Optical imaging is one of the molecular imaging modalities,and it consists of three imaging methods (fluorescence,bioluminescence and diffusion imaging).For fluorescence imaging,quantum dots (QDs) are inorganic semiconductor nanocrystals with a diameter from 2 to 100 nm.Compared with organic fluorescent dye,QDs have several unique optical properties,such as wide and continuous excitation spectra,narrow and symmetrical emission spectrum,strong fluorescence intensity and high resistance to photobleaching.This article reviews the optical properties of QDs and their development in the field of molecular imaging from in vitro and in vivo applications,as well as the limitations and problems.

In this study, a novel technique for the preparation of (125)I-5-trimethylstannyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) urail (FIAU) was developed, (125)I-FIAU biodistribution profile was detected in Kunming mice and the possibility of using FTAU radio-labeling for reporter gene imaging was explored. 5-trimethylstannyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) urail (FTAU) was labeled with radioiodine ((125)I). A rotary evaporation method was used to remove excess methanol. The reactant was purified through a Sep-Pak C18 reversal phase column. The radiochemical purity and in vivo stability were determined using silica gel thin layer chromatography (TLC). The biodistribution of (125)I-FIAU in Kunming mice was also detected. The results showed that (125)I-FIAU could be radiolabeled effectively with FTAU, with mean labeling rate being (81±0.38)% (n =5). The mean radiochemical purity of (98.01±0.40)% (n=5) was achieved after a reversal phase Sep-park column purification. (125)I-FIAU was stable when incubated in normal human serum or in saline at 37°C, with a radiochemical purity >96% during a 0.5-24 h time period. Biological experiments exhibited rapid clearance of (125)I-FIAU from the blood pool. (125)I-FIAU was mostly excreted by kidneys. (125)I-FIAU in myocardium dropped conspicuously after 8 h and there was hardly retention at 24 h. We were led to concluded that the new method of radioiodinization of FTAU for the preparation of (125)I-FIAU is easy, highly effective and stable in vivo. The biodistribution of (125)I-FIAU in Kunming mice showed it can serve as an imaging probe for myocardial reporter genes.

Objective To prepare a kind of 99Tcm-labeled estrogen receptor (ER) SPECT imaging agent,and evaluate its binding characteristics with ER by in vitro and in vivo studies.Methods EDL was prepared from estrone and then reacted with GAP to synthesize GAP-EDL.Then,GAP-EDL was labeled with 99Tcm to obtain 99Tcm-GAP-EDL.Cell uptake and blocking assays were performed in vitro on MCF-7and MDA-MB-231 cells.The biodistribution study of 99Tcm-GAP-EDL was performed on normal BALB/c mice at 30,60,120,180 and 240 min post injection.Nude mice bearing either MCF-7 or MDA-MB-231derived tumors were injected with 99Tcm-GAP-EDL,and subjected to γimaging at 1,2,4 h post injection.The mice injected with excess unlabeled GAP-EDL or estradiol were used as the blocking control.Two-sample t test was used for data analysis.Results The radiolabeling yield of 99Tcm-GAP-EDL was (98.8 ±0.5) ％ and the radiochemical purity after 24 h was over 90％.The cell uptake rate of MCF-7 cells at 240min was (4.84± 0.21) ％,which was significantly higher than that of MDA-MB-231 cells ((2.11±0.21) ％;t =15.96,P＜0.05).99 Tcm-GAP-EDL uptake rate of MCF-7 cells in blocking groups ((2.31 ± 0.28) ％ and (2.05±0.35) ％) decreased significantly compared to that of non-blocking group(t=11.52,11.16,both P＜0.05).Biodistribution studies showed that 99Tcm-GAP-EDL was mainly metabolized by the liver and kidneys,and exhibited quick blood clearance.Gamma imaging showed high uptake in MCF-7 tumors 1 h post injection and the uptake reached the highest at 4 h,while there was little 99Tcm-GAP-EDL uptake in MDA-MB231 tumors and blocked MCF-7 tumors.Conclusions 99Tcm-GAP-EDL may be prepared under mild conditions with high labeling purity and stability.The in vitro and in vivo characteristics of 99Tcm-GAP-EDL suggest that it may be a promising probe for ER positive tumor imaging.

Fibroblast activation protein (FAP) is an important molecular marker of cancer-associated fibroblasts (CAFs). FAP is selectively expressed in more than 90% of epithelial carcinomas, but barely expressed in normal tissues. In recent years, a variety of radiolabeled molecular probes based on FAP inhibitor (FAPI) have been developed and used for imaging of malignant tumors. FAP is also highly expressed in some non-neoplastic diseases related to chronic inflammation and tissue remodeling, including arthritis, atherosclerosis, fibrosis of myocardial infarction, cirrhosis, and idiopathic pulmonary fibrosis. FAPI imaging shows a potential in these diseases. This paper reviews the current status of radionuclide labeled FAPI and the application of which in non-neoplastic diseases.

In this study,a novel technique for the preparation of 125I-5-trimethylstannyl1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) urail (FIAU) was developed,125I-FIAU biodistribution profile was detected in Kunming mice and the possibility of using FTAU radio-labeling for reporter gene imaging was explored.5-trimethylstannyl-l-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) urail.(FTAU) was labeled with radioiodine (125I).A rotary evaporation method was used to remove excess methanol.The reactant was purified through a Sep-Pak C18 reversal phase column.The radiochemical purity and in vivo stability were determined using silica gel thin layer chromatography (TLC).The biodistribution of 125I-FIAU in Kunming mice was also detected.The results showed that 125I-FIAU could be radiolabeled effectively with FTAU,with mean labeling rate being (81±0.38)％ (n =5).The mean radiochemical purity of (98.01±0.40)％ (n=5) was achieved after a reversal phase Sep-park column purification.125I-FIAU was stable when incubated in normal human serum or in saline at 37℃,with a radiochemical purity ＞96％ during a 0.5-24 h time period.Biological experiments exhibited rapid clearance of 125I-FIAU from the blood pool.125I-FIAU was mostly excreted by kidneys.125I-FIAU in myocardium dropped conspicuously after 8 h and there was hardly retention at 24 h.We were led to concluded that the new method of radioiodinization of FTAU for the preparation of 125I-FIAU is easy,highly effective and stable in vivo.The biodistribution of 125I-FIAU in Kunming mice showed it can serve as an imaging probe for myocardial reporter genes.