Electrophoretic transport of biomolecules through carbon nanotube membranes

Abstract

Electrophoretic transport of proteins across electrochemically oxidized multi-walled carbon nanotube (MWCNT) membranes has been investigated. A small charged protein, lysozyme, was successfully pumped across MWCNT membranes by an electric field while rejecting larger bovine serum albumin (BSA). Transport of lysozome was reduced by a factor of about 30 in comparison to bulk mobility and consistent with the prediction for hindered transport. Mobilities between 0.33 and 1.4 × 10(-9) m(2) V(-1) s(-1) were observed and are approximately 10-fold faster than comparable ordered nanoporous membranes and consistent with continuum models. For mixtures of BSA and lysozyme, complete rejection of BSA is seen with electrophoretic separations.

Figure 1

Schematic U-tube diffusion set-up and schematic of membrane with oxidized CNTs for biomolecular electrophoresis transport study.

Figure 2

Typical SEM top-view images of (a) microtome cut and (b) electrochemically oxidized MWCNT membranes.

Figure 3

(a) SEC-HPLC chromatograms of the permeate solution collected at -1V and pH 7.0 electrophoresis for 24 hr and (b) 12.5 μg/ml (0.87 nmol/ml) lysozyme standard prepared in pH7.0 PB.

Figure 4

Voltage dependence of the membrane area based electrophoresis flux of positively charged lysozyme dissolved in pH 7.0 PB.

Figure 5

Electrophoresis enhancement E_ep, for lysozyme (diamond), Ru²⁺ (square) and MV²⁺ (triangle) at different applied voltage. Lysozyme and MV²⁺ were dissolved in pH 7.0 PB and Ru²⁺ was dissolved in DI water.

Figure 6

Chromatograms of (left) permeate collected in the electrophoretic separation of charged lysozyme from neutral BSA in pH 4.7 PB at applied voltage of -2 V, and (right) standard mixture containing 2.5 μg/ml BSA and 2.5 μg/ml lysozyme to demonstrate detection limit of SEC-HPLC analysis.