Toxicity of Functional Nano-Micro Zinc Oxide Tetrapods: Impact of Cell Culture Conditions, Cellular Age and Material Properties

Abstract

With increasing production and applications of nanostructured zinc oxide, e.g., for biomedical and consumer products, the question of safety is getting more and more important. Different morphologies of zinc oxide structures have been synthesized and accordingly investigated. In this study, we have particularly focused on nano-micro ZnO tetrapods (ZnO-T), because their large scale fabrication has been made possible by a newly introduced flame transport synthesis approach which will probably lead to several new applications. Moreover, ZnO-T provide a completely different morphology then classical spherical ZnO nanoparticles. To get a better understanding of parameters that affect the interactions between ZnO-T and mammalian cells, and thus their biocompatibility, we have examined the impact of cell culture conditions as well as of material properties on cytotoxicity. Our results demonstrate that the cell density of fibroblasts in culture along with their age, i.e., the number of preceding cell divisions, strongly affect the cytotoxic potency of ZnO-T. Concerning the material properties, the toxic potency of ZnO-T is found to be significantly lower than that of spherical ZnO nanoparticles. Furthermore, the morphology of the ZnO-T influenced cellular toxicity in contrast to surface charges modified by UV illumination or O2 treatment and to the material age. Finally, we have observed that direct contact between tetrapods and cells increases their toxicity compared to transwell culture models which allow only an indirect effect via released zinc ions. The results reveal several parameters that can be of importance for the assessment of ZnO-T toxicity in cell cultures and for particle development.

Toxicity of Metal Oxide Nanoparticles: Mechanisms, Characterization, and Avoiding Experimental Artefacts

“…The interaction between the nanomaterial and the cell wall may contribute to the toxicity. In many reports, the contact with the cells was required to observe or enhance the toxicity of MO nanomaterials . The nanoparticles remained firmly attached to the bacteria membrane even after washing the bacteria .…”

“…In the evaluation of toxicity, it should be noted that different organisms have different sensitivity to nanomaterials, with algae and crustaceans being the most sensitive ones . In cell culture toxicity tests, the cell density and the number of preceding cell divisions can also affect the toxicity . The toxicity of MO nanomaterials also varies from one material to another, but cytotoxicity and/or DNA damage has been reported for a number of MOs.…”

Fabrication of Macroscopically Flexible and Highly Porous 3D Semiconductor Networks from Interpenetrating Nanostructures by a Simple Flame Transport Approach

“…It is important to mention that these ZnO tetrapods show negligible cytotoxicity against normal human dermal fibroblasts cells even at high concentrations (>0.1 mg mL −1 ) . A further processing step in this second variant finalizes the 3D network formation, where the harvested metal‐oxide nano‐microstructures are appropriate building blocks.…”

Versatile Fabrication of Complex Shaped Metal Oxide Nano-Microstructures and Their Interconnected Networks for Multifunctional Applications

“…Similar phenomenon was observed in case of SnO 2 nanowire networks, synthesized by FTS approach shows strong potential of blocking the HSV-1 entry into the cells 62) . For biomedical applications of different nano -microstructures, cytotoxicity is very important issue and these nano-micro scale ZnO tetrapods exhibit very low level of cytotoxicity as compared to conventional spherical nanoparticles and ZnCl 2 reference 71) , which implies towards better utilization in biomedical engineering.…”