Direct observation of long-strand DNA conformational changing in microchannel flow and microfluidic hybridization...

Conformational control of macromolecules is useful for efficient chemical and biochemical reactions. This article reports a direct observation method for macromolecules, such as long-strand DNA, in microchannel flow as well as a simple method for stretching DNA strands by microfluidics. Stretching and orientation of DNA molecules by control of flow within a microchannel was observed by optical microscopy. This DNA stretching is explained by coil-stretch transition of polymer molecules. This technique is useful for creating chemical reactions with macromolecules. It offers high selectivity and efficiency that are impossible to achieve in bulk solution. We also demonstrate that our microfluidic stretching method can accomplish efficient hybridization of long-strand DNA. This method will be useful for direct hybridization assay of long-strand DNA.