Understanding protein adsorption phenomena at solid surfaces

TLDR: In this review recent achievements and new perspectives on protein adsorption processes are comprehensively discussed and the main focus is put on commonly postulated mechanistic aspects and their translation into mathematical concepts and model descriptions.

About: This article is published in Advances in Colloid and Interface Science.The article was published on 2011-02-17 and is currently open access. It has received 1328 citations till now.

Figures

Fig. 6.4. Correlation between the macroscopic parameter α and the microscopic value of rcoop.

Fig. 4.11. Model calculations on BSA. A) Comparison of the models including (black, solid lines) and neglecting (red, dashed lines) transport processes. The bulk concentration of the model that does not include transport processes was varied to ‘fit’ the model that does include transport at varying rates. B) General view on the influence that the transport rate has on the shape of adsorption kinetics. Three sets of different curve shapes, upwards concave ( onon kk 12 2 ⋅= , left), almost linear ( onon

Fig. 8.10. Schematic illustration of the mechanism of the spreading process of a protein cluster in time on the hydrophobic (A) and the hydrophilic (B) surface.

Fig. 6.7. Statistical evaluation of density variations in the scan images at different adsorption stages. The average difference between intensity maximum and minimum on all scan images was plotted as a function of surface coverage for both cases, cooperative (red line) and non-cooperative (black line) adsorption. Error bars indicate the standard error calculated from 100 (A) and 30 (B) values at each point, respectively. (A) Simulation; (B) Experiment.

Fig. 5.10. A) Adsorption kinetics of Fib in citrate buffer (50 mM) at varying pH: pH 3 (8 nM, ○), pH 4 (8nM, ), and pH 5 (8 nM, ◊). B) Rate-coverage plots of the kinetics presented in Fig. 5.10. Solid lines refer to the best fit obtained with the proposed model.

Fig. 7.7. A) Presentation of the kinetic model. The plot shows the contribution of the initial (green line), the reversible (red line), and the irreversible (blue line) state to the total coverage (black line) calculated for a bulk protein concentration of 4.0 × 10-8 M. The kinetics of the total coverage are compared to experimental data (circles). B) Calculated adsorption and desorption kinetics of an alternative model in which the direct adsorption of proteins in the reversible state is forbidden. This alternative model may either fit correctly the overshooting behavior (red, solid line) or the behavior upon buffer rinse (red, dashed line) but not both features with the same set of parameters. Arrows mark the point in time when rinsing was started.

Frequently asked questions

Q1. What is the pathological component of Parkinson’s disease?

Inversely to protein aggregation in solution, the direct growth of aggregates on the surface can also be observed using the protein α-Synuclein which is the pathological component of Parkinson’s disease. 

Q2. What contributions have the authors mentioned in the paper "Understanding protein adsorption phenomena on solid surfaces" ?

The present dissertation aims to advance the understanding of protein adsorption and to systematically unravel the underlying molecular mechanism. One of the comprehensively studied adsorption phenomena is cooperativity which refers to the effect that the adsorption of proteins is enhanced by the presence of pre-adsorbed proteins. The significance of this work results from the successful combination of substantial experimental investigations with efficient theoretical methods giving access to a clear and illustrative view on some exciting adsorption phenomena. Instead, a macroscopic model description is suggested that simply assumes the overlap of two parallel adsorption pathways, one for the adsorption at isolated surface positions and one for the adsorption near other surface-bound proteins. Further, a microscopic treatment of the mechanism behind cooperativity is realized through Monte-Carlo simulations which reproduce the experimental data accurately and thereby confirm the suggestion that approaching proteins can be tracked to favorable binding sites near other pre-adsorbed proteins. 

Q3. What are the future works in "Understanding protein adsorption phenomena on solid surfaces" ?

The most important method used to study the corresponding model systems was FRET imaging. Evaluating the effects of the discussed mechanism on the biological activity and cytotoxicity of the proteins and designing interfaces that allow for a certain control over aggregation processes will be important topics for future research. As a consequence, the deposition of protein clusters on the surface can be suppressed by a dense protein monolayer provided that it displays a low surface mobility of adsorbed proteins. This suggests that the growth of the fibrils starts at the initially determined positions which in the end remain the surface anchoring sites and proceeds in a certain direction not necessarily along the surface. 

Q4. What is the significance of this work?

The significance of this work results from the successful combination of substantial experimental investigations with efficient theoretical methods giving access to a clear and illustrative view on some exciting adsorption phenomena. 

Q5. Was ist die mikroskopische Herangehensweise an den vorgeschlagenen Mechanismus?

Entgegen einer weit verbreitenden Ansicht kann gezeigt werden, dass Kooperativität nicht zwangsläufig mit der Aggregation von Proteinen auf der Oberfläche einhergeht. 

Q6. What is the main idea of the paper?

Whereas the on-surface growth mechanism is the typically proposed one when protein aggregates are detected on a surface, the discovery that protein aggregates can also come from the solution and spread on the surface opens a completely new perspective on this topic.