Synthesis And Activity Research Of Series Of RGD Targeting Photosensitizers

Photodynamic therapy(PDT)is a clinically approved modality for cancer treatment.It utilizes an external light source to selectively illuminate the tumor site to activate the photosensitizer at the tumor site,which will activate oxygen molecules to produce singlet oxygen and kill cancer cells.PDT is a localized treatment with little side effects on the body,and it is also expected to increase the patient's anti-tumor ability by activating the body's anti-tumor immune response.For this reason,PDT has been a promising modality for clinical cancer treatment.However,as much as possible to increase the degree of enrichment of photosensitizers at the tumor site is still critical for photodynamic therapy,although it is a localized treatment.By improving the enrichment of photosensitizers at the tumor site,the increase of the concentration of photosensitizer in tumor is beneficial to improve the photodynamic killing ability,which is very helpful for the treatment of large tumors and deep seated tumors.On the other hand,due to the infiltration of tumors into normal tissues,it is difficult to precisely distinguish tunors from normal tissues by selective light irradiation.Improving the selectio:n of photosensitizes to tumor is necessary to further reduce the damage to surrounding normal tissues.Based on this,over decades,a large amount of research has been devoted to the development of a variety of targeted drug delivery systems that effectively deliver photosensitizers,and to enhance the enrichment ability of photosensitizers at tumor sites.For example,the conjugate of photosensitizers and ligands such as antibodies,peptides,carbohydrates and folic acid can effectively improve the biocompatibility and tumor targeting of photosensitizers.Among these ligands,the cyclic RGD peptide has attracted attention due to high specificity to cancer cells,low imruunogenicity,and high tissue permeability.This research consists of two parts.The main contents of first part are as follows:Firstly,a series of RGD-targeted modified photosensitizer compounds cRGDfK-Pyro,cRGDfK-Ce6,eRGDfK-Verteporfin,cRGDfK-Pc3Zn were synthesized;then separated and purified by semi-preparative high performance liquid chromatography(HPLC);Then,the photophysical and chemical properties were studied by UV absorption spectroscopy and fluorescence spectroscopy,and their biological activities were researched at the cellular level and animal level.The feasibility of these compounds for photodynamic therapy was comprehensively evaluated.In terms of photochemical and photophysical properties,the absorption and emission spectra of these compounds in DMSO showed that the photosensitizers are typically non-aggregating and have strong singlet oxygen production ability,indicating that the modification of the ligand does not affect The macrocyclic n system of thephotosensitizers.There are some differences in the absorption spectra in different solvents,which are caused by the difference in properties of the Pyro,Ce6,Verteporfin and Pc3Zn3 but after coupling with the cRGD ligand,they showed an increase in anti-aggregation.hn terms of biological activity studies,cytotoxicity experiments showed that cRGDfK-Pyro,cRGDfK-Verteporfin had high cell killing power(IC50=374.8/719.6 nM)in these compounds.The main purpose of the cell flow experiment is to study the entry of drugs into cells.The results showed that cRGDfK-Pyro enters the cells more than other photosensitizing drugs.In vivo imaging is mainly to observe the enrichment and metabolism of drugs in mice.cRGDfK-Ce6,cRGDfK-Pc3Zn is relatively weak in water solubility and affinity to tumor cells,thus has a fast metabolism.eRGDfK-Verteporfin accumulates mainly in the liver and kidney,while eRGDfK-Pyro has a certain enrichment in the tumor site of mice.On this basis,the compound cRGDfK-Pyro is selected preferentially.The cRGDfK-Pyro conjugate improved the solubility of Pyro to some extent.The in vivo imaging of the animal also showed that the coupling of the cyclic peptide RGD with Pyro increased the enrichment ability of Pyro at the tumor site,but the enrichment effect was still not ideal.Therefore,this thesis carried out the second part of the study:the effect of multiple RGD peptides on Pyro enrichment.First,we designed a single RGD,a dimeric RGD and a trimer RGD coupled Pyro conjugates.Their optical properties,including UV absorption spectroscopy,singlet oxygen quantum yield determination and fluorescence excitation and emission spectroscopy,were studied.The results showed that the linker and cRGD(cRGDfD)ligand had no significant effects on the optical properties of Pyro.Finally,their tumor accumulation ability was evaluated by in vivo distribution experiments.The results showed that multimerization significantly increased the enrichment of the drug at the tumor site.Pyro-2cRGD and Pyro-3cRGD significantly improved the tumor enrichment and selectivity of Pyro compared with Pyro-cRGD,but Pyro-3cRGD was the best.This strategy is expected to be used to prepare novel anti-tumor photodynamic drugs with high tumor enrichment.