Nanometer Semiconductors for DNA Modification

A new method to initiate and control chemical reactions on DNA strands using nanometer-sized semiconductors has recently been developed. Details of the methodology were released on October 4, 2002, by the U.S. Department of Energy's Argonne National Laboratory (Argonne, IL, USA).

The technology is based on small organic molecules that connect the electronic properties of semiconductors to biological or organic molecules. These "conductive linkers” were used to connect strands of DNA to titanium dioxide crystals measuring only 4.5 nm in diameter.

In the presence of light, the titanium dioxide nanocrystals act as semiconductors, generating strong oxidizing power that acts on the organic molecules. By using different conductive linkers, the investigators were able to selectively control oxidation.

These nanoparticles have a wide range of potential applications in DNA-based sensing devices. As the four bases that make up DNA oxidize at different rates (guanine is the most readily oxidized, followed in decreasing order of reactivity by adenine, cytosine and thymine), it is possible to determine the base sequence by comparing the speed and efficiency of the reactions.

Another potential application is in the field of gene therapy. The DNA-titanium dioxide hybrid molecules may be used as "artificial restriction enzymes” to remove unwanted DNA sequences in a manner that can be focused and controlled by light. For example, a synthetic DNA single strand containing the sequence of a genetic defect can be linked to titanium dioxide. The DNA strand will carry the attached titanium dioxide to the cell nucleus and presumably to the site of the genetic defect on the chromosome. Light will initiate the oxidative chemistry, which clips the defective gene and permits repair with a healthy gene sequence.



Related Links:
Argonne National Laboratory