Recording ion channels across soy-extracted lecithin bilayer generated by water-soluble quantum dots

Abstract

We report on the quantum dot (QD)-induced ion channels across a soya-derived lecithin bilayer supported on a laser drilled of ~100 μm aperture of cellulose acetate substrate that separates two electrolytic chambers. Adequate current bursts were observed when the bilayer was subjected to a gating voltage. The voltage-dependent current fluctuation, across the bilayer, was attributed to the insertion of ~20 nm sized water-soluble CdSe QDs, forming nanopores due to their spontaneous aggregation. Apart from a closed state, the first observable conductance levels were found as 6.3 and 11 nS, as for the respective biasing voltages of −10 and −20 mV. The highest observable conductance states, at corresponding voltages were ~14.3 and 21.1 nS. Considering two simplified models, we predict that the non-spherical pores (d_nspore) can be a better approximation over spherical nanopores (d_spore) for exhibiting a definite conductance level. At times, even d_nspore≤ 4d_spore and that the non-spherical nanopores were associated with a smaller No. of QDs than the case for spherical nanopores, for a definite conductance state. It seems like the current events are partly stochastic, possibly due to thermal effects on the aggregated QDs that would form nanopores. The dwell time of the states was predicted in the range of 384–411 μs. The ion channel mechanism in natural phospholipid bilayers over artificial ones will provide a closer account to understand ion transport mechanism in live cells and signaling activity including labelling with fluorescent QDs.

Keywords:

• quantum dot
• absorption
• emission
• bilayer
• ion channel

Acknowledgements

The authors thank DST, New Delhi for extending financial support (Project No. SR/FTP/PS07/2008). The authors gratefully acknowledge Dr. P.K. Gupta of Raja Ramanna Centre for Advanced Technology (RRCAT), Indore for making micropores in the desired substrate used in this study. We also extend our sincere thanks to SAIF-NEHU, Shillong for providing HRTEM facility. One of the authors (RS) is thankful to Mr. R. Arondhara and to the Department of Food Engineering and Technology, TU for extending help in the extraction of lecithin from soybean seeds.