Micropatterned Electrospun Nanofibers:Fabrication,Characterization And In Vitro Cell Responses

The interaction between cells and materials and its internal molecular mechanism was a basic scientific issue of tissue engineering and regenerative medicine.Past research has shown that cells behaviors were influenced by many factor of materials itself,so it was hard to define how a specific factor affect cells behavior.Micro patterning technology that appeared in recent years provided a way to have an exact control of surface chemical constitute,topography structure and mechanical property of materials.By this way,people could mimic extracellular matrix and micro environment in microstructure and then study the mechanism how the defined factor affected cells behavior,such as adhesion,proliferation,migration,differentiation and apoptosis.Electrospinning as a convenient technology to obtain continuous nanofiber has been widely used.Electrospun nanofibers have high surface to volume ratio and are similar to natural extracellular matrix and electrospinning that using biocompatibility materials to obtain nanofibers was a common scaffold material preparation in current tissue engineering and regenerative medicine.In this paper,Designed electrospun nanofibers were fabricated by integrating electrospinning with micropatterning technology,by electrospinning,we can change alignment and composition of nanofibers,by micropatterning,we can control shape and size of micropattern,,by this way,a series of materials that structure and materials could be control in micro/nano scale were fabricated.We also have preliminarily study of the cell responses to such materials.The main achievements in this thesis are summarized as follows:(1).Traditional electrospinning process was used to obtain random and aligned poly(ε-caprolactone)(PCL)and poly(L-lactic acid)(PLLA)nanofibers successfully and agarose hydrogel stamps contained micro pattern feature was fabricated by soft lithography.After soaked in relevant solvent,agarose was contacted with nanofibers to fabricated pattern PCL nanofibers and PLLA nanofibers.What’s more,more complex hierarchical microstructures can be fabricated through multiple electrospinning and microcontact patterning.(2)Patterned nanofibers were further characterized by fluorescence microscopy and energy dispersive X-ray spectroscopy(EDX).PCL nanofibers that contacted with agarose formed coalesced membrane and that didn’t contact with agarose was partly coalesced.PLLA nanofibers that contacted with agarose only exposed glass surface and that didn’t contact with agarose was still nanofibers without coalesced.In order to explore how two different patterns fabricated,we compare the speed of diffusion of pure solvent on two different nanofibers and found that high diffusion speed let PCL nanofibers was partly coalesced while PLLA nanofibers was still nanofibers for its low diffusion speed.Also,High solvent concentration let PLLA nanofibers remove while low solvent concentration let PCL nanofibers form membrane on the area that contacted with agarose.The fluorescence images of agarose stamps after microcontact printing are smooth and distributed evenly on the contacted surface of hydrogel stamps which mean the removal coalesced membrane didn’t enter into the inside of agarose.(3)Preliminary cells characterization were proceed on two different pattern nanofibers,The results show as follows: at the nanoscale,elongated cells with an orientation parallel to the nanofibers while randomly oriented cells without obvious cell alignment are distributed at the contacted area;at the micro scale,by control the scale of pattern,we can control cells growth of designated area.After all,by control micro/nano structures of material surface,cell growth could be affected,which provide ideas to design tissue engineering scaffold in the future.