Dynamic changes of protein corona compositions on the surface of zinc oxide nanoparticle in cell culture media

Surface Chemistry of Biologically Active Reducible Oxide Nanozymes

Reducible metal oxide nanozymes (rNZs) are a subject of intense recent interest due to their catalytic nature, ease of synthesis, and complex surface character. Such materials contain surface sites which facilitate enzyme-mimetic reactions via substrate coordination and redox cycling. Further, these surface reactive sites are shown to be highly sensitive to stresses within the nanomaterial lattice, the physicochemical environment, and to processing conditions occurring as part of their syntheses. When administered in vivo, a complex protein corona binds to the surface, redefining its biological identity and subsequent interactions within the biological system. Catalytic activities of rNZs each deliver a differing impact on protein corona formation, its composition, and in turn, their recognition, and internalization by host cells. Improving the understanding of the precise principles that dominate rNZ surface-biomolecule adsorption raises the question of whether designer rNZs can be engineered to prevent corona formation, or indeed to produce "custom" protein coronas applied either in vitro, and preadministration, or formed immediately upon their exposure to body fluids. Here, fundamental surface chemistry processes and their implications in rNZ material performance are considered. In particular, material structures which inform component adsorption from the application environment, including substrates for enzyme-mimetic reactions are discussed.

Protein-corona formation on aluminum doped zinc oxide and gallium nitride nanoparticles

The interaction of semiconductor nanoparticles with bio-molecules attracts increasing interest of researchers, considering the reactivity of nanoparticles and the possibility to control their properties remotely giving mechanical, thermal, or electrical stimulus to the surrounding bio-environment. This work reports on a systematic comparative study of the protein-corona formation on aluminum doped zinc oxide and gallium nitride nanoparticles. Bovine serum albumin was chosen as a protein model. Dynamic light scattering, transmission electron microscopy and X-ray photoelectron spectroscopy techniques have been used to demonstrate the formation of protein-corona as well as the stability of the colloidal suspension given by BSA, which also works as a surfactant. The protein adsorption on the NPs surface studied by Bradford Assay showed the dependence on the quantity of proteins adsorbed to the available sites on the NPs surface, thus the saturation was observed at ratio higher than 5:1 (NPs:Proteins) in case of ZnO, these correlating with DLS results. Moreover, the kinetics of the proteins showed a relatively fast adsorption on the NPs surface with a saturation curve after about 25 min. GaN NPs, however, showed a very small amount of proteins adsorbed on the surface, a change in the hydrodynamic size being not observable with DLS technique or differential centrifugal sedimentation. The Circular Dichroism analysis suggests a drastic structural change in the secondary structure of the BSA after attaching on the NPs surface. The ZnO nanoparticles adsorb a protein-corona, which does not protect them against dissolution, and in consequence, the material proved to be highly toxic for Human keratinocyte cell line (HaCaT) at concentration above 25 µg/mL. In contrast, the GaN nanoparticles which do not adsorb a protein-corona, show no toxicity signs for HaCaT cells at concentration as high as 50 µg/mL, exhibiting much lower concentration of ions leakage in the culture medium as compared to ZnO nanoparticles.

Formation and biological effects of protein corona for food-related nanoparticles

The rapid development of nanoscience and nanoengineering provides new perspectives on the composition of food materials, and has great potential for food biology research and applications. The use of nanoparticle additives and the discovery of endogenous nanoparticles in food make it important to elucidate in vivo safety of nanomaterials. Nanoparticles will spontaneously adsorb proteins during transporting in blood and a protein corona can be formed on the nanoparticle surface inside the human body. Protein corona affects the physicochemical properties of nanoparticles and the structure and function of proteins, which in turn affects a series of biological reactions. This article reviewed basic information about protein corona of food-related nanoparticles, elucidated the influence of protein corona on nanoparticles properties and protein structure and function, and discussed the effect of protein corona on nanoparticles in vivo. The effects of protein corona on nanoparticles transport, cellular uptake, cytotoxicity, and immune response were reviewed, and the reasons for these effects were also discussed. Finally, future research perspectives for food protein corona were proposed. Protein corona gives food nanoparticles a new identity, which makes proteins bound to nanoparticles undergo structural transformations that affect their recognition by receptors in vivo. It can have positive or negative impacts on cellular uptake and toxicity of nanoparticles and even trigger immune responses. Understanding the effects of protein corona have potential in evaluating the fate of the food-related nanoparticles, providing physicochemical and biological information about the interaction between proteins and foodborne nanoparticles. The review article will help to evaluate the safety of protein coronas formed on nanoparticles in food, and may provide fundamental information for understanding and controlling nanotoxicity.

Zinc Oxide Nanoparticles Protected with Terpenoids as a Substance in Redox Imbalance Normalization in Burns

Preliminary protection of zinc oxide nanoparticles (ZnO NPs) with terpenoids such as betulin, its derivatives, and essential oils components has been proposed to produce gel-like oleophilic and hydrophilic formulations. We studied the properties of gel-like dispersions of ZnO NPs with immobilized terpenoids and their effects on the activity of LDH, GR, G6PDH, restoration of redox balance of co-enzyme pairs NAD+/NADH and NADP+/NADPH, as well as the activity of SOD, catalase, AlDH in erythrocytes in the treatment of burns in rats. Hysteresis loops on the rheograms of studied dispersions characterize their thixotropic properties. ZnO NPs with betulin diphosphate in the water-ethanol medium lead to a 20-fold increase in the hydrodynamic radius at pH 7.3 compared to the initial ZnO NPs, and facilitate the formation of Zn2+ ions and their penetration into the viable epidermis, unlike oleophilic dispersions. All dispersions reduce the healing time by one and a half times compared with the untreated control group, increase the activity of LDH, GR, G6PDH, SOD, catalase, AlDH, and contribute to the normalization of coenzyme balance. Normalization of the redox balance and wound state was more effective using hydrophilic dispersions due to Zn2 + penetration.

Wound Healing Composite Materials of Bacterial Cellulose and Zinc Oxide Nanoparticles with Immobilized Betulin Diphosphate

A design of new nanocomposites of bacterial cellulose (BC) and betulin diphosphate (BDP) pre-impregnated into the surface of zinc oxide nanoparticles (ZnO NPs) for the production of wound dressings is proposed. The sizes of crystalline BC and ZnO NPs (5-25%) corresponded to 5-6 nm and 10-18 nm, respectively (powder X-ray diffractometry (PXRD), Fourier-infrared (FTIR), ultraviolet (UV), atomic absorption (AAS) and photoluminescence (PL) spectroscopies). The biological activity of the wound dressings "BC-ZnO NPs-BDP" was investigated in rats using a burn wound model. Morpho-histological studies have shown that more intensive healing was observed during treatment with hydrophilic nanocomposites than the oleophilic standard (ZnO NPs-BDP oleogel; p < 0.001). Treatment by both hydrophilic and lipophilic agents led to increases in antioxidant enzyme activity (superoxide dismutase (SOD), catalase) in erythrocytes and decreases in the malondialdehyde (MDA) concentration by 7, 10 and 21 days (p < 0.001). The microcirculation index was restored on the 3rd day after burn under treatment with BC-ZnO NPs-BDP wound dressings. The results of effective wound healing with BC-ZnO NPs-BDP nanocomposites can be explained by the synergistic effect of all nanocomposite components, which regulate oxygenation and microcirculation, reducing hypoxia and oxidative stress in a burn wound.

Nanoparticle-induced inflammation and fibrosis in ex vivo murine precision-cut liver slices and effects of nanoparticle exposure conditions

Chronic exposure and accumulation of persistent nanomaterials by cells have led to safety concerns on potential long-term effects induced by nanoparticles, including chronic inflammation and fibrosis. With this in mind, we used murine precision-cut liver tissue slices to test potential induction of inflammation and onset of fibrosis upon 72 h exposure to different nanomaterials (0–200 µg/ml). Tissue slices were chosen as an advanced ex vivo 3D model to better resemble the complexity of the in vivo tissue environment, with a focus on the liver where most nanomaterials accumulate. Effects on the onset of fibrosis and inflammation were investigated, with particular care in optimizing nanoparticle exposure conditions to tissue. Thus, we compared the effects induced on slices exposed to nanoparticles in the presence of excess free proteins (in situ), or after corona isolation. Slices exposed to daily-refreshed nanoparticle dispersions were used to test additional effects due to ageing of the dispersions. Exposure to amino-modified polystyrene nanoparticles in serum-free conditions led to strong inflammation, with stronger effects with daily-refreshed dispersions. Instead, no inflammation was observed when slices were exposed to the same nanoparticles in medium supplemented with serum to allow corona formation. Similarly, no clear signs of inflammation nor of onset of fibrosis were detected after exposure to silica, titania or carboxylated polystyrene in all conditions tested. Overall, these results show that liver slices can be used to test nanoparticle-induced inflammation in real tissue, and that the exposure conditions and ageing of the dispersions can strongly affect tissue responses to nanoparticles.

Monodispersity of Poly(ethylene glycol) Matters for Low-Fouling Coatings

Poly(ethylene glycol) (PEG) is the most used hydrophilic polymer for low-fouling coatings to minimize nonspecific interactions. The PEG molecular weight or its length as well as surface density are typically considered as the main impacts on the control over low-fouling properties. However, the influence of PEG monodispersity on such investigations is typically ignored and rarely reported. Herein, we report the assembly of PEGylated coatings on planar surfaces and Au nanorods (AuNRs) using a series of monodisperse PEG (Mono-PEG) with exact molecular weights and commonly used polydisperse PEG (Poly-PEG) to investigate the effect of the PEG molecular weight and monodispersity on the low-fouling properties. Nonspecific interactions with proteins or cells on PEGylated planar surfaces can be significantly reduced when Mono-PEG with a molecular weight of 752 Da and above is used, while a higher average molecular weight of 2000 Da is required for Poly-PEG-modified surfaces. Cell association of PEGylated AuNRs further confirms that a low molecular weight of Mono-PEG is sufficient to achieve low-fouling properties. This study provides an insight and general guidance into the engineering of low-fouling surfaces by the appropriate choice based on the PEG monodispersity and/or molecular weights.

The investigation of the parameters affecting the ZnO nanoparticle cytotoxicity behaviour: a tutorial review

In the last 30 years the research about zinc oxide nanoparticles (ZnO NPs) and their related toxicity has shown a boom. ZnO NPs show cytotoxicity for both prokaryotic and eukaryotic cells and many studies demonstrated their selective toxicity towards cancer cells. However, with the increasing number of publications, it is observed an increase in the discrepancies obtained between the various results. Soon the scientific community understood that the ZnO NC toxicity behaviour is affected by many factors, related not only to the ZnO NPs themselves, but also to the experimental conditions used. Many recent reviews discussed these parameters by reporting experimental evidence and tried to assess the general statements about the ZnO NP cytotoxicity. This information is extremely useful for the evaluation of which type of ZnO NPs is more or less suitable for a specific study or application. However, despite that, a deep comprehension of the ZnO NP behaviour in relation to the different experimental conditions is still lacking. Actually, a full understanding of the reasons behind the NP behaviour is essential to better assess their biological activity and in particular their therapeutic application, avoiding undesired effects both in the experimental and clinical contexts. This tutorial review aims to be an experimental and practical guide for scientists that faced with the use of ZnO NPs for biomedical applications and, in particular, for their therapeutic purposes. The driving idea is to not simply summarize the results reported in the literature, but to provide instruments for a deep comprehension of the mechanisms affecting the ZnO NP cytotoxicity and behavior. This review also aims to point out the critical experimental parameters to be considered when working with these NPs, as well as the main related risks and limitations that scientists have to face.

Sea Urchin Extracellular Proteins Design a Complex Protein Corona on Titanium Dioxide Nanoparticle Surface Influencing Immune Cell Behavior

Extensive exploitation of titanium dioxide nanoparticles (TiO₂NPs) augments rapid release into the marine environment. When in contact with the body fluids of marine invertebrates, TiO₂NPs undergo a transformation and adhere various organic molecules that shape a complex protein corona prior to contacting cells and tissues. To elucidate the potential extracellular signals that may be involved in the particle recognition by immune cells of the sea urchin Paracentrotus lividus, we investigated the behavior of TiO₂NPs in contact with extracellular proteins in vitro. Our findings indicate that TiO₂NPs are able to interact with sea urchin proteins in both cell-free and cell-conditioned media. The two-dimensional proteome analysis of the protein corona bound to TiO₂NP revealed that negatively charged proteins bound preferentially to the particles. The main constituents shaping the sea urchin cell-conditioned TiO₂NP protein corona were proteins involved in cellular adhesion (Pl-toposome, Pl-galectin-8, Pl-nectin) and cytoskeletal organization (actin and tubulin). Immune cells (phagocytes) aggregated TiO₂NPs on the outer cell surface and within well-organized vesicles without eliciting harmful effects on the biological activities of the cells. Cells showed an active metabolism, no oxidative stress or caspase activation. These results provide a new level of understanding of the extracellular proteins involved in the immune-TiO₂NP recognition and interaction in vitro, confirming that primary immune cell cultures from P. lividus can be an optional model for swift and efficient immune-toxicological investigations.