Adsorption of Urinary Proteins on the Conventionally Used Urine Collection Tubes: Possible Effects on Urinary Proteome Analysis and Prevention of the Adsorption by Polymer Coating

Abstract

One possible factor determining recovery of trace amount of protein biomarker candidates during proteome analyses could be adsorption on urine tubes. This issue, however, has not been well addressed so far. Recently, a new technical device of surface coating by poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)) (poly(MPC-co-BMA)) has been developed mainly to prevent the adsorption of plasma proteins. We assessed whether conventionally used urine tubes adsorb trace amount of urinary proteins and, if any, whether the surface coating by poly(MPC-co-BMA) can minimize the adsorption. Proteinuric urine samples were kept in poly(MPC-co-BMA)-coated and noncoated urine tubes for 15 min and possibly adsorbed proteins and/or peptides onto urine tubes were analyzed by SDS-PAGE, 2-DE, and the MALDI-TOF MS. It was found that a number of proteins and/or peptides adsorb on the conventionally used urine tubes and that surface coating by poly(MPC-co-BMA) can minimize the adsorption without any significant effects on routine urinalysis test results. Although it remains to be clarified to what extent the protein adsorption can modify the results of urinary proteome analyses, one has to consider this possible adsorption of urinary proteins when searching for trace amounts of protein biomarkers in urine.

Effect of common storage temperatures and container types on urine protein : creatinine ratios in urine samples of proteinuric dogs

“…Previously published articles evaluating storage of human urine samples suggest that there would be less urine albumin binding to the homopolymer surfaces than to a glass or propylene surface, but this may not apply to canine urine. [20][21][22][23] Therefore, we cannot rule out the possibility that collection and storage in glass or PC containers only (no contact with a homopolymer of any kind) before analysis would result in even less variation in measured protein concentrations.…”

“…At low concentrations, adsorption to the surface of polymer and glass containers can lead to significant decreases in measured albumin concentration in human urine samples. [20][21][22][23] Clear food plastic storage containers are commonly made of propylene copolymers (PC), which decrease refraction of light and increase clarity. 24,25 Homopolymer polypropylene containers are more appealing for biospecimen storage because of their resistance to protein adsorption.…”