| The success of long-term blood-contacting implanted devices greatly depends upon the interaction of the blood components with the device material. The search for a perfect hemocompatible biomaterial has not yielded success yet, largely due to the incomplete understanding of blood-material interactions, especially at sub-cellular and molecular levels. In this work, critical aspects of blood-material interactions are probed at the molecular scale using Atomic Force Microscopy (AFM). Conventional AFM imaging techniques are not capable of detecting specific plasma proteins on clinically relevant polymeric biomaterials, mostly due to the surface roughness of the biomaterial. This work has developed AFM techniques which will not require the topographical features otherwise needed by conventional AFM methods to detect proteins. Fibrinogen, the third most abundant plasma protein, plays a crucial role in surface induced thrombosis in blood contacting devices. AFM is used to characterize fibrinogen, in terms of its spatial location, on ultrasmooth mica substrate and a clinically relevant polymer substrate, poly (dimethyl-siloxane). Gold labels are used as immunological tags to detect adsorbed fibrinogen from a two-protein layer at molecular resolution. Force spectroscopy is used to calculate the time dependent activity of the platelet binding dodecapeptide epitope of fibrinogen. These nanoscale results are corroborated with macroscale platelet adhesion experiments. The effects of concentration and co-adsorption of bovine serum albumin with fibrinogen are studied on hydrophilic mica substrates. Polyethylene glycol (PEG) is investigated as a potential tether to attach proteins to the AFM probe. Modified PEG-probes are more efficient in decreasing the non-specific recognition problems which is the main problem with glutaraldehyde linkers especially in the case of hydrophobic substrates. Taken together, this work fills the gaps in the current understanding of the blood-material interactions at the molecular level and provides important tools for future studies. |
