Characterizing the Role of Biologically Relevant Fluid Dynamics on Silver Nanoparticle Dependent Oxidative Stress in Adherent and Suspension In Vitro Models

Zinc Oxide Nanoparticles Prime a Protective Immune Response in Galleria mellonella to Defend Against Candida albicans

Purpose: Zinc oxide nanoparticles (ZnO-NPs) have exerted antimicrobial properties. However, there is insufficient evaluation regarding the in vivo antifungal activity of ZnO-NPs. This study aimed to investigate the efficacy and mechanism of ZnO-NPs in controlling Candida albicans in the invertebrate Galleria mellonella. Methods: Galleria mellonella larvae were injected with different doses of ZnO-NPs to determine their in vivo toxicity. Non-toxic doses of ZnO-NPs were chosen for prophylactic injection in G. mellonella followed by C. albicans infection. Then the direct in vitro antifungal effect of ZnO-NPs against C. albicans was evaluated. In addition, the mode of action of ZnO-NPs was assessed in larvae through different assays: quantification of hemocyte density, morphology observation of hemocytes, characterization of hemocyte aggregation and phagocytosis, and measurement of hemolymph phenoloxidase (PO) activity. Results: Zinc oxide nanoparticles were non-toxic to the larvae at relatively low concentrations (≤20 mg/kg). ZnO-NP pretreatment significantly prolonged the survival of C. albicans-infected larvae and decreased the fungal dissemination and burden in the C. albicans-infected larvae. This observation was more related to the activation of host defense rather than their fungicidal capacities. Specifically, ZnO-NP treatment increased hemocyte density, promoted hemocyte aggregation, enhanced hemocyte phagocytosis, and activated PO activity in larvae. Conclusion: Prophylactic treatment with lower concentrations of ZnO-NPs protects G. mellonella from C. albicans infection. The innate immune response primed by ZnO-NPs may be part of the reason for the protective effects. This study provides new evidence of the capacity of ZnO-NPs in enhancing host immunity and predicts that ZnO-NPs will be attractive for further anti-infection applications.

A Study on Myogenesis by Regulation of Reactive Oxygen Species and Cytotoxic Activity by Selenium Nanoparticles

Reactive oxygen species (ROS) are continuously produced by skeletal muscle during contractile activity and even at rest. However, the ROS generated from excessive exercise or traumatic damage may produce more ROS than can be neutralized by an antioxidant capacity, which can be harmful to muscle function. In particular, selenium is a known antioxidant that regulates physiological functions such as cell differentiation and anti-inflammatory function. In this study, we developed nano-sized antioxidative biomaterials using selenium to investigate the protective and differentiation effects against C2C12 myoblasts in an H₂O₂-induced oxidative stress environment. The selenium nanoparticles (SeNPs) were produced with a size of 35.6 ± 4.3 nm and showed antioxidant effects according to the 3,3′,5,5′-tetramethylbenzidine assay. Then, SeNPs were treated to C2C12 cells with or without H₂O₂. Our results showed that SeNPs reduced C2C12 apoptosis and intracellular ROS levels. Additionally, SeNPs effectively up-regulated in the presence of H₂O₂, MyoD, MyoG, α-actinin, and myosin heavy chain, which are well known to increase during myoblast differentiation as assayed by qRT-PCR, immunocytochemistry-staining, western blotting. These results demonstrate that SeNPs can accelerate differentiation with its protective effects from the ROS environment and can be applied to the treatment of skeletal muscle in a cellular redox environment.

Implementation of a Dynamic Co-Culture Model Abated Silver Nanoparticle Interactions and Nanotoxicological Outcomes In Vitro

The incorporation of engineered nanoparticles (NPs) into everyday consumer goods, products, and applications has given rise to the field of nanotoxicology, which evaluates the safety of NPs within biological environments. The unique physicochemical properties of NPs have made this an insurmountable challenge, as their reactivity and variable behavior have given rise to discrepancies between standard cell-based in vitro and animal in vivo models. In this study, enhanced in vitro models were generated that retained the advantages of traditional cell cultures, but incorporated the modifications of (1) inclusion of an activated immune element and (2) the presence of physiologically-relevant dynamic flow. Following verification that the human alveolar epithelial and macrophage (A549/U937) co-culture could be successfully sustained under both static and dynamic conditions, these cultures, in addition to a standard A549 static model, were challenged with 10 nm citrate coated silver NPs (AgNPs). This work identified a reshaping of the AgNP-cellular interface and differential biological responses following exposure. The presence of dynamic flow modified cellular morphology and reduced AgNP deposition by approximately 20% over the static exposure environments. Cellular toxicity and stress endpoints, including reactive oxygen species, heat shock protein 70, and secretion of pro-inflammatory cytokines, were found to vary as a function of both cellular composition and flow conditions; with activated macrophages and fluid flow both mitigating the severity of AgNP-dependent bioeffects. This work highlights the possibility of enhanced in vitro systems to assess the safety of engineered NPs and demonstrates their effectiveness in elucidating novel NP-cellular interactions and toxicological profiles.