ABSTRACT
Objective:To prepare 68Ga-2-(4, 7-bis(carboxymethyl)-1, 4, 7-triazonan-1-yl)pentanedioic acid (NODAGA)-YHWYGYTPQNVI (GE11) and evaluate its feasibility of PET imaging for pancreatic cancer. Methods:GE11 peptide was conjugated with NODAGA and then labeled with 68Ga. The labeling yield, radiochemical purity, hydrophilicity, stability and specificity in vitro were determined. Human pancreatic cancer BxPC3 nude mice models ( n=9) were established. MicroPET imaging was then obtained after 30 and 90 min, and mice were sacrificed at 90 min to acquire the radioactivity distribution of main organs and tumors. Pair t test was used to analyze the data. Results:The labeling yield was (73.5±5.4)% and radiochemical purity was more than 98%. After incubation 120 min in mouse serum at 37 ℃, radiochemical purity was more than 92%. The uptake was specific in BxPC3 cell lines. MicroPET images showed that 68Ga-NODAGA-GE11 could accumulate quickly in tumor. Value of tumor uptake was significantly higher than that of normal pancreas at 90 min ((1.38±0.25) vs (0.49±0.07) %ID/g; t=12.67, P<0.05), and the radio-uptake of blood, muscle and bone was lower than that of tumor. Conclusions:68Ga-NODAGA-GE11 is easy to be prepared with high radiochemical purity and good stability, and can specifically target BxPC3 xenograft tumor. However, due to the high uptake in the kidneys and liver, the value of 68Ga-NODAGA-GE11 in PET imaging for pancreatic tumor needs further study.
ABSTRACT
Liposomes, as one of the most successful nanotherapeutics, have a major impact on many biomedical areas. In this study, we performed laser scanning confocal microscope (LSCM) and immunohistochemistry (IHC) assays to investigate the intra-tumor transport and antitumor mechanism of GE11 peptide-conjugated active targeting liposomes (GE11-TLs) in SMMC7721 xenograft model. According to classification of individual cell types in high resolution images, biodistribution of macrophages, tumor cells, cells with high epidermal growth factor receptor (EGFR) expression and interstitial matrix in tumor microenvironment, in addition, their impacts on intra-tumor penetration of GE11-TLs were estimated. Type I collagen fibers and macrophage flooded in the whole SMMC7721 tumor xenografts. Tumor angiogenesis was of great heterogeneity from the periphery to the center region. However, the receptor-binding site barriers were supposed to be the leading cause of poor penetration of GE11-TLs. We anticipate these images can give a deep reconsideration for rational design of target nanoparticles for overcoming biological barriers to drug delivery.