Graphene Oxide Apply To The Design Of Biosensor

Parallell with the advancement of nanomaterial science and biotechnology,various nanomaterial have been realized in the areas of biological device design,biomolecule detection, bioassays, and molecular medicine. Graphene, a single layer of carbon atoms in a closely packed honeycomb two-dimensional structure, is a new kind of carbon nanostructure material. It possesses many novel and unique physical and chemical properties because of its unusual monolayer atomic structure.Graphene and graphene oxide(GO) have received a great deal of attention in fundamental and applied research. Biological modification in turn benefits graphene by improving its biocompatibility, solubility and selectivity.There is increasing interest in the use of graphene or graphene oxide for the development of FRET biosensors, FRET involves the transfer of energy from a donor fluorophore to an acceptor fluorophore, and is one of the advanced tools available for measuring nanometer-scale distance and changes, theoretical and experimental studies have shown that graphene can be a highly efficient quencher for various organic dyes and quantum dots (QDs) Compared with organic quenchers, graphene has shown superior quenching efficiency for a variety of fluorophores, with low background and high signal-to-noise ratio. In this paper, we have developed several detection methods for proteolytic enzyme and samll molecules based on GO-based FRET biosensors.The detailed content described as follows:(1) Pepides are absorbed onto GO surface by the stacking interactions with the largely hydrophobic basal plane of GO via aromatic and hydrophobic residues. we design a GO-based biosensing platform using peptides as probe biomolecules to specifically recognize the target, and demonstrate its application for the caspase-3 protease activity assay based on FRET (fluorescence resonance energytransfer) between a dye-labeled peptide(donor) and GO (acceptor). The results revealed that our approach exhibited a good dynamic response toward caspase-3 range from1.45 ng/ml-72.5 ng/ml, with a readly achieved detection limit of 1.45 ng/ml. This peptide-GO probe design offers many advantages, including simplicity of preparation and manipulation compared with other methods that employ specific strategies. Moreover, the concept can easily be extended to construct a series of probes by simply changing the peptide substrate sequence for detect activity of other proteases. (2) we presented a novel graphene-based strategy to develop protease sensors based on covalent conjugation of graphene oxide and peptide substrates with fluorophore labels. Compared with nowadays prevailed strategy of non-covalent assembly forgraphene-based biosensor construction, the use of covalent conjugate could eliminate effectively the displacement of peptide probes caused by protein adsorption, thus substantially improving the stability of protease sensors in protein-abundant media. The results revealed that our approach exhibited a good dynamic response toward caspase-3 range from7.25 ng/ml-362 ng/ml, with a readly achieved detection limit of 7.25 ng/ml .It was demonstrated using the apoptosis-related caspase-3 activation system. It revealed that the GO-peptide conjugate provided a robust, sensitive and selective sensor for quantitative detection of caspase-3.(3) we construct a biosensing platform for selecting quadruplex-binding ligands by using GO sheet as a new fluorescent quencher. When the quadruplex-binding ligands are added, the single-stranded signal probe folds to form the G-quadruplex structure and leads to release from the surface of GOs. Once the G-quadruplex structure is constructed, the interaction between signal probe and GOs become weaker and induce the flourescence recovery. Here, three series of traditional Chinese medicine monomers were chosen to explore the natural quadruplex-binding liagands. A family of planar flavonoid molecules was found to be effective G-quadruplex ligands. The datas indicate that this method estabilishes a simple, rapid, effective approach to screen the G-quadruplex ligands with potential application in cancer therapies.