Protein immobilization into hollow nanostructures : effects of concave surfaces on adsorbed protein structure and function

Abstract

In this thesis study, we have synthesized nanocages (AuNG) and use their hollow cores as a concave protein immobilization surface. Lysozyme was used as a model to probe interactions between a protein and nanostructures. Solid Au nanoparticles with a similar morphology and surface chemistry were also used as a reference. Protein's through-pore diffusivity into and out from AuNG was the key to distinguish proteins at the concave surfaces, allowing the removal of externally bound lysozyme in high ionic strength buffer. Through a series of quantitative analyses of protein adsorption profiles, structures and enzymatic activities, a general understanding of protein behavior at concave surfaces has been established. According to our investigations on lysozyme-nanocage nanobioconjuagtes, the concave surfaces inside AuNG induced more perturbation on internally adsorbed lysozyme, but since the cages also reduced the formation of macro nano-bio aggregations, adsorbed lysozyme on them has a higher apparent activity compared with those on other gold nanoparticle conjugates previously studied. Hence, this thesis study has probed the nano-bio interactions on concave surfaces, and also established a platform on which more studies alike can be performed.

The novel physical/chemical properties of nanomaterials have already endowed them with unprecedented potentials in biomedical applications, yet a biological property known as the "morphology effect" enables them with further possible abilities to tailor attached proteins. Basically, nanomaterials interact with a biological system via its surface proteins, and since proteins are usually several nanometers in size, they are able to sense different nanoscale morphologies and adjust themselves in response, resulting in conformational perturbations and functional changes. Therefore, understanding the nanostructure-protein interactions is the corner stone in bridging nanotechnology and biology. During the last decade, in-depth studies have been performed on the effect of nanoscale surface topography on adsorbed protein structure and function by developing and characterizing a variety of nanoparticle-protein conjugates. However, a fundamental understanding of nano-bio interactions at concave surfaces is limited, despite the abundance and importance of such nanostructures. Unfortunately, this lack of understanding is not only epistemological, but also methodological. As a methodological perspective, the greatest challenges are to create a concave nanostructure that allows such interactions to occur, and to distinguishingly characterize the proteins at concave surfaces.