Simulations of Protein Adsorption on Nanostructured Surfaces

Berardo M Manzi,Russell J Crawford,Elena P Ivanova,Vladimir A Baulin,Marco Werner

doi:10.1038/s41598-019-40920-z

Abstract

Recent technological advances have allowed the development of a new generation of nanostructured materials, such as those displaying both mechano-bactericidal activity and substrata that favor the growth of mammalian cells. Nanomaterials that come into contact with biological media such as blood first interact with proteins, hence understanding the process of adsorption of proteins onto these surfaces is highly important. The Random Sequential Adsorption (RSA) model for protein adsorption on flat surfaces was modified to account for nanostructured surfaces. Phenomena related to the nanofeature geometry have been revealed during the modelling process; e.g., convex geometries can lead to lower steric hindrance between particles, and hence higher degrees of surface coverage per unit area. These properties become more pronounced when a decrease in the size mismatch between the proteins and the surface nanostructures occurs. This model has been used to analyse the adsorption of human serum albumin (HSA) on a nano-structured black silicon (bSi) surface. This allowed the Blocking Function (the rate of adsorption) to be evaluated. The probability of the protein to adsorb as a function of the occupancy was also calculated.

Highlights

Recent progress in the miniaturization of electronics at the nanoscale[1] and the development of experimental techniques allowing the visualization of nanostructures below the diffraction limit[2,3], has allowed the design of certain nanostructures on substrata, the properties of which can be precisely controlled
Classical Langmuir adsorption is limited to a single species adsorbing onto a flat surface that contains a finite number of adsorption sites
Experimental data can often appear to be compatible with a Langmuir adsorption isotherm, with “effective” equilibrium constants able to be obtained from the modelling process, the underlying mechanism of adsorption is not necessarily reversible

Summary

Introduction

Recent progress in the miniaturization of electronics at the nanoscale[1] and the development of experimental techniques allowing the visualization of nanostructures below the diffraction limit[2,3], has allowed the design of certain nanostructures on substrata, the properties of which can be precisely controlled. Apart from the complex adsorption kinetics that can exist, cooperative adsorption between proteins[14] may lead to the development of even more complex kinetics under physiological conditions such as those found in blood plasma, which contains more than 1000 proteins[15] This plethora of interaction phenomena makes it difficult to construct a generalized theoretical framework that is capable of describing protein adsorption at the molecular level. These are: (i) all adsorption sites are equivalent; (ii) only one molecule can adsorb onto a given site at any time; (iii) no interaction is present between the adsorbing molecules; and (iv) the process of adsorption is reversible Despite these assumptions potentially limiting the validity of the model, its simplicity allows the model to be applied to a broad range of systems that do not meet these assumptions, including, in most cases, protein adsorption. The resulting values obtained from the model of surface saturation and the adsorption constant can be misleading as a consequence of an erroneous interpretation, as previously demonstrated by Latour[17], and emphasized again in the present work

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Conclusion