Investigation of Electrophoretic Exclusion Method for the Concentration and Differentiation of Proteins

Abstract

This work presents a technique termed as "electrophoretic exclusion" that is capable of differentiation and concentration of proteins in bulk solution. In this method, a hydrodynamic flow is countered by the electrophoretic velocity to prevent a species from entering into a channel. The separation can be controlled by changing the flow rate or applied electric potential in order to exclude a certain species selectively while allowing others to pass through the capillary. The exclusion of various proteins is investigated using a flow-injection regime of the method. Concentration of myoglobin of up to 1200 times the background concentration in 60 s was demonstrated. Additionally, negatively charged myoglobin was separated from a solution containing negatively charged allophycocyanin. Cationic cytochrome c was also differentiated from a solution with allophycocyanin. The ability to differentially transport species in bulk solution enables parallel and serial separation modes not available with other separations schemes.

Simulation and visualization of velocity fields in simple electrokinetic devices

“…While this thought experiment itself is unimportant, it certainly foretells of more recent work exploiting a stagnation region near a capillary or channel entrance which exceeds diffusion/dispersion. 5,10,11,27,28 Within the chosen system, the velocities vary dramatically and are a good test of the simulation and visualization. Four points are noted on the 2D velocity map (Figure 4), where points B and D are noted to contrast the predominance of either horizontal or vertical components while A and C differ greatly in magnitude.…”

“…According the quantitative logic presented here, the closed form expression of a linear velocity field is used to obtain the particle path position equation which is of the same form as Equation 11.Then particles are generated with random initial positions and the next position is computed after a fixed time interval. Simultaneously, the modified Eulerian method is also used for solving the ODE with given interval of time to generate future particle positions for the same starting positions.…”

“…In the example shown ( Figure 5), the device area covered by the streamlines and the final profile during a steady flow (parabolic flow profile with higher velocities near the center) was well behaved. In the design of an electrophoresis experimental setup, and specifically for the ones where capture of some particular species is envisioned, 5,10,11,27,28 it is important to know within-the-fluid connection paths between points within the device. While spatial velocity components might exist for the complete region-of-interest (ROI) (and apparent from the velocity vector fields) this does not inherently indicate the possibility of movement (transfer) of particles from one point to another within the ROI.…”

“…This general format is used in gradient moving boundary electrophoresis, 1, 2 stacking and supercharging, 3-5 transient isotachophoresis, [6][7][8][9] and electrophoretic exclusion. [10][11][12][13] Defining and analyzing the forces within the interfacial region can be performed rather trivially for fundamental equations (e.g. the Navier Stokes) with finite element analysis (FEM) using distributed gridpoints throughout 2D space.…”

Tunable Ionic Mobility Filter for Depletion Zone Isotachophoresis

“…8 A similar exclusion effect was used by Meighan et al, who concentrated and differentiated proteins in bulk solution near the entrance of a channel. 9 The integration of nanofluidic components into microfluidic networks has opened up many interesting new perspectives. In some cases, electrostatic or size-based exclusion has been used as a filtering principle.…”