Isoelectric focusing array with immobilized pH gradient and dynamic scanning imaging for diabetes diagnosis.

A traditional immobilized pH gradient (IPG) has a high stability for isoelectric focusing (IEF) but suffers from time-consuming rehydration, focusing and staining-imaging as well as complex performance. To address these issues, an IEF system with an array of 24 IPG columns (10 mm × 600 μm × 50 μm) and dynamic scanning imaging (DSI) was firstly designed for protein focusing. Moreover, two IPG columns (pH 4-9 and pH 6.7-7.7 of 10 mm in length) were firstly synthesized for IEF. A series of experiments were carried out based on the IEF array. In contrast to a traditional IPG IEF with more than 10 h rehydration, 5-14 h IEF and ca 10 h stain-imaging, the IEF array had the following merits: 25 min rehydration for sample loading, 4 min IEF, and 2 min dynamics scanning of 24 columns, well addressing the issues of traditional IEF. Furthermore, the IEF array had fair sensitivity (LOD of 60 ng), good recovery (95%), and high stability (1.02% RSD for intra-day and 2.16% for inter-day). Finally, the developed array was successfully used for separation and determination of HbA1c (a key biomarker for diabetes diagnosis) in blood samples. All these results indicated the applicability of the developed IEF array to diabetes diagnosis.