the nanoparticles were purchased from sigma and they have a size range (35-50 nm). i tried to dissolve it in DMSO ( 5% of the nanoparticle solution) and i also tried to sonicate it for 30 minutes and they still do not work on pseudomonas aeruginosa ( control strain- ATCC 9027/12924). i tried the MIC and the disc diffusion methods
I think the low toxicity and the concentration of Zn NPS are interpretations for that
Zinc oxide nanoparticles do not have to show activity against Pseudomonas aeruginosa. You are dealing with a very protected bacterium. Pseudomonas aeruginosa is not susceptible to many agents. However, check your nano-preparation again. Also re-consider the concentration of the nanoparticle used against the bacterium. Contact between nanoparticles and bacterial cell wall is sufficient to cause toxicity, therefore, large amounts of metal nanoparticles are required to completely envelop bacterial cells and shield them from ithe environment leaving no chance for nutrition to be absorbed to continue life process.
MIC, from what I know about it, is a parameter that could be determined for an antimicrobial agent. It is not a method. But, is zinc really that toxic? Please see the attached documents:Article An assessment of the toxicity of metals to Pseudomonas aerug...
Article Properties of Zinc Oxide Nanoparticles and Their Activity Ag...
I think the low toxicity and the concentration of Zn NPS are interpretations for that
Yeah, I second the opinions of Prof Khaled and Maurice. When your ZnO nparticles haven't been answering the MIC as well, then probably, you should check them with a positive control (known bacterial species, which has detrimental activity due to ZnO action). Then, head to MIC (at times, species specific MIC are given on the MSDS). My modest opinion would be to use a control experiment everytime you perform a test.
There may be several factors at play there, although I think that your NPs were simply agglomerated. Second thought is that 5% is not very informative. Please use values in milligrams or micrograms per liter or milliliter. Sonication may not be enough to break the aglomerates and disperse the material correctly. ZnO NPs can have antimicrobial activity, although it will be greatly diminished when the bacterium has the right environment around (medium) or forms a biofilm. We have discussed some agglomeration problems in our paper Article Antimicrobial Activity of Al2O3, CuO, Fe3O4, and ZnO Nanopar...
Best of luck!
Maurice Ekpenyong thank you for answering my questionArticle Properties of Zinc Oxide Nanoparticles and Their Activity Ag...
in this article it was mentioned that zinc oxide nanoparticles are toxic to Pseudomonas aeruginosa with MIC value of 500 μg/ml. i have tried this concentration and i also have tried a concentration as high as 5 mg/ml and found no activity.sorry i meant the broth dilution method to find the MIC
I agree with Khaled Khleifat and Adrian Augustyniak's answer for this question
Salma Mukhtar thank you for answering. what about the articles that mentioned that ZnO nanoparticles have a good antimicrobial activity?
Adrian Augustyniak by the 5% i mean that each 1 mL of the nanoparticle dispersion contains 50 microliter of DMSO. can you suggest a way to break the aglomerates?
Hadeel Ali Ayyad try this paper: Article Dispersion of Nanomaterials in Aqueous Media: Towards Protoc...
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