Design, Preparation And Properties Of Biomimetic Anti-bioadhesive Surfaces

The harm of adverse bioadhesion has been a fundamental problem that has commonfeatures and popularly exists in the research and application areas of biomedical materials,biochemical analysis, bological chemical engineering and antifouling of marine vessels. Innature, many biological surfaces can exhibit an excellent anti-bioadhesive performance. Forinstance, a shark skin can keep marine organisms away from it, a lotus leaf unstained by dirtshows an outstanding self-cleaning effect, phosphorylcholine (PC) or headgroups of a cellouter membrane is inert to bioadhesion, and so forth. The chemical compositions, specificchemical structure and micro-nano structures of these biological surfaces provide perfectbiomimetic templates and ways for constructing anti-bioadhesive surfaces. Judging from thecurrent research ideas, methods and findings involving the anti-bioadhesive surfacesconducted by domestic and foreign scholars, constructing biomimetic surfaces is undoubtedlythe most effective strategy. However, most biological surfaces play a role in the course ofanti-bioadhesion as a part of a complete life system, and thus it is often difficult to build astable anti-bioadhesive surface just by a single means of imitating morphology or chemicalcharacteristics of a biological surface, not to mention a multi-functional biomimetic surface.Based on the above analysis and understanding, and inspired by the anti-adhesive non-smoothsurfaces of plants and animals in nature and the chemical composition and molecularstructures of the cell outer membrane, herein we first put forward a research thought ofconstructing compound biomimetic surfaces with resistance to bioadhesion via a novelmethod involving (a) the combination of the micron-scale structures of biological non-smoothsurfaces and their nanoscale structures producing special wettability, and (b) the combinationof the biomimetic strategies of both the surface morphology and the surface chemistry. Themain research work and results are described below.(1) Using shark skin and grass leaves (Green Bristle grass Herb) as a template,respectively, the biomimetic surfaces with micro-nano hierarchical structures were fabricatedby constructing nanoscale structure producing “lotus effect” on the biomimetic micron-scalestructured surfaces, which was conducted by combining the micro-replication method withthe flame treatment of a surface. The studies indicated that the microstructures on the natural templates can be exactly replicated by means of surface micro-replication, while thenanostructures are difficult to be faithfully replicated. Flame-treatment is an effective methodto construct nanostructures on the biomimetic surfaces prepared via the micro-replication. Theas-prepared hierarchical (micro-nano) surfaces can exhibit super-hydrophobic performance,whose measured water contact angle is greater than150°. And the slip angle for water dropletmerely reaches a limiting value of1°.(2) Inspired by the chemical composition and molecular structures of a cell outermembrane, a few of betaine zwitterionic compounds, zwitterionic silane (SINNS-2),3-dimethyl(3-(N-methacrylamido) propyl) ammonium propane sulfonate (DMAPMAPS), andso on, were designed and synthesized. Then these functional molecules were used to preparechemically biomimetic self-assembled layer and polymer hydrogel layer by means ofmolecular self-assembly and UV curing of organic-inorganic hybrid transition layer bondingtechnology, respectively. Besides, zwitterionic polymer was grafted onto the surface ofbiomimetic shark skin via photo-induced polymerization. So as to form the mucus-likehydration layer with the aid of the electrostatic action between zwitterions and watermolecules. In this way, the prepared surfaces can possess unique compound biomimeticstructures. On this basis, the chemical parameters, morphology and wettability of the preparedbiomimetic surfaces were characterized and analyzed by modern testing techniques. The dragreduction effect of the biomimetic surfaces was preliminarily investigated based on rheometry,the results show that the slip phenomenon of slip phenomenon can occur on the zwitterionichydrophilic surface.(3) The organic-inorganic nanocomposites comprising zwitterionic carboxybetaine silanecopolymer and silica nanoparticles was prepared via an organic-inorganic hybrid technology.Using these nanocomposites as interfacial materials and a glass slide as a substrate, a series ofpolymer-SiO2hybrid coatings with different physical and chemical properties were obtainedby spray-deposition and heat treatment. The influence of the chemical and morphologicalfactors of a surface on its wettability was investigated. Furthermore, the fogging behavior ofthe hybrid coating was measured. The results indicate that the biomimetic surface uniquewettability, or superhydrophilicity in air and underwater super-oleophobicity, can beconstructed by regulating the chemical features and morphology of surface. And such a biomimetic surface can possess good antifogging performance.(4) According to the theories of classical Young’s equation, Wenzel’s equation andCassie’s equations, the effects of the chemical composition and roughness of variousbiomimetic surfaces on their wettability were analyzed and explained, and the conditionsunder which a super-hydrophobic, super-hydrophilic and/or underwater super-oleophobicsurface can be formed were explored and discussed. Owing to the fact that thezwitterion-containing hydrophilic surface can exhibit underwater super-oleophobicity, a newinsight is proposed that the hydration of the hydrophilic groups on the zwitterion-containinghydrophilic surface plays a key role in making it possess underwater oleophobiccharacteristic.(5) The structure-property relationships between the anti-bioadhesive properites ofbiomimetic surface and their physical, chemical properties and microstructures were studiedby a few of bioadhesion experiments including protein adhesion test, bacteria attachmenttest using S. aerues and E. coli as a test strain and algae adsorption tests in the static anddynamic aqueous environment. The following conclusions can be drawn from theexperimental results.(a) The surface with biomiemtic shark skin microstructure cannot exhibit resistance tobioadhesion. On the contrary, a large number of organisms will adhere firmly to thesurface.(b) As a physical barrier, the thin air layer adsorbed on the micro-nano hierarchical structureof the compound biomimetic surface can hinder the attachment of organisms, therebyplaying an important role in resisting bioadhesion. The adsorption of proteins and theother substances on the micro-nano structured surface will drive air away and make the airlayer disappear gradually, thus degrading the durability and stability of itsanti-bioadhesive performance.(c) The PDMS-based surface with low surface energy can exhibit better anti-bioadhesiveperformance than do the PU-based surface with microphase separation structure. Due tothe existence of hydration shell, the zwitterion-containing surfaces imitating the chemicalfeatures of a cell outer membrane, including self-assembly molecular layer, polymeric gel,polymer surface obtained by surface graft polymerization, and hybrid coating, were a novel mimic of the cell outer membrane, and such surfaces often possessed excellentanti-bioadhesion performance.(d) The biomimetic surface with anti-bacterial adhesion property using polymer-SiO2hybridnanocomposites as an interfacial material can be achieved through tailoring the chemicalfunctional groups of the hybrid nanocomposites. The surface SiO2-PCM bearingquaternary ammonium salt group can sterilize bacterial cells and inhibit bacterialreproduction; and the surface SiO2-PCMZ obtained by the alkaline hydrolysis can possessgood anti-bacterial adhesion property, but SiO2-PCMZ will lost its function of sterilizingbacterial cells.