Surfaces Modified With Amphiphilic Diblock Copolymers And Their Interactions With Protein And Cell

Protein adsorption on the material surface is a common but complex phenomenon. The type and amount of adsorbed proteins on the surface have a decisive impact on the biocompatibility of a given material and the propagation of microorganism on the surface. Thus, in the biomedical and marine fields, it's an important task to design the low protein adsorption materials which could avoid organism adherence. Diblock copolymer grafts covalently attached to surfaces have attracted considerable attention because of their special structure and novel properties.In this dissertation, a novel anti-biofouling surface based on an amphiphilic diblock copolymer was introduced by combining the hydrophilic and hydrophobic polymer brushes. Poly (oligo(ethylene glycol) methacrylate) (POEGMA), poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) and poly (oligo(ethylene glycol) methacrylate)-b-poly(2,2,2-trifluoroethyl methacrylate) (POEGMA-b-PTFEMA) brushes were prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) on initiator-immobilized silicon surfaces. The surface properties were investigated by ellipsometry and X-ray photoelectron spectroscopy (XPS). Due to the difference between the chemical prosperities of these two blocks, the modified diblock amphiphilic surfaces exhibited solvent responsivity which can be characterized by measuring water contact angle and atomic force microscope(AFM). After the treatment with water and THF, the static water contact angle of this surface varied from 65°to 80°reversibly and had phase separation while immersed in water. The adsorption of two proteins (human serum albumin (HSA) and lysozyme) with different sizes and charges on the modified surfaces was evaluated using a radio-labeling method. The results indicated that the adsorption amount of both proteins on the flat surfaces modified with this amphiphilic diblock copolymer was about 80% lower, compared with the unmodified flat silicon surface, suggesting its good resistance to non-specific protein adsorption. The Si-POEGMA and Si-POEGMA-b-PTFEMA surfaces had the lowest cell adhesion while the hydrophobic Si-PTFEMA had the highest.Meanwhile, we investigated the effects of nanoscale roughness on the properties of the surface using silicon nanowire arrays (SiN). First, SiN were prepared via a chemical etching method. The results of static water contact angle indicated the introduction of nanoscale roughness generated the amplification effect of the hydrophilic and hydrophobic properties. SiN and SiN-POEGMA surfaces were found to be superhydrophilic while SiN-POEGMA-b-PTFEMA and SiN-PTFEMA surfaces were superhydrophobic, whose water contact angle were above 150°. The introduction of nanoscale roughness also enhanced the solvent responsivity. After the treatment with water and THF, the static water contact angle of this surface varied from 135°to 155°reversibly. The result of protein adsorption showed the amount of both proteins adsorption on SiN-POEGMA and SiN-POEGMA-b-PTFEMA surfaces were about 99% lower the unmodified silicon nanowire arrays, suggesting their good resistance to non-specific protein adsorption. The results of cell adhesion indicated the introduction of nanoscale structure could restrict cell spreading to some extend. On the other hand, PTFEMA polymer brushes grafted from the silicon nanowire arrays would enhance cell adhesion and spreading obviously.