Preparation And Imaging Of Bicyclic Peptide Targeting Nuclear Magnetic Contrast Agent Gd-DOTA-E-[c?RGDfK?]₂

Nuclear magnetic contrast agent is an important auxiliary drug for nuclear magnetic resonance imaging.Studies have shown that the rational use of nuclear magnetic contrast agent will not cause harm to human health,but also enhance the strength of tissue scan sig nals,so that the diagnosis of clinical conditions is more accurate.Therefore,in today's rapid development of nuclear magnetic resonance imaging technology,the development of nuclear magnetic contrast agents with excellent performance has become a hot spot today.At present,because of its excellent biocompatibility and various physiological functions,polypeptides are firstly applied to aspartic acid,glycine,arginine,lysine and phenylamphetamine by F-moc solid phase synthesis.Synthesis of Bicyclopeptide E-[c(RGDf K)]2 with Targeting Effect by Acid and Glutamate and Reuse of Chelating A gent 1,4,7,10-tetraazacyclododecyl-1,4,7,10-tetraacetic Acid Pair The modified DOTA-E-[c(RGDf K)]2 was prepared by modifying it to possess the ability of chelating metalions,and its yield and purity were calculated.The synthesis process was optimized by comparing different condensation reagents,different feed ratios,and different loadings of the resin,and the use of high performance liquid chromat ography-mass spectrometry,nuclear magnetic resonance spectroscopy,nuclear magnetic resonance spectroscopy,and the ligand DOTA-E-[c(RGDf K)]2 Perform structural characterization.According to the results of the optimization experiments,the most reasonable synthesis process was to select the DIC/HOBt combination for the condensat ion reagent,the amino acid feed ratio was 2.5 times,and the starting amino acid resin was 2-chlorotrityl chloride resin(load 0.98 mm ol·g-1),the target product DOTA-E-[c(RGDf K)]2 was obtained with a purity of 95.4% and a yield of 1.50%.The results of ESI-MS characterization showed that the mass ratio of intermediate Asp-Gly-Arg-Lys(Dde)-Phe-Fmoc was 504.55 [M+2H]2+,1007.3[M+H]+,and single ring c(RGDf K).Mass-to-charge ratio is 384.80[M+2H]2+,768.25[M+H]+,E-[c(RGDf K)]2-Fomc mass-to-charge ratio is 771.05[M+2H]2+,1405.50[M+H]+,and the target product DOTA-E-[c(RGDf K)]2 mass-to-charge ratio is 853.15[M+2H]2+,569.15[M+3H]3+,427.10[M+4H]4+,and theory The molecular weight is consistent.The DOTA-E-[c(RGDf K)]2 nuclear magnetic resonance spectrum and hydrogen spectrum analysis results indicate that the DOTA-E-[c(RGDf K)]2 was successfully synthesized and used DOTA-E-[c(RGDf K)]2 as a ligand for the preparation of targeted contrast agents lays the experimental basis.Through the ligand DOTA-E-[c(RGDf K)]2 synthesized in the previous chapter,using its chelate metal ion function and Gd3+ reaction to form a coordination bond,a targeted magnetic resonance imaging agent Gd3+ was prepared Gd-DOTA-E-[c(RGDf K)]2 was character ized by high performance liquid chromatography and high performance liquid chromatography-mass spectrometry and the yield and purity were calculated.In comparison with DOTA-Gd,a clinical contrast agent,PDTA meglumine injection,Gd-DOTA-E-[c(RGDf K)]2 was measured by relaxation efficiency,tetrazolium salt colorimetric meth od(MTT),and living body mouse MRI.Performance is evaluated.The characterization results showed that the peak retention time of 18.15 min for Gd-DOTA-E-[c(RGDf K)]2 was different from the peak retention time of 16.140 min for DOTA-E-[c(RGDf K)]2;the ESIMS detected Results The results of 930.30[M+2H]2+ and 620.80[M+3H]3+ were consistent with the theoretical values,indicating that the target contrast agent Gd-DOTA-E-[c(RGDf K)]2 was successfully pre pared with a purity of 95.4%.The yield was 56.5%.The relaxation efficiency was measured as the relaxation rate of Gd-DOTA-E-[c(R GDf K)]2 k=9.551 mmol-1·L·s-1,which was 1.84 times that of DOTA-Gd.The results of MTT experiments showed that Gd-DOTA-E-[c(RGDf K)]2 was lower than that of DOTA-Gd.The MRI results of living mice showed that Gd-DOTA-E-[c(RGDf K)]2 could be enriched in the tumor site and the normal tissues and tumor sites of mice.The scan signal intensity ratio is 1:1.6.The experimental results show that Gd-DOTA-E-[c(RGDf K)]2 not only has a targeting effect,but also has better performance in relaxation efficiency,cytotoxicity,and body core magnetic resonance imaging than the clinical contrast agent DOTA-Gd.This study provides a specific preparation method for targeted bicyclopeptide contrast agent Gd-DOTA-E-[c(RGDf K)]2,and studies the relaxation efficiency,cytotoxicity,and living body of Gd-DOTAE-[c(RGDfK)]2 in mice.The MRI imaging results lay a foundation for the development of high-relaxation efficiency,low cytotoxicity,and good performance contrast agents with good tumor stability and tumor targeting in vivo,and have research and application value.