title: Size-dependent antimicrobial properties of CuO nanoparticles against Gram-positive and -negative bacterial strains.
abstract: BACKGROUND
  CuO is one of the most important transition metal oxides due to its captivating properties. It is used in various technological applications such as high critical temperature superconductors, gas sensors, in photoconductive applications, and so on. Recently, it has been used as an antimicrobial agent against various bacterial species. Here we synthesized different sized CuO nanoparticles and explored the size-dependent antibacterial activity of each CuO nanoparticles preparation.
  
  
  METHODS
  CuO nanoparticles were synthesized using a gel combustion method. In this approach, cupric nitrate trihydrate and citric acid were dissolved in distilled water with a molar ratio of 1:1. The resulting solution was stirred at 100°C, until gel was formed. The gel was allowed to burn at 200°C to obtain amorphous powder, which was further annealed at different temperatures to obtain different size CuO nanoparticles. We then tested the antibacterial properties using well diffusion, minimum inhibitory concentration, and minimum bactericidal concentration methods.
  
  
  RESULTS
  XRD spectra confirmed the formation of single phase CuO nanoparticles. Crystallite size was found to increase with an increase in annealing temperature due to atomic diffusion. A minimum crystallite size of 20 nm was observed in the case of CuO nanoparticles annealed at 400°C. Transmission electron microscopy results corroborate well with XRD results. All CuO nanoparticles exhibited inhibitory effects against both Gram-positive and -negative bacteria. The size of the particles was correlated with its antibacterial activity.
  
  
  CONCLUSIONS
  The antibacterial activity of CuO nanoparticles was found to be size-dependent. In addition, the highly stable minimum-sized monodispersed copper oxide nanoparticles synthesized during this study demonstrated a significant increase in antibacterial activities against both Gram-positive and -negative bacterial strains.
authors: Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia. azam222@rediffmail.com
authors: Ameer
authors: A
authors: Azam
authors: Arham S
authors: AS
authors: Ahmed
authors: M
authors: M
authors: Oves
authors: M S
authors: MS
authors: Khan
authors: Adnan
authors: A
authors: Memic
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D003300:Copper / Q000737:chemistry / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure*; D008826:Microbial Sensitivity Tests; D010316:Particle Size; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D003300:Copper; C030973:cupric oxide