Practice Of USPIOs With CRGD And Gelatinase Dual Target For Gastric Cancer MRI Test

Part one:MMP2/MMP9 targeted polymeric micelle loading with USPIOs as a novel MRI ultrasensitive agent for detection of gastric cancerObjective MMP2/MMP9 targeted polymeric micelle loading with USPIOs were synthesized as a novel MRI ultrasensitive agent for detection of gastric cancer. Materials and Methods copolymer of poly5k(ethylene glycol) and poly6.5k(ε-caprolactone) was inserted a peptide of six amino acids(PVGLIG) which could be degraded by MMP2/MMP9(gelatinase), whereas these gelatinases were secreted by major gastric tumor and tumoral infiltrated immune cells. This new copolymer was synthesized and used to encapsulated ultrasmall superparamagnetic iron oxide nanoparticle (USPIO) to obtain a hydrophilic tumor-targeted MRI contrast agent which was applied in detection of gastric cancer. The length of PCL segment was shortened to 6.5K Da in order to keep the final diameter of USPIO loaded PEG-Pep-PCL micelles (PEG5k-Pep-PCL6.5k-USPIOs) at 95nm approximately,which is beneficial to utilize the EPR effect in maximum.Results PEG-Pep-PCL-USPIOs,PEG-PCL-USPIOs and Resovist were cocultured with gastric cancer cell lines respectively. Quantitative study and Perl’s staining identified that the amount of PEG-Pep-PCL-USPIOs were absorbed by tumor cells much more than PEG-PCL-USPIOs and Resovist(P< 0.01). In vivo study, PEG-Pep-PCL-USPIOs solution was injecting into nude mice with subcutaneous xenografts of human SGC7901 gastric carcinoma and imaged by 7.0T MRI. The signal of tumor was decreased in T2-weighted test compared with PEG-PCL-USPIOs group. However, the retention time of detective signal is longer than contrals (P<0.01). Moreover, prussian blue staining of the tumor sections excised also proved the results.Conclusion In this study, we demonstrated that PEG-Pep-PCL-USPIOs with tumor targeted characters would be used as a potential MRI probe for gastric tumor detection in vivo.Part two:Practice of USPIOs with cRGD and gelatinase dual target for gastric cancer MRI testObjective Current MRI contrast agents seldom satisfied the aim of specific accumulation in gastric tumor based on single targeting method. It’s imperative to construct a MRI agent to achieve the goal.Methods Boc protected amine-PEG-carboxyl(Mw 5000) linking poly6.5k(ε-caprolactone) with a peptide of six amino acids(PVGLIG) which could be degraded by MMP2/MMP9(gelatinase). (BOC)2O-PEG-Pep-PCL was synthetized at first and then the (BOC)2O was replaced by cRGD. The final product was cRGD-PEG-Pep-PCL which was used to encapsulated ultrasmall superparamagnetic iron oxide nanoparticle (USPIO) to obtain a hydrophilic tumor-targeted MRI contrast agent.Results cRGD-PEG-Pep-PCL-USPIOs、PEG-Pep-PCL-USPIOs and PEG--PCL-USPIOs were cocultured with gastric cancer cell lines respectively. Quantitative study and Perl’s staining identified that the amount of cRGD-PEG-Pep-PCL-USPIOs were absorbed by tumor cells much more than PEG-Pep-PCL-USPIOs and PEG -PCL-USPIOs (P<0.01). In vivo study, cRGD-PEG-Pep-PCL-USPIOs solution was injecting into nude mice with subcutaneous xenografts of human SGC7901 gastric carcinoma and imaged by 7.0T MRI. The signal of tumor was decreased in T2-weighted images compared with PEG-Pep-PCL-USPIOs group, However, the retention time of detective signal is longer than contrals (P<0.01). Moreover, prussian blue staining of the tumor sections excised also proved the results.Conclusion In this study, we demonstrated that cRGD-PEG-Pep-PCL-USPIOs with tumor targeted characters would be used as a potential MRI probe for gastric tumor detection in vivo.