A Study of the Chemistries, Growth Mechanisms, and Antibacterial Properties of Cerium- and Yttrium-Containing Nanoparticles.

Under the current climate, physicians prescribe antibiotics for treating bacterial infections, and such a limitation to a single class of drugs is disadvantageous since antibiotic-resistant bacteria have adapted to withstanding their stresses. Antibiotic alternatives are sought, and herein metal nanoparticles comprised of the rare earth elements cerium and yttrium were determined to invoke toxicity on methicillin-resistant Staphylococcus aureus (MRSA) and a multi-drug-resistant strain of Escherichia coli (MDR E. coli). Ceria nanoparticles, yttrium-doped ceria nanoparticles, and cerium-doped yttria nanoparticles were fabricated by a wet chemical route, homogeneous precipitation in hexamethylenetetramine (HMT). To demonstrate the drastic variations in nanoparticle structure and toxicity that occur when the synthesis method and solvent are substituted, two additional approaches involving solvothermal and hydrothermal reactions were pursued in the production of yttrium-containing nanoparticles. Intrinsic nanoparticle features of size, morphology, and composition were construed by physiochemical characterizations, which aided in the elaboration of chemical reaction and growth mechanisms. It was determined by in vitro plate count assays that ceria nanoparticles which had been doped using the yttrium metal precursor after 30 min of the HMT reaction, at 500 μg/mL, were the most effective at inhibiting MRSA growth without imposing significant cytotoxicity on human dermal fibroblast cells. A total of 500 μg/mL of cerium- and yttrium-containing nanoparticles, prepared in a 1:1 molar ratio, were similarly biocompatible and antimicrobial, in the case of MDR E. coli. Indeed, as this study showed, nanoalternatives to antibiotics are feasible, adaptable, and can be facilely produced. The possible clinical applications of the rare earth metal nanoparticles are variegated, and ceria and yttria nanoparticles are additionally credited in the literature as dynamic antioxidants, regulators of tissue regeneration, and anticancer agents.