The Basic Study Of Radioactive Iodine-131 Labeled Dendritic Nanoparticle Delivery System For Tumor Therapy

ObjectiveWith increasing expectations for successful malignant tumour treatment,the traditional combination of radiotherapy and chemotherapy is falling short of providing the necessary efficacy.As a result,a more efficient and precise treatment approach is urgently needed.This study aims to develop a targeted polytherapy system that delivers anti-cancer drugs in a precise and targeted manner while maintaining the effectiveness of internal radiation therapy.A novel targeted drug delivery probe:¹³¹I-RGDy C-PEG-PAMAM-DTX(hereinafter referred to as ¹³¹I-RPPD),was constructed based on previous research to accomplish this goal.This study examines the physical and chemical characteristics as well as the biological activities of a tumor-targeted polytherapy probe for potential use in tumor treatment.Methods1.According to the previous proposal of the group,RGDy C-PEG-PAMAM（hereinafter referred to as RPP）was synthesized chemically and the labeled precursor RGDy C-PEG-PAMAM-DTX（hereinafter referred to as RPPD）was synthesized by solvent volatilization method to encapsulate the chemotherapeutic drug docetaxel.The regression curves of DTX were constructed by HPLC to determine the drug loading capacity.2.The chloramine-T method was used to synthesize ¹³¹I-RPPD by radionuclide iodine-131 labeling.The labeled products underwent purification through Sephadex-G50 column chromatography and were tested for labeling rate and radiochemical purity via paper chromatography.Further evaluation included testing for p H,in vitro stability,radiochemical concentration,lipid-water partition coefficient,and other physicochemical properties.3.Cellular uptake and retention assays were conducted to assess the binding and retention ability of ¹³¹I-RPPD in A549 cells.Moreover,CCK-8 assay was used to evaluate its effect on cell proliferation while flow cytometry was utilized to determine its pro-apoptotic effect on A549 cells.4.In animal experiments,a human lung adenocarcinoma（A549）tumor model was first prepared and its radioactive distribution in various organs of the tumor-bearing nude mice was explored by tail vein injection of ¹³¹I-RPPD.SPECT imaging was performed by intratumoral injection of ¹³¹I-RPPD and ¹³¹I at different time points to initially assess the imaging and retention of ¹³¹I-RPPD in the tumor.The changes in body weight and tumor volume of each group of tumor-bearing nude mice were observed by intratumoral injection of ¹³¹I-RPPD,RPPD,¹³¹I,DTX,and saline,and the tumor tissues of each group were dissected for HE staining after treatment to study the in vivo therapeutic effects of ¹³¹I-RPPD.Results1.RPPD was prepared via solvent volatilization,achieving approximately 4.4±0.018%drug loading.Following chloramine-T labeling,¹³¹I-RPPD exhibited a labeling rate of 74.09%～76.09%,with radiochemical purity of 88.9%～92.6%after purification.The radioactive concentration was approximately 7.19×10⁴k Bq/m L（1.944 m Ci/m L）,resulting in a colorless,clear solution with a p H of 7.5.Over 72 hours and at both room temperature and 37°C,the radiochemical purity remained above 80%after incubation in PBS or FBS.The lipid-water partition coefficient was Log P=-1.7871±0.14640,indicating excellent water solubility.2.In vitro cellular uptake and retention assays showed that ¹³¹I-RPPD could be specifically taken up by A549 cells compared to free ¹³¹I and could remain in the cells for a longer period of time;CCK-8 assay showed that RPPD had a significant inhibitory effect on A549 cells compared to free DTX（P<0.05）;¹³¹I-RPPD had a significant inhibitory effect on A549 cell proliferation compared to free ¹³¹I（P<0.01）.¹³¹I-RPPD significantly inhibited the proliferation of A549 cells compared with free ¹³¹I（P<0.01）;¹³¹I-RPPD significantly induced apoptosis compared with free ¹³¹I,DTX,and the blank control group by flow cytometry（P<0.001）.3.¹³¹I-RPPD injected through the tail vein had high radioactivity concentrations in tumor tissue,liver,spleen,kidney,and blood.SPECT imaging disclosed the drug’s significant accumulation in the tumor,with prolonged retention of radionuclides even after 144 hours of injection.The ¹³¹I-RPPD group demonstrated a significant reduction in tumor volume compared to the other four groups.This decline was observed within 21 days of observation（P<0.001）.Furthermore,the ¹³¹I-RPPD group showed the least bodyweight change compared to the other four groups,（P<0.05）.HE staining demonstrated that the ¹³¹I-RPPD group exhibited the most significant cancerous tissue degeneration and necrosis.ConclusionIn this study,the ¹³¹I-RPPD probe was successfully prepared with a simple labeling process,high radiochemical purity,and good in vivo and ex vivo stability;¹³¹I-RPPD was specifically taken up by A549 cells,resulting in a significant decrease in the proliferation capacity and a significant increase in the apoptosis rate of A549 cells;in vivo animal studies was found that it had a certain inhibitory effect on the tumor growth of A549 tumor-bearing nude mice in vivo.