Preparation And Application Of Luminescent Lanthanide Complex-Modified Apoferritin

As an ultrasenstive bioanalytical method, time-resolved fluorescence (TRF) bioassay technique based on long-lived fluorescence of lanthanide labels can effectively eliminate the background fluorescence from biological samples, and has been widely used in clinical diagnostics and biotechnology. However, luminescent lanthanide biolabels have the problem of biocompatibility, which limits their effective application to time-resolved luminescence bioassays.In this work, proteins that can emit red, orange and green fluorescence were prepared by encapsulating Eu(Ⅲ), Eu(Ⅲ)/Tb(Ⅲ)(Eu:Tb=1:1) and Tb(Ⅲ) fluorescent complexes with the ligand (4’-phenyl-2,2’:6’,2"-terpyridine-6,6"-diy1) bis (methylenenitrilo) tetrakis (acetic acid) into apoferritin. The proteins not only keep the surface properties of apoferritin, but also keep the optical properties of the lanthanide complexes.The protein-labeled streptavidin was prepared and used for the time-resolved fluoroimmunoassay (TR-FIA) of human prostate-specific antigen (PSA). The results indicate that the protein-labeled streptavidin still has a good bio-reactivity, and can be used for the highly sensitive TR-FIA of human PSA. In addition, the protein was successfully used for the time-resolved fluorescence imaging detection of HeLa cells. All of above results demonstrate that the lanthanide complex-modified apoferritin can be used as a fluorescent bioprobe for time-resolved fluorescence bioassays.