Single Cell Electroporation

The ability to precisely deliver molecules into single cells is of great interest to biotechnology researchers for advancing applications in therapeutics, diagnostics, and drug delivery toward the promise of personalized medicine. The use of bulk electroporation techniques for cell transfection has increased significantly in the last decade, but the technique is nonspecific and requires high voltage, resulting in variable efficiency and low cell viability. In Prof. Espinosa's lab, I have developed a new tool for electroporation using nanofountain probe (NFP) technology that can deliver molecules into cells in a manner that is highly efficient and gentler to cells than bulk electroporation or microinjection.

To trigger formation of nanopores on the cell membrane by electroporation, a transmembrane electric potential in the range of 0.2~1 V is required. An accurate prediction of this local field is essential to determine the critical applied voltage for nanopore formation and optimal probe location with respect to the cell membrane. Unlike bulk electroporation where each individual cell is exposed to a uniform electric field, the electric field for single cell electroporation is often non-uniform and hence an analytical solution is not feasible. Therefore, I used COMSOL Multiphysics to simulate the distribution of the electric potential through a cell membrane.

The multiphysics analysis of the mechanism of NFP-E reveals that application of the voltage creates a localized electric field between the NFP cantilever tip and the region of the cell membrane in contact with the tip. Therefore, NFP-E can deliver molecules to a target cell with minimal effect of the electric potential on the cell. In addition, the model predicted that the onset of cell-NFP contact can be accurately monitored by measuring the electrical resistance between the NFP tip and cell, which would increase suddenly with a gap size between NPF tip and cell of <50nm. This predicted detection method for cell-NFP contact was experimentally confirmed as we observe a sudden increase, up to 143%, in the resistance. Further experimental studies confirm that NFP-E offers single cell selectivity, high transfection efficiency (>95%), dosage control, and very high viability (92%) of transfected cells.

The schematic above shows Nanofountain Probe Electroporation (NFP-E) system and transfection of the dextran Alexa Fluor 488 dye into a targeted HeLa cell using NFP-E [2].

Reference

1. W. Kang, R. McNaughton, and H. Espinosa, In Vitro Micro- and Nano-scale Technologies for Delivery into Adherent Cells, DOI:10.1016/j.tibtech.2016.05.003, Trends in Biotechnology, 2016 (Highlighted in BRIC.org).
2. J. Giraldo-Vela, W. Kang, R. McNaughton, A. Chen, A. Tsourkas, and H. Espinosa, Single Cell Detection of mRNA Expression Using Nanofountain Probe Electroporated Molecular Beacons, 11 (20), 2386-2391, Small, 2015 (Cover article above).
3. W. Kang, F. Yavari, M. Minary-Jolandan, J. Giraldo-Vela, A. Safi, R. McNaughton, V. Parpoil, H. Espinosa, Nanofountain Probe Electroporation of Single Cells, 13(6), 2448-2457, Nano Letters, 2013. (Highlighted in ScienceDaily, Bio-Medicine, Technology Network, FierceDrugDelivery, National Institute of General Medical Sciences, etc)
4. W. Kang, R. McNaughton, F. Yavari, M. Minary-Jolandan, A. Safi, and H. Espinosa, Microfluidic Parallel Patterning and Cellular Delivery of Molecules with a Nanofountain Probe, 19(1), 100-109, Journal of Laboratory Automation , 2014.
5. A. Safi, W. Kang, D. Czapleski, N. Moldovan, and H. Espinosa, Optimized Nanofountain Probes Geometry and Microfabrication Throughput for Large-Scale Nanopatterning, Journal of Micromechanics and Microengineering, 23(12), 125014, 2013.