Synthesis Of ¹⁸F Labelled Mini-PEG-RGD Dimer (¹⁸F-FPRGD2) And Radiosynthesis And MicroPET Imaging Of 2-¹⁸F-A-85380

[Background]Positron Emission Tomography(PET) is a medical imaging technology which uses a PET camera to measure the concentration and movement of a radiotracer labelled positron(¹¹C. ¹⁸F,¹⁵O,¹³N) in the living body.This technology has a very important role in cancer and cardiovascular diseases for their diagnosis and treatment monitoring.Current PET imaging agents,such as ¹⁸F-FDG and ¹¹C-Acetic acid,have well-known limitations for accurately diagnosing for some diseases,which motivate researchers to develop new PET imaging agents so that we can get a new specific tracer to make up the limitations.In recent years, the application of biologically active peptides labelled with positron-emitting nuclides has emerged as a useful and interesting field in nuclear medicine.Small synthetic receptor-binding peptides are currently the preferred agents over proteins and monoclonal antibodies for diagnostic imaging of various tumors.Due to the smaller size of peptides, both higher target-to-background ratios and rapid blood clearance can often be achieved with radiolabelled peptides.Hence,short-lived positron emission tomography(PET) isotopes are potential candidates for labelling peptides.Among a number of positron-emitting nuclides,fluorine-18 appears to be the best candidate for labelling bioactive peptides by virtue of its favorable physical and nuclear characteristics.The major disadvantage of labelling peptides with ¹⁸F is the laborious and time-consuming preparation of the ¹⁸F labelling agents.In recent years,various techniques have been developed,which allow efficient labelling of peptides with ¹⁸F without affecting their receptor-binding properties.Moreover,the development of a variety of prosthetic groups has facilitated the efficient and site-specific labelling of peptides with ¹⁸F.The ¹⁸F-labelled peptides hold enormous clinical potential owing to their ability to quantitatively detect and characterise in a wide variety of human diseases.Recently,a number of ¹⁸F-labelled bioactive peptides have shown great promise as diagnostic imaging agents.One of the most promising ¹⁸F-labelled bioactive peptides is ¹⁸F-labelled RGD peptides,which contain arginine-glycine-aspartic(RGD) tripeptide sequence. Integrinαvβ3 plays a significant role in tumor angiogenesis and is a receptor for the extracellular matrix proteins with the exposed arginine-glycine-aspartic(RGD) tripeptide sequence.lntegrinαvβ3 is expressed at low levels on epithelial cells and mature endothelial cells,but it is overexpressed on the activated endothelial cells of tumor neovasculature and some tumor cells.The highly restricted expression of integrinαvβ3 during tumor growth, invasion,and metastasis presents an interesting molecular target for both early detection and treatment of rapidly growing solid tumors.In the past decade,many radiolabelled linear and cyclic RGD peptide antagonists have been evaluated as the integrinαvβ3 targeted radiotracers.Significant progress has been made on their use for imaging tumors of different origin by positron emission tomography(PET) in several tumor-bearing animal models.[Objective]This research is to synthesize the N-succunimidy-4-¹⁸[F]Fluorobenzoate(¹⁸F-SFB), which is one of the best prosthetic groups for the ¹⁸F labeling of bioactive molecules,using the modified Chemistry Process Control Unit(CPCU).The ¹⁸F-SFB was treated properly and used to label mini-PEG-RGD peptide.[Method]After the Chemistry Process Control Unit(CPCU) was modified,I synthesized the N-succunimidy-4-¹⁸[F]Fluorobenzoate(¹⁸F-SFB),which was used as the prosthetic groups for the ¹⁸F labelling of biomolecules like proteins,mono-antibodies and peptides,with the ethyl-4-trimethyammoniumbenzoate-triflate as the precursor.And the radiochemical purity and specific radioactivity of the product were measured by High Performance Liquid Chromatograph(HPLC).The mini-PEG-RGD was labelled with ¹⁸F-SFB in the same condition using borate buffer solution or DMSO as solvent.The reaction solution was tested by HPLC and final products were separated by semi-preparative chromatographic column.[Results]The decay-corrected radiochemical yield of ¹⁸F-FBA was 80%±5%(n=4) while ¹⁸F-SFB was 25%±5%(n=5) within 100 min total reaction time using the one-pot method.The radiochemical purity was around 99%by the analytical HPLC.As contrast,when the two-pot method was used,the decay-corrected radiochemical yield of ¹⁸F-FBA was 80%±5%(n=4) while ¹⁸F-SFB was 40%±5%(n=20) within 80 min total reaction time. DMSO was not suit for the reaction solvent during the ¹⁸F labelling process of mini-PEG-RGD in the condition studied.As lack of the required equipment for purification of final product,we did not get the purified expected product.The retention time for ¹⁸F-FPRGD2 was about 18min under the same HPLC condition as analysis of ¹⁸F-SFB.[Conclusion]¹⁸F-SFB can be conveniently synthesized with modified CPCU and the labelling yield was stable.The radio-purity was more than 99%,which was easily used for the labelling of bioactive compounds.The analysis for the labelling reaction solution of two methods showed that the borate buffer solution was suit for as reaction solvent. [Background]In recent years central nervous system receptor imaging studies are the most attention research field in nuclear medicine and neurology.Nicotinic Acetylcholine Receptors (nAChRs) imaging agents are one important kind of new tracers,nAChRs are widely distributed throughout the central and the peripheral nervous system,where they modulate several central nervous system functions including neurotransmitter release,cognitive function,anxiety,analgesia and control of cerebral blood flow.In the brain,a major subtype of nAChRs is composed of theα₄β₂ subunit combination.Density of this subtype has been shown to be decreased in patients with neurodegenerative disease,such as Alzheimer's disease and Parkinson's disease,schizophrenia and epilepsy.We can further research the function of nAChRs via PET receptor imaging technology,which can help us explain the mechanism of diseases related to nAChRs.It also plays a key role in early diagnosing these diseases and monitoring the treatment.[Objective]Synthesize the 2-¹⁸F-A-85380 using the modified Chemistry Process Control Unit (CPCU).Measure the radiochemical purity and specific radioactivity of the final product and evaluate its feature in animal brain with MicroPET.[Method]After the Chemistry Process Control Unit(CPCU) was modified,I synthesized the 2-¹⁸F-A-85380 with the Me₃N⁺-Boc-A-85380.CF₃SO₃ as precursor.And the radiochemical purity and specific radioactivity of the product were measured by High Performance Liquid Chromatograph(HPLC).After the tail vein injection of 2-¹⁸F-A-85380,the rat was scanned with MicroPET to evaluate the feature of this tracer in animal brain.[Results]The decay-corrected radiochemical yield of 2-¹⁸F-A-85380 was 50%±5%(n=6) within 45 min total reaction time.The radiochemical purity was around 99%-by the analytical HPLC. The specific radioactivity was 0.35±0.02 pBq/g.MicroPET imaging study showed that in the thalamus,which is rich of nAChRs,2-¹⁸F-A-85380 concentration was significantly higher than ther tissues.[Conclusion]2-¹⁸F-A-85380 can be conveniently synthesized with modified CPCU and the labelling yield was stable,the MicroPET imaging result indicates that 2-¹⁸F-A-85380 can be suitable for clinical translation.