ABSTRACT Most of the toxicity data presented in the literature are obtained in relatively simple media, like distilled water. The literature reported that nanoparticles agglomerate immediately upon being added to cell culture media and if the agglomerates are used directly in antimicrobial studies, the interpretation of the toