Inhibiting Bacterial Growth --- a Novel Biomedical Application of Ceria Nanoparticles

Inhibiting Bacterial Growth --- a Novel Biomedical Application of Ceria Nanoparticles

Qi Wang¹, J. Manuel Perez², Thomas J. Webster^1,3

¹Bioengineering Program, ³Department of Chemical Engineering, College of Engineering, Northeastern University, Boston, MA 02115

²Nanoscience Technology Center, University of Central Florida, Orlando, FL 32826

As a highly abundant material, ceria (or cerium oxide, CeO₂) is technologically important due to its wide-range of applications, for example in catalysts for the elimination of toxic auto-exhaust gases,^[1-2] oxygen sensors,^[3] electrochromic thin-films^[4] and so on. Upon the transition from a macro-sized particle into a nanocrystalline particle, ceria significantly changes its physicochemical properties to usually possess a high density of nanocrystalline ceria interfaces.^[5] Thus, nanostructured ceria has attracted extensive attention in such applications due to improvements in  redox properties, transport properties, and high surface to volume ratios.

However, although ceria nanoparticles have been studied for numerous applications in traditional science and engineering applications, there have been almost no studies regarding the potential biomedical applications of ceria until recently when researchers demonstrated that ceria nanoparticles possess antioxidant properties at physiological pH values. The ability of these nanoparticles to act as an antioxidant lies in their ability to reversibly switch from Ce³⁺ to Ce⁴⁺.^[6] In recent studies, this antioxidative ability enables the application of ceria nanoparticles to protect against radiation damage, oxidative stress and inflammation.^[7]

To build off of these exciting applications of ceria nanoparticles, the present study investigated for the first time the influence of ceria nanoparticles on bacteria growth. Specifically, dextran or polyacrylic acid coated ceria nanoparticles were studied in the bacterial experiments involving Pseudomonas aeruginosa. Results showed that the growth of P. aeruginosa was significantly inhibited in the presence of dextran or polyacrylic acid coated ceria nanoparticles. Ceria nanoparticles with either coating inhibited bacteria growth by about 20% compared with blank controls after treatment for 1 hour. After 6 hours of treatment, the inhibition of bacterial growth reached 99.94% and 98% for dextran coated ceria nanoparticles and polyacrylic acid coated ceria nanoparticles, respectively, compared with blank controls. After 24 hours of treatment, there were at least 98.69% bacteria inhibition for polyacrylic acid coated ceria nanoparticles and almost complete (~100%) inhibition for dextran coated ceria nanoparticles. This study revealed a promising biomedical application of ceria nanoparticles to prevent bacterial infections that is worthwhile to be further explored.

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