The interaction of carbon nanomaterials with serum proteins and cholinesterases
published: May 23, 2017, recorded: April 2017, views: 928
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In recent years, nanomaterial (NM) production has been rising and NM application in biology and medicine has been developing quickly. Biomedical applications of NM (as drug carriers or platforms for tissue growth) are dependent on the interaction of NM with biomolecules. Upon entering a biological system, most materials are immediately coated by a layer of proteins. This is especially relevant for NM, which have a large surface-to-volume ratio and can therefore bind many proteins relative to their volume. This layer of proteins is called a protein “corona” and represents what the organism actually “sees” when encountering a NM, rather than the original NM surface. Proteins that compose the corona govern the destiny of the NM in the body, therefore knowing the composition of the NM protein corona is very important for predicting the possibility of the use of a NM in biomedical purposes. Carbon-based NM are among the most sorbent ones. Furthermore, it has been shown that carbon-based NM can adsorb physiologically important enzymes such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) to their surface, alter their tertiary structure and inhibit their enzymatic activity. In our study we have coated carbon-based NM of different shape and surface properties (amorphous carbon black - CB, graphene oxide - GO and multi-walled carbon nanotubes - MWCNT) with either bovine serum albumin or human serum and studied their influence on the structure and function of the isolated electric eel AChE, isolated horse serum BChE and intrinsic human serum BChE. The effect of the coated NM on the activity of enzymes was assayed using the modified Ellman assay. Carbon-based nanoparticles, pre-coated with albumin, had a considerably lower ability to adsorb and therefore to inhibit the activity of AChE and BChE. This effect was less prominent with GO, which, though it bound the highest amount and diversity of serum proteins, bound less serum albumin than the other two studied NMs. When mixed with human serum, GO, unlike CB and MWCNT, reduced the activity of the intrinsic BChE, which we assume is also the consequence of its weaker affinity towards serum albumin. The analysis of the composition of the human serum protein corona of the studied NM, showed that the corona is enriched in apolipoproteins and complement factors. The complement system represents an important part of the immune and inflammatory response towards foreign substances such as NM and can play an important role in the formation of allergies. The binding of lipoproteins E, A-I and B-100 facilitates the translocation of NM through the blood-brain barrier. Thus, the apolipoproteins in the corona of the investigated NM could be either beneficial – for example for targeted drug delivery to the brain – or harmful, when the translocation of the environment-present NM to the brain would be uncontrolled.
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