An FRET-based Organic Dye Nanoparticles For Their Bio-applications

Traditional small-molecule organic dyes have been widely used as fluorescentprobes because their abundant sources and simple synthetic methods. However, mostorganic dyes are hydrophobic and easy to quench the fluorescence in biologicalsurroundings. With the development of nanotechnology, it appears a variety ofnanocarrier which loading small-molecule organic dyes, such as polymeric micelles,dendrimer, liposomes and so on. All those structures have very limited dye-loadingcapacity and relatively high carrier proportion that lead to high quantum yield and lowabsorption cross section per particle, it will result in low brightness of the probe.Meanwhile, Stokes shift of conventional dye probes is usually small and opticalinterferences (light scattering and autofluorescence) caused by biosubstrates often exist,which greatly reduces detection sensitivity.Based on the above problems, we prepare organic dyes into non-carriernanoparticles and combine with the principles of fluorescence resonance energytransfer (FRET), the main studies are summarized as follows:1. We prepare a red-emitting organic dye2,3-bis(4’-(diphenylamino)-[1,1’-biphenyl]-4-yl)fumaronitrile (NPAFN), then usingNPAFN nanoparticles (NPs) to encapsulate near-infrared dyes (NIR712) to form theNIR712-doped NPs. In our design, host NPAFN NPs are used as not only carriers totrap and stabilize NIR712dyes, but also light-harvesting agent to transfer energy toNIR712dyes to enhance their brightness. In comparison with pure NIR712dyes, ourorganic dye nanoparticles possess almost50-fold increased brightness, large Stokesshifts (~250nm) and dramatically enhanced photostability. With surface modification,these NIR-emissive organic nanoparticles have water-dispersity and size-and fluorescence-stability over pH values from2to10for almost60days. With thesesuperior advantages, these NIR-emissive organic nanoparticles can be used for highlyefficient folic-acid aided specific targeting in vitro cellular imaging. During in vivoimaging, most nanoparticles were taken up by tumor sites via EPR effect. In vivotoxicity assessments indicate the NIR712-doped NPs are not noticeably toxic to miceat the injected dose, which means that they could be a safe fluorescence probe forbioimaging.2. We design a ratiometric pH sensor that is based on small-molecule organic dye(TBADN) NPs. Fluorescein isothiocyanate (FITC), a pH-sensitive dye, is covalentlyattached to the thin silicon shell which is coated onto the surface of TBADN NPs, theTBADN@SiO2@FITC NPs and the resultant FRET system are formed. Herein,TBADN NPs are used as not only enenry donor, but also a carrier to load enenryacceptor-FITC. We used the ratios between the fluorescence intensity of FITC andTBADN as detection parameters, bacause it can efficiently decreaseinterfering backgrounds and test errors. Meanwhile, the sensor exhibited outstandingstability and could play a role in monitoring pH changes in cells.