The Effect Of Polymer Surface Topography On Protein Adsorption And Cell Adhesion

Protein adsorption,the first response after biomaterials contacting the biological environment,plays a crucial role in mediating the subsequent reactions such as platelet/cell adhesion and in determining the final biocompatibility of biomaterials. Both surface chemistry and topography have evident effects on protein adsorption. Therefore,the single effect of either surface chemistry or topography and the synergic effect of their combination on protein adsorption and cell adhesion need to be investigated in order to rationally design biomaterial's surface properties and effectively improve biomaterial's biocompatibility.Chemical homogeneous and heterogeneous topographic patterns were fabricated on polymeric biomaterials surfaces using soft lithography and ultraviolet lithography, respectively.Inspired from bionic concept,biomaterial with lotus-leaf-like surface topography was also prepared.The effects of prepared topographies on protein adsorption and cell adhesion were studied as follows:1.Chemical homogeneous microtopography on poly(dimethylsiloxane)(PDMS) was fabricated using soft lithography technique.Patterned polyurethane(PU) was then prepared using the obtained PDMS as template.The individual effects of PDMS surface microtopography on fibrinogen(Fg) adsorption and platelet adhesion were studied.After microtopography being introduced on PDMS surface,the surface area only increased by 8.3%whereas the Fg adsorption increased by 34.6%.Laser scanning confocal microscope(LSCM) result showed that Fg randomly adsorbed on flat surface whereas regularly distributed on patterned surface.Additionally, fluorescent images showed that very considerable amount of Fg adsorbed on the flanks and valleys of protrusions.These results suggest that surface microtopography can affect the amount and distribution of adsorbed Fg.Furthermore,the results of platelet adhesion from platelet rich plasma(PRP) and flowing whole blood(FWB) showed that the morphologies and activation states of adhered platelets were different under PRP and FWB situations.However,the distribution of most adhered platelets resembled that of adsorbed Fg under both conditions,indicating that patterned surface indirectly influenced the location of platelets via affecting plasma proteins adsorption, especially Fg.2.Monoallyl-polyethylene glycol(APEG) was grafted to PDMS surface (PDMS-APEG) using hydrosilylation.Infrared spectrum,X-ray photoelectron spectroscopy(XPS) and water contact angle characterizations confirmed the modification.Chemical heterogeneous topographic pattern was fabricated on PDMS-APEG surface using ultraviolet lithography at 172nm.The APEG region with irradiation was etched while without irradiation was kept.LSCM result showed that Fg only adsorbed to the irradiation region without APEG whereas the reserved APEG region effectively resisted Fg adsorption,forming a regular protein pattern.3.Lotus-leaf-like topography was fabricated on PU,poly(propylene carbonate) (PPC) and PU blend Pluronic^? F-127(PUF) surfaces using natural lotus leaf as template.Scanning electron microscope(SEM) result showed that a mass of micro-papilla formed on these polymer surfaces,causing the enhancement of hydrophobicity on PU and PPC surfaces.The synergic effect of surface chemistry and topography endowed PUF surfaces with specific wettability.Sessile droplet and captive bubble water contact angles were similar on flat PUF surfaces.In contrast, captive bubble water contact angles were significantly lower than sessile droplet on lotus-leaf-like PUF surfaces(PUFL) and PUFL20(blend 20%Pluronic^? F-127) surface achieved super-hydrophilicity.The protein adsorption resistant capacity of PUF surface was influenced by the pre-equilibrium in buffer solution.PUF surfaces without pre-equilibrium had better ability to resist non-specific protein adsorption. The amount of adsorbed Fg reduced from 0.289μg on PU flat surface to 0.016μg on PUFL20 surface(94%decrease).In conclusion,the correlation between surface properties and protein adsorption as well as cell adhesion was further understood by the investigation on topographic patterns and lotus-leaf-like surface topography.This research may be helpful to the rational devise and modification of biomaterial surface properties.