Analysis Of Antibacterial Activity Of ZnO

ZnO is a potential antimicrobial agent that was investigated earlier. ZnO in various forms shows various antimicrobial properties against different pathogens. A major problem for achieving efficient rate in these applications is a quick recombination rate of photo induced charge carriers. To overcome this problem, a competent method is needed to deposit noble/transition/rare earth metals on semiconductors. ZnO is a promising material that acts against food borne pathogens like Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus). As ZnO has antimicrobial property it plays a wide role in various instruments, surgical materials, band aids, ointments that are used in hospitals and health care centers. Apart from this, it has been widely used by various pharmaceutical industries for drug discovery as well as for research purpose. It is also used as a fabric coating to make bed clothing, T- shirts, and gloves for defence people that would help protecting them from common pathogens like S.aureus and Klebsiella pneumoniae and also to avoid cross contamination. The noble metals, Silver (Ag) and gold (Au) have been used for biomedical applications because of its known antimicrobial property and more over these metals are becoming day by day very costlier. In order to make these activities economic, there is essential need to find cheaper ways of using ZnO nanoparticles proficiently without jeopardizing their functionality.

The most important factors that play a vital role in governing the toxicity mechanism are the generation of radical oxygen vacancies, the electrostatic interaction between the ions, membrane and crystal defects. Hence, it is necessary to study the influence of doping on optical and structural properties in ZnO nanostructures. The growing interest in doped semiconductors for health care applications, make it crucial to study the investigations of doped ZnO nanostructures for antibacterial applications. Antibacterial agents are broadly of two types, organic and inorganic. At high temperatures/pressures organic antibacterial materials are found to be less stable compared to inorganic antibacterial agents. Thus ZnO has proved to be a powerful antibacterial agent in the formulation of the micro scale and nanoscale systems for therapeutic applications. ZnO nanoparticles showed greater antibacterial activity apparently than micro particles. ZnO nanoparticles have bactericidal effects on both Gram-positive and Gram-negative bacteria. They even have antibacterial activity against spores which are resistant to high temperature and high pressure. From the research reports, it is evident that the antibacterial activity of ZnO nanoparticles depends on the surface area and concentration, while the crystalline structure and particle shape have little effect. Further the smaller the size of ZnO particles, better is its antibacterial activity.

The antibacterial activity increases with the increase in concentration of nanomaterial as well as the size. The ZnO nanoparticle disrupts the cell membrane integrity where the cell membrane increases its permeability leading to loss of cell organelles and molecular components resulting in cell death. Some researchers have proposed in their studies that the induction of intercellular reactive oxygen species including hydrogen peroxide, (a strong oxidizing agent) harms the bacterial cell. Also H2O2 has the capability to penetrate the bacterial cell wall, while it also indicates that the binding of the particles on the bacterial surface due to the electrostatic forces could be another factor. Silver nanoparticles are highly antimicrobial to several species of bacteria, including the common kitchen microbe, E.coli and B. subitilus commonly found in soil and S. sonnei normally found in humans. According to the mechanism reported, silver nanoparticles interact with the outer membrane of bacteria, and arrest the respiration and some other metabolic pathway that leads to the death of the bacteria.

New technology advances, reducing silver compound chemically to nanoscale sized particles have enabled the integration of this valuable antimicrobial into a larger number of materials-including plastics, coatings, foams as well as natural and synthetic fibers. Nano-sized silver already provides a more durable antimicrobial protection, often for the life of the product.