On-Line Preconcentrator on a Glass Capillary with Electrokinetic Trapping Technique

In proteomics, the needs for concentrating the low-abundant molecules from the target samples are rapidly increased, since the concentration of low abundant ones might fall below the detection limit of biosensors.¹ In many cases, the samples are needed with several separation steps so that the preconcentration step is even more important when using microfluidic sensing systems.

Recently, protein preconcentrator are intensively investigated with micro/nanofluidic channel networks.^{2, 3} More recently, the microfluidic chips with perm-selective ion nanoporous material have been developed for enhancing their performance⁴. The microfluidic preconcentrator based on electrokinetic trapping technique was intensively studied with PDMS, however, the surface of PDMS is unstable, which lead to inefficient use of electrokinetic trapping. 

Here, we suggest the capillary based preconcentrator for collecting target proteins. It is well-known that the capillary has well-defined surfaces and could be connected easily with other analytical equipment. For this, we developed preconcentrator on a glass capillary simply by coating the ion-permslective membrane inside the glass channels. For operating protein preconcentration, we applied 20 V at both side electrodes in reservoir and tested the negative pressures to operate the ICP, then observed ion concentration polarization formed around ion permselective nanoporous material pattern. We tested the BDNF protein directly connected from the inserting tube in a mouse and measured real-time BDNF protein quantities with times

 This simple and powerful method can provide a high sensitivity and a high reliability for preconcentration of other analysis equipment such as electro-spray components for the Mass Spec applications.

References

1. J. H. Lee and J. Han, Microfluid Nanofluid 9, 973-979 (2010).

2. Y.-C. Wang and J. Han, Lab Chip 8, 392 - 394 (2008).

3. J. H. Lee, Y.-A. Song and J. Han, Lab Chip 8 (4), 596-601 (2008).

4. J. H. Lee, B. D. Cosgrove, D. A. Lauffenburger and J. Han, J. AM. CHEM. SOC. 131, 10340-10341 (2009).