title: Single-probe multistate detection of DNA via aggregation-induced emission on a graphene oxide platform.
abstract: Graphene and graphene oxides (GO), or their reduced forms, have been introduced in a variety of biosensing platforms and have exhibited enhanced performance levels in these forms. We herein report a DNA sensing platform consisting of aggregation-induced emission (AIE) molecules and complementary DNA (comDNA) adsorbed on GO. We experimentally turned the AIE molecule on and off by adjusting its distance, which correlates with DNA structures as shown in our computational results, from the GO sheet, which quenches depending on its distance from the graphene plane. The changes in florescence are reproducible, which demonstrates the probe's ability to identify the binding state of the DNA. Our molecular dynamics simulation results reveal strong π-π interactions between single-strand DNA (ssDNA) and GO, which enable the ssDNA molecule to move closer to the graphene oxide. This reduces the center of mass and binding free energies in the simulation. When hybridized with comDNA, the increased distance, evidenced by the reduced interaction, eliminates the quenching effect and turns on the AIE molecule. Our protocol use of the AIE molecule as a probe thus avoids the complicated steps involved in covalent functionalization and allows the rapid and label-free detection of DNA molecules.
  
  
  
  A simple, rapid method of fluorescent measurement of DNA hybridization in the presence of graphene (oxide) is presented. Conventional fluorescent dyes offer high performance in biosensors. However, labeling procedures are synthetically demanding in time and resources making it less cost-effective. Molecules with aggregation-induced-emission (AIE) property have advantages over traditional fluorescent molecules because of their intrinsic preference for detection as a turn-on probe and their single-molecule detection ability. Previous work has shown AIE dyes act as excellent "label-free" bioprobes with high sensitivity but with limited selectivity. Graphene oxide (GO) with its unique optical properties and affinity to different kinds of biomolecules can be used as an auxiliary to enhance selectivity of AIE dyes. In this work, we report a label-free strategy to detect DNA of particular sequence by water-soluble AIE probes with the aid of GO, supported by the computational explanations for this phenomenon.
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Tyagi
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Kin Leung
authors.initials: KL
authors.lastname: Chu
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Irfan Haider
authors.initials: IH
authors.lastname: Abidi
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Aldrine Abenoja
authors.initials: AA
authors.lastname: Cagang
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Qicheng
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Division of Biomedical Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Nelson L C
authors.initials: NLC
authors.lastname: Leung
authors.affiliation: Department of Chemistry and Division of Biomedical Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Engui
authors.initials: E
authors.lastname: Zhao
authors.affiliation: Department of Chemistry and Division of Biomedical Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Ben Zhong
authors.initials: BZ
authors.lastname: Tang
authors.affiliation: Department of Chemical and Biomolecular Engineering and The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong. Electronic address: keztluo@ust.hk.
authors.forename: Zhengtang
authors.initials: Z
authors.lastname: Luo
mesh_terms: D003198:Computer Simulation; D018076:DNA, Complementary / Q000032:analysis*; D006108:Graphite / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D013057:Spectrum Analysis
chemical_list: D018076:DNA, Complementary; D015335:Molecular Probes; D006108:Graphite
keywords: Aggregation-induced emission (AIE); DNA; Graphene oxide; Molecular dynamics simulations