Antibacterial Function of Chromium Nanoparticles Against K. Pneumonia, E. coli and P. typhus

The bioactive chromium nanoparticles were synthesized by calcination followed by thermal decomposition method. The antibacterial activity of chromium nanoparticles diffused in Dimethyl sulphoxide (DMSO). The antibacterial activity of chromium nanoparticles carried out against signicant human pathogens (gram negative bacteria) viz, K. pneumonia, E. coli and P. typhus using agar diffusion cup plate method at 100 µg/ml concentration. The highest zone of inhibition was observed (12.0 mm) against K. pneumonia and lowest zone of inhibition (7.0 mm) E. coli. Thus, the outcomes of these studies suggest that synthesized chromium nanoparticles are of clinical importance.


Introduction
Nanoparticles of transition metal oxide represent wide range of materials that have been researched extensively due to their versatile electronic, medicinal, magnetic, catalytic and thermal properties. Chromium (Cr) metal is a heavy metal and widely used in pigment, electroplating, textile dyeing, paper and pulp industries [1]. Material developed at Nano range are applied in various elds i.e biomarkers, optical sensors, antimicrobial agent and drug delivery systems [2]. The nanotechnology studies have concentrated on the medicinal use of nanoparticles for the treatment and antimicrobial effect. Chromium and chromium oxide nanoparticle have gained wide recognition due to their importance in nanotechnology as well as medical eld. Chromium nanoparticles have become the subject to immense research interest in the current years due to their broad application as antimicrobial agent, medical devices and water puri cation systems [3]. Nanoparticles shows a versatile property due their high surface to volume area as compared to bulk material. One of most important thing of nanotechnology plan is to identify e cient synthesis process of nanoparticles. Various method have been reported for the preparation for chromium nanoparticles such as hydrothermal [4][5], sol-gel [6], combustion [ 7], precipitation [8], gelation [9], microwave irradiation [10] micro-emulsion [11] method. Metallic nanoparticles have favourable application in biomedical sciences such as nano-diagnosis, drug delivery and biolabeling [12]. Previous work by many researchers reported that the chromium nanoparticles bring antimicrobial activity against pathogenic microorganism. For example, Ramesh et al. and Khatoon et al. reported Cr 2 O 3 nanoparticles inhibit the growth of Escherichia coli [13][14] and Pseudomonas aeruginosa. El-Ajaily et al. [15] reported the antibacterial activity of Cr (VI) and Cr (III) complexes against P. aeruginosa bacteria. Singh et al. [16] reported viability of an environmentally relevant bacterium, E. coli exposed to varying concentrations of Cr 2 O 3 nanoparticles was evaluated. Finally, it is very important to note that the antimicrobial activity of chemically synthesized chromium nanoparticles have not been studied for all three microorganisms. Therefore the purpose of this study were synthesis and characterization of chromium nanoparticles and their antibacterial function against K. pneumonia, E. coli and P. typhus.

Material And Methods
Throughout the present study analytical grade chemical Phenol, formaldehyde, chromium Chloride, and acetic acid (CDH Pvt. Ltd) and HCl (Fisher Scienti c) were used. Chromium nanoparticle have been prepared by calcination method using phenol-formaldehyde resin as precursor. The studies of chromium nanoparticles characterized by Fourier Transform Infra-Red spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) spectroscopy, X-Ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM). The detail method of synthesis and characterization of metallic nanoparticles has already been given in our earlier publication [17].

Antimicrobial Activity
Bioassay of chromium nanoparticles was investigated by employing agar diffusion cup plate method at 100 µg/mL against known bacterial strain viz. K. pneumonia, E. coli and P. typhus relying on commercial drug cipro oxacin as control. 0.001 g of synthesized chromium nanoparticles was weighed and dissolve in 10 ml DMSO. 100 µg/mL concentration of chromium nanoparticles was prepared from stock and used for the analysis. Prepared luria agar medium was dispended into petri dishes and allowed for 1 hour to set. The plates were labelled and inoculated with 50µL of appropriate test organism. Wells of diameter 7 mm were bored in each plate using sterile cork borer, the wells were lled halfway with 100 µg/ml concentration of the synthesized metal nanoparticles solution. The plates were incubated at 37 0 C for 24 hours, after which the zone of inhibition was measured.
Proper safety measures were adopted by the researcher during the analysis to prevent any bio-hazard.

Result And Discussion
Antimicrobial activity of Cr NPs on K. pneumonia, E. coli and P. typhus ZOI observed for chromium nanoparticles against three pathogens are show in the Table1 below: The ZOI observed for chromium nanoparticles showed (Fig. 1) that the transition metal nanocomposite is most active against K. pneumonia, evident in ZOI observed 12.0 mm. In contrast, a ZOI of 7.00 mm was observed for E. coli, thus indicating a poor activity of the metal nanoparticles against test organism. The afore reported observations on bioassay of chromium nanoparticles rationalized our conclusion that chromium nanoparticles are highly suitable for incorporation into drugs designed to mitigate diseases caused by K. pneumonia.
The higher Zone of Inhibition in case of K. pneumonia by the chromium oxide nanoparticles synthesized by sol-gel technique was reported earlier [18] and systematic antimicrobial activity of chromium nanoparticles against pathogenic bacteria also reported earlier (Uma et al. 2019 and Kanakalakshmi et al. 2017. [3,19] Conclusion The bioactive chromium nanoparticles were synthesized by simple chemical precipitation followed by thermal decomposition method. The antibacterial activity of chromium nanoparticles compared with other microorganism using agar diffusion cup plate method. The highest zone of inhibition was observed against K. pneumonia (12.0 mm). The synthesized chromium nanoparticles were found to be better antibacterial agent. Furthermore, the extraordinary antibacterial activity of Cr NPs can be employed in their drug delivery, biomedical and pharmaceutical applications.

Funding statement
This research did not receive any speci c grant from funding agencies in the public, commercial, or notfor-pro t sectors.
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