"Many techniques for genomic studies require stretched molecules of DNA in order to observe sequence-specific binding of probe molecules," Leon Bellan of Cornell University told nanotechweb.org. "[This] technique is a quick, inexpensive, and straightforward method to obtain many stretched molecules that are individually isolated as well as embedded in another medium."
Bellan and colleagues incorporated fluorescently-labelled λ bacteriophage DNA molecules in polyethylene oxide nanofibres. The electrospinning process applies a high voltage to a conducting tip coated with a solution of the desired material. Once a threshold voltage is reached, the solution flies off the tip in a thin jet towards a grounded substrate. In the case of polymers, solvent evaporation as the polymer travels towards the substrate results in solid polymer nanofibres.
In this study, the team used a scanned electrospinning technique in which they rotated glass coverslip substrates to avoid tangling of the nanofibres. The resulting nanofibres were 100 - 350 nm in diameter.
"We decided to use electrospinning because it is a simple, inexpensive, and biocompatible fabrication technique, and there is much interest in biological applications of electrospun nanofibres," said Bellan. "Previous studies have demonstrated DNA stretching in elongational flows in microfluidic channels, and we realized that the strong elongational forces present in electrospinning jets could serve to stretch DNA in a similar fashion."
Fluorescence microscopy of the nanofibres revealed the tagged DNA in the form of isolated discrete fluorescent lines.
"This technique is a simple and inexpensive process for encapsulating stretched DNA molecules in polymer fibres that may be analyzed mechanically or optically at a later time," said Bellan. "The concentration of the DNA relative to that of the carrier polymer can be adjusted so that the DNA molecules in the fibres are isolated from each other, allowing for single molecule analysis."
Now the researchers plan to use the method, together with genomic labelling techniques, for biomolecular analysis. "We also hope to explore the behaviour of electrospinning jets using fluorescent indicator molecules in other polymer systems," said Bellan.
The researchers reported their work in Nano Letters.