Abstract
The protein adsorption plays a very important role in biotechnology, biomolecular engineering and it is one of the main factors determining bio- and hemocompatibility of biomedical materials in medical applications, such as blood purification and wound healing. Here we report adsorption properties of two carbon-based materials, thermally expanded graphite (EGr) and graphene nanoplatelets (GnP), for bovine serum albumin (BSA), the most abundant blood plasma protein. The influence of the surface chemistry of expanded graphite on the mechanism of BSA adsorption was studied by using EGr modified with oxygen or nitrogen functionalities. Having low microporosity and the specific surface area in the range of 5 to 50 m2/g, the expanded graphite exhibits high protein adsorption capacity at high equilibrium concentrations, which makes this material a potential candidate for biomedical applications as a carrier for high molecular weight (HMW) drug delivery or adsorption of HMW metabolites. At low equilibrium concentrations, the effect of specific protein-surface functional groups interaction reveals the differences between the adsorption affinity of different surface modified EGr materials to BSA. The adsorption of BSA on GnP with a specific surface area of 286 m2/g and a developed micro-/mesoporous structure did not follow the same mechanism as seen with EGr materials. At low equilibrium concentration of BSA, GnP exhibits high adsorption efficiency. An important finding is that no release of nanoparticles from expanded graphite adsorbents was observed, which makes them potentially suitable for direct contact with blood and other tissues while very small nanoparticles were noticed in the case of graphene nanoplatelets.
Highlights
Carbon materials have been used in biomedical applications for many decades
We have investigated the adsorption of bovine serum albumin (BSA) on “flat” expanded graphite surfaces with different surface chemistry and porous textures
Expanded graphite’s “accordion-like” texture consisting of large graphite flakes facilitates adsorption of large amount of protein which reveals their potential as large molecular weight drug delivery carriers and high protein fouling resistance if they are used as membranes
Summary
Carbon materials have been used in biomedical applications for many decades. Among the earliest applications are the use of graphite and pyrolytic carbon for constructing artificial heart valves [1] and activated carbon in hemoperfusion devices for the treatment of exo- and endogenous poisonings of different etiology [2]. Development of novel nanostructured carbons and methods for their surface modification expanded the choice of materials and led to the applications in biosensors, coatings for medical devices, drug and gene delivery carriers and bioimaging [3]. Current interest to biomedical applications of novel nanostructured carbon materials is based on their structural, mechanical, physical and chemical properties, which are often superior to other materials [4,5]. This interest is supported by the fact that many carbon materials have good biocompatibility and can be used in direct contact with blood and human tissues [6]. The phenomenon of biocompatibility is very complex and its key factors have not been fully understood yet, it is known to be associated with the protein adsorption
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