The Application Of Long Persistent Luminescent Nanoparticles In Bioimaging

In various bioimaging probes,optical probes can be used to track biological activity at the cellular and molecular level,thus contributing to early detection,accurate diagnosis and monitoring of the disease.The optical probe based on fluorescence,compared with other imaging probes,possess much advantages of easy operation,high sensitivity,low cost,and non-ionizing radiation.However,the traditional optical probes have limitations in biological application due to the instability of luminescence in the organism,high toxicity for the organisms and low signal-to-noise ratio.Probes based on near infrared(NIR)long persistent luminescent nanoparticles(PLNPs)have attracted considerable attention in the field of biological imaging because this type of probes has excellent characteristics of high optical and chemical stability,deep tissue penetration and no biological background luminescence.In addition,combination of the long persistent luminescent nanoparticles,with other contrast agents could achieve multimodal imaging with high resolution and sensitivity in disease diagnosis,subsequent treatment and monitoring process,which allows us to obtain more accurate and reliable results.The most currently available ZGC nanoparticles,however,have one or more of the following disadvantages: the large particle size with a broad size distribution,poor water solubility,and low fluorescence quantum efficiency.In this thesis,a one-step hydrothermal method was used to successfully prepare long last persistent luminescent nanoparticles Zn Ga2O4:Cr3+ with the highest yield(absolute quantum yields are about 20%-27%).The nanoparticles were functionalized for targeted multimodal bioimaging.The results and conclusions of this thesis can be summarized as follows:(1)Small modification makes big difference.The ZGC nanocrystals with high absolutely quantum yield(QY)of 20% were prepared through one-step hydrothermal method by controlling the precursor concentration(Zn2+,Ga3+,Cr3+),which is much higher than that of currently available ZGC nanoparticles(10%).The QY can be further improved to 27% by replacing ammonia solution or sodium hydroxide with Na HCO3.(2)The resultant ZGC nanoparticles are size-tunable,and their afterglow luminescence can last for 5 days.What's more,the nanoparticles were functionalized with polyethylene glycol(HOOC-PEG-COOH)and polymethylene acrylic acid(PAA)to show better water solubility,biocompatibility and stability.(3)It is the first time to label the ZGC nanoparticles with clinical radioisotope 99 mTc to achieve multimodal imaging(i.e.,optical imaging and SPECT/CT imaging)for acquiring accurate information,as SPECT/CT imaging has high resolution and high sensitivity.(4)Oral administration of ZGC nanoparticles is a non-invasive delivery approach,and these nanoparticles become more acceptable due to the excellent performance such as alleviating pain and discomfort,and reducing the possibility of side effects...