Paper-Based Device for Naked Eye Urinary Albumin/Creatinine Ratio Evaluation

Abstract

This paper introduces the concept of “Drawing-PADs” (Drawing paper-based microfluidic analytical devices) allowing to intuitively evaluate the urinary albumin (Alb) index, a clinically important parameter used for the early detection of renal deficiencies related to diabetes, among others. To enable regular monitoring of the Alb index, a simple examination method suitable for self-diagnosis is highly desirable. The Drawing-PADs rely on the simultaneous naked eye detection of Alb and creatinine (Cre) on a single device according to the distance-based microfluidic PAD (μPAD) approach. The Alb index is visualized by simply drawing a straight line connecting the top of two color-changed assay channel sections (Alb and Cre channels), followed by visually confirming the position of the intercept of the drawn straight line. The semiquantitative Alb index evaluation performed with Drawing-PADs does not require any equipment such as a camera, software, or a color reference chart. The obtained results are independent of the sample volume and are not influenced by changes in the absolute Alb and Cre concentrations caused by urine excretion variations, making spot urine assays possible. Classification of Alb index values according to clinically relevant criteria (normoalbuminuria, microalbuminuria, and macroalbuminuria) is readily achieved within 15 min and has been validated for 15 human urine samples including diabetic patients and healthy volunteers.

Serum Albumin: A Multifaced Enzyme

“…This method is based on a staining protocol based on the use of: (i) Fast Blue BB (0.12%) dye to stain the (pseudo-) esterase activity of HSA both on agarose and Native PAGE; (ii) 2-naphthyl acetate, an ester substrate of HSA, and (iii) neostigmine, a selective acetyl-cholinesterase inhibitor [ 123 ]. This method could find application in either HSA pharmaceutical preparation (e.g., to check adulteration of human milk with cow milk) [ 123 , 124 , 125 ] or in diagnostic detection (e.g., to highlight the (pseudo-)esterase activity of HSA in urine representing a sign of microalbuminuria) [ 123 , 126 ].…”

“…During its long lifetime, HSA molecule makes about 15,000 passes through the circulation [ 1 ] undergoing damages that impairs its ligand binding and anti-oxidant properties [ 4 , 126 ]. The HSA anti-oxidant activity depends on: (i) the reactivity of the Cys34 residue, which in turn is affected by chemical modifications (e.g., oxidation and cysteinylation), (ii) post-translational modifications like glycation, (iii) FAs binding, and (iv) aging.…”

Lab-on-Paper Devices for Diagnosis of Human Diseases Using Urine Samples—A Review

“…As a result, the effective treatment period is curtailed, leading to serious lesions and a significant deterioration in quality of life [104]. However, recent research has shown that lab-on-paper platforms provide a feasible means of detecting early-stage kidney disease by evaluating the concentrations of creatinine (Cre) and albumin (Alb) [105][106][107][108][109][110][111], micro-albumin and protein [112][113][114][115][116], and uric acid [117][118][119][120][121][122][123] in urine samples.…”

“…The urine Alb to Cre ratio can also be used as a screening strategy for kidney disease [109]. Hiraoka et al [110] developed a Drawing lab-on-paper device for urinary Alb-to-Cre ratio analysis to support the early detection of renal insufficiency. In the proposed device, the Alb-to-Cre ratio was determined simply by drawing a straight line between the top of the two color-changed assay channel sections (Alb and Cre) and then observing the position of the intercept point on an Alb-to-Cre scale placed between them.…”

Flexible cotton-AuNP thread electrode for non-enzymatic sensor of uric acid in urine

“…The electrochemical sensor was also integrated into a diaper and used for the detection of UA in arti cial urine. The arti cial urine solution was prepared as described in a previous report (Hiraoka et al 2020) with UA concentrations (1-3 mM).…”