Novel flow synthesized phase pure and doped zinc oxides with tailorable properties for potential anticancer applications

Abstract

Cancer is a leading cause of nearly 10 million deaths each year and it's expected to increase up to 30 % in low-income countries by 2040. Traditional methods of treating most cancers rely on varying combinations of chemotherapy and surgeries. Chemotherapeutic drugs have significant side effects but remain the main cornerstone of current treatments. Nanotechnology has recently offered potentially viable alternatives as certain inorganic nanoparticles display selectivity towards cancer cells. Oxides such as Zinc Oxides have been the focus of significant interest due to their cancer cell selectivity and antibacterial properties. Doped Zinc Oxides exhibit enhanced biological performance. Traditional routes of Zinc Oxide synthesis are mostly multistep, require stringent control over reaction parameters and are time consuming. Flow Synthesis of inorganic nanoparticles is a high throughput approach that aids discovery through tunability and its continuity. This work forms the first comprehensive report on synthesis and characterization of low temperature flow synthesis of phase pure and doped zinc oxides (Cerium, Potassium, Calcium, Iron and Magnesium in the 0.5–2.0 mol% range). X-ray diffraction confirmed the synthesis of phase pure and doped zinc oxides (and an effect on dopant type and its concentration on particle size and overall crystallinity). Transmission and Scanning Electron Microscopy confirmed that the type of dopant, dopant ion concentration and heat-treatments affect particulate morphology and size, which in-turn are expected to have an effect on biological performance. UV–Vis Diffuse Reflectance spectroscopy revealed that the band-gap decreased from 3.1 eV for phase-pure Zinc Oxide to 2.62 eV for 2.0 mol% Fe doping (theoretical). This also corresponded to the highest cancer cell killing potential (MCF-7 breast cancer and neuroblastoma IMR-32 cells, respectively) determined using cytotoxicity results. Summarily, this work demonstrated the tailorability of the flow synthesis process through its effect on particle size, morphology, dopant ion concentration, crystallinity, and biological performance of phase-pure and doped zinc oxides. This work also successfully demonstrated the anticancer potential of novel flow synthesized phase pure, and ion doped zinc oxides.