title: Hairpin DNA switch for ultrasensitive spectrophotometric detection of DNA hybridization based on gold nanoparticles and enzyme signal amplification.
abstract: A novel DNA detection platform based on a hairpin DNA switch, nanoparticles, and enzyme signal amplification for ultrasensitive detection of DNA hybridization has been developed in this work. In this DNA assay, a "stem-loop" DNA probe dually labeled with a thiol at its 5' end and a biotin at its 3' end, respectively, was used. This probe was immobilized on the gold nanoparticles (AuNPs) anchored by a protein, gamma-globulin, on a 96-well microplate. In the absence of target DNA, the immobilized probe with the stem-loop structure shields the biotin from being approached by a bulky horseradish peroxidase linked streptavidin (streptavidin-HRP) conjugate due to the steric hindrance. However, in the presence of target DNA, the hybridization between the hairpin DNA probe and the target DNA causes significant conformational change of the probe, which forces biotin away from the surface of AuNPs. As a result, the biotin becomes accessible by the streptavidin-HRP, and the target hybridization event can be sensitively detected via the HRP catalyzed substrate 3,3',5,5'-tetramethylbenzidine using a spectrophometric method. Some experimental parameters governing the performance of the assay have been optimized. At optimal conditions, this DNA assay can detect DNA at the concentration of femtomolar level by means of a signal amplification strategy based on the combination of enzymes and nanoparticles. This approach also has shown excellent specificity to distinguish single-base mismatches of DNA targets because of the intrinsic high selectivity of the hairpin DNA probe.
authors.affiliation: Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, People's Republic of China.
authors.forename: Youyu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhiwen
authors.initials: Z
authors.lastname: Tang
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Wu
authors.forename: Aihui
authors.initials: A
authors.lastname: Maham
authors.forename: Yuehe
authors.initials: Y
authors.lastname: Lin
mesh_terms: D001710:Biotin / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry*; D015342:DNA Probes / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism; D055029:Inverted Repeat Sequences; D053768:Metal Nanoparticles / Q000737:chemistry*; D009693:Nucleic Acid Hybridization / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D019809:Streptavidin / Q000737:chemistry / Q000378:metabolism; D005719:gamma-Globulins / Q000737:chemistry
chemical_list: D015342:DNA Probes; D005719:gamma-Globulins; D001710:Biotin; D006046:Gold; D004247:DNA; D019809:Streptavidin; D006735:Horseradish Peroxidase