THE JUNCTION of two nanofibers can serve as an attoliter-volume reaction vessel suitable for synthesis and direct analysis of zeptomole-scale (10-21) chemical reactions, according to chemists at Bowling Green State University, in Ohio (Nature Chem., DOI: 10.1038/nchem.125).
Carrying out reactions on an ultrasmall scale can reduce the amount of reagent and energy used and of waste created. Other groups have investigated various approaches to reaction miniaturization, including micro- and nanofluidic reactors and self-assembled capsules, but many of these techniques are costly and require complicated preparations. The new method has the potential to overcome both of these drawbacks, according to the researchers.
To make their "attoreactors," associate professor of chemistry Pavel Anzenbacher Jr. and graduate student Manuel A. Palacios applied reaction starting materials to electrospun polyurethane fibers with diameters of 100–300 nm. Exposing the crossed fibers to heat or solvent vapors fuses the fibers, causing an attoreactor to form at the fusion point and initiating a chemical reaction inside.
For example, crossing and heating fibers doped with different nonfluorescent reagents (dansyl chloride and triethylenetetramine) yields a fluorescent product (a dansylamide). Anzenbacher says he and Palacios have also used the system for reactions involving polymeric reagents, nucleic acids, and proteins. They used spectroscopy to monitor products within the attoreactors.
What is perhaps most remarkable is that each 5-aL reactor contains on average just 1,500 molecules, write Andrew J. deMello of Imperial College London and Robert C. R. Wootton of Liverpool John Moores University in a commentary about the work.
Generally, the smaller the reactor is, the higher its price tag becomes. But Anzenbacher says the new method enables controlled reactions using only a few hundred molecules and equipment costing less than $1,000.
Some researchers are excited about the possibilities of the new method, but others are skeptical about its usefulness. Anzenbacher suggests uses could include combinatorial chemistry and, potentially, reaction dynamics at the single-molecule level.