mean tHcys concentration for the whole group, including exercise was 6.6 ± 8.0 (range 0.2 - 29.6 nmol/mL). Overall, concentration of tHcys was greater in males than the females but not significantly (p > 0.05). The mean EA concentration was significantly (p < 0.05) greater than NA for both males (p = 0340) and females (p = 0.0045). There were large within-subject variations (coefficient of variation; CV%; 24% to 103%). The limits of detection (LOD) and quantification (LOQ) were 0.07 and 0.22 nmol/mL, respectively. The procedure potentially provides a convenient means of analyzing salivary Hcys as a diagnostic disease marker.

Simultaneous determination of three aminothiols in human plasma by high performance liquid chromatography with gold nanoparticle enrichment

A high performance liquid chromatography (HPLC) method with ultraviolet detection (UVD) for the simultaneous determination of cysteine (Cys), homocysteine (Hcys) and glutathione (GSH) in human plasma was established. Tween 20-capped gold nanoparticles (Tween 20-AuNPs) were used as selective probes for the extraction and enrichment of amino-thiols. The aminothiols removed from the Tween 20-AuNPs by dithiothreitol were separated on a Spursil C18 column (250 mm x 4.6 mm, 5 microm) with a mobile phase of 60 mmol/L phosphate buffer solution (pH 2.0). The column eluent was monitored using UVD at the wavelength of 200 nm. The linear ranges were found between peak area and concentration in the ranges of 0.025-350 micromol/L for Cys, 0.02-60 micromol/L for Hcys and 0.01-50 micromol/L for GSH, with linear regression coefficients all above 0.99. The limits of detection (LOD, signal to noise ratio of 3) for the aminothiols were between 2.5 nmol/L and 6.0 nmol/L and the recoveries were between 92.8% and 106.0%. Due to the significant interference reduction of endogenous substances in the plasma and the subsequent improvement of the selectivity and sensitivity of HPLC-UVD, the present method was applied for the simultaneous analysis of the forementioned aminothiols in the plasma samples of cardiovascular disease patients. The results showed that the levels of Hcys and GSH had significant differences between the patients and the controls, while that of Cys had no significant difference.

Simultaneous determination of homocysteine and asymmetric dimethylarginine in human urine by liquid chromatography–tandem mass spectrometry

Increased circulating concentrations of homocysteine (HCY) and asymmetric dimethylarginine (ADMA) are associated with vascular disease and vascular risk factors. HCY has been shown to inhibit the activity of endothelial dimethylaminohydrolase (DDAH), causing the accumulation of ADMA and the inhibition of nitric oxide synthesis. The concentrations of HCY and ADMA in biological fluids are used in the clinical diagnosis of cardiovascular diseases and this necessitates the development of a rapid and sensitive method for simultaneous determination of HCY and ADMA. A rapid, simple and sensitive method for simultaneous determination of HCY and ADMA by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with electro spray ionization (ESI) in human urine was reported here. The methodology designed here was used to estimate these molecules in urine samples collected from patients reported to Cardiology Department of our hospital. Chromatographic separation was performed on Atlantis HILIC silica (100mm×2.1mm, 5μm, Waters). Positive multiple reactions monitoring (MRM) mode was chosen for quantification of each analyte and cystamine dihydrochloride (CYA) was used as the internal standard (IS) for the assay. The intra-assay precision and accuracy were in the range of 2.4-4.8 and -1.8% to 3.1%, respectively. The inter-assay precision and accuracy were in the range of 3.0-4.2% and -1.2% to 3.2%, respectively. The recoveries were between 94.9% and 101.4%. Our approach is simple, rapid and could be extended to routine urine assay.

Correlation study on the determination of homocysteine and high sensitive C reaction protein in pregnancy-induced hypertension syndrome patients

Objective To study plasma homocysteine (Hcy) and high sensitive C reaction protein (HsCRP) of the joint determination of pregnancy-induced hypertension syndrome (PIH) patients in the diagnostic value of Hcy and HsCRP,in correlation of PIH syndrome.Methods 116 cases of patients with PIH were divided into 3 groups:40 cases of mild PIH,40 cases of moderate PIH,36 cases of severe PIH.Randomly selected normal late pregnant patients and 40 cases of normal late pregnant control group by enzymatic cycling method for detection of plasma Hcy,serum HsCRP immunoturbidimetric assay.Results In PIH group,mild,moderate,severe PIH syndrome in patients with Hcy and normal late pregnant group showed significant differences (P＜0.01); in PIH group,mild,moderate,severe PIH syndrome in patients with HsCRP and normal late pregnant group were significantly different (P＜0.01);correlation between Hcy and HsCRP mild,moderate,severe PIH group regression curve estimation,like a straight,positive correlation.Conclusions Hcy and HsCRP are PIH risk factors evaluation indexes,correlation regression curve estimation,like a straight,positively correlated,and positively related to the severe degree,effectively reflect the progress of PIH disease.The combined detection of Hcy and HsCRP is early PIH analysis,development and prognosis has guiding significance to the project. Key words: Pregnancy-induced hypertension syndrome; Homocysteine (Hcy); High sensitive C reaction protein (HsCRP); Correlation; Joint application