Distance Based On Gold Nanoparticles Depend On The Optical Properties Of Chemiluminescence Analysis Application Of Resonance Energy Transfer System Research

Chemiluminescence resonance energy transfer(CRET) involves nonradiative energy transfer from a chemiluminescence(CL) donor to a suitable acceptor molecule. Compared with fluorescence resonance energy transfer(FRET), CRET occurs by oxidation of a CL compound. The absence of an external excitation source eliminates the unwanted strong background light, reduces the fluorescence bleaching and lessens the autofluorescence of system.Lately, Gold nanoparticles(AuNPs) have gained increasing attention in optical detection for its extremely high extinction coefficient and strongly color-tunable behavior that depends on the interparticle distance. Easy synthesis and modification, high stability and biocompatibility make it to be one of the most widely used nanomaterials.The CRET systems were first summarized in this thesis. And then.a label—free, non-derivatization CRET detection platform is developed for the detection of non-fluorescent small molecule compounds based on distance-dependent optical properties of AuNPs. In the system, fluorescein molecules absorb the energy of TCPO-H2O2reaction and reach the excited state. The excited state of fluorescein molecules return to the ground state accompanying by the radiation with the maximum emission wavelength at the521.6nm. The colour of dispersed AuNPs is red, its maximum absorption wavelength lies at520.0nm. The absorption spectrum of dispersed AuNPs has excellent degree of spectral overlapping with the CL spectrum of TCPO-H2O2-fluorescein system, The excited state of fluorescein molecules transfer their energies to AuNPs, resulting in a significant decrease in the CL signal of TCPO-H2O2-fluorescein reaction. Analyte can induced AuNPs from the dispersed turning to the aggregation, accompanying with the color of the solution changing from red to purple and even blue. The absorbance of dispersed AuNPs at520.0nm decreases dramatically concomitant with a new absorption band around721.0nm appearing. This new absorption band no longer overlaps with the CL spectrum of TCPO-H202-fluorescein system, so CRET doesn’t happen and the CL signal is retrieved.Part one.6-mercaptopurine, a purine metabolic type of anti-cancer drug, can assemble on the surface of AuNPs by forming Au-S covalent bond. The dispersed AuNPs turnes to the aggregation concomitant with a red shift in the absorption band of AuNPs. This new absorption band no longer overlaps with the CL spectrum of TCPO-H2O2-fluorescein system, so CRET doesn’t happen and the CL signal is retrieved. The presence of Cu2+dramatically accelerates the degree of aggregation of AuNPs, shortens the detection time and improves the detection sensitivity. Under the optimal condition, the proposed CRET system presents a wide concentration range of linear response, from9.0×10-9mol/L to1.8×10-5mol/L, and a low detection limit of6.2×10-10mol/L for6-mercaptopurine. The relative standard deviation is2.0%for9.0x10-7mol/L6-mercaptopurine solution in11repeated measurements. The applicability of the proposed CRET system was evaluated by analysis of6-mercaptopurine in spiked human plasma samples.Part two. melamine is an organic base and a trimer of cyanamide, with a1,3,5-triazine skeleton. Melamine could induce the aggregate of AuNPs. It has been used to develop colorimetric and spectrophotometric method for the detection of melamine. We here reported a highly sensitive CRET method for melamine by using the fact that melamine can induce the aggregate of AuNPs. Under the optimal condition,the linear range was3.2×10-13-3.2x10-7mol/L melamine and the low detection limit was9.5x10-14mol/L. The relative standard deviation is3.3%for3.2×10-10mol/L melamine solution in11repeated measurements. The proposed CRET system was applied to analysis of melamine in milk samples.In summary, a label-free, non-derivatization CRET detection platform is developed for the detection of non-fluorescent small molecule compounds. The assay proves to be simple and time-consuming. The marriage of high molar absorptivity of AuNPs and high sensitivity of CL detection promises the method with high sensitivity. The present CRET system can easily be emplored as a general detection scheme for the determination of other non-fluorescent species, such as small organic molecules and heavy metal ions. The present CRET detection platform can also be explored to immunoassays and nucleic acid hybridization if using functional nanomaterials as the probe.