Highly specific colorimetric detection of DNA oxidation biomarker using gold nanoparticle/triplex DNA conjugates

DNA oxidation causes a variety of diseases including cancer. The oxidized DNA nucleobases are excised by cellular repair enzymes and released into extracellular fluids. Specifically, the excised DNA oxidation product, such as 8-oxoGua, has been suggested as a biomarker for early cancer diagnosis. We previously developed an artificial receptor for the free base of 8-oxoGua on a triplex DNA backbone. The receptor contained a pre-organized cavity, which bounded 8-oxoGua with strong affinity and excellent selectivity over other nucleobases. However, accurate detection of 8-oxoGua in urine samples was affected by the presence of a large excess of guanine. Herein, we report a strategy to convert our receptor to a colorimetric biosensor by conjugating DNA strands to gold nanoparticles (GNP), specifically for 8-oxoGua. By simply incubating our sensor with a urine sample, 8-oxoGua can be detected at submicromolar concentrations with UV-vis spectrometer or even by naked eye.