Ricerc@Sapienza

The interaction of gold nanoparticles (AuNPs) with the electromagnetic radiation is characterized by a resonant absorption in the visible spectral range, the Localized Surface Plasmon Resonance (LSPR). The dependence of the LSPR frequency on the AuNPs size and shape, and on the dielectric constant of the environment, provides high versatility in the design of novel systems with the desired optical properties. In particular, hybrid systems made up of AuNPs conjugated with biomolecules exploit the synergistic interaction between the plasmonic and the biological components, exhibiting enormous potential for nanomedicine and nanobiotechnology applications.
In this context, we propose a study of the adsorption of a globular protein, lysozyme, on (anionic) AuNPs colloids and of their aggregation subsequently induced by patch-charge interactions.
The general idea of this project is to design a novel system whose plasmonic properties can be manipulated acting on several degrees of freedom. Specifically, we will investigate the effects of AuNPs size, lysozyme-AuNPs relative molar ratio and pH to point out the conditions to obtain bio-plasmonic assemblies with the desired finite size, exhibiting colloidal stability. Furthermore, the possibility to switch between aggregation and disaggregation of the formed clusters by changing the environmental condition such as pH and temperature will be investigated.
The aggregation will be characterized by measuring the size and the surface charge of the aggregates by photo-correlation techniques (Dynamic Light Scattering and Z-potential measurements), while their LSPR will be monitored by UV-Visible absorption spectroscopy.
Lastly, considering that lysozyme performs an antibacterial activity through the lysis of bacterial cellular walls, the functionality of lysozyme confined in the clusters will be also tested by means of an enzyme catalytic assay, probing the possibility to enhance this effect due to the interactions with AuNPs.