Effect of lanthanum substitution on shape and cytotoxicity of zinc oxide (LaxZn1−XO) nano-colloids

Abstract

The objective of this study was to observe the role of lanthanum (La) substitution upon cytotoxic potential and morphology of zinc oxide (ZnO) nano-colloids. A very simple and low cost sonochemical method was used for synthesis of nano-colloids (LaxZn1−xO; where x = 0, 0.1 and 0.2 M). Structural and surface morphological characterizations were performed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis confirmed the hexagonal wurtzite structure. SEM explained the substitution effect of La on ZnO nano-colloids by morphological changes. On increasing La concentration, particles morphology shifted from spherical to rod like with decrease in average crystallite size (from 61–35 nm). Raman spectroscopy confirmed molecular vibrations modes at wavelengths (330, 379.6, 436.6 and 581.6 cm−1), which confirmed its hexagonal structure. Hydrodynamic size and zeta potential were studied using dynamic light scattering. In vitro cytotoxicity analysis revealed that La substitution at 20% (particle size 35 nm) showed significant antibacterial activity against pathogenic bacteria; Staphylococcus aureus, Pseudomonas aeruginosa (p ≤ 0.01) and Shigella flexneri (p ≤ 0.05) when compared with pure ZnO nano-colloids. About 50.3 ± 4.5% mortality (p ≤ 0.05) was achieved against brine shrimp at a dose of 10 μg ml−1. Enhancement in cytotoxicity can be explained by change in morphology (rod shaped) and decrease in size (35 nm) which aids in better penetration inside the cell and increased oxidative stress. However, further in vitro studies need to be done to access the potential of LaxZn1−xO in therapeutics and detailed mechanism of action.