Atomic Force Microscopy Investigation of Protein Adsorption on Hydrogenated Amorphous Carbon
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Atomic Force Microscopy Investigation of Protein Adsorption on Hydrogenated Amorphous Carbon Muhammad Zeeshan Mughal, Patrick Lemoine, Gennady Lubarsky Nanotechnology and Integrated BioEngineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Newtownabbey, BT37 0QB, United Kingdom
ABSTRACT Protein adsorption is the first phenomenon which occurs at nanoscale level when a given surface came into contact with a living fluid cell such as blood. Investigation of this adsorption at nanoscale provides useful information about kinetics and mechanism of conformation of proteins on a given surface. The present study investigates the adsorption of proteins using tapping/intermittent mode atomic force microscopy (T-AFM). The approach taken here is that hydrogenated amorphous carbon coating (a-C:H) is used as a model surface because it is amorphous, smooth, inert and hydrophobic. Two proteins namely albumin and fibrinogen in phosphate buffer (PBS) and de-ionized water are drop casted to study the adsorption kinetics. First and second resonance AFM data was used to investigate the adsorbed layer of proteins. AFM force curve and scratch experiment were used to verify the adhesion and thickness of the adsorbed layer. Combination of height, phase images along with the AFM force curve and scratch experiment shows inhomogeneous distribution of albumin protein in phosphate buffer compared to other protein solutions.
INTRODUCTION Protein adsorption onto surfaces is key to a wide range of biological issues. Although biological cells have micrometer dimensions but their adhesion to a surface, and hence the biocompatibility of implant devices, is linked to the surface adsorption of proteins. The conformational changes which occurs when protein adsorbed onto a surface results in change of their biological function, hence is an important aspect of the potential nano-toxicity of this new class of materials [1]. Finally, protein adsorption is obviously a crucial aspect of protein condensation diseases (Arthritis, Alzheimer, and Cataract) and the performances of anti-fouling coatings. Since proteins have nanoscale dimensions, the influence of nanoscale topography on protein adsorption has been investigated by a number of authors [2, 3] but with conflicting results and is still an active research area. One issue is that medical grade materials have poorly controlled topographies with features ranging from the nanoscale to the micron scale. One investigative strategy is to use a model surface and structure it with a nano-patterning technique to obtain controllable nanoscale topographic features. This approach has been attempted on silica [4] and polymeric surfaces [5, 6]. In the present study, the rationale has been to use hydrogenated amorphous carbon (a-C:H) as the model surface since it is amorphous and smooth (Ra< 5 nm). This material has already been studied for its bio-compatibility, inertness and hydrophobic nature [7, 8] but not yet as a model surface for protein adsorption studies.
To focus the scope of this invest
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