A High-Affinity and Selective DNA Aptamer for the N-Linked C8-Deoxyguanosine Adduct Produced by the Arylamine Carcinogen 4-Aminobiphenyl.

Abstract

4-Aminobiphenyl (4-ABP) is a known human carcinogen that is implicated in the development of bladder cancers in smokers. The amine substituent undergoes bioactivation to generate nitrenium ions capable of covalently modifying DNA nucleobases. The primary adduct of 4-ABP, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP), is a bulky N-linked C8-dG adduct that serves as a biomarker for assessing the cancer risk associated with aromatic amine exposure. In this study, the capture-SELEX method was utilized to isolate DNA aptamers for dG-C8-ABP with high affinity and specificity. Using thioflavin T fluorescence spectroscopy and isothermal titration calorimetry, the parent aptamer PdG-1 has a K_d value below 100 nM and over 50-fold selectivity for dG-C8-ABP against competing analytes. A turn-on fluorescent sensor for dG-C8-ABP diagnostics, developed using a strand displacement assay, is also presented with a limit of detection of 68 nM. Our work represents the first selection of a DNA aptamer for a bulky DNA adduct produced by a known human carcinogen and sets the stage for the creation of ultrasensitive aptasensor platforms to meet the challenge of dG-C8-ABP detection in clinical settings.