Construct Stretchable Electrochemical Sensor For Real-time Monitoring Of Mechanosensitive Cell

Endothelial cells situated at the interface between blood and the vessel wall play a crucial role in mechanotransduction and act as a dynamic,heterogeneous,disseminated organ that possesses vital secretory,synthetic,metabolic,and immunologic functions.Dysregulation of such precise system will result in various kinds of diseases.NO is one of the most important endotheliumderived relaxing factor and play a central role in control of vascular homeostasis.It is of great significance to real-time monitor the NO level from mechanically sensitive cells during defomation because NO generation from cells in mechanotransduction is dramatically influenced by mechanical forces such as strain and shear stress.Electrochemical technique has unique advantages in real-time and in situ monitoring of signaling molecule release from living cells or tissues,due to its high sensitivity,fast response.However,due to the rigidity of metal electrode with a larger value of elastic modulus,current sensors do not possess mechanical compliance during deformation,and thus fail to detect and quantify biochemical signals from biosystems.In addition,it's also a challenge to detect biomarks in vitro models that better mimic the complex structures and functions of real 3D microenvironment.Toward this goal,this thesis aimed at developing stretchable electrochemical sensors for real-time monitoring of biochemical signals from mechanically stretched cells.Some innovative and systematic works are summarized as follows:(1)Separation between individual CNTs during stretching would dramatically increase the sheet resistances,further restricting CNTs film as a stretchable electrochemical sensor.To solve this problem,we developed a facile and versatile strategy to construct CNTs-based stretchable and transparent electrochemical sensors,by binding SWNT with conductive polymer to form composite films.The films of nanometer thickness are produced by coating individual SWNTs with a thin layer of PEDOT followed by vacuum filtration.As a conductive polymer possessing high conductivity,good electrochemical activity,and biocompatibility,PEDOT coating effectively eliminates surface defects and improves electrochemical activity of SWNTs.In addition,PEDOT provides favorable joint connections between individual SWNTs and prevents separation of SWNTs during stretch.As a result,the conductivity,electrochemical performances and stability of composite films are greatly enhanced.(2)We tested the electrochemical performance of the highly stretchable and flexible sensors and results indicated the electrochemical activity was improved by coating and binding SWNTs.The stretchable SWNTs@PEDOT/PDMS electrode showed a sensitive response of NO and the detection limit was calculated to be about 0.75 n M.HUVECs were seeded on the surface of SWNTs@PEDOT/PDMS electrode for detection to test our sensors in real-time monitoring of NO release from mechanically sensitive cells.And we proposed preliminary discussion about the mechanism of endothelial mechanotransduction.(3)In order to construct a natural hydrodynamic 3D microenvironment closer to the real vessel,we builted a devices biomimetic by incorporating a micropatterned stretchable EC sensor into a microfluidic blood vessel-on-a-chip to simulate vascular parameters and monitor at the same time the biochemical signals.In the device,we simulated the in vivo strain magnitude exposed to endothelial cells from hypotensive,normal to hypertensive states.Hence,within this device,the circumferential stretch with different strains exerted on endothelium was recapitulated,and the stretch-induced signaling molecules release from the deformed endothelial cells was simultaneously monitored.According to our results,1)the NO pathway could be only obviously triggered when circumferential strain exceeds a certain threshold,2)circumferential stretches at a normal physiological strain of 10% could effectively activate e NOS to produce NO,3)NO release was observed together with the simultaneous release of ROS when circumferential deformation of cells reached to 18%.In summary,we reported the integration of a flexible sensor into an organ-on-a-chip system.The microfluidic chip was used for mimicking in vivo situations and in-situ monitoring of biochemical signals was achieved by the stretchable EC sensor.This provides a novel and powerful approach to keep gaining insight into the biomechanical response to hypertension at the molecular level.We believe that the strategy combining flexible EC sensor with organ chip will open a new way for lucubrating the mechanisms of vascular diseases.