Isoelectric Focusing in Liquid Plasticine for Protein Analysis

摘要

Protein analysis has found widespread applications in biomedical fields (e.g., disease diagnosis and precision medicine), especially recently in point-of-care testing (POCT). Conventional protein analysis is large-equipment-dependent, which limits its applications in POCT. Herein, we proposed a strategy using a shaped liquid entity, termed liquid plasticine (LP), as a platform to perform isoelectric focusing (IEF)-based protein analysis. The LP-IEF system mainly consisted of a separation channel, a catholyte module and an anolyte module, which were all in the form of self-standing liquid micro-containers with specific shapes and connected together. The basic functions of the LP-IEF system were examined using three standard proteins, with the results showing a clear separation, 10-folds concentration, and a resolution of 0.03 pH, meaning that this system could serve for pretreatment and analysis of proteins from complex physiological samples. The developed LP-IEF system was further demonstrated as a colorimetric quantitative analytical platform of clinical microalbuminuria with a relative error of <9.4% compared to the results obtained by the traditional clinical detection methods. Moreover, the LP-IEF system was coupled to MALDI-TOF-MS and successfully used to identify α-l-microglobulin/bikunin precursor (AMBP) in clinical diabetic urines. The LP-IEF system proposed in this work opens a flexible, versatile, and low-cost way for POCT of proteins, which could inspire many practical applications in future.