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Gold nanobeacons are gold nanoparticles functionalized with a fluorophore-labelled hairpin-DNA, i.e. gold-nanobeacon to follow RNA synthesis in real time in bulky solutions and for antisense DNA and RNA interference (RNAi), from gene specific silencing to silence-the-silencers. Under hairpin configuration, proximity to gold nanoparticles leads to fluorescence quenching; hybridization to a complementary target restores fluorescence emission due to the gold nanobeacons’ conformational reorganization that causes the fluorophore and the gold nanoparticle to part from each other. ==Gold Nanobeacons for Theranostics== Gold nanoparticle-based molecular beacon have shown the capability to specifically detect DNA target sequences,〔Song,S. et al. Gold-nanoparticle-based multicolor nanobeacons for sequence-specific DNA analysis. Angew. Chem. Int. Ed Engl. 48, 8670-8674 (2009).〕 with better discriminating power for single-mismatch than regular molecular beacons.〔Dubertret,B., Calame,M., & Libchaber,A.J. Single-mismatch detection using gold-quenched fluorescent oligonucleotides. Nat. Biotechnol. 19, 365-370 (2001).〕 Nevertheless, the systems described so far rely on the detection of nucleic acids in bulk solution and can only be used in in vitro applications without translation to cell/tissue/organism testing. Recently, Conde et al. developed a new theranostic system capable of intersecting all RNA pathways: from gene specific downregulation to silencing the silencers, i.e. siRNA and miRNA pathways. The authors reported the development of new nanomaterials, i.e. gold nanoparticles functionalized with a fluorophore labeled hairpin-DNA - Gold nanobeacons - capable of efficiently silencing single gene expression, exogenous siRNA and endogenous miRNAs while yielding a quantifiable fluorescence signal directly proportional to the level of silencing.〔Conde J, Rosa J, de la Fuente JM, Baptista PV. Gold-nanobeacons for simultaneous gene specific silencing and intracellular tracking of the silencing events. Biomaterials. 2013;34(10):2516-23. (doi: 10.1016/j.biomaterials.2012.12.015. )〕 This method describes a gold nanoparticle-based nanobeacon as an innovative theranostic approach for detection and inhibition of sequence-specific DNA and RNA for ''in vitro'' and ''ex vivo'' applications.〔Rosa J, Conde J, de la Fuente JM, Lima JC, Baptista PV. Gold-nanobeacons for real-time monitoring of RNA synthesis. Biosens Bioelectron. 2012;36(1):161-7. (doi: 10.1016/j.bios.2012.04.006 ).〕 This concept can easily be extended and adapted to assist the in vitro evaluation of silencing potential of a given sequence to be later used for ex vivo gene silencing and RNAi approaches, with the ability to monitor real-time gene delivery action.〔Conde J, Rosa J, Baptista P. Gold-Nanobeacons as a theranostic system for the detection and inhibition of specific genes. Community Contributed Protocol Exchange. 27/11/2013. (doi:10.1038/protex.2013.088 ).〕 The mechanism proposed in the gold-nanobeacon tool has got several clear advantages compared with traditional methods. Firstly, naked/unmodified oligonucleotides show extremely short half-lives inside cellular environment, feeble protection against RNases and other nucleases, poor chemical stability, and common dissociation from vector. In fact, the major obstacle to clinical application is the uncertainty about how to deliver therapeutic DNAs (antisense oligonucleotides) and RNAs (e.g., microRNA and/or siRNA) with maximal therapeutic impact due to systemic loss of cargo from traditional vectors. This method offers an unprecedented opportunity to overcome these problems as these nanoconjugates can readily interact with biomolecules on both the surface of cells and inside cells for longer periods of time, due to their small size and protective environment for DNA/RNA oligonucleotides provided by the metal nanoparticle core. The gold-nanobeacons are also highly soluble, homogenous and stable and are not prone to aggregation. In addition, these nanoparticles are thermodynamically stable and can remain inside cells for long periods of time and at low concentrations. Secondly, gold-nanobeacons are capable of efficiently silencing single gene expression, exogenous siRNA and endogenous miRNAs.〔Conde J, Rosa J, de la Fuente JM, Baptista PV. Gold-nanobeacons for simultaneous gene specific silencing and intracellular tracking of the silencing events. Biomaterials. 2013;34(10):2516-23. (doi: 10.1016/j.biomaterials.2012.12.015. )〕 Thirdly, it allows real-time detection of the beacon’s signal while yielding a quantifiable fluorescence directly proportional to the level of gene silencing.〔Rosa J, Conde J, de la Fuente JM, Lima JC, Baptista PV. Gold-nanobeacons for real-time monitoring of RNA synthesis. Biosens Bioelectron. 2012;36(1):161-7. doi: 10.1016/j.bios.2012.04.006.〕 This can be used to track the silencing events inside the cell as they occur. All this is achieved in a simple approach that can be straightforwardly adapted and tailored to any specific target. Finally, a significant attribute of these gold-nanobeacons is the ability to attain similar levels of inhibition of gene expression with lower amounts than those of free oligonucleotides without increasing cell death. This extraordinary efficiency occurs probably due to the large payload capacity of the NPs and the longer half-life when inside the cells. The gold-nanobeacons may represent in the near future an economically viable and commercial-scale production for a cell and cell-free system.〔Conde J, Rosa J, Baptista P. Gold-Nanobeacons as a theranostic system for the detection and inhibition of specific genes. Community Contributed Protocol Exchange. 27/11/2013. doi:10.1038/protex.2013.088.〕 Contrary to conventional gene delivery chemistry, which is often associated to systemic toxicity and adverse effects as well as lack of specificity and lower product life-cycle, this method represents a safe, efficient, specific and non-pathogenic vehicle for gene delivery and cell tracking system – a theranostic tool.〔Conde J, Larguinho M, Cordeiro A, Raposo LR, Costa PM, Santos S, Diniz MS, Fernandes AR, Baptista PV. (Gold-nanobeacons for gene therapy: evaluation of genotoxicity, cell toxicity and proteome profiling analysis. ) Nanotoxicology.(2013).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gold nanobeacons」の詳細全文を読む スポンサード リンク
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