LAUSR

Developing miniaturized and rapid protein analytical platforms is urgently needed for on-site protein analysis, which is important for disease diagnosis and monitoring. Liquid marbles (LMs), a kind of particle-coated droplets, as ideal micro-reactors have been used in various fields. While their application as analytical platforms is limited due to the difficulty of pretreating complex samples in simple LMs. Herein, inspired by microfluidic chip, we propose a strategy through fabricating fluid channels using deformable LM, termed liquid plasticine (LP), to achieve sample pretreatment function. Through combing isoelectric focusing (IEF) with LP channel, a LP-LEF platform with simultaneous protein separation and concentration functions is realized. The pretreatment capability of LP-IEF system for proteins in physiological samples is proven using standard proteins and human serum with the results of a clear separation, 10-folds concentration and a resolution of 0.03 pH. Through cutting the LP after IEF to LMs and transiting isolated LMs containing target proteins for further downstream colorimetric and mass spectrometry measurements, the quantitative analysis of clinical microalbuminuria and identification of α-1-microglobulin/bikunin precursor in clinical diabetic urines are achieved. This work proposes a strategy of developing LMs/LPs as multifunctional integrated analytical platform and the miniaturized LP-IEF device as rapid protein analytical platform.