^1*Department of Biotechnology, Meerut Institute of Engineering and Technology, Meerut, Uttar Pradesh, India

²Department of Biotechnology, Mewar University, Gangrar, Chittorgarh, Rajasthan, India

Metal nanoparticles have been intensively studied within the past decade. Nanosized materials have been an important subject  in basic and applied sciences. Zinc oxide nanoparticles have received considerable attention due to their unique antibacterial, antifungal, and UV filtering properties, high catalytic and photochemical activity. The objective of this work is to synthesize Zinc oxide nanoparticles using chemical method and characterize zinc oxide nanoparticles. Further antibacterial activity of Zinc oxide nanoparticles and antibiotics was analyzed against various pathogenic bacteria. It was found that thte minimum of zones of inhibition was found (0.2cm)   in P. aeruginosa, S. typhimurium, M. luteus, and A. hydrophila. The maximum of zones of inhibition was observed (0.5 cm) in S. epidermis and E. aerogens. The observed results, indicates higher antibacterial activities in Tetracycline then Cholramphenicol> Penicillin and the antibacterial activities of antibiotics are slightly less against eight pathogenic bacterial species as compared to chemically synthesized zinc oxide nanoparticles.

Nanoparticles, Zinc oxide, Antibacterial activity, Antibiotics,  Pathogenic bacteria,  Photochemical activity

Nanotechnology is emerging as a rapidly growing field with its application in science and technology for the purpose of manufacturing new materials at the nanoscale level (Albrecht et al. 2006). Nanotechnology is understood as research and technology development at the atomic, molecular or macromolecular levels using a length scale of approximately 1-100 nm in any dimension including the ability to control or manipulate matter on an atomic scale. An important additional distinction should be made between nanostructured thin films or other fixed nanometer-scale objects (such as the circuits within computer microprocessors) and free nanoparticles (Tyagi et al. 2012).Ultrafine semiconductors particles are of great scientific interest as they are effectively a bridge

between bulk materials and atomic or molecular structures. They possess special properties such as a  large  surface to volume ratio, increased activity, special electronic properties and unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. Among various semiconducting materials, zinc oxide (ZnO) is a distinctive electronic and photonic wurtzite n-type semiconductor with a wide direct band gap of 3.37 eV and a high exciton binding energy (60 meV) at room temperature (Wang 2004). The high exciton binding energy of ZnO would allow for excitonic transitions even at room temperature, which could mean high radiative recombination efficiency for spontaneous emission as well as a lower threshold voltage for laser emission microorganisms such as bacteria, actinomycetes, yeasts, and fungi continue to be researched and investigated in synthesis of metallic nanoparticles, the use of parts of whole plants for similar nanoparticle biosynthesis methodologies is an exciting possibility that is relatively unexplored and underexploited (Tyagi et al. 2012).Synthesis of AgNPs by reduction of aqueous Ag+ ions by the extract of onion, garlic, papaya and apple and their toxicity has been reported (Tyagi et al. 2016).ZnO nanoparticles are promising candidates for various applications, such as nanogenerators (Gao et al. 2005), gas sensors (Cheng et al. 2004), biosensors (Topoglidis et al. 2001), solar cells (Hames et al. 2010), varistors (Jun et al. 2002), photodetectors (Sharma et al. 2003), and photocatalysts (Kamat et al. 2002). ZnO is a mechanical actuators and piezoelectric sensors (Ko et al. 2003;  Zaouk et al. 2006). Zinc Oxide is widely used in a number of application like varistors (Rana et al. 2010) UV lasers, gas sensors, photoprinting, electrochemical nanodevice, sunscreen lotion cosmetics  and  medicated  creams (Ravichandrika et al. 2012) due to its several properties such as good  transparency,  high  electron mobility, strong room temperature luminescence. From the literature survey, it was found that various approaches for the preparation of ZnO nanopowders have been developed, namely, sol-gel, microemulsion, thermal decomposition of organic precursor, spray pyrolysis, electrodeposition, ultrasonic, microwave-assisted  techniques, chemical vapor deposition, and hydrothermal and precipitation methods (Singhai et al. 1997;  Rataboul et al. 2002; Okuyama & Wuled Lenggoro 2003; Wei & Chang 2008; Hu et al. 2004; Wu & Liu 2002; Zhai et al. 2008; Bitenc et al. 2008). Most of these techniques were not extensively used on a large scale, but chemical synthesis has been widely used due to its simplicity and is less expensive. In the present work, ZnO nanoparticles were synthesized by wet chemical method which was then characterized using UV-VIS spectroscopy and FTIR analysis. The antibacterial activity of synthesized ZnO nanoparticles was checked against various pathogenic bacteria and three antibiotics.

