Simultaneous determination of multiple urine biomarkers for kidney injury using SPE combined with LC-MS/MS.

BACKGROUND AND OBJECTIVES: Urinary biomarkers such as low molecular weight proteins and small molecular weight metabolites are crucial in the diagnosis of kidney injury. The objective of this study was to develop and preliminarily validate a sensitive and specific method using solid-phase extraction (SPE) in conjunction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous measurement of these biomarkers in human urine. METHOD: This study presents the development of a solid-phase extraction method integrated with LC-MS/MS analyzing biomarkers including creatinine, urea, ß2-microglobulin, α1-microglobulin, and cystatin C in human urine. An enhanced solid-phase cartridge technique was employed for peptide purification and dilution of small molecule metabolites during sample preparation. RESULTS: The developed LC-MS/MS method achieved satisfactory separation of the five analytes within 15 min. Accuracy levels ranged from -8.6% to 13.6%. Both intra-assay and inter-assay imprecision rates were maintained below 7.9% for all analytes. CONCLUSIONS: The established LC-MS/MS method effectively quantifies creatinine, urea, ß2-microglobulin, α1-microglobulin and cystatin C concurrently. This offers a viable alternative for the detection of kidney injury biomarkers in human urine, demonstrating potential for clinical application in kidney injury diagnosis.

Development and application of a high accuracy method for measuring Pb in blood.

BACKGROUND: Lead (Pb) is an environmental pollutant, and human exposure is assessed by measuring blood Pb concentrations. Today, the use of Pb-based products is restricted, but the health effects of low Pb concentrations require investigation. For this, a high-accuracy method is needed. Here, we report a new inductively coupled plasma mass spectrometry (ICP-MS) method for quantifying Pb in blood. METHODS: Blood samples and calibrators were gravimetrically spiked with bismuth as an internal standard, digested with ultrapure nitric acid, and diluted 100 times. The calibrators were made from high-purity reference materials supplied by the National Institute of Standards and Technology, and the sample concentration was measured using the calibration bracketing method. The analytical performance and application of the new method were investigated. RESULTS: The method had good specificity and a negligible matrix effect. The intra- and inter-assay coefficients of variation (CVs) were <1.34 % and <1.88 %, respectively, and the total CV was <1.74 %. The range of recovery was 98.9 %-99.4 %. SRM955d, BCR-635, and BCR-636 were within the certified intervals, with mean relative bias values of 0.93 %, -0.13 %, and -0.56 %, respectively. The limit of quantification was 1.1 µg/l. The method was used to assign target values to external quality assessment samples and to assess routine methods, showing good results at high concentrations. However, at low concentrations, two laboratories did not pass. CONCLUSIONS: This ICP-MS method is a simple, accurate method and can be a candidate reference method for blood Pb measurement. But more research will be needed to verify this.

A standard addition method to quantify serum lithium by inductively coupled plasma mass spectrometry.

BACKGROUND: Therapeutic monitoring of lithium (Li) is important because of its narrow therapeutic range and therapeutic index. Here, the authors present the evaluation of an accurate method for the determination of lithium in serum. METHOD: Serum samples were diluted with 0.3% ultrapure nitric acid and were spiked with an internal standard germanium (Ge). The Li/Ge ratio was detected in He mode; we utilized standard addition method to quantify lithium in human serum. The new inductively coupled plasma mass spectrometry (ICP-MS) assay was characterized for linearity, specificity, imprecision, trueness, accuracy, and comparison. RESULTS: The correlation coefficients (r) of linearity were all > 0.9999. The specificity proved to be good. The total coefficients of variation (CV) were 1.11% and 0.49% for the two serum samples. The mean bias from target values of standard reference materials (SRM 956d) was -0.71% for Level I, -017% for Level II, and 2.20 for Level III. External Quality Assessment Scheme for Reference Laboratories in Laboratory Medicine (RELA) gave satisfied results for the new method. Comparison with the ion-selective electrode routine method got reasonable results. CONCLUSION: This high accuracy method is an attractive alternative for lithium measurement and can be used as a candidate reference method to improve quality of serum lithium in China.

Ferrocene-Labelled Electroactive Aptamer-Based Sensors (Aptasensors) for Glycated Haemoglobin.

Glycated haemoglobin (HbA1c) is a diagnostic biomarker for type 2 diabetes. Traditional analytical methods for haemoglobin (Hb) detection rely on chromatography, which requires significant instrumentation and is labour-intensive; consequently, miniaturized devices that can rapidly sense HbA1c are urgently required. With this research, we report on an aptamer-based sensor (aptasensor) for the rapid and selective electrochemical detection of HbA1c. Aptamers that specifically bind HbA1c and Hb were modified with a sulfhydryl and ferrocene group at the 3' and 5'-end, respectively. The modified aptamers were coated through sulfhydryl-gold self-assembly onto screen printed electrodes, producing aptasensors with built in electroactivity. When haemoglobin was added to the electrodes, the current intensity of the ferrocene in the sensor system was reduced in a concentration-dependent manner as determined by differential pulse voltammetry. In addition, electrochemical impedance spectroscopy confirmed selective binding of the analytes to the aptamer-coated electrode. This research offers new insight into the development of portable electrochemical sensors for the detection of HbA1c.

Establishment and application of a new serum sodium candidate reference method.

BACKGROUND: Levels of serum sodium (Na) are widely determined in clinical laboratories. Accordingly, sodium quantification must be performed using reliable methods. Herein are reported the results of the evaluation of a new inductively coupled plasma mass spectrometry (ICP-MS) method for sodium quantification. METHODS: Serum samples were diluted 100 × by 0.3% ultrapure nitric acid, and germanium (Ge) was used as an internal standard. Sodium calibration solutions with different concentrations were added to serum matrix solutions. The serum sodium concentration was calculated according to the standards addition method. The analytical performance of the method, as well as a comparison with other sodium method, was investigated. RESULTS: The correlation coefficients (r) between the measured Na/Ge ratios and the analyte concentration ratios were all > 0.9999. Intra- and between-assay coefficients of variation (CVs) were < 0.64% and < 0.57%, respectively, and the total CV was < 0.67%. The trueness of the method was verified by measuring a certified reference material, SRM 956d. The new ICP-MS method was compared with the 2017 and 2018 External Quality Assessment Scheme for Reference Laboratories in Laboratory Medicine (RELA). The results were well correlated with those obtained by the routine indirect ion selective electrode (ISE) method: sodium (ICP-MS, mmol/L) = 0.9895 × sodium (ISE, mmol/L) + 1.3049 (r = 0.9914, n = 40). The mean deviation between the results of the ICP-MS method and the indirect ISE method was -0.15%. CONCLUSIONS: The new ICP-MS method proved to be accurate, reliable, simple, and fast and may be used as a candidate reference method for setting target values in the standardization of serum sodium measurements.

Impact of MTHFR gene C677T polymorphism on Bcl-2 gene methylation and protein expression in colorectal cancer.

OBJECTIVE: To investigate the impact of MTHFR C677T polymorphism on Bcl-2 gene promoter CpG island (CGI) methylation and Bcl-2 protein expression. MATERIAL AND METHODS: MTHFR polymorphisms of 86 sporadic colorectal cancer (CRC) patients and 100 healthy volunteers were analyzed by PCR-based restriction fragment length polymorphism, and Bcl-2 promoter CGI methylation in 86 CRC tissues and 86 paired nonneoplastic adjacent tissues was determined by methylation-specific PCR. Bcl-2 oncoprotein expression in 70 CRC tissues and paired nonneoplastic adjacent tissues was detected by immunohistochemistry. RESULTS: The frequency of MTHFR 677 T allele and combined variant genotypes (677CT + TT) in CRC patients was significantly higher than that in healthy controls (p = 0.023 and p = 0.035, respectively), and there is a significant association between 677TT or 677(CT + TT) genotypes and CRC (OR = 2.534, p = 0.045 and OR = 1.888, p = 0.035, respectively). The frequency of methylated Bcl-2 promoter CGI in tumor tissues was significantly lower than that in nonneoplastic adjacent tissues (p = 0.014). The frequency of methylated Bcl-2 promoter CGI in CRC tissues of the individuals with CC genotype was significantly higher than that of those with CT/TT genotypes (p = 0.018), there was significant distribution difference of C and T alleles between individuals with methylated and unmethylated Bcl-2 promoter CGI in colorectal cancer tissues (p = 0.023). Bcl-2 promoter hypomethylation was significantly correlated with Bcl-2 oncoprotein expression in colorectal cancer tissues (r = 0.558, p < 0.001). CONCLUSION: Bcl-2 promoter is hypomethylated in colorectal cancer tissue, and there is a significant correlation between MTHFR 677 TT or CT/TT genotypes and CRC or Bcl-2 promoter CGI methylation/oncoprotein expression in CRC.

Effect of the methylenetetrahydrofolate reductase gene C677T polymorphism on C-erbB-2 methylation status and its association with cancer.

Methylation abnormalities of cancer-related genes are recognized to play an important role in carcinogenesis. Methylenetetrahydrofolate reductase (MTHFR) regulates DNA methylation by affecting synthesis of S-adenosylmethionine, which is a universal methyl donor for methylation reactions. MTHFR gene polymorphisms that affect enzymatic activity may be associated with DNA methylation and cancer susceptibility. In the present study, we investigated the MTHFR C677T polymorphism in 247 cancer patients and 100 healthy subjects using PCR-RFLP, as well as the methylation status of the CpG island in the promoter region of the C-erbB-2 oncogene in 247 tumor and matched adjacent tissue samples using methylation-specific PCR. The results revealed that the methylation rate of the C-erbB-2 gene was significantly lower in the tumor tissues than in the matched adjacent tissues (43.3 vs. 69.2%, P=0.000). No correlation was observed between the methylation patterns of C-erbB-2 in tumor tissues and the clinicopathological characteristics of the patients. The frequency of the MTHFR gene 677 T allele was significantly higher in cancer patients than in the healthy subjects, and the combined variant genotypes (677CT+TT) significantly increased the risk of developing cancer (OR=1.619, 95% CI 1.012-2.588, P=0.043). Among the cancer patients, the methylation rate of the C-erbB-2 gene was higher in indi-viduals with the CC genotype than in those with the CT/TT genotype (50.0 vs. 39.4%). This difference was not significant (P=0.103). However, a significant difference was found in patients with breast cancer (P=0.008). In conclusion, the C-erbB-2 promoter CpG island was hypomethylated in cancer patients, and the MTHFR 677 CT/TT genotype increased the risk of developing the disease. Moreover, in breast cancer patients, the MTHFR gene C677T polymorphism had an effect on the methylation status of the C-erbB-2 gene.