Research Of Multi-mode Imaging Basing On Au Clusters And Diagnose Of Tumor Marker

As populations grow,aging and the environment changes,cancer（malignancy）has become a global threat of human health.Especially in our country,cancer incidence and mortality is rising.According to the National Cancer Center（NCCR）published in the"Cancer Statistics in China,2015"shows:it is expected that 4.92 million new cancer cases and 2.84 million cancer patients will die from cancer in China by 2015,it means there are 12,000 newly diagnosed cases and 7000 people who die from cancer every day.Therefore,the reduction of cancer risk factors,improvement of the effectiveness of cancer prevention,early diagnosis and clinical care services is the key method to reduce cancer incidence and mortality,and has always been the focus of medical research.Methods of clinical diagnosis cancer mainly include:the detection of hematological markers,histopathological analysis and molecular medical imaging methods for tumorigenesis,the assessment of development process.Therefore,developing accurate detection methods and multi-functional imaging agents will achieve the diagnosis of cancer,identification and individualized treatment process.Among them,molecular imaging methods have become an important tool for assisting clinicians to perform pathological progress judgment,treatment plan selection and prognosis evaluation,and only a single molecular imaging technique is difficult to obtain comprehensive pathology and physiological structure information of tumor site.Each imaging modality has its own advantages and disadvantages,in order to combine the advantages of various equipments,multi-modal imaging modality is also the hotspot in recent years.However,it is difficult to overcome the inherent disadvantage of various imaging equipment in a short time.Therefore,the development of multimodal imaging nanoprobe can also complement our data from various imaging devices.Noble metal cluster is a nanomaterial consisting of several to hundreds of atoms and having a size of less than 2 nm.It has an adjustable number of atoms,a range of fluorescence from ultraviolet to near infrared,an X-ray attenuation capability and a good biocompatibility.In recent years,the preparation of multimodal nanoprobe,and covalently modifying metal clusters with other nanoparticles realizing fluorescence,MR and other detection signals has become another hot spot.However,in order to make the nanoprobe more stable,the data obtained are more comparable.In this thesis,a series of nanoprobes based on gold nanoclusters were synthesized by in-situ biomineralization,or coupling of Gd elements etc.,and further prepared by covalent modification and functionalization to construct multifunctional nanoprobe.And application in in vivo imaging and cell surface marker molecular imaging studies were studied,the main research work is summarized as follows:1.Label-Free Au Cluster used for optical/CT dual-mode imaging of mouse kidneysBased on the fluorescence properties of gold clusters and the attenuation ability of X-ray,BSA-Au clusters were prepared by using mineralization method with bovine serum albumin as a temple.The clusters exhibited excellent near-infrared fluorescence emission ability,as well as CT imaging ability,uniform dispersion,good stability.The factors of the ratio of bovine serum albumin to gold salt were also investigated,and the physicochemical property of the material was also characterized.The results show that the CT imaging ability of the probe is three times higher than the iodine contrast agent used in clinical diagnosis.At the same time,the gold cluster with BSA as template has good dispersibility,good stability and biocompatibility.Through in vivo fluorescence imaging and CT imaging,we observed that the material mainly distributed in the spleen,liver and kidney,and by the kidneys excreted into urine.Under the optimal conditions,we achieved a two-dimensional three-dimensional contour imaging of the kidney,and observed the renal pelvis,calyx and other anatomical structures clearly.2.Preparation of Gadolinium-doped Composite Clusters and in vivo Optical/MRI/CT Three-modal Tumor ImagingOn the basis of the above-mentioned dual-mode imaging probe,the gadolinium oxide and Au clusters Doped（AuGd NCs）nanoparticles were prepared by bio-coprecipitation method with bovine serum albumin（BSA）as a template.The ratio of gold salt to gadolinium for preparing AuGd NCs was also investigated.The AuGd NCs show red fluorescence at⁶60 nm for optical imaging,strong X-ray absorption（around700 HU）for CT imaging,and a high r₁ value(¹2.39 mM^-1s^-1)for MR imaging.After being chemically modified with folic acid,the AuGd NCs agent can high specifically target folate receptors on KB tumor cells,and permit in vivo optical,MR,and CT imaging of xenografted tumor.By comparing these three imaging modalities,very clear structural and functional information on the in vivo tumor can beobtained.The Au Gd NCs agents showed good biocompatibility,quick renal clearance,and did not cause normal tissue pathological changes.3.Selective identification and imaging for cell surface integrin,epidermal growth factor receptor 2（Her-2）markers with Au clustersThe expression and distribution of markers at the cellular level were closely related to the stage of the cancer disease.The Au clusters were prepared with functional polypeptide as template in situ mineralization,we studied the empact of the location of mineralization sequence to targeting ability of the probe.Two probes targeting to integrins and surface growth factor receptor 2 were prepared,respectively,which has provided a good basis for the subsequent single cell quantification of proteins.