Objective:To fabricate tAu@glutathione(GSH)@Gd nanoprobe for tumor angiogenesis bimodal (MR/CT) imaging, and evaluate its characteristics and potential for MR/CT imaging in vivo. Methods:The tAu@GSH@Gd nanoprobes were constructed by encapsulating Au and Gd atoms into the GSH shell with cyclic asparagine-glycine-arginine (cNGR) peptide conjugation. EMT-6 BALB/c mice subcutaneous transplantation tumor models were established ( n=30) and divided into blank control group (saline), control group (Au@GSH@Gd nanoparticles) and experimental group (tAu@GSH@Gd nanoprobes) ( n=10 in each group). In vivo MR/CT imaging and distribution study were performed at different time points after tail intravenously injection. Relative MR signal value and relative CT value of tumor site and main organs in mice were used to evaluate MR/CT imaging property and biological distribution. After that, tumor tissues were collected for silver staining to study the accumulation of Au@GSH@Gd nanoparticles and tAu@GSH@Gd nanoprobes. Independent-sample t test was used for data analysis. Results:The tAu@GSH@Gd nanoprobes were (6.40±0.22) nm with high T 1 relaxation efficiency ((36.91±0.07) mmol·L -1·s -1). MR/CT imaging of tAu@GSH@Gd nanoprobes showed good performance in vitro. In vivo MR/CT imaging demonstrated MR/CT imaging of tumor was significantly enhanced by tAu@GSH@Gd nanoprobes after 2 h post injection. The strongest enhancement was observed at 24 h, with an increased relative MR signal value from 1.04±0.12 (before injection) to 1.84±0.26 ( t=12.61, P=0.006), and increased relative CT value from 1.01±0.04 (before injection) to 1.95±0.05 ( t=15.34, P=0.004). The highest MR/CT effect in control group appeared at 16 h, with the relative MR signal value of 1.50±0.06 and the relative CT value of 1.53±0.10, which were significantly lower than those in experimental group (1.84±0.26 and 1.95±0.05; t values: 5.35 and 16.46, both P<0.05). Distribution in normal tissues showed that most of tAu@GSH@Gd nanoprobes were metabolized through the kidneys. Tissue silver staining experiment verified the tumor angiogenesis targeting effect. Conclusion:The tAu@GSH@Gd nanoprobes exhibit favorable tumor angiogenesis target MR/CT imaging ability, providing a new design concept and basis for assessing tumor angiogenesis.

Objective To explore the effects from the synergy of substrate stiffness and hypoxia on epithelial mesenchymal transition (EMT) of colon cancer cells SW480 by simulating the microenvironment of human colon cancer tissues. Methods Polyvinyl alcohol gels with different stiffness ( 4. 5, 20, 40 kPa) were prepared to simulate the stiffness of each part of colon cancer tissues. The morphological change of cells on substrate with different stiffness was detected under simulated hypoxia ( CoCl2 ) environment. The expression of hypoxia inducible factor (HIF-1α), and EMT markers E-cadherin, Vimentin, Snail 1 were detected by Western blot. The mRNA expression of E-cadherin, Vimentin, Snail 1, matrix metalloproteinase-2 ( MMP-2), and MMP-9 was detected by quantitative real-time PCR ( qRT-PCR). Results Under simulated hypoxia environment, with the increase of substrate stiffness, the SW480 cells spreading area increased, and transformed from round shape into irregular polygon. The EMT of SW480 could be enhanced through up-regulating expression of Vimentin, Snail 1, MMP-2, MMP-9, and down-regulating expression of E-cadherin. Conclusions This study is important for exploring the synergistic effect of substrate stiffness and hypoxia on the EMT of colon cancer cells as well as the molecular mechanism.