| AVS 60th International Symposium and Exhibition | |
| Applied Surface Science | Thursday Sessions |
| Session AS+BI+EM+NL+NS+SS-ThM |
| Session: | Nanoparticle Surface Chemistry |
| Presenter: | C. Minelli, National Physical Laboratory, UK |
| Authors: | C. Minelli, National Physical Laboratory, UK N.C. Bell, National Physical Laboratory, UK A.G. Shard, National Physical Laboratory, UK |
| Correspondent: | Click to Email |
The ability to quantitatively describe protein coronas of nanoparticles in biological fluids is highly sought for to understand protein corona formation, nanoparticle fate and their interaction with biological systems. A quantitative description of the nanoparticle biomolecular interface is challenging and chemical information along with structural and biofunctional characterization requires the use of complementary techniques.
The parallel use of different techniques provides in fact a range of complementary information of the materials under study, each technique being based on a specific physical principle. Here, we combine the use of liquid-based size measurement techniques such as Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA) and Differential Centrifugal Sedimentation (DCS), with vacuum techniques such as X-ray Photoelectron Spectroscopy (XPS) to provide quantitative information of core/shell nanoparticle systems.
We used a set of spherical gold nanoparticles having diameters from 20 nm to 80 nm and coated with different amount of Immunoglobulin G (IgG) antibodies as a model system. The shift of the nanoparticle Localized Surface Plasmon Resonance (LSPR) frequency measured by UV-Vis spectroscopy is known to relate to the amount of molecules adsorbed at nanoparticles’ interface. We measured the LSPR shifts along with the nanoparticle sizes in liquid by using DLS, NTA and DCS. When the nanoparticles had a complete protein shell, shell thickness measurements were consistent for all the techniques. DCS sedimentation times showed excellent correlation with LSPR frequency shifts, indicating that analytical centrifugation can provide precise measurement of the thickness of complete protein shells on nanoparticles. However, in the low coverage regime, NTA and DLS techniques provided the best correlation with LSPR frequency shifts. By combining the information from the different techniques we estimated the amount of IgG molecules per nanoparticle as a function of the IgG concentration in solution. Data analysis in the high concentration regime suggested that nanoparticle curvature strongly influences the ability of a surface to allow the further adsorption of IgG.
Core/shell nanoparticle systems were also characterized by XPS. A methodology for the preparation of nanoparticle samples for analysis in vacuum was developed. XPS data was collected from nanoparticles of different core size and analysis provided quantitative chemical information of the nanoparticle. The combined use of XPS with liquid-based techniques for particle characterization provided quantitative chemical and structural information of core/shell nanoparticle systems.