Electrostatic-Based DNA Microarray Technique Simplified for Diagnostics

A technique has been developed in which DNA or RNA assays, which are used for disease detection and genetic profiling, can be read and evaluated without the need of elaborate chemical labeling or sophisticated instrumentation.

The technique is relatively simple and is based on electrostatic repulsion in which objects with the same electrical charge repel one another. Inexpensive to implement, the technique can be carried out in a matter of minutes.

A fluid containing thousands of electrically charged microscopic beads or spheres made of silica (glass) is dispersed across the surface of a DNA microarray and the Brownian motion of the spheres provides measurements of the electrical charges of the DNA molecules. The measurements are then used to interrogate millions of DNA sequences at a time. These measurements can be observed and recorded with a simple hand-held imaging device--even a cell phone camera will do.

One of the most amazing things about our electrostatic detection method is that it requires nothing more than the naked eye to read out results that currently require chemical labeling and confocal laser scanners, said Professor Jay Groves, a chemist with joint appointments at Berkeley lab's physical biosciences division (CA, USA) and the chemistry department of the University of California at Berkeley (UC; CA, USA), who led team that developed the technique. We believe this technique could revolutionize the use of DNA microarrays for both diagnostics and research.

Until now, the use of DNA microarray assays has been limited because current techniques typically depend upon fluorescence detection, a demanding methodology that requires time-consuming chemical labeling, high-power excitation sources, and sophisticated instrumentation for scanning. Such demands are generally well beyond the capabilities of individual laboratories or clinics, especially in developing countries. While label-free DNA detection strategies do exist, they require either complex device fabrication or sophisticated instrumentation for readouts. None are compatible with conventional DNA microarrays, where up to one million sequences are available for interrogation in a single experiment.

We have demonstrated parallel sampling of a microarray surface with micron-scale resolutions over centimeter-scale lengths, said Professor Groves. This is four orders of magnitude larger than what has been achieved to date with conventional scanning-electrostatic-force microscopy.

The technique was described in the June 2008 online edition of Nature Biotechnology.


Related Links:
Berkeley Lab's Physical Biosciences Division
Chemistry Department of the University of California at Berkeley