acetylcellulose and Proteinuria

Point-of-care testing is currently one of the subjects of growing interest in analytical chemistry. Elevated levels of urinary protein imply renal failure, which is one of the world's biggest public health problems. In spite of the urgent necessity for a screening test of protein in urine, there are no reports of a simple yet sensitive method for its detection. In this study, we developed a new visual method, using Erythrosin B and a cellulose acetate membrane film as the substrate for a new spot test of urinary protein in the presence of poly(ethylene glycol) (PEG). The noteworthy point of our work is that when a drop of dye-protein solution containing PEG is set on a membrane film, a red ring-shaped stain of the dye-bound protein is formed on the film surface. PEG plays a significant role in eliminating the reagent blank, thus providing a clear contrast. Measurements taken using a dynamic light scattering particle size analyzer indicated that the underlying mechanism of this contrast is brought about by the different sizes of the excess dye and dye-protein particles. The visual detection limit is 0.5 mg dm(-3) for human serum albumin (HSA), the main protein in urine. Our visual method is sufficiently sensitive to detect urinary protein even for healthy subjects, providing a higher sensitivity than test strips by a factor of 60-200. When 0.15 cm(3) of urine is used to prepare 10 cm(3) of sample solution, the practical detection threshold is 30 mg dm(-3) in urine using a 67x dilution factor. The proposed method will be useful as a simple, rapid, and cost-effective screening test for the diagnosis of renal failure at an early stage.

Topics: Albuminuria; Cellulose; Coloring Agents; Erythrosine; Humans; Point-of-Care Systems; Polyethylene Glycols; Proteinuria; Renal Insufficiency; Spectrophotometry

We designed a semiquantitative analysis of urinary low protein levels using silver dot blot assay. In this method, 3 microl of urine are blotted to one dot onto a cellulose acetate membrane, which is stained by a colloidal silver staining reagent, and the optical density of the silver stained urinary protein is measured at 500 nm using a densitometer. There was a good linearity between 2.5 mg/L and 100 mg/L and a gentle linearity between 100 mg/L and 200 mg/L, and the minimum sensitivity was 2.5 mg/L. This method is suitable for semiquantitative analysis of urinary protein levels less than 300 mg/L, which can not be determined precisely by dipstick.

Topics: Albuminuria; Aniline Compounds; Bence Jones Protein; Cellulose; Colloids; gamma-Globulins; Humans; Indicators and Reagents; Mucoproteins; Proteinuria; Sensitivity and Specificity; Silver Staining; Uromodulin