Study of Antibacterial Effect of Cerium Oxide Nanoparticles on Escherichia Coli Microorganism

In the present work antibacterial effect of NCO (Nano-Cerium Oxide) particles on E.Coli (Escherichia Coli) Bacteria was studied. NCO (Nano Cerium Oxide) particles were synthesized via microwave induced combustion method. XRD (X-Ray Diffraction), SEM (Scanning Electron Microscope) and FTIR (Fourier Transform Infrared Spectroscopy) characterized. NCO particles. Using Scherrer equation it was noted that NCO particles of 14-25 nm size were produced. The SEM and XRD results showed that size of NCO particles was decreased with increasing synthesization time. Synthesization time played vital role on the size of NCO particles. It was also noted that antibacterial action of NCO particles is size dependent. Antibacterial study through disc diffusion method revealed that NCO particles enhanced the efficiency of Amikin Grasil, Terivid and spraxin drugs against the E.Coli bacteria appreciably.


INTRODUCTION
C erium oxide commonly known as ceric oxide or ceria is most abundant rare earth metal oxide.
NCO particles are currently being used as antibacterial catalyst, oxygen sensor and in production of oxidation resistant coating [1][2][3]. Due to small size, NCO particles possess unique physical and chemical properties such as high magnetic moment, large conductivity and extremely high complexation reactivity [3][4]. NCO particles are insoluble in water and has slightly hygroscopic nature which means it can absorb some amount of CO 2 and moisture from the atmosphere [5].
Some microorganisms are harmful for human body and cause diseases in different ways such as E.Coli bacteria, staphylococcus aureus, and pseudomonas [6]. NCO particles are pale-yellow-white powder. NCO particles has FCC crystal structure and is highly stronger than other rare earth oxides such as Bi 2 O 3 (Bismuth Dioxide), ThO 2 (Thorium Dioxide) and ZrO 2 (Zirconia) [7][8]. Many methods are used to prepare NCO particles such as microwave energy, hydrothermal synthesis, sol-gel methods, precipitation and emulsion methods. Microwave induced method is simple, rapid and efficient method as compared with other conventional methods [9][10].

E.Coli bacteria is a gram-negative microorganism found
in digestive tracts of humans as well as animals and cause haemolytic uremic syndrome, bloody diarrhea and kidney failure which can cause to death [11]. NCO particles are used with different antibiotics to inhibit the growth of E.Coli bacteria. NCO particles material is one of important example of a metal oxide nanomaterial with many biomedical applications [12][13][14]. Previous research work mostly focused on effect of NCO particles on staphylococcus aureus and pseudomonas microorganism The present study aims to investigate the antibacterial effect of NCO particles on E. Coli bacteria which has not been found in literature.

Disc Diffusion Method
The resistance E.coli for the antibiotic drugs namely

Measurement of Inhibition Zone
The diameter of inhibition zone was measured using

Phase Analysis of Nano Cerium Oxide particles
Phase analysis of NCO was determined by XRD. XRD pattern of NCO particles synthesized at different time intervals is shown in Fig. 1. The Fig. 1   Bacteria is not resistant to specific antibiotic; therefore its growth was inhibited by the drug effectively.

FTIR Analysis
2. +1-2 Intermediate (I) Bacteria is less resistant to specific antibiotic, therefore its growth could inhibited to some extent by the drug.

0-1 Resistant (R)
Bacteria is resistant to specific antibiotic, therefore its growth could not inhibited by the drug effectively.

Particle Size Analysis of NCO
Particle size of NCO particles was determined by scherrer equation (d XRD =0.9/cos) given in Table 2. It can be seen in table that average crystalline size of NCO particles ranging from 25.9-13.9 nm. Substantial decrease in size of NCO particles was occurred with increasing the synthesis time.
During synthesization of NCO when we increase synthesis time size of particles are decreased due to dissipation of particles.

Morphology of NCO Particles
Morphology of NCO particles was investigated using SEM. SEM images shown in Fig. 3(a-c) Fig. 3(a-c) that with increasing the synthetization time porosity is increased and irregularity in NCO particles was decreased and Fig. 3(d) indicated that well regular spherical particles were developed having size 100 nm.  Table 3 indicates that 20 mg/ml NCO 15min along with 30 mg of antibiotic drugs namely Terivid, Velosef, Amikin Grasil, Spraxin and Enoxabid failed to inhibit against the growth of E.Coli bacteria.

Antimicrobial Analysis of NCO Particles on E.Coli Bacteria
Antimicrobial activity of NCO 25min particles results given in Table 3 indicates that diameter of inhibition zone was increased to some extent when terivid and amikin grasil drugs were supplemented with NCO 25min particles. Moreover, the efficiency of, velosef, spraxin and enoxabid antibiotics could not improve with the addition of NCO 25min particles.
Antimicrobial analysis with NCO 40min particles are quite encouraging as compared to results with NCO 15min particles and NCO 25min particles. It can be seen in Table 3 that size of inhibition zone in case of grasil, terivid and spraxin was substantially increased with the addition of NCO 40min particles.
It is appreciable to note that with addition of NCO 40min particles inhibition zone could not increase rather decreased like NCO 15min particles and NCO 25min particles. The evidence of decrease or increase in the inhibition zone was also can see in images of the diffusion disks after 24 h incubation period. Fig. 4(a-c) illustrates the images of few of the diffusion disks and demonstrate where and when the inhibition zone was increased with the effect of NCO particles.
Results of the paper compared with literature: The XRD pattern of CeO 2 nanoparticles is shown in Fig. 5. The XRD pattern was scanned from 10- (2) Crystallite size was obtained by using Scherrer equation (Fig. 6): The FTIR spectrum of NOC nanoparticles is shown in Fig. 7. The spectrum was recorded in the wave number range of 400-4000 cm -1 .
Explanation for all results, why?