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Issue 12, 2012
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Oil-sealed femtoliter fiber-optic arrays for single molecule analysis

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This paper describes a novel method for fabricating and sealing high-density arrays of femtoliter reaction chambers. We chemically etch one end of a 2.3 mm diameter glass optical fiber bundle to create an array of microwells. We then use a contact printing method to selectively modify the surface of the material between microwells with a hydrophobic silane. This modification makes it possible to fill the wells with aqueous solution and then seal them with a droplet of oil, forming an array of isolated reaction chambers. Individual β-galactosidase molecules trapped in these reaction chambers convert a substrate into a fluorescent product that can be readily detected because a high local concentration of product is achieved. This binary readout can be used for ultra-sensitive measurements of enzyme concentration. We observed that the percentage of wells showing enzyme activity was linearly dependent on the concentration of soluble β-galactosidase in the picomolar range. A similar response was also observed for streptavidin-β-galactosidase captured by biotinylated beads. These arrays are also suitable for performing single-molecule kinetics studies on hundreds to thousands of enzyme molecules simultaneously. We observed a broad distribution of catalytic rates for individual β-galactosidase molecules trapped in the microwells, in agreement with previous studies using similar arrays that were mechanically sealed. We have further demonstrated that this femtoliter fiber-optic array can be integrated into a PDMS microfluidic channel system and sealed with oil on-chip, creating an easy to use and high-throughput device for single-molecule analysis.

Graphical abstract: Oil-sealed femtoliter fiber-optic arrays for single molecule analysis

  • This article is part of the themed collection: Focus on USA
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Supplementary files

Article information

15 Nov 2011
09 Jan 2012
First published
09 Jan 2012

Lab Chip, 2012,12, 2229-2239
Article type

Oil-sealed femtoliter fiber-optic arrays for single molecule analysis

H. Zhang, S. Nie, C. M. Etson, R. M. Wang and D. R. Walt, Lab Chip, 2012, 12, 2229
DOI: 10.1039/C2LC21113K

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