Two-Components Colloidal Solutions: Tuning the Interactions of Functionalized Nanoparticles with Proteins
Zusammenfassung der Projektergebnisse
Nanoparticles (NPs) functionalized by self-assembled monolayers (SAMs) and proteins (known as bioconjugates) are widely used in many bio-related areas, such as biomolecular detection and diagnostic applications. In this work, we aimed to understand the phase behavior of these two-component (NPs plus proteins) systems under various environmental conditions. As the first step of our research, we have used small angle scattering together with liquid theoretical approaches to investigate the protein interactions in solution. The globular proteins BSA and ovalbumin are used as examples. Due to the negative charge of the proteins at neutral pH, the protein-protein interactions without any salt addition are dominated by electrostatic repulsion. Upon addition of NaCl, with the ionic strength below that of physiological conditions (150 mM), the effective interactions are still dominated by the surface charge of the proteins and the scattering data can be understood using the same model. For high protein concentrations in solutions containing concentrated electrolytes, the protein interactions are dominated by the excluded volume effect, but also sensitive to the nature of the added salts, i.e. follows the effects of the Hofmeister series. The knowledge of protein interactions in solution can help our understanding on the interactions in the two-component system of proteins and functionalized nanoparticles (FNP). For such a two-component system (protein and FNP), the pair interactions include proteinprotein, FNP-FNP and protein-FNP interactions. In this context, we have performed a series of studies using gold colloids functionalized with protein resistant OEG SAMs in aqueous solutions. The stability of the FNPs as a function of added protein and salt concentration has been used to quantify the interactions between protein and FNP. A systematic study on the influence of the nature of the added salt on the stability of this two-component colloid-protein system also shows interesting results: chaotropic salts stabilize the system with increasing salt concentration, while kosmotropic salts lead to the aggregation of colloids with increasing salt concentration. These observations indicate that the Hofmeister effects can be enhanced in two-component systems, i.e. the modification of the colloidal interface by ions changes significantly the effective depletion interaction via proteins. To further understand the enhanced Hofmeister effects in protein-FNP system, we have performed a study of the interactions between FNP with proteins in solutions using electrophoretic and dynamic light scattering (ELS and DLS). The results are compared with poly(ethylene glycol) (PEG) thiol coated AuNPs (AuPEG). We show that both AuOEG and AuPEG particles carry a low net negative charge and are very stable (remaining so for more than a year). When the decorated AuNPs were mixed with the negatively charged protein, bovine serum albumin (BSA), both effective size and zeta-potential of the AuNPs remained unchanged, indicating no adsorption of BSA to the colloid surface. However, when mixed with positively charged protein (lysozyme), zeta-potential values increased with protein concentrations and led to a charge inversion, indicating adsorption of lysozyme to the colloid surface. The effective charge inversion and rather strongly bound lysozyme on the colloid surface suggest that in addition to the charges formed at the SAM/water interface, there are defects on the surface of the colloid, which are accessible to the proteins. Finally, we have extended our study of the surface engineering using OEG / PEG SAMs to bacterial adhesion on implants, which is a first step in the development of chronic implant-associated infections. Finding strategies to minimize bacterial adhesions may contribute to minimize such infections. In this context, we studied the role of serum proteins on Staphylococcus aureus adhesion on gold surfaces coated with OEG and PEG thiols. Our finding suggests that serum can significantly inhibit the bacterial adhesion on different surfaces might have some therapeutic implications in minimizing implant-associated infections.
Projektbezogene Publikationen (Auswahl)
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(2009) Gold nanoparticles decorated with oligo(ethylene glycol) thiols: Enhanced Hofmeister effects in colloidprotein mixtures. J. Phys. Chem. C 113:4839-4847
Zhang F, Skoda MWA, Jacobs RMJ, Dressen DG, Martin RA, Martin CM, Clark GF, Lamkemeyer T, Schreiber F
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(2010) Protein-protein interactions in ovalbumin solutions studied by small-angle scattering: Effect of ionic strength and the chemical nature of cations. J. Phys. Chem. B 114:3776-3783
Ianeselli L, Zhang F, Skoda MWA, Jacobs RMJ, Martin RA, Callow S, Prévost S, Schreiber F
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(2012) Hydration and interactions in protein solutions containing concentrated electrolyte studied by small-angle scattering. Phys. Chem. Chem. Phys. 14:2483-2493
Zhang F, Roosen-Runge F, Skoda MWA, Jacobs RMJ, Wolf M, Callow P, Frielinghaus H, Pipich V, Prévost S, Schreiber F
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(2013) Tuning Interactions in Protein Solutions by Charges Institut für Angewandte Physik, Habilitation. Universität Tübingen, Tübingen
Zhang F
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(2014) Gold nanoparticles decorated with oligo(ethylene glycol) thiols: Surface charges and interactions with proteins in solution. Journal of Colloid and Interface Science 426:31-38
Schollbach M, Zhang F, Roosen-Runge F, Skoda MWA, Jacobs RMJ, Schreiber F
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(2014) The role of immunoglobulin and albumin on bacterial adhesion at OEG/PEG SAM- coated gold surfaces. International Journal of Medical Microbiology
Schuster S, Nega M, Yu W, Zorn S, Zhang F, Götz F, Schreiber F
