Silk Fibroin Micro-structures:from Design To Applications

Silk fibroin,as a general natural material,has great advantages based on its unique properties on mechanical strength,optical properties,biocompatibility and controllable degradation.Based on its great universality,high efficiency on constructing,low energy cost and environmental friendly,silk fibroin has intriguing lots of researchers digging on their structures and applications.With the continuous development of related technologies,precise spatial patterns and micro and nanostructures of proteins have widespread applications in tissue engineering,bioelectronics,photonics,and therapeutics.However,the balance of high resolution and complex structure means great challenges.One of the main problems is the technologies for making precise protein patterns.To date,micro-architectures of silk have been formed using techniques such as imprinting,molding via soft-lithography,embossing and inkjet printing,and these techniques usually need high temperature and pressure or expendable molding masters.Photolithography,as one of the common micro-fabrication methods which can provide an option for rapid and direct fabrication of complex features with high fidelity,has little urse on the patterning of fibroin protein.On the other hand,since the gelation of protein were determined by the self-assembly process at mesoscale,inducing this process by adding other component with self-assembly property,to achieve a co-assembly structure,like photonic crystals,is also an intriguing issue.Thus,extending optical and self-assembly technologies for fibroin micro-fabrication is an important and challenge task.This paper introduces one photolithography method for fibroin,that is creating light-induced fibroin gelation with non-covalent bond.Besides,the possibility of co-assembly process of polystyrene nanoparticles and fibroin protein at different conditions were also studied.And finally,we determined the cell toxicity for the micro-patterned fibroin and made some demos for the integration of functional protein patterning.The main achievements are summarized as follows:1.Development of fibroin micro-manufacture photolithography technology via non-covalent self-assembly process.2-nitrobenzaldehyde(2-NBA),as a photosensitive super-molecule,can release protons when activated by ultraviolet light.By adding some 2-NBA into amorphous fibroin films,the pH of water blocked by the fibroin can be declined under the isoelectric point of silk fibroin by UV-light.In this way,when the fibroin films meet water,proteins will assemble at the domains with less pH degree,while others dissolved by water.Thus,micropatterns under 10?m was achieved.2.Development of technologies for fabricating silk fibroin inverse opal structure by using colloidal nanoparticles as mold and investigating the possibility of co-assembly system,such as polystyrene nanoparticles and silk fibroin.Here,we compared two similar systems:TEOS-polystyrene nanoparticle binary system and fibroin-polystyrene nanoparticle binary system.Then,we studied the possible conditions for fibroin-polystyrene binary system,and compared the silk fibroin inverse opal structures manufactured from co-assembly technology and traditional molding methods.3.Determining the cell toxicity of silk fibroin and its possibility for functional modifying,communicating its potential applications as a memristor by adding nanoclusters.First of all,we cultured the cells onto the fibroin patterns to determine toxicity and cell orientation of fibroin micro-structure.Secondly,we integrated fluorescent molecule,Rhodamine B,into silk micropatterns to determine the possibility of multifunctional modifying.Finally,we measured the iv curves of fibroin films,which sprawled onto the ITO glasses and doped BSA-Ag clusters,to determine whether fibroin films have the possibility to make memristor.