Colorimetric Urinalysis for On-Site Detection of Metabolic Biomarkers

Abstract

Over the past few decades, colorimetric assays have been developed for cost-effective and rapid on-site urinalysis. Most of these assays were employed for detection of biomarkers such as glucose, uric acid, ions, and albumin that are abundant in urine at micromolar to millimolar levels. In contrast, direct assaying of urinary biomarkers such as glycated proteins, low-molecular-weight reactive oxygen species, and nucleic acids that are present at significantly lower levels (nanomolar to picomolar) remain challenging due to the interferences from the urine sample matrix. State-of-the-art assays for detection of trace amounts of urinary biomarkers typically utilize time-consuming and equipment-dependent sample pretreatment or clean-up protocols prior to assaying, which limits their applicability for on-site analysis. Herein, we report a colorimetric assay for on-site detection of trace amount of generic biomarkers in urine without involving tedious sample pretreatment protocols. The detection strategy is based on monitoring the changes in optical properties of poly(3-(4-methyl-3′-thienyloxy)propyltriethylammonium bromide) upon interacting with an aptamer or a peptide nucleic acid in the presence and absence of target biomarkers of relevance for the diagnosis of metabolic complications and diabetes. As a proof of concept, this study demonstrates facile assaying of advanced glycation end products, 8-hydroxy-2′-deoxyguanosine and hepatitis B virus DNA in urine samples at clinically relevant concentrations, with limits of detection of ∼850 pM, ∼650 pM, and ∼ 1 nM, respectively. These analytes represent three distinct classes of biomarkers: (i) glycated proteins, (ii) low-molecular-weight reactive oxygen species, and (iii) nucleic acids. Hence, the proposed methodology is applicable for rapid detection of generic biomarkers in urine, without involving sophisticated equipment and skilled personnel, thereby enabling on-site urinalysis. At the end of the contribution, we discuss the opportunity to translate the homogeneous assay into a paper-based format.

A Perspective on Polythiophenes as Conformation Dependent Optical Reporters for Label-Free Bioanalytics

“…Our group has worked on the translation of solution to membraneand paper-based assays for point-of-care applications. 87,147,148 In addition, translation into paper-based assays also reduce the need for tedious sample pretreatment steps as filtration and sample enrichment strategies can be easily integrated with such platforms.…”

“…Thus, the translation of these solution-based assays into paper, lateral-flow, or dipstick formats would be essential for the development of future point-of-care solutions. Our group has worked on the translation of solution to membrane- and paper-based assays for point-of-care applications. ,, In addition, translation into paper-based assays also reduce the need for tedious sample pretreatment steps as filtration and sample enrichment strategies can be easily integrated with such platforms.…”

Inorganic–organic hybrid materials to detect urinary biomarkers: recent progress and future prospects

“…The unique information of urine may be analysed using a variety of approaches. Currently, the routine detection methods of urine biomarkers include colorimetry, 37 immunoassay, 38 chromatography 39 and mass spectrometry. 40 Concretely, colorimetry exhibits simple operation and low cost, but the same color of interfering materials will cause errors in results.…”

Rapid Detection of Escherichia coli: Optimized Peptide-Polythiophene Interactions Help Reduce Assay Time and Improve Naked-Eye Detection

“…Upon photoexcitation, the pi-conjugation allows for the rapid intra- and interchain transfer of the exciton along the polymer backbone resulting in fluorescence amplification or in superquenching. − Unlike traditional organic fluorophores, most CPs have a flexible backbone that is sensitive to minor perturbations and conformational changes that can directly affect its optical properties such as absorption, fluorescence and FRET efficiency. ,, For example, the twisting or flattening of CP’s flexible backbone can cause changes in effective conjugation length leading to reversible optical changes in the form of a wavelength shift in absorption. , Alternatively, optical transitions can also occur due to stacking and unstacking of the aromatic rings of adjacent polymer chains which affects intermolecular radiative and nonradiative relaxation leading to spectral shifts and changes in fluorescence quantum efficiency. The sensitivity of the CP backbone to minor perturbations makes them useful as reporters or transducers of target analytes in many bioassays − and was most recently exploited by our group to develop the fluorescence-based Omptin-Polythiophene assay (the assay) for the qualitative detection of Escherichia coli (Figure ).…”