Fabrication Of Upconversion Fluorescent Nanoprobes For Small Molecules Assay In Live Cells

With the development of life science technologies and modern biomedicine,we need eagerly more fast and accurate methods to diagnose diseases.Due to high sensitivity,high spatiotemporal resolution and simplification,fluorescence imaging technique is widely applied to detect small molecular,protein,DNA in living cells.It is important to exploit novel fluorescent materials in using fluorescence imag ing techniques.Compared to conventional fluorescent materials,upconversion nanopartical and two-photon dyes is based on absorption of two-photon or multiphoton,converting low frequent exciting light into high frequent emitting light.Due to the special luminous mechanism,upconversion nanopartical and two-photon dyes have some advantages:1)improve biological tissue penetration;2)reduce light damage on biological samples;3)avoid effectively the disturbance of autofluorescence from biological samples.Therefore,upconversion nanopartical s and two-photon dyes have wide applications in detection of biomolecular and imaging of living organism.To date,it has some problems in applications of upconversion nanopartical s and two-photon dyes,such as poor biocompatibility,hard to synthesize the materials with functional groups.To solve above mentioned problems,in this dissertation we construct conjugate nanoprobes by connection upconversion materials and SiO ₂ nanoparticals,silver nanoparticals,DNA to det ect biomolecular,Specific research content are as follows:1.Core/shell-structured upconversion fluorescent nanoprobe for detection and imaging of nitric oxideNO,as a messenger molecule,plays an important role in regulation of various physiological and pathophysiological processes.At high concentration,NO can cause cytotoxic.Therefore,monitoring and imaging of NO in biological surrounding is of great importance.As anti-stokes luminescence material,upconversion nanoparticle has exhibited some outstanding advantages in determination and bioimaging in organism.In this study,we synthesized core/shell-structured upconversion nanoparticles with encapsulating RB-NO into the silica shell covalently for detection and imaging of NO by the change of the FRET process.Using the ratio of fluorescence intensity as output signal,which provides a built-in correction for environmental effects,NO concentration is found in the range of 0 to 1.2 mM in phosphate buffer.More importantly,the nanoprobe exhibited the ca pacity of in vivo imaging of NO.2.Two-photon AgNP/DNA-TP dye nanosensing conjugate for biothiol probing in live cellsIn this paper,we present the study to fabricate a AgNPs/DNA-two-photon dye?TPdye?conjugate as two-photon nanoprobe for biothiols detection and imaging in live cells.The DNA-templated AgNPs can be not only an efficient quencher,but also provide a biocompatible carrier for delivery of the DNA in to live cells.In the presence of biothiols,the stronger interaction between silver and thiol group makes TPdye-labeled ssDNA to be released from the silver nanoparticals surface,resulting in recovery of the TPdye's fluorescence emission,thus realizing the detection of biothiols.Our results prove that the AgNPs/DNA-TP dye nanosensing conjugate not only is a selective and sensitive sensor for quantitative detection of biothiols in the complex biological environment but also can be efficiently delivered into live cells and act as a“signal-on”sensor for specific,high-contrast imaging of target biomolecules.