The Organic Macromolecules-initiated In Situ Fabrication Of Inorganic Materials With Biomedical Functions

With the increasing demands of high-performance materials,the development of new materials with excellent properties has become one of the most fascinating fields.The organic/inorganic composite materials exhibit good designability and functional diversity,thus the investigation of novel organic/inorganic composite materials has become an important way for the exploring of new materials in recent years.The approach using organic macromolecules as templates for in situ deposition of inorganic materials provides the molecular level reactions between the organics and the inorganics to regulate the size,shape and distribution of inorganics with a very stable interaction.In this work,we fabricate two kinds of composites,poly[2-(dimethylamino)ethyl methacrylate](PDMAEMA)/silicon oxides and nanocrystalline cellulose(NCC)/silver nanoparticles(AgNPs)by depositiong silicon oxides and AgNPs in situ on the templates of PDMAEMA and NCC respectively.The PDMAEMA/silicon oxides are used to modify the surface of materials to endow hydrophobic substrate with hydrophilic performance and to encapsulate enzymes for fabrication of immobilized enzymes.The NCC/AgNPs are applied to the glucose detection and antibacterial agents.Materials including polystyrene plates,polystyrene channels,polystyrene fibers and gauze fibers,are successfully modified with PDMAEMA through layer-by-layer(LbL)self-assembly and atom transfer radical polymerization(ATRP)techniques,followed by in situ silicon oxides deposition,which indicates the universality of this method for materials with different morphologies and different chemical compositions.Taking the PDMAEMA modified polystyrene plates as templates,we evaluate the coverage area,thickness,silicon content and stability of the silicon oxides deposition with three kind of silicon sources including tetramethoxysilane,3-aminopropyltrimethoxysilane and 3-mercaptopropyl trimethoxysilane(MPTMS)at pH 5.8 or 7.2.We get the best silicon oxides deposition with uniform coverage,moderate thickness and the best stability on the polystyrene substrate by using MPTMS as silicon source at pH 5.8.The mechanism of enzyme immobilization is also discussed by comparing the activities of adsorbed and co-deposited enzyme.The results prove that the majority of the immobilized enzyme is encapsulated within the silicon oxides.The contact angles between water and polystyrene plates modified by the silicon oxides are smaller than those on the unmodified ones,which confirm that the hydrophilization of polystyrene plates can be achieved simply by the surface modification with silicon oxides.Auto-injection of dye solution and biological samples are achieved after the coating of silicon oxides on the channels of polystyrene microfluidic chips.Further,we make efforts for the dual readouts of one sample by immobilizing glucose oxidase and cholesterol oxidase in different analysis regions of microfluidic chips and in virtue of a smart-phone equipped with color scanner software.Moreover,we successfully get standard curves with good linear range by using glucose and cholesterol solutions diluted by PBS.However,for the real blood samples,due to the difference between PBS and serum,the standard curves and sample readouts do not match well.To disperse polystyrene fibers in water for a uniform modification,we collect the electrospun polystyrene fibers in the aqueous solution of ethanol.With the grafting of the PDMAEMA on the surface of fibers,laccase is encapsulated with silicon oxides derived from MPTMS.As the protection of the silicon oxides,the immobilized laccase works more stable in the condition with extreme acid,high temperature or existence of proteinase compared with the free enzyme.The glucoamylase is also encapsulated on the PDMAEMA modified surface of the gauze fibers.As the catalytic deposition of silicon oxides,the speed of enyzme immobilization is very fast.The surface of gauze fibers is almost fully covered by the deposited silicon oxides after 45 min.In addition,the catalytic activity of immobilized glucoamylase is tested repeatedly for 100 cycles' reuses during 3 months,and 93%of the initial activity was kept in the immobilized glucoamylase.These results indicate that the PDMAEMA/silicon oxides-encapsulated enzymes have an excellent reusability.Nanocrystalline cellulose(NCC)can serve as the substrate,allowing glucose to reduce Tollen's reagent to produce silver nanoparticles(AgNPs)in situ on the surface of NCC at room temperature.The generation of AgNPs is affected by the factors such as the concentrations of silver ions,NCC and glucose,as well as the different reaction temperatures according to the investigation by orthogonal experiment design.The NCC plays an indispensable role in the generation of AgNPs at room temperature as AgNPs is not produced at room temperature without the addition of NCC.Based on the facts that the concentration of glucose determines the concentration of AgNPs,which linearly affects both the color and the absorbance at 410 nm of the product solutions,the AgNPs with NCC are applied for the development of a visual,quantitative,non-enzymatic and high-sensitive assay for glucose detection.This assay is also used for monitoring the concentration of glucose in both human serum and culture medium during cell culture.Compared to the conventional method based on the glucose oxidase(Roche),the analysis developed here has a wider linear range(0.116 ?M-0.4 mM)and lower detection limit(0.116 ?M)without any enzyme involved in.For the antibacterial activity,the minimal inhibitory concentration of the generated AgNPs with NCC is much lower than that of commercial AgNPs,possibly due to the good dispersion of AgNPs with the presence of NCC.As NCC exhibits unique advantages including green,stable,inexpensive,and abundant,the NCC-based generation of AgNPs may find promising applications in clinical diagnosis,environmental monitoring,and the control of bacteria.In summary,this thesis systematically studies the fabrications and applications of PDMAEMA/silicon oxides and NCC/AgNPs composites,in which silicon oxides and AgNPs deposit in situ on the templates of PDMAEMA or NCC.PDMAEMA/silicon oxides are used to hydrophilia-modify the surface of polystyrene and to achieve the auto-injection of hydrophilic biological samples in the polystyrene channels of microfluidic chips.In addition,benefited from the mild preparation conditions,PDMAEMA/silicon oxides-encapsulated laccase and glucoamylase have very stable activity.Utilizing the surface plasmon resonance induced absorbance of AgNPs at 410 nm,we detect glucose based on the NCC/AgNPs generation.Furthermore,the NCC/AgNPs show better antibacterial activities than pure AgNPs.