Polyacrylamide gel electrophoresis (PAGE) is a ubiquitous technique used in biochemical research laboratories to characterize protein samples. Despite its popularity, PAGE is relatively slow and provides limited separation resolution, especially for native proteins. This report describes the development of a microfluidic thermal gel transient isotachophoresis (TG-tITP) method to rapidly separate native proteins with high resolution. Thermal gels were employed as a separations matrix because of their unique ability to change viscosity in response to temperature. Proteins were added into thermal gel and loaded into a microfluidic device. Electrolyte optimization was conducted to achieve robust tITP to isotachophoretically preconcentrate proteins and then electrophoretically separate them. Electropherograms were collected through both time and distance to enable both small and large proteins to be measured within a single analysis. The effects of temperature were evaluated and found to exhibit a pronounced effect on the separation. Temperature gradients were then employed to alter thermal gel viscosity over time to maximize separation resolution between proteins. The results herein demonstrate how gradient TG-tITP achieves rapid, high-performance separations of native proteins. This analysis provided a wide mass range (6-464 kDa) with two-fold higher resolution than native PAGE while requiring 15,000-fold less protein loading and providing five-fold faster analysis times.

Chiral recognition is an emerging field of modern chemical analysis, and the development of health-related fields depends on the production of enantiomers. Cellulose is a kind of natural polymer material with certain chiral recognition ability. Limited by the chiral recognition ability of natural cellulose itself, more cellulose derivatives have been gradually developed for chiral recognition and separation. Based on the difference in action between cellulose derivatives and enantiomers, this work synthesized cellulose-tris(4-methylphenylcarbamate) (CMPC) chiral recognition mediators and a CMPC-functionalized extended-gate organic field effect transistor (EG-OFET) was constructed for the first time. Three chiral molecules were selected as model analytes to evaluate the enantiomeric recognition ability of the platform, including threonine (Thr), 2-chloromandelic acid (CA), and 1,2-diphenylethylenediamine (DPEA). The detection limit for 1,2-diphenylethylenediamine (DPEA) is down to 10-13 M. Through the amplification effect of the EG-OFET platform, the difference in the interaction between CMPC and three chiral molecules with different structures is converted into a current signal output. At the same time, the enantiomer discrimination mechanism of CMPC was further studied by means of spectroscopy and nuclear magnetic resonance.

We present here an ionophore-based ion-selective optode (ISO) platform to detect potassium and sodium concentrations in serum through flow cytometry. The ion-selective microsensors were based on polyethylene glycol (PEG)-modified polystyrene (PS) microspheres (PEG-PS). Ratiometric response curves were observed using peak channel fluorescence intensities for K+ (10-6 M to 0.1 M) and Na+ (10-4 M to 0.2 M) with sufficient selectivity for clinical diagnosis. Due to the matrix effect, proteins such as albumin and immunoglobulin caused an obvious increase in response for serum sample determination. To solve this problem, 4-arm PEG chains were covalently attached onto the surface of PS microspheres through a two-step reaction, which improved the stability and combated pollution of microspheres. As a preliminary application, potassium and sodium concentrations in human serums were successfully determined by the PEG-PS microsensors through flow cytometry.