Establishing Biomimetic Microenvironment For Regulation Of Cell Behavior Towards Tissue Engineering Applications

Cells are embedded within a complex and dynamic microenvironment consisting of the surrounding extracellular matrix(ECM),growth factors,and cytokines,as well as neighboring cells.The local interactions between cells and their surrounding microenvironment can regulate cellular behavior and function.To mimic the native microenvironment of cell,biomaterials with different physical and chemical properties are aiming to explore the in vitro construction of extracellular microenvironment.Understanding the biomaterial-cell interface and designing biomaterials with optimized structure and multifunction have great significance in establishing the extracellular microenvironment and developing the relevant biomedical application.This dissertation will investigate the establishment of biomimetic microenvironment by using variable biomaterials,with the purpose of treating different diseases.We established the different microenvironment created from different materials including gradient hydrogel,agarose,PDMS,and nanofibers.This dissertation aims to demonstrate the interactions between microenvironments and cell behaviors,which will benefit for better designing biomaterials for biomedical applications.The detailed works are as follows:(1)Microenvironment established by gradient hydrogel for three-dimensional(3D)cell culture.We produced gradient hydrogels based on Poly(ethylene glycol)(PEG)hydrogels,which were crosslinked by thrombin-activated FXIIIa.Since this reaction is pH-dependent,acidic gradients generated in the vicinity of an anodized electrode can be exploited to locally inhibit the polymerization.The presented gradient hydrogel enables the simple establishment of 3D hydrogel-based cultures by seeding different cells for different models,such as epithelial cyst formation,neuron model,angiogenesis,and co-cultures.The 3D models established through gradient gel are promising for further research in the treatment of different diseases.(2)Microenvironment established by agarose and PDMS for cardiac tissues and heart-on-a-chip system.First,the 3D pillar electrodes were fabricated by stencil printing of Platinum(Pt)-PDMS paste.Then,we used agarose and PDMS as the base material to get the two different heart-on-a-chip devices.And the seeded cardiomyocytes in the channel formed a 3D microtissue.We successfully measured physical and functional tissue parameters such as beating rate,beating force(related to systolic and diastolic pressure)and electrical propagation speed.Moreover,electrical pacing through Pt-PDMS pillar electrodes promoted expression of cardiac markers indicating functional maturation of the microtissue.And contraction force measurements were done via optical PDMS post deflection measurements.This platform for creating and analyzing in vitro 3D cardiac tissues has the potential to serve as a model system that can help predicting human cardiac drug response by in situ monitoring of biophysical parameters during testing cardiotoxicity or exposure to drugs.(3)Microenvironment established by electrospun nanofibrous for spontaneous osteogenic differentiation of MSCs.In this study,aligned and random-oriented PHBV nanofibrous scaffolds loaded with HA nanoparticles were fabricated through electrospinning technique.The introduction of HA nanoparticles accelerated osteogenic differentiation of MSCs better than PHBV without HA.This study indicates that osteogenic differentiation of MSCs induced on HA-containing PHBV nanofibrous scaffolds involves Wnt/?-catenin,BMP-Smad,and MAPK(ERK1/2 and p38)signaling pathways.Promisingly,the elucidation of interaction between electrospun nanofibrous scaffolds and MSCs provides a guidance for design of desirable biomaterial scaffolds which is essentially useful for the further application in bone tissue engineering and regeneration.