Preparation Of Materials For Early Diagnosis And Real-time Monitoring Of Peritoneal Metastases From Colorectal Cancer

Colorectal cancer（CRC）is a common malignant tumor in the digestive tract.The high incidence of peritoneal metastasis in CRC makes its treatment challenging,and early detection and real-time diagnosis of CRC peritoneal metastasis are crucial for improving patient survival rates and quality of life.Conventional clinical diagnostic techniques,such as X-ray computed tomography（CT）and positron emission tomography（PET）,have certain radiation hazards,and other methods have their own drawbacks,such as low accuracy,low patient compliance,low sensitivity,and low specificity.As a result,early diagnosis and real-time monitoring of peritoneal metastasis have been challenging for clinical practitioners worldwide.Real-time fluorescence imaging and photothermal therapy have gained popularity due to their non-invasive,damage-free,highly specific,and sensitive nature,which allow for in situ,quantitative,and real-time detection of specific tissues and organisms.In this thesis a series of polyethylene glycol-polyamino acid block polymers are designed and synthesized,and graphene quantum dots are incorporated as the fluorescence and photothermal agents to form an integrated diagnostic and therapeutic system.The relationship between polymer block ratios and sequences and molecular self-assembly properties is investigated,as well as the fluorescence and photothermal properties of the composite system.First,polyethylene glycol-polyamino acid copolymers with various block ratios and sequences are synthesized by ring-opening polymerization of L-alanine N-carboxyanhydride（A-NCA）and L-valine N-carboxyanhydride（V-NCA）using aminated monomethyl polyethylene glycol（m PEG-NH₃）and polyethylene glycol（NH₃-PEG-NH₃）as initiators.The effects of different block ratios and sequences on molecular self-assembly properties and performance are discussed,and m PEG₁₁₀-V₂₄ and A₈-PEG₁₃₂-A₈are ultimately selected as the carrier materials for the composite.Second,graphene oxide（GO）is prepared using an improved Hummers method,and graphene quantum dots（GQDs）are prepared by reduction and secondary cutting.The GQDs are modified with various amino acids,and their fluorescence and photothermal properties are compared.L-alanine-modified GQDs（A-GQDs）with a Stokes-shift of 90nm and a photothermal efficiency of 2°C/W·s are chosen as the fluorescence and photothermal materials for the composite.Finally,composite materials of A₈-PEG₁₃₂-A₈,m PEG₁₁₀-V₂₄,m PEG₂₂-A₃V₇,and A-GQDs are prepared,and their structure and performance are characterized,confirming their application prospects in early diagnosis and real-time detection of CRC.In conclusion,we based on amino acid-modified GQDs with polyethylene glycol-poly（amino acid）block copolymers to form composites,endowing the composite material with excellent fluorescence and photothermal properties.The research results of this thesis will provide valuable practical data and theoretical references for the early diagnosis and real-time detection of CRC peritoneal metastasis.