Space-selective DNA Deposition Controlled by Photothermal Heating of Gold Nanoparticles
AuthorRajewale, Sarita B.
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Mono-layers of bio-molecules exhibit poor optical absorption. However, nanoparticles of metals such as gold are efficient light absorbers. Surface plasmons generated by laser excitation of gold nanoparticles lead to an enhanced absorption cross section, ultimately producing photothermal energy. This dissertation is focused on implementing laser-induced photothermal energy for space-selective DNA deposition onto a solid surface for high density micro-gene array fabrication. The fabrication method uses visible wavelength laser-irradiation of gold nanoparticles to locally de-hybridize fluorescently labeled DNA oligonucleotides immobilized on a substrate surface. Fluorescently labeled complimentary DNAs were then added to the samples to validate space-selective DNA re-hybridization. Under optimum conditions, the addition of complimentary DNA caused a restoration of fluorescence in the laser-irradiated region thereby confirming successful DNA de-hybridization and re-hybridization. Subsequent experiments were performed to identify optimum conditions for photothermal de-hybridization of DNA. These experiments evaluated the performance of the de-hybridization process with respect to variations in gold nanoparticles size, gold nanoparticle concentration, laser repetition rate, laser exposure time, sample buffer temperature, sample buffer pH, and sample buffer ionic concentrations. Feature sizes as small as 5 micrometers could be attained.This study identified and refined a photothermal method that can be used in generating high density, micro-featured, and uniform DNA arrays that have applications in the DNA chip fabrication technology.