Introduction
Biomarkers generally refer to some characteristic biochemical indicators in a common physiological or pathological or therapeutic process that can be objectively measured and evaluated. Through the measurement of biomarkers, the biological process of the body can be known. Therefore, biomarkers play an important role in the identification, early diagnosis and monitoring of disease prevention and treatment. However, the quantitative analysis of biomarkers is required. Stable-isotope dilution (SID) methodology, a quantitative method to determine the content of unlabeled compounds with stable isotope-labeled compounds as internal standard, which is in combination with LC-MS provides the highest possible analytical specificity for quantitative determinations of biomarkers and has been widely concerned [1].
Applications
The method of SID-LC-MS based on stable isotope-labeled compounds can be used in determination of various biomarkers such as amino acid biomarkers, protein and peptide biomarkers, steroid biomarkers. There are some examples as follows [2].
Amino acid biomarkers
N-acetylaspartic acid (NAA) is a specific urinary marker of Canavan disease (autosomal recessive leukodystrophy). The SID-LC-MS method was developed to determine urinary NAA using deuterium D3-NAA internal standard. L-arginine (ARG) and its metabolites asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are an important marker of a series of human diseases. An lC-MS/MS method was performed to determine quantitative analysis of these three substances in human plasma using 13C6-ARG, D7-ADMA, D6-SDMA as internal standard, which can promote clinical research in related fields.
Fig. 1 The structure of L-arginine.
Protein and peptide biomarkers
DcR3 and GDF15 are biomarkers for colorectal cancer. Quantitative detection of DcR3 and GDF15 in human serum was performed by SID-LC-MS with 15N-labeled peptides. Plasma C-peptide is an important marker of insulin secretion. The determination of C-peptide level can be used to classify diabetes mellitus and understand the function of islet β cells in diabetic patients. A method for quantifying human serum C-peptide by ID-LC-M using d8-Val2-C peptide as internal standard has been developed, and this method can also be applied to the highly sensitive quantification of peptides in biological body fluids. Cysteine protease inhibitor C is a cationic non-glycosylated low molecular weight protein that can be used as a clinical marker of renal function status. A method for the determination of cysteine protease inhibitor C in human serum can be established by adding two 13C-labeled peptides to serum samples, which can be used in the diagnosis of renal function.
Fig. 2 The Schematic diagram of quantitative determination of protein by ID-LC-MS.
Steroid biomarkers
It has been found that elevated estrone levels are associated with increased risk of breast cancer in postmenopausal women. Using 13C labeled compound as internal standard, an ultra-sensitive and highly specific ID-LC-MS SRM method was established for determination of serum estrone. Cortisol is an important diagnostic marker of steroid hormone production. Accurate measurement of serum cortisol is necessary for accurate diagnosis of adrenal function. An efficient method for the determination of cortisol in human serum was established by adding isotope-labeled internal standard (d4-cortisol) into the samples.
What can we do?
Alfa Chemistry has many years of experience in the synthesis and development of stable isotope-labeled products. We can provide various D, 13C, 15N, 18O labeled compounds for biomarker analysis, including amino acids, peptides, lipids, fatty acids, steroids and many others. And our professional technology teams that can also provide customers with high-quality stable isotope-labeled compounds design and customization services. No matter what design ideas you have, we will implement them together with you. Please contact us immediately to order or cooperate in research and development with high quality and reasonable price.
References
- Ciccimaro, E. and Blair, I. A. Stable-isotope dilution LC-MS for quantitative biomarker analysis[J]. Bioanalysis, 2010, 2(2): 311-341.
- Gu, Y. and Piao, X. Application of stable isotope dilution liquid chromatography-mass spectrometry in medical research[J]. Journal of International Pharmaceutical Research, 2017, 44: 326-331.
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