Adsorption of Myoglobin and Corona Formation on Silica Nanoparticles.

Kelly Lannigan,Jin Gyun Lee,Bhuvnesh Bharti,Jens Meissner,William A. Shelton

doi:10.1021/acs.langmuir.0c01613

Abstract

The adsorption of proteins from aqueous medium leads to the formation of protein corona on nanoparticles. The formation of protein corona is governed by a complex interplay of protein–particle and protein–protein interactions, such as electrostatics, van der Waals, hydrophobic, hydrogen bonding, and solvation. The experimental parameters influencing these interactions, and thus governing the protein corona formation on nanoparticles, are currently poorly understood. This lack of understanding is due to the complexity in the surface charge distribution and anisotropic shape of the protein molecules. Here, we investigate the effect of pH and salinity on the characteristics of corona formed by myoglobin on silica nanoparticles. We experimentally measure and theoretically model the adsorption isotherms of myoglobin binding to silica nanoparticles. By combining adsorption studies with surface electrostatic mapping of myoglobin, we demonstrate that a monolayered hard corona is formed in low salinity dispersions, which transforms into a multilayered hard + soft corona upon the addition of salt. We attribute the observed changes in protein adsorption behavior with increasing pH and salinity to the change in electrostatic interactions and surface charge regulation effects. This study provides insights into the mechanism of protein adsorption and corona formation on nanoparticles, which would guide future studies on optimizing nanoparticle design for maximum functional benefits and minimum toxicity.

Highlights

While most of the current studies focus on the biological activity of the protein within the corona, the mechanism of its formation and local orientation of proteins within the corona remain poorly understood.[10,11]. This lack of understanding of protein corona characteristics is due to anisotropic shape and nonuniform distribution of chemical functional groups on the surface of protein molecules forming the corona.[12,13]
The silica NPs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), ζ-potential measurement, and nitrogen gas adsorption
Silica NPs were characterized for their size and polydispersity using DLS and TEM

Summary

INTRODUCTION

The integration of nanoscience with biomedicine has resulted in numerous technological advances in molecular sensing, targeted delivery, in vivo imaging, and gene therapy.[1−4] For these applications, nanoparticles (NPs) are the fundamental units that provide the necessary biological response and functionality.[5,6] When NPs are introduced in in vivo environments, proteins from biological fluids instantaneously bind to the NP surface, leading to the formation of a shell known as the “protein corona”.7 any further interaction of NPs with biomolecules is mediated by the protein corona.[8,9] While most of the current studies focus on the biological activity of the protein within the corona, the mechanism of its formation and local orientation of proteins within the corona remain poorly understood.[10,11] This lack of understanding of protein corona characteristics is due to anisotropic shape and nonuniform distribution of chemical functional groups on the surface of protein molecules forming the corona.[12,13] To develop the generation of functional nanomaterials for biomedical applications, it is critical to understand the local interactions driving the formation of the protein corona and thermodynamic state of the protein on the NPs. Myoglobin is a globular protein found in skeletal and cardiac muscle cells It acts as a local oxygen reservoir to provide temporary oxygen when blood oxygen delivery is insufficient during periods of intense muscular activity.[22,23] Myoglobin contains 153 amino acids, a heme group where an iron ion is bonded to four nitrogen atoms of the porphyrin ring, a proximal histidine group (His-93), and a distal histidine group (His-64) with a net isoelectric point (IEP) of pH 7.24 Here, we use hydrophilic silica nanospheres of diameter 30 nm as model NPs. The silica NPs have been widely used as a model to study adsorption and delivery of proteins due to their low toxicity, hydrophilicity induced by surface by the silanol groups (Si−O−H), and well-established synthetic procedures to precisely control their physical and chemical properties.[25] The neutral point of bare silica NPs is pH ∼2, i.e., the NPs are negatively charged at pH >2. We calculate the surface electrostatic maps for myoglobin, providing a better understanding of the adsorption process and corresponding protein corona formation

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES