CuO NANOPARTICLES: SYNTHESIS, CHARACTERIZATION AND THEIR BACTERICIDAL EFFICACY

Objective: In the present study copper oxide (CuO) nanoparticles were synthesized and characterized. The antibacterial activity of CuO nanoparticles was carried out against Escherichia coli, Proteus vulgaris, Staphylococcus aureus and Streptococcus mutans.Methods: The synthesis was carried out by coprecipitation method using copper sulfate and sodium hydroxide as precursors. The synthesized copper oxide nanoparticles were characterized by using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), UV-vis spectroscopy and scanning electron microscope (SEM) with Energy Dispersive X-ray Analysis (EDX) techniques. Besides, this study determines the antibacterial activity and minimum inhibitory concentration (MIC) of CuO nanoparticles against gram-positive (Staphylococcus aureus and Streptococcus mutans) and gram-negative (E. coli and Proteus vulgaris) bacteria.Results: The average crystallite size of CuO nanoparticles was found to be 19 nm by X-ray diffraction. FT-IR spectrum exhibited vibrational modes at 432 cm-1, 511 cm-1 and 611 cm-1were assigned for Cu-O stretching vibration. According to UV-Vis spectrum, two bands were observed at 402 nm and 422 nm. ED's spectrum shows only elemental copper (Cu) and oxide (O) and no other elemental impurity was observed. The antimicrobial assay revealed that Proteus vulgaris showed a maximum zone of inhibition (37 mm) at 50 mg/ml concentration of CuO nanoparticles.Conclusion: In conclusion, copper oxide is a good antibacterial agent against both gram positive and gram-negative organisms

Aflatoxins B1 in different grades of chillies (Capsicum annum L.) in India as determined by indirect competitive-ELISA

Samples of the three grades of chilli pod (grades 1 to 3) were collected during surveys in 1998 and 1999 from the principal market yards and cold storage facilities of the major chilli-growing areas of Andhra Pradesh (AP), India. Chilli powders were collected from different supermarkets in Hyderabad, AP. They were analysed for aflatoxin B1 (AFB1) content by an indirect competitive ELISA. To avoid the influence of interfering substances present in chilli extracts, it was necessary to prepare the aflatoxin standards in methanol extracts of chillies free from aflatoxins. For nine representative samples there was good agreement between ELISA and HPLC estimations of AFB1 and the results suggested that the ELISA procedure adopted was dependable. Of the 182 chilli samples tested, 59% of the samples were contaminated with AFB1 and 18% contained the toxin at non-permissible levels. The highest AFB1 concentration of 969 µg/kg was found in one sample representing grade 3. Overall the maximum percentage of chilli pods showing AFB1 levels higher than 30 μg/kg (non-permissible levels) was in grade 3. Chilli pods stored in refrigerated rooms showed the lowest proportion of samples containing aflatoxin. Nearly 9% of the chilli powders sold in supermarkets contained non-permissible aflatoxin levels. This report highlights the importance of using grade 1 chilli pods to minimize aflatoxin contamination