Pegylated Study Of Fischer Carbene-derived Carbon Monoxide Release Molecules

The challenge of synthesizing therapeutic carbon monoxide releasing molecules(CORM)is to introduce the water-soluble ligands into the metal carbonyl core and construct the leading structure with controlled CO-releasing rate,low cytotoxicity and decent water solubility.Herein,we synthesized a series of Fischer Carbene CORM with introducing the non-ionic polyethylene glycol tether(PEG-FcCORM),in which Fischer Carbene carbonyl unite carry five CO and amino acid serve as a bridge.In this paper,twenty-four PEG-FcCORM were synthesized and fully characterized.The single crystal structure of compound 2a was analyzed by X-ray single crystal diffraction.The CO-releasing under physiological condition were investigated by myoglobin assay,indicating some CORMs released CO via hydrolysis,and all CORMs can release CO via UV radiation(365 nm).The water solubility experiments showed that the PEGylation can significantly improve the water solubility of Fischer Carbene.The cytotoxicity experiments showed that PEG-FcCORM were relative non-toxic,shed light on the potential of its clinical application.This thesis is summarized as the following:1.Three types of Fischer Carbene carbonyls complexes,1a-9a,1b-4b with a variety of amino acid mPEG esters ligands pentacarbonyl chromium or molybdenum Fischer Carbene complexes and lc-6c were designed and synthesized with different peptide amino acid mPEG esters ligands.Water soluble ld-5d were prepared by introducing amino acid mPEG esters ligands.All PEG-FcCORM have been characterised by 1H NMR,13C NMR,FT-IR,ESI-MS and Elemental Analysis.The structures of these CORM are consistent with expectation.To determine the molecular structure,we also analyzed the single crystal structures of compound 2a.2.The water-solublility of PEG-FcCORM were investigated.To assess the water solubility of CORM,the oil-water partition coefficient of PEG-FcCORM was determined by shake flask method.The results showed that the water solubility of PEG-FcCORM depends on the amino acid and mPEG in the order of Glycine>tyrosine>leucine>phenylalanine.PEG tether significantly improved the water-solubility of PEG-FcCORM.3.The carbon monoxide release performance of PEG-FcCORM were determined comprehensively.The CO release of PEG-FcCORM were measured in vitroaccurately by myoglobin assay.The experimental results showed that water soluble Glycine,tyrosine(la,3a,4a,6a,9a,1b,3b,lc,4c)and macromolecular amino acid mPEG esters ligands Fischer Carbene carbonyls complexes(1d-5d)hydrolyzed spontaneously and released CO.While low hydrophilic PEG-FcCORM were stable in the physical condition and did not released CO,showing the potential as Photo-CORM.Undering the radiation of 365 nm UV light,PEG-FcCORM release CO smoothly(2a,5a,7a,8a,2b,4b,2c,3c,5c,6c).4.The biological activity of PEG-FcCORM were evaluated.The cytotoxicity of la and 2a were determined with MTT assay.The experimental results showed that IC50 of RAW264.7 and MNK45 cells were 238.5 ?M/L and 242.6 ?M/L for la,respectively;IC50 of RAW264.7 and MNK45 cells were.201.7 ?M/L and 224.5 ?M/L for 2a respectively.The toxicity of PEG-FcCORM are relative low,basically suitable for the safety requirements of therapeutic CORM.5.The photolytic degradation pathway of PEG-FcCORM were investigated systematically.The 365 nm ultraviolet light initiated the degradation of la,which was followed by FT-IR and 1H NMR.ESI-MS identified few intermediates during the photolysis process.The mechanistic experiments showed that the CO-releasing of PEG-FcCORM was the dissociation of the carbonyl ligands,in which each carbonyl leave as CO gas,and metal fragments and polyethylene glycol glycine esters were the degradation products.