Review: Detection and quantification of proteins in human urine

Abstract

Extensive medical research showed that patients, with high protein concentration in urine, have various kinds of kidney diseases, referred to as proteinuria. Urinary protein biomarkers are useful for diagnosis of many health conditions – kidney and cardio vascular diseases, cancers, diabetes, infections. This review focuses on the instrumental quantification (electrophoresis, chromatography, immunoassays, mass spectrometry, fluorescence spectroscopy, the infrared spectroscopy, and Raman spectroscopy) of proteins (the most of all albumin) in human urine matrix. Different techniques provide unique information on what constituents of the urine are. Due to complex nature of urine, a separation step by electrophoresis or chromatography are often used for proteomics study of urine. Mass spectrometry is a powerful tool for the discovery and the analysis of biomarkers in urine, however, costs of the analysis are high, especially for quantitative analysis. Immunoassays, which often come with fluorescence detection, are major qualitative and quantitative tools in clinical analysis. While Infrared and Raman spectroscopies do not give extensive information about urine, they could become important tools for the routine clinical diagnostics of kidney problems, due to rapidness and low-cost. Thus, it is important to review all the applicable techniques and methods related to urine analysis. In this review, a brief overview of each technique’s principle is introduced. Where applicable, research papers about protein determination in urine are summarized with the main figures of merits, such as the limit of detection, the detectable range, recovery and accuracy, when available.

Urinary sediment microRNAs can be used as potential noninvasive biomarkers for diagnosis, reflecting the severity and prognosis of diabetic nephropathy

“…Urine contains many disease biomarkers that reflect an individual’s health status and that are good indicators of kidney disease [ 33 ]. Recent studies have reported that many types of kidney diseases, such as primary IgAN, lupus nephritis, and minimal change nephropathy, could be detected by biomarkers in urinary sediment [ 34 , 35 ].…”

Time-gated Raman spectroscopy and proteomics analyses of hypoxic and normoxic renal carcinoma extracellular vesicles

“…RS gives a classifying “fingerprint” of an EV sample, indicating changes in proteins, lipids, and nucleic acids, while Mass spectroscopy provides much more detailed analysis of sample molecular composition. While RS does not offer as extensive information about EV samples as quantitative proteomics, it has clear advantages towards clinical diagnostics, due to its relative rapidness and lower workload 51 . Though it is rather challenging to make direct comparison between results obtained by using RS and proteomics studies, certain spectral peaks noted in RS may indicate characteristic features of protein composition.…”

Liquid crystal-amplified optofluidic biosensor for ultra-highly sensitive and stable protein assay

“…Highly sensitive and selective identification and quantification of proteins are crucial due to their great importance for medical research and disease diagnoses in indicating pathological biological conditions [ 1 , 2 ]. For example, albumin in human urine has a significant value in the diagnoses of diabetic nephropathy, cardiovascular and renal disease [ 3 ]. During current pandemic period, IgG and its antibody provide reliable biomarkers related to COVID-19 [ 4 , 5 ], their detection can help prevent and control the virus infection at an early stage.…”