Dana Westmeier

The protein corona protects against size- and dose-dependent toxicity of amorphous silica nanoparticles.

Summary Besides the lung and skin, the gastrointestinal (GI) tract is one of the main targets for accidental exposure or biomedical applications of nanoparticles (NP). Biological responses to NP, including nanotoxicology, are caused by the interaction of the NP with cellular membranes and/or cellular entry. Here, the physico-chemical characteristics of NP are widely discussed as critical determinants, albeit the exact mechanisms remain to be resolved. Moreover, proteins associate with NP in physiological fluids, forming the protein corona potentially transforming the biological identity of the particle and thus, adding an additional level of complexity for the bio–nano responses. Here, we employed amorphous silica nanoparticles (ASP) and epithelial GI tract Caco-2 cells as a model to study the biological impact of particle size as well as of the protein corona. Caco-2 or mucus-producing HT-29 cells were exposed to thoroughly characterized, negatively charged ASP of different size in the absence or presence of proteins. Comprehensive experimental approaches, such as quantifying cellular metabolic activity, microscopic observation of cell morphology, and high-throughput cell analysis revealed a dose- and time-dependent toxicity primarily upon exposure with ASP30 (Ø = 30 nm). Albeit smaller (ASP20, Ø = 20 nm) or larger particles (ASP100; Ø = 100 nm) showed a similar zeta potential, they both displayed only low toxicity. Importantly, the adverse effects triggered by ASP30/ASP30L were significantly ameliorated upon formation of the protein corona, which we found was efficiently established on all ASP studied. As a potential explanation, corona formation reduced ASP30 cellular uptake, which was however not significantly affected by ASP surface charge in our model. Collectively, our study uncovers an impact of ASP size as well as of the protein corona on cellular toxicity, which might be relevant for processes at the nano–bio interface in general.

The bio-corona and its impact on nanomaterial toxicity

Abstract The rapidly growing application of nano-sized materials and nano-scaled processes will result in increased exposure of humans and the environment. The small size of nanomaterials (NM) comparable with molecular building blocks of cells raises concerns that their toxic potential cannot be extrapolated from studies of larger particles due to their unique physico-chemical properties. These properties are also responsible that NM rapidly adsorb various (bio)molecules when introduced into complex physiological or natural environments. As the thus formed protein/biomolecule ‘corona’ seems to affect the NM’ in situ identity, an understanding of its toxicological relevance and the biophysical forces regulating corona formation is needed but not yet achieved. This review introduces our current concept of corona formation and evolution and present analytical methods for corona profiling. We discuss toxicity mechanisms potentially affected by the biomolecule corona, including NM cellular uptake and impact on components of the blood system. Further, we comment on pending knowledge gaps and challenges, which need to be resolved by the field. We conclude by presenting a tiered systems biology-driven approach recommended to mechanistically understand the coronas’ nanotoxicological relevance and predictive potential.

Tuning the Surface of Nanoparticles: Impact of Poly(2-ethyl-2-oxazoline) on Protein Adsorption in Serum and Cellular Uptake.

Due to the adsorption of biomolecules, the control of the biodistribution of nanoparticles is still one of the major challenges of nanomedicine. Poly(2-ethyl-2-oxazoline) (PEtOx) for surface modification of nanoparticles is applied and both protein adsorption and cellular uptake of PEtOxylated nanoparticles versus nanoparticles coated with poly(ethylene glycol) (PEG) and non-coated positively and negatively charged nanoparticles are compared. Therefore, fluorescent poly(organosiloxane) nanoparticles of 15 nm radius are synthesized, which are used as a scaffold for surface modification in a grafting onto approach. With multi-angle dynamic light scattering, asymmetrical flow field-flow fractionation, gel electrophoresis, and liquid chromatography-mass spectrometry, it is demonstrated that protein adsorption on PEtOxylated nanoparticles is extremely low, similar as on PEGylated nanoparticles. Moreover, quantitative microscopy reveals that PEtOxylation significantly reduces the non-specific cellular uptake, particularly by macrophage-like cells. Collectively, studies demonstrate that PEtOx is a very effective alternative to PEG for stealth modification of the surface of nanoparticles.

Synthesis and Characterization of Stimuli‐Responsive Star‐Like Polypept(o)ides: Introducing Biodegradable PeptoStars

Star-like polymers are one of the smallest systems in the class of core crosslinked polymeric nanoparticles. This article reports on a versatile, straightforward synthesis of three-arm star-like polypept(o)ide (polysarcosine-block-polylysine) polymers, which are designed to be either stable or degradable at elevated levels of glutathione. Polypept(o)ides are a recently introduced class of polymers combining the stealth-like properties of the polypeptoid polysarcosine with the functionality of polypeptides, thus enabling the synthesis of materials completely based on endogenous amino acids. The star-like homo and block copolymers are synthesized by living nucleophilic ring opening polymerization of the corresponding N-carboxyanhydrides (NCAs) yielding polymeric stars with precise control over the degree of polymerization (Xn = 25, 50, 100), Poisson-like molecular weight distributions, and low dispersities (Đ = 1.06-1.15). Star-like polypept(o)ides display a hydrodynamic radius of 5 nm (μ2 < 0.05) as determined by dynamic light scattering (DLS). While star-like polysarcosines and polypept(o)ides based on disulfide containing initiators are stable in solution, degradation occurs at 100 × 10-3 m glutathione concentration. The disulfide cleavage yields the respective polymeric arms, which possess Poisson-like molecular weight distributions and low dispersities (Đ = 1.05-1.12). Initial cellular uptake and toxicity studies reveal that PeptoStars are well tolerated by HeLa, HEK 293, and DC 2.4 cells.

Bio–Nano Interactions

There is widespread use of engineered nanomaterials in technical products and their application in biotechnology and biomedicine is steadily increasing. Therefore, the exposure of humans and the environment to nanomaterials is continuously increasing. Notably, the characteristics of nanomaterials change in complex physiological environments; biomolecules immediately adsorb onto the nanomaterial surface, forming a so-called biomolecule corona which alters the (patho)biological identity of the nanomaterial. Furthermore, the biomolecule corona is able to affect cellular processes including the toxicity of nanomaterials. In this chapter, we present an overview of our current understanding of the biomolecule corona concept, discuss the impact of corona formation for in vitro and in vivo studies of nanomaterials, and provide some insights concerning the role of the biomolecule corona in the field of nanotoxicology.

Nanoparticle decoration impacts airborne fungal pathobiology

Significance In this work, we demonstrate that nanoparticles rapidly assemble on spores under physiologically and ecologically relevant conditions. We provide in vitro and in vivo evidence that nanoparticle coating of the clinically most relevant airborne fungal pathogen, Aspergillus fumigatus, can affect the pathobiological identity and fate of both fungal spores and nanoparticles. Our findings suggest that nanoparticle coating of bioaerosols may be relevant for ecology and human health. Airborne fungal pathogens, predominantly Aspergillus fumigatus, can cause severe respiratory tract diseases. Here we show that in environments, fungal spores can already be decorated with nanoparticles. Using representative controlled nanoparticle models, we demonstrate that various nanoparticles, but not microparticles, rapidly and stably associate with spores, without specific functionalization. Nanoparticle-spore complex formation was enhanced by small nanoparticle size rather than by material, charge, or “stealth” modifications and was concentration-dependently reduced by the formation of environmental or physiological biomolecule coronas. Assembly of nanoparticle-spore surface hybrid structures affected their pathobiology, including reduced sensitivity against defensins, uptake into phagocytes, lung cell toxicity, and TLR/cytokine-mediated inflammatory responses. Following infection of mice, nanoparticle-spore complexes were detectable in the lung and less efficiently eliminated by the pulmonary immune defense, thereby enhancing A. fumigatus infections in immunocompromised animals. Collectively, self-assembly of nanoparticle-fungal complexes affects their (patho)biological identity, which may impact human health and ecology.

Changing environments and biomolecule coronas: consequences and challenges for the design of environmentally acceptable engineered nanoparticles

Nanomaterials (NMs) are gaining increasing commercial importance due to a variety of properties that cannot be achieved with bulk materials. Yet the assessment of their environmental impacts lags behind the technological development. First attempts towards designing inherently safer NMs have been made, yet we are still unable to formulate rules of green nano-design, especially in terms of mitigating (long-term) toxicity and bioaccumulation. Importantly, NMs released to the environment acquire a so called ‘environmental corona’ – a complex layer of spontaneously adsorbed biomolecules – that significantly impacts their behaviour and fate. This review integrates the current literature on the impact of environmental conditions on NMs fate and behaviour, including corona formation, colloidal stability, reactivity, and toxicty, using a broad range of environmentally relevant NMs. Collectively, components of natural waters (such as salts and/or natural organic matter) often mitigate negative impacts of NMs via different mechanisms including surface passivation and stabilisation against dissolution. The review concludes by discussing some initial strategies on how to rationally design more environmentally acceptable NMs.