Fingerprinting Single Living Cells with Molecular Precision

Abstract

The secretome of a single living cell contains the totality of its secreted proteins,(1) and therefore can act as a fingerprint by which to identify cell type. Although between 10 % and 20 % of the human genome encodes proteins that are secreted, measuring the secretome from an individual living cell is challenging as the secreted proteins are present in vanishingly small concentrations due to the very large dilutions involved.However, a nanopore is able to detect single proteins through the distinctive blockage profile that develops in the ionic conductance current when a protein passes through the nanopore.(2,3) Using a synthetic nanopore in a silicon membrane we investigate the distinctive blockage patterns, in essence the fingerprint, that arise from a single living cell. The cell is placed in proximity to the nanopore using optical tweezers and held stationary. The ionic conductance current is measured across the nanopore, and translocation events (distinct blockage currents) are observed and measured. When the events are plotted in scatter plots (as dwell time versus average blockage current) the distinct fingerprint of individual cells can be observed. For instance, lymphoma cells (U937) and breast cancer cells (MCF7) produce distinct event patterns that enable them to be distinguished. This shows for the first time cell identification based entirely on the secretome, measured using a simple, non-invasive, non-destructive nanopore.(1) Skalnikova, H.; Motlik, J.; Gadher, S.; Kovarova, H. Proteomics, 2011, 11 691-708.(2) Nelson, E. M.; Kurz, V.; Shim, J.; Timp, W.; Timp, G. Analyst, 2012, 137, 3020.(3) Kurz, V.; Nelson, E. M.; Shim, J.; Timp G. ACS Nano, 2013, 7(5), 4057-4069