A novel polysaccharide-based surface engineering strategy for nanomedicines

Abstract

This dissertation presents the development and evaluation of a novel polysaccharide-based surface engineering strategy for nanomedicines. Chapter one summaries the current status of nanoparticle toxicology. Nanoparticles from natural and anthropogenic sources are abundant in the environment, thus human exposure to nanoparticles is inevitable. Due to this constant exposure, it is critically important to understand the potential acute and chronic adverse effects that nanoparticles may cause to humans. In this chapter, we explore and highlight the current state of nanotoxicology research with a focus on mechanistic understanding of nanoparticle toxicity at organ, tissue, cell, and biomolecular levels. We discuss nanotoxicity mechanisms, including generation of reactive oxygen species, nanoparticle disintegration, modulation of cell signaling pathways, protein corona formation, and poly(ethylene glycol)-mediated immunogenicity. We conclude with a perspective on potential approaches to advance current understanding of nanoparticle toxicity. Such improved understanding may lead to mitigation strategies that could enable safe application of nanoparticles in humans. Advances in nanotoxicity research will ultimately inform efforts to establish standardized regulatory frameworks with the goal of fully exploiting the potential of nanotechnology while minimizing harm to humans. (Chapter 1) Chapter two introduces the use of polysaccharide heparosan (HEP) surface modification on nanoparticles as an alternative to poly(ethylene glycol) (PEG) and showed the investigation of the biological interaction of HEP coated nanoparticles with cells. Nanoparticle modification with PEG is a widely used surface engineering strategy in nanomedicine. However, since the artificial PEG polymer may adversely impact nanomedicine safety and efficacy, alternative surface modifications are needed. Here, we explored the ‘self’ polysaccharide HEP to prepare colloidally stable HEP-coated nanoparticles, including gold and silver nanoparticles and liposomes. We found that the HEP-coating reduced the nanoparticle protein corona formation as efficiently as PEG coatings upon serum incubation. Liquid chromatography-mass spectrometry revealed the protein corona profiles. Heparosan-coated nanoparticles exhibited up to 230-fold higher uptake in certain innate immune cells, but not in other tested cell types, than PEGylated nanoparticles. No noticeable cytotoxicity was observed. Serum proteins did not mediate the high cell uptake of HEP-coated nanoparticles. Our work suggests that HEP polymers may be an effective surface modification technology for nanomedicines to safely and efficiently target certain innate immune cells. (Chapter 2) Chapter three describes the HEP-AuNPs uptake behavior and pathways in immune cells and established controlling strategies for nanoparticle cellular uptake. Our findings indicate that HEP-coated nanoparticles were endocytosed in a time-dependent manner by innate immune cells via both clathrin-mediated and macropinocytosis/phagocytosis pathways. Upon endocytosis, HEP-coated nanoparticles were found in intracellular vesicles as well as in the cytoplasm, demonstrating the potential for nanoparticle escape from these intracellular vesicles. Competition with other glycosaminoglycan types inhibited the endocytosis of HEP-coated nanoparticles only partially. We further found that nanoparticle uptake into innate immune cells can be controlled by more than 3 orders of magnitude via systematically varying the HEP surface density. Our results suggest there exists substantial potential for HEP-coated nanoparticles to target innate immune cells for efficient intracellular delivery, including into the cytoplasm. This HEP nanoparticle surface engineering technology may be broadly used to develop efficient nanoscale devices for drug and gene delivery as well as gene editing and immuno-engineering applications. (Chapter 3)