Green Synthesis of Cadmium Sulfide Quantum Dots from Nerium Oleander Leaves Extract and Detection of Its Antibacterial Effects Onsome Gram- Negative and Gram- Positive Bacteria

The distribution of multiple-drug resistance among pathogenic bacteria is an increasing serious problem for medicine and the pharmaceutical industry. The aim of this study was to evaluate the antibacterial effects of green synthesized Cadmium Sulfide Quantum dots (CdS QDs) using Nerium oleander leaves extract,due to its anti- cancer and  anti- inflammatoryeffects, on some gram negative and gram positive bacteria.

In this experimental study, the green synthesis of Cadmium Sulfide quantum dots was carried out using Nerium oleander leaves extract, which were collected from mountains around Ilam city, using three different methods including: ultrasonic (15 minutes at 37°C), microwave (15 minutes under 300W radiation), and flotation (soaking in water 3 days in Balloon packed. Then, dehydrated Cadmium acetate and Sulfide sodium were added. After that, the antibacterial effect of supernatant of different synthetic QDs wereevaluated on E.coli ATCC 25922, Salmonella enterica ATCC 14028, S.aureus ATCC 25923, and clinical isolates of Bacillus cereus using disc diffusion method on Muller Hinton agar, and those were compared with ceftazidime (30µg), chloramphenicol (30µg), penicillin (10µg), and imipenem (10µg). Also, Mean and standard deviation were used for descriptive analysis, and U- mann- whitney test was used to comparevariables.

The antibacterial effects of Cadmium sulfide quantum dots prepared by ultrasonic, microwave and flotation methods were stronger than ceftazidime, chloramphenicol and penicillin, while their antimicrobial effects were less than imipenem. The means effects and standard deviation of ceftazidime were respectively attained 11.50 ± 1.9, for chloramphenicol and for imipenem attained 13.2±1.5, 27.75 ± 2.2, respectively (P < 0.05).

It seems that the aqueous and methanolic extracts of cadmium sulfide quantum dots have had strong antibacterial effects and this effect had a direct relation with the concentrations of aqueous and methanolic extract of QDs, so if they won’t have any side effects, they can be usedas alternatives for antibiotics.