Immobilizing proteins at interfaces is highly wanted for many fields of application including biosensing and diagnostics, biomaterials science and tissue engineering, and biocatalysis. It is very challenging to obtain a high immobilized protein amount and stable layers while keeping the protein molecules active, ie while preventing their denaturation. Current methods for protein immobilization include the use of specific interactions or of covalent chemistry, with the drawback that a new strategy must be designed for each pair of protein and supporting material. Spontaneous adsorption can also be used, but is usually limited to (sub)monolayer coverage. Moreover, all these strategies may lead to strong protein denaturation and thus to a loss of bioactivity.
In a recent paper, we report on the use of protein-polyelectrolyte complexes (PPCs) as building blocks for the layer-by-layer assembly of thin films. The mechanisms of PPCs formation and of their layer-by-layer assembly are thoroughly studied, revealing that this assembly is independent of protein properties, and in particular of protein electrical charge. The proposed method thus overcomes limitations related to protein surface heterogeneity and provides a general route for protein immobilization on the surface of virtually any kind of material. The architecture of the obtained protein-based thin films can be tuned to adjust their protein, polyelectrolyte and water content. The environment provided by polyelectrolytes is highly suitable for biological applications as it keeps proteins in a hydrated state and prevents their denaturation.
Reference: Aurélien vander Straeten, Anna Bratek-Skicki, Alain Jonas, Charles-André Fustin, Christine Dupont-Gillain. Integrating proteins in layer-by-layer assemblies independently of their electrical charge. ACS Nano 2018, 12, 8372 [https://pubs.acs.org/doi/10.1021/acsnano.8b03710]