In vivo dual-modality MR and near-infrared fluorescence imaging of gastric cancer neovasculature with targeted multi-functionalized nanoparticles

Abstract

Objective: To explore the feasibility of dual-modality probe to in vivo target angiogenesis of gastric cancer on MRI and near-infrared fluorescence (NIRF) optical imaging. Methods: Cy5.5-GX1 with magnetic FeO nanoparticles were conjugated, resulting in dual-modality probe DPs. The hydrodynamic size and Zeta potential of DPs were analyzed by nano-ZS. Twelve male nude mice were obtained and established gastric adenocarcinoma subcutaneous transplantation tumor model. Twelve nude mice were divided into experimental group and control group (n=6 for each) by using completely random experimental design, then intravenously injected the same volume of DPs and FeO-Cy5.5. MRI was applied before and 4, 8, 12, 18, 24 hours respectively after injections of nanoparticles to follow the changes of signals. For the evaluation of the MR images, the contrast to noise ratio (CNR) were calculated, and the different groups were compared with analysis of variance. MR images of the same level were selected before and 12 h after injections of nanoparticles in two groups and the percentage of reduced pixels was calculated, which were compared with the paired t test. At the same time, the time-resolved accumulation of the nanoparticles in the tumors were observed by using in vivo fluorescence imaging at 0, 4, 8, 12, 18, 24 hours after injecting nanoparticles, respectively. Then tumor and normal tissues were collected, and ex vivo optical imaging and histopathology were performed on the tissues. Results: At room temperature, the hydrodynamic size of FeO-Cy5.5 was(38.23 ± 0.06)nm and the Zeta potential was (0.29 ± 0.16)mV, and the hydrodynamic size of DPs was (39.49 ± 0.16) nm and the Zeta potential was (- 4.15 ± 0.79) mV. The coupled rate of DPs with polypeptide was >90%. The MRI signals of reticuloendothelial system were reduced significantly in experiment and control group. The tumor CNR of experiment group before and 4, 8, 12, 18, 24 h after injection were 18.27 ± 2.19, 18.40 ± 2.00, 10.22 ± 1.97, 9.25 ± 0.44, 20.28 ± 1.46 and 22.41 ± 1.71 (F= 49.55, P 0.05). The percentage of MR signals decrease of the tumor periphery and central area were(33.0 ± 2.7)% and (22.0 ± 1.6)%, respectively in experiment group and that of control group were (8.3 ± 1.2)% and (3.8 ± 0.9)% respectively (t values were - 7.872 and 6.678, P< 0.01). The tumor fluorescence intensity of experimental group showed the high contrast to background tissue during 2 to 48 h p.i, but there was no significant difference in control group. Furthermore, ex vivo evaluation of excised organs showed DPs was predominantly taken up by the lumor and lung at 48 h p.i. Tumor neovascularization was mainly distributed in the tumor periphery area. Iron-positive cells were detected in the tumor of experiment group. The normal kidney tissues of the two groups and the tumor of control group were consistently negative for iron staining. Conclusion: DPs can selectively be delivered into gastric cancer and this novel receptor-targeted nanoparlicle could be used for MRI and NIRF optical imaging.