We studied the structural and antimicrobial properties of copper oxide nanoparticles (CuO NPs) synthesized by a very simple precipitation technique. Copper (II) acetate was used as a precursor and sodium hydroxide as a reducing agent. X‐ray diffraction patter (XRD) pattern showed the crystalline nature of CuO NPs. Field emission scanning electron microscope (FESEM) and field emission transmission electron microscope (FETEM) demonstrated the morphology of CuO NPs. The average diameter of CuO NPs calculated by TEM and XRD was around 23 nm. Energy dispersive X‐ray spectroscopy (EDS) spectrum and XRD pattern suggested that prepared CuO NPs were highly pure. CuO NPs showed excellent antimicrobial activity against various bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterococcus faecalis, Shigella flexneri, Salmonella typhimurium, Proteus vulgaris, and Staphylococcus aureus). Moreover, E. coli and E. faecalis exhibited the highest sensitivity to CuO NPs while K. pneumonia was the least sensitive. Possible mechanisms of antimicrobial activity of CuO NPs should be further investigated.

Copper oxide nanoparticles (CuO NPs) are heavily utilized in semiconductor devices, gas sensor, batteries, solar energy converter, microelectronics and heat transfer fluids. It has been reported that liver is one of the target organs for nanoparticles after they gain entry into the body through any of the possible routes. Recent studies have shown cytotoxic response of CuO NPs in liver cells. However, the underlying mechanism of apoptosis in liver cells due to CuO NPs exposure is largely lacking. We explored the possible mechanisms of apoptosis induced by CuO NPs in human hepatocellular carcinoma HepG2 cells. Prepared CuO NPs were spherical in shape with a smooth surface and had an average diameter of 22 nm. CuO NPs (concentration range 2–50 µg/ml) were found to induce cytotoxicity in HepG2 cells in dose-dependent manner, which was likely to be mediated through reactive oxygen species generation and oxidative stress. Tumor suppressor gene p53 and apoptotic gene caspase-3 were up-regulated due to CuO NPs exposure. Decrease in mitochondrial membrane potential with a concomitant increase in the gene expression of bax/bcl2 ratio suggested that mitochondria mediated pathway involved in CuO NPs induced apoptosis. This study has provided valuable insights into the possible mechanism of apoptosis caused by CuO NPs at in vitro level. Underlying mechanism(s) of apoptosis due to CuO NPs exposure should be further invested at in vivo level.

The experiments reported herein are the first MRI investigations of the orientational dependence of T₂ relaxation in articular cartilage at microscopic resolution over the 360° angular space. For each of six canine cartilage specimens, 48 independent T₂‐weighted proton images were acquired for 12 different specimen orientations. Pixel‐wise monoexponential fits of these proton images produced 12 T₂ relaxation images, each with an in‐plane pixel resolution of 13.7 μm. Cartilage T₂ as a function of specimen orientation was shown to follow approximately the angular dependence of the nuclear dipole–dipole interaction, with local maxima at approximately 55°, 125°, 235°, and 305°. However, the relative amplitudes of the T₂ maxima deviated somewhat from those expected from the dipolar interaction. The amplitudes of these maxima also varied with tissue depth: the largest amplitudes were found in the radial zone, intermediate amplitudes were found in the superficial zone, and there was a continuous decrease in amplitude approaching the transitional zone from the superficial zone above and the radial zone below. We explain the discrepancy between the observed T₂ anisotropy and the angular dependence of the dipolar interaction by means of a simple model which considers the average of one isotropic and two anisotropic spin populations—the first being associated with “free” water, and the latter two arising from collagen‐associated waters. We show that even for the “long” T₂ components, which arise in multiple‐compartment studies of collagen‐water systems, there appears to be two subpopulations. Each has the same peak value of T₂, but the angular dependence of one is shifted in phase by 90° relative to the other by virtue of the fact that each is associated with groups of mutually perpendicular fibrils. Magn Reson Med 48:460–469, 2002.