A Microwave-Assisted Synthesis of Zinc Oxide Nanocrystals Finely Tuned for Biological Applications

Abstract

Herein we report a novel, easy, fast and reliable microwave-assisted synthesis procedure for the preparation of colloidal zinc oxide nanocrystals (ZnO NCs) optimized for biological applications. ZnO NCs are also prepared by a conventional solvo-thermal approach and the properties of the two families of NCs are compared and discussed. All of the NCs are fully characterized in terms of morphological analysis, crystalline structure, chemical composition and optical properties, both as pristine nanomaterials or after amino-propyl group functionalization. Compared to the conventional approach, the novel microwave-derived ZnO NCs demonstrate outstanding colloidal stability in ethanol and water with long shelf-life. Furthermore, together with their more uniform size, shape and chemical surface properties, this long-term colloidal stability also contributes to the highly reproducible data in terms of biocompatibility. Actually, a significantly different biological behavior of the microwave-synthesized ZnO NCs is reported with respect to NCs prepared by the conventional synthesis procedure. In particular, consistent cytotoxicity and highly reproducible cell uptake toward KB cancer cells are measured with the use of microwave-synthesized ZnO NCs, in contrast to the non-reproducible and scattered data obtained with the conventionally-synthesized ones. Thus, we demonstrate how the synthetic route and, as a consequence, the control over all the nanomaterial properties are prominent points to be considered when dealing with the biological world for the achievement of reproducible and reliable results, and how the use of commercially-available and under-characterized nanomaterials should be discouraged in this view.

Photocatalytic properties of zirconium oxide–zinc oxide nanoparticles synthesised using microwave irradiation

“…ZrO 2 -ZnO (10%) before and after the sorption process and the photodegradation of the MB. The XRD pattern of the prepared crystalline ZnO is in accordance with the hexagonal zincite crystalline structure of ZnO, with sharp and strong peaks at 2θs of 31.75°, 34.40°, 36.24°, 47.54° and 56.61°, which correspond to (100), (002), (101), (012) and (110), respectively (Garino et al 2019;Hasanpoor et al 2015). The XRD pattern for pure ZrO 2 confirmed characteristic planes at 2θs of 30.23°, 34.92° and 50.26° (Singh and Nakate 2014;Manjunatha and Dharmaprakash 2016).…”

The Synergistic Effect of Nanocrystals Combined With Ultrasound in the Generation of Reactive Oxygen Species for Biomedical Applications

“…As evidenced by FESEM and TEM analysis (Figures 2A,B), the ZnO-NH 2 nanomaterials can be ascribed to single nanocrystalline structures, with an average diameter of 20 ± 5 nm, see also Garino et al (2019a) for comparison. Aminefunctionalized ZnO nanocrystals have an average hydrodynamic diameter of 122 nm in their original ethanolic suspension and also in water ( Figure 2C) and a Z-Potential value of +22 mV in double distilled water.…”

“…ZnO nanoparticles were synthesized through a microwaveassisted synthesis, as previously reported (Garino et al, 2019a). The reaction path is based on the hydrolysis of the zinc precursors (zinc acetate dihydrate) due to the presence of sodium hydroxide as the base in methanol.…”

“…The reaction path is based on the hydrolysis of the zinc precursors (zinc acetate dihydrate) due to the presence of sodium hydroxide as the base in methanol. The as-synthesized ZnO were then functionalized with amino-propyl groups with a post-grafting approach using 3-(AminoPropyl)-TriEthoxySilane (APTES) at 10 mol% with respect to the molar amount of ZnO, as in Dumontel et al (2017) and Garino et al (2019a).…”

Structure and Properties of ZnO Coatings Obtained by Atomic Layer Deposition (ALD) Method on a Cr-Ni-Mo Steel Substrate Type

“…Considering, first of all, the biomedical properties of zinc oxide, it should be emphasized that there is a need to constantly assess the potential adverse health effects of metal nanoparticles and metal oxides, including ZnO, in order to ensure their safe use [ 29 , 30 , 31 , 32 , 33 , 34 ]. Particular attention should be paid to the assessment of the cytotoxicity of ZnO nanoparticles in the human body in short- or long-term exposures.…”