Construction,Properties And Applications Of Host-guest Supramolecular Fluorophores

Small molecule fluorescent probes based on organic fluorescent dyes have the advantages of simple synthesis,high sensitivity,great selectivity and visual detection,and have been widely used for the non-destructive detection of biological molecules in cells and in vivo.However,most conventional fluorescent probes developed so far after injection into living bodies are easily and rapidly captured by the organs of the reticuloendothelial system,mainly the liver and spleen,and cleared from the blood,which hinders the precise targeting and efficient delivery of fluorescent probes to other organs and tumor lesions.Supramolecular chemistry refers to the integration of two or more molecules under non-covalent bonding weak interaction forces to form complex ordered and functionally specific molecular assemblies,which have now attracted widespread interest in a variety of fields including chemistry,physics,materials and biomedicine.In particular,fluorescent diagnostic probes constructed based on macrocyclic hosts can effectively overcome some inherent limitations of traditional diagnostic reagents,such as improved water solubility,biocompatibility and stability,while also promoting optical performance and therapeutic efficacy.How to make full use of the features and advantages of the host-guest strategy to design and construct novel supramolecular fluorophores for regulating the probe’s own in vivo metabolic pathway,improving the optical properties of the probe,and applying them to the efficient targeting and specific imaging and treatment of focal sites in mice is the main aim of this thesis.To address the problems that conventional fluorescent probes are easily captured by the organs of the reticuloendothelial system in vivo and hinder the targeting and delivery of lesions,this thesis designs and cconstructs a series of supramolecular fluorophores with excellent optical properties that can regulate the biometabolic pathway of the probe,and applies them to live mouse imaging,kidney function detection,tumor imaging and surgical navigation.The details are as follows.1)In Chapter 2,supramolecular fluorescent dyes and probes based on macrocyclic monovalent assemblies with excellent optical properties were constructed with the"adamantane-cucurbit[7]uril"interaction as the main driving force.A series of diadamantane modified heptamethanocyanine dyes were firstly synthesized,and further supramolecular compounds were constructed by host-guest interactions with cucurbit[7]uril.The experimental results demonstrated that the host-guest assembly strategy could significantly improve the solubility and fluorescence brightness of heptamethocyanine dyes in the aqueous solution.Meanwhile,the inclusion ratio（2:1）and the binding constant of the host-guest inclusion(K_a=2.48×10⁶ M^-1)were obtained.Subsequently,the in vivo organ enrichment of supramolecular fluorescent dyes was explored and it was confirmed that supramolecular dyes based on the macrocyclic monovalent assembly of cucurbit[7]uril somewhat alter the original hepatic metabolic pathway of the dye and can be cleared by the kidney.In addition,high signal-to-noise imaging of endogenous NO in inflammatory regions of mice was achieved using the screened supramolecular NO probe NOOMe@CB[7].This work provides a novel approach to the design of renal clearance supramolecular activated fluorescent probes capable of being used for biosensing and imaging.2)In Chapter 3,to further optimize the in vivo metabolic pathway of the supramolecular fluorescence system while enhancing the optical properties of the fluorophores and the stability of the host-guest inclusion complex,we developed supramolecular fluorophores based on a multivalent assembly strategy.Firstly,we have synthesised a family of modular cyanine dye-like multivalent assemblies of guests with different emission wavelengths（from the visible to the near infrared region）.The optical properties,complexation constants,chemical stability and serum protein binding ability of the cyanine-polycyclodextrin supramolecular fluorophore were investigated.It was found that the multivalent host-guest assembly strategy could effectively improve the optical properties of the cyanine dyes,including increasing the solubility of the fluorescent dyes in physiological environments,enhancing the absolute fluorescence quantum yield of the fluorescent dyes in the aqueous solution（the absolute fluorescence quantum yield of bcy3A@CDP up to 74%）,improving the chemical stability of the fluorescent dyes and avoiding the binding of the fluorescent dyes to serum proteins.Furthermore,the multivalent host-guest assembled supramolecular fluorophores have dramatically enhanced affinity(the complexation constants of bcy7A@CDP can reach10⁸ M^-1)compared to the host-guest inclusion complexes constructed based on monomeric cyclodextrins.Subsequently,the superiority of the multivalent assembly and the biocompatibility of the supramolecular fluorophores were explored.3)In Chapter 4,we first demonstrate that the multivalent assembly strategy proposed in the previous chapter can effectively overcome the problem that traditional lipid-soluble organic probes are easily captured by the liver,resulting in poor targeting to non-liver organs,and demonstrate that the supramolecular probe ICGA@CDP can be metabolized through renal tubular secretion and reabsorption by in vivo metabolism comparison experiments and drug inhibitor experiments.Then,utilizing the supramolecular probe ICGA@CDP renal tubular clearance,the probe was applied to imaging renal injury induced by different concentrations of cisplatin and to monitoring early renal function at different times of cisplatin induction.Compared to clinical bioindicator methods,both ICGA@CDP-based optical imaging analysis and online urinalysis enable early imaging detection of cisplatin-induced kidney injury.4)In Chapter 5,inspired by the ability of the supramolecular fluorescent probe ICGA@CDP to escape capture by the organs of the reticuloendothelial system and metabolized by the renal tubules,this chapter investigated its blood circulation time and tumor enrichment capacity.The experimental results showed that ICGA@CDP had a significantly prolonged blood circulation time（about 3.5 hours longer half-life）compared to the small molecule fluorescent probe indocyanine green（ICG）.In addition,ICGA@CDP has an excellent signal-to-noise ratio for NIR-II imaging and circumvents the disadvantage that conventional NIR-II fluorophores are prone to fluorescence quenching under physiological conditions.Subsequently,utilizing the long blood circulation time of ICGA@CDP,we successfully applied the probe ICGA@CDP for high signal-to-noise imaging of subcutaneous tumors,orthotopic breast cancer,peritoneal metastases and orthotopic colon cancer of mice,while accomplishing precise resection of subcutaneous tumors and orthotopic breast cancer under the guidance of NIR-II fluorescence,demonstrating potential clinical applications and translational value.