Investigations Of Techniques For Preparation Of Micro-nano Hybrid Patterns On Material Surface

With the development of tissue engineering and regenerative medicine, much attention has been paid upon cell-material interactions. Surface patternning offers an effective way to precisely manipulate chemical composition and topographical properties of surface microenvironments to mimic extracellular matrix (ECM). Surface-patterning techniques have been applied in many fields for simplifying the complicated problems. Micropatterning techiniques have been used to control position and shape etc. of various cells, and provide a platform to explore cell-material interactions on the cellular level. Despite the encouraging advances made with micropatterning techniques, patterns merely on a microscale are insufficient to mimic ECM. For example, integrins are receptors that link ligands in ECM with some specific peptide sequences such as arginine-glycine-aspatate (RGD). These transmembrane receptors mediate cellular interactions with the underlying ECM and form adhesion sites that play an important role in governing many aspects of cellular behaviors such as focal adhesion. An integrin is about 10～12 nm faced to the extracellular side. So, surface pattern at such a nanoscale is much helpful for understanding cell-ECM interactions on a molecular or supermolecular level. Combination micropattern with nanopattern can systematically investigate cell-material interactions on different levels. Furthermore, the so-far patterning technique limited to inorganic substrates, few reports concern fabrication of patterns on soft and wet hydrogels. To study cell-material interactions, patterned surfaces with significant cell-adhesion contrast are required. It is thus important to passivate background. Self-assembly or grafting of poly(ethylene glycol) (PEG) molecules is usually used to resist cell adhesion for its bio-fouling resistance, but PEG molecules can't offer long-term cell resistance. So it is meaningful for studies of cell-material interactions to develop approaches to fabricate appropriate micro-nano hybrid patterns on hydrogel with highly effective cell-adhesion contrast. The main achievements in this thesis are summarized as follows:1 Three approaches for fabricating Au micro-nano hybrid patterns on solid surface were developed. By combination with photolithography, self-assembly of block copolymer, wet etching and plasma etching, we successfully prepared Au micro-nano hybrid patterns. Compared with merely micropatterning and nanopatterning techniques, these three methods can manipulate Au nanoarrays in micro-scale regions. Biocompatibility of the process of preparing patterns and feasibility used in cell-material interactions were confirmed by preliminary cell experiments.2 We have fabricated three novel Au-Pt bimetallic micro-nano hybrid patterns, namely a nanopattern of Au-Pt core-shell particles (Pattern-1), micropatterned nanoarray of Au-Pt core-shell particles and regular Au nanoarray (Pattern-2) and interlaced pattern of Pt microsheet and Au nanoarray (Pattern-3). As patterning techniques are concerned, preparation of Pattern-2 is central. Fabrication of Pattern-1 acts as a pre-technique of generation of Pattern-2, and Pattern-3 is an extension of Pattern-2. The approaches suggested in the present thesis is neither limited to fabricating Au-Pt bimetallic arrays, nor to the demonstrated patterns. The methodology is ready to be extended to generate more hybrid micro-nano-structures designed towards potential applications such as studies of catalysis, spectrum and other biosensor fields besides cell-material interactions.3 Micro-nano patterns of gold on the surface of PEG hydrogel were prepared. The hybrid patterns on PEG hydrogel were obatined through a linker-assistance transferring techinique following preparation of Au micro-nano hybrid patterns on solid surface. The cell-adhesion contrast of the patterned hydrogel surface was confirmed by preliminary cell experiments. Au micro-nano patterned hydrogel was used to manipulate cell location and orientation. We reasonably expect that hybrid micro-nano patterns of metals on the surfaces of polymeric hydrogels might be very powerful for extensive researches in biomaterial and related fields, and then, fruitful results might be obtained via adjustment of the parameters of micropatterns, nanopatterns and substrate rigidity. 4 A micro-nano hybrid patterns of gold functionalized with RGD on PEG hydrogel was prepared. We systemically researched the effect of the sizes of micropattern of micro-nano hybrid patterns on cell adhesion. The data showed that with the increase of the sizes of micropattems, cells were easily to adhere on patterned areas. With the help of micro-nano hybrid pattern of RGD and RGD micropatteming techniques, the effect of projection area on cell adhesion was observed and researched in detail. With the same projection area, more cells adhered on micropattems of RGD than those on RGD-micro-nano patterns. Our results revealed that the amount of RGD sites played an important role in cell adhesion on patterned surface.