Synthesis And Application Of A New Tumor Vessels Targeting Molecular Probes

PurposePreparetumorimagingagents⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7and¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 against tumor vascular surface receptor Annexin A1（Anxa1）.Evaluate there SPECT or PET imaging efficacy and distribution in Balb/c mice bearing U87 tumors.Methods1.ThemodifiedpeptideGGGRDN-IF7wasmixedwith S-2-（4-isothio）-diethylenetriaminepentaaceticacid（p-SCN-DTPA）or S-2-（4-isothio）-1,4,7-triazacyclononane-1,4-dicarboxylic acid（p-SCN-NODA）（mole ratio1:1.2）and dissolved in DMF.After stirring at 37℃water bath overnight,the mixture was purified by semipreparative HPLC with a linear gradient.2.Thefractionscontainingp-SCN-DTPA-GGGRDN-IF7or p-SCN-NODA-GGGRDN-IF7werecollectedandlyophilized.100μgof p-SCN-DTPA-GGGRDN-IF7 was dissolved in 10μL of DMSO and charged with nitrogen.⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7 was prepared by adding 10μL of hydrochloric acid solution of 1 mg/mL of SnCl₂（pH=4.0）,adding about 111MBq Na⁹⁹Tc^mO₄ and reacting at37℃for 30 min.A 1mL vial was charged with 6μL of a solution of aluminum chloride（2mmol）in 0.2 mol/L pH 4 sodium acetate buffer.Then p-SCN-NODA-GGGRDN-IF7（100μg）in 0.2 mol/L pH 4 sodium acetate buffer was added,followed by cyclotron target water containing 740 MBq ¹⁸F fluoride.The resulting solution was heated at 100°C for 10 min.Thestabilityof⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7or¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 was tested in human serum.Characters of the tracer in vitro were performed in U87 cells.3.The radioactiviy counts were measured afer U87 cells incubated with⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7 or ¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7.The uptake rates were calculated.4.SPECT or PET imaging and biodistribution studies were conducted on BALB/c mice bearing U87 tumors.Results1.⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7 or ¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 can be efficiently produced within 30 min withyield of 95%and 41%,repectively.The radiochemicalpurityof⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7or¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 are greater than 95%.The imaging agent was stable in human serum for at least 2 h with radiochemical purity greater than 92%.2.ThevitroU87cellsuptakeof⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7and¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 can reach highest at 60 min（7.35±1.02%AD and8.95±1.34%AD,respectively）.Excessive GGGRDN-IF7 can significantly reduce the uptake rates.3.SPECT and Micro-PET imaging showed that the tumor clearly visible with good contrast to background.The uptake values of ⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7 were3.56±0.44%ID/g,2.56±0.54%ID/g and 1.98±0.38%ID/g,respectively,at 2h,4h and6h after injection.The uptake values of ¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 were 5.74±1.13%ID/g,3.92±0.78%ID/g,1.30±0.43%ID/g,respectively,at 30min,60 min and120 min after injection.Tumor uptake can be specifically blocked by high doses of p-SCN-NODA-GGGRDN-IF7.Theuptakevaluesof¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 was 0.80±0.21%ID/g at 60min after blocked.4.In vivo distribution of experimental results and SPECT or Micro-PET imaging results are consistent,showing that drugs are cleared faster in plasma.The high liver and kidney uptake showed the drugs were excreted mainly throughliver and kidney.The uptake ratio of tumor to muscle,tumor to blood were 30.20±7.98,36.45±8.87,22.33±4.34 and8.13±2.54,8.53±3.28,6.38±2.25 at 30min,60min and 120min after injection of¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7.Conclusion⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7 and ¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 are simple in synthesis with highradiochemical purity.The radiotracers show favorable characteristics such as ideal biodistribution and good targetability.Therefore,it is a promise tracer for tumor imaging.SPECT and Micro-PET imaging showed the U87 tumor wassignificantlyobseved⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7and¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7 with ideal biodistribution and targeting.Both⁹⁹Tc^m-p-SCN-DTPA-GGGRDN-IF7and¹⁸F-AlF-p-SCN-NODA-GGGRDN-IF7are potential tumor imaging agents.