title: The unfolding of G-quadruplexes and its adverse effect on DNA-gold nanoparticles-based sensing system.
abstract: The adsorption of DNAs in G-quadruplex solution onto 13 nm gold nanoparticles (AuNPs) was studied through monitoring of the localized surface plasmon resonance (LSPR) absorbance of 13 nm AuNPs at 520 and 650 nm (A650/A520) in the solutions of three widely studied guanine-rich sequences, TBA(5'-GGTTGGTGTGGTTGG-3'), PW17(5'-GGGTAGGGCGGGTTGGG-3'), and PSO (5'-GGGTTAGGGTTAGGGTTAGGG-3'). It was found that the degree of adsorption of DNAs in Pb(2+) stabilized G-quadruplex (G-Pb(2+)) solutions is up to 93% after more than 5h of incubation. Furthermore, the lead concentrations in the solutions containing G-quadruplex and AuNP were analyzed by an inductively coupled plasma atomic emission spectrometer. The results showed that Pb(2+) had been released from the G-quadruplexes, which means the G-quadruplexes may be unfolded in the presence of AuNP. This interaction between G-quadruplexes and AuNP demonstrated that long time incubation between DNAs and AuNPs would possibly make it unable to distinguish G-quadruplex from ssDNA. Thus, a biosensing system consisting of PW17 and AuNPs was developed to detect Pb(2+). It was found that the LSPR responses at A650/A520 were sensitive to [Pb(2+)]. However, the sensitivity of the system was interfered by the potential unfolding of PW17-Pb(2+) in the presence of AuNPs. This unexpected adverse effect of AuNPs on DNA-based biosensors should be taken into consideration in the future development of biosensing systems that are based on ssDNA aptamers and unmodified AuNPs.
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China and USTC-CityU Joint Advanced Research Center, Suzhou, PR China; Department of Biology and Chemistry, City University of Hong Kong and USTC-CityU Joint Advanced Research Center, Suzhou, PR China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Cheng
authors.forename: Bin
authors.initials: B
authors.lastname: Zheng
authors.forename: Mozhen
authors.initials: M
authors.lastname: Wang
authors.forename: Xuewu
authors.initials: X
authors.lastname: Ge
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Michael Hon-Wah
authors.initials: MH
authors.lastname: Lam
mesh_terms: D000327:Adsorption; D052157:Aptamers, Nucleotide; D015374:Biosensing Techniques / Q000379:methods*; D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D006046:Gold / Q000737:chemistry; D006147:Guanine / Q000737:chemistry; D006801:Humans; D007854:Lead / Q000097:blood / Q000302:isolation & purification*; D053768:Metal Nanoparticles / Q000737:chemistry; D020349:Surface Plasmon Resonance
chemical_list: D052157:Aptamers, Nucleotide; D007854:Lead; D006147:Guanine; D006046:Gold; D004247:DNA
keywords: Biosensor; G-quadruplex; Gold nanoparticle; Lead ion; Unfolding