All chemicals used in this experiment were of the highest purity and obtained from Sigma and Merck. Zinc nitrate soluble starch and sodium hydroxide of analytical grade were used for chemical  synthesis  of  zinc  oxide nanoparticles. A solution of 0.1mol was prepared with 1% starch soluble starch and 300ml (0.2 Mol)  sodium  hydroxide  was prepared. For antibacterial activities against antibiotics  we  procured antibiotics    disc.

The toxic effects of zincoxide nanoparticles against eight pathogenic bacteria were used for and three antibiotics (Tetracycline, Chloramphenicol  and  Penicillin)  were  used.  Pseudomonas  aeroginosa  (MTCC-3160),  Bacillus cereus (MTCC-1305), Salmonella typhimurium (MTCC-1253), Micrococcus luteus (MTCC-1809), Staphylococcus epidermis (MTCC-3086), Aeromonas pneumonia (MTCC-3384), Aeromonashydrophila (MTCC-1739) and Enterobacter  aerogens  (MTCC-2823)  obtained from  IMTECH Chandigarh.

The ZnO nanoparticles was prepared by wet chemical method using zinc nitrate and sodium hydroxides  precursors and soluble starch as stabilizing agent. Soluble starch (0.5%) was dissolved in 500 ml of distilled water and treated in microwave oven for complete solubilization. Zinc nitrate, 14.874 g (0.1 Mol), was added in the above solution. Then the solution will keep under constant stirring at room temperature using magnetic stirrer for one hour. After complete dissolution of zinc nitrate, 300ml (0.2 Mol), of sodium hydroxide solution was added under constant stirring, drop by drop touching the walls of the vessel. The reaction was allowed to proceed for 2 hrs after complete addition of sodium hydroxide. After the completion of reaction, the solution was allowed to settle for overnight and then supernatant solution was discarded carefully. The remaining solution was centrifuged at 10,000 × g for 10 min and the supernatant was discarded. These produced nanoparticles were washed three times using distilled water. Washing was carried out to remove the byproducts and the excessive starch that were bound with the nanoparticles. After washing, the nanoparticles were dried at 80°C for overnight. During drying, complete conversion of Zn(OH)2 into ZnO takes place.

In our study we did comparative analysis of antibacterial activity of chemical synthesized  zinc oxide nanoparticles   and commercially available  antibiotics  such  as  Tetracycline,  Chloramphenicol  and  Penicillin.Secondly we  wanted to investigate whether chemically synthesized zinc oxide can exhibit syngerstic effect with commercially available antibiotics to effectively target multidrug restistant bacteria? Our results demonstrates that the synerstic effect of chemically synthesized zinc oxide nanoparticles  and  antibiotics  results  in  the  maxium  antibacterial  activity  and can  even  target  multidrug  resistant bacteria.

Zinc oxide nanoparticles have some excellent properties like exceptional mechanical strength and good antistatic, antibacterial and UV absorption properties. The zinc oxide nanoparticles were synthesized using wet chemical method (Figure 1).

Zinc Oxide nanoparticles were synthesized using starch sodium hydroxide and zi c nitrate. The chemically synthesized zinc oxide nanoparticles were characterized using UV-Vis spectroscopy and FTIR spectroscopy. Microorganisms used for antibacterial activity are P. aeroginosa, B.  cereus,  S.  typhimurium,  M.  luteus,  S.  epidermis, A. pneumonia, A. hydrophila and E. aerogens. The three antibiotics were used  Chloramphenicol,  Tetracyclin and Penicillin for the antibacterial activity. The antibacterial activity performance of ZnO nanoparticles  was done by using disc diffusion method. From the above study it was assumed that the zone of inhibition was observed against different pathogenic bacteria for zinc  oxide nanoparticles and the antibiotics. But when antibiotic  disc was mixed zinc oxide nanooparticles zone of inhibition was increased which illustrates that the anitibacterial activity was increased when zincoxide nanoparticles  was  mixed  with  antibiotics  against  various  pathogenic  bacteria