| Cellular recognition is essential for disease diagnosis and treatment.Membrane proteins are functional proteins present on the surface of cell membranes that mediate communication between cells and the external environment.The expression of membrane proteins is closely correlated with cell type and thus are important biomarkers of cell recognition.In addition,membrane proteins have both biological functions,and most of the cell biological behaviors such as cell migration,proliferation,communication and apoptosis are controlled by signal transduction activated by membrane proteins.The rich variety of membrane proteins on the cell surface makes the correspondence of a single membrane protein with a specific cell inadequate.Based on the biomarker properties of membrane proteins and their biological functions,responding to multiple membrane proteins can be used for both accurate cellular identification and provide opportunities for cellular regulation.DNA molecules have attracted much attention in the study of membrane proteins because of their strong recognition ability,biocompatibility,design flexibility and labeling diversity.However,membrane proteins exist in specific locations,embedded in the cell membrane in contact with the internal and external environment.Simple DNA strands are susceptible to digestion and degradation in both the internal and external cellular environments,leading to false signals and limiting regulatory effects.DNA nanostructures are assembled from highly programmable DNA strands with enhanced rigidity and resistance to degradation,allowing the preparation of one-dimensional two-dimensional and three-dimensional structures and grafting of recognition sequences for analysis.The stability,ease of synthesis and component integration of DNA nanostructures can be used to cellular recognition and regulation based on membrane proteins,providing new ideas for the diagnosis and treatment of related diseases.In this dissertation,we constructed multiple membrane protein responsive DNA nanostructures,realized specific recognition of target cells through the detection of multiple membrane proteins,and realized effective regulation of cells through the regulation of the relative position of membrane proteins,which provided ideas for developing new strategies for cancer cell diagnosis and treatment.This dissertation is divided into three chapters:Chapter 1 is an introduction,which outlines membrane proteins and their research significance,traditional detection methods for membrane proteins and novel aptamer-based detection methods for membrane proteins,the development of DNA nanostructure and its applications in biosensing,and introduces the work done in this thesis.In Chapter 2,a folding DNA triangular prism is constructed that can respond to both human epidermal growth factor receptor 2(HER2)and the transmembrane mucin 1 oncoprotein(MUC1),two membrane proteins whose co-expression promotes tumor cell proliferation and migration.When the two receptors are both expressed on cell membrane,the DNA prism can recognize them in "AND" logic manner via its extended arm sequences.In this process,the DNA prism becomes folded,inducing the proximity of fluorescence donors and receptors.An enhanced fluorescence resonance energy transfer(FRET)can be observed on the cell membrane.This also avoids the interference of false positive signals.The folded DNA prism is further internalized into cells by HER2,move relatively easily in the intracellular microenvironment and significantly shorten the time to reach the lysosome.The folded DNA prism show faster regulation of apoptosis induction and reduced cell migration compared to unfolded DNA prism.In Chapter 3,a dimer DNA tetrahedron nanostructure contains two tetrahedrons and can respond to both HER2 and nucleolin(NCL)proteins on the cell membrane.The interaction of overexpressed NCL with HER2 can activate the HER2 signaling pathways and promote tumor cell growth.Through aptamer recognition and binding of two membrane proteins,the DNA strand labeled by quenched groups is replaced from the structure,causing fluorescence recovery and realizing the recognition of target cells.And this probe can also inhibit the activation of HER2 and reduce the viability of HER2-positive tumor cells by blocking the interaction between the two proteins through the steric hindrance of the structure itself. |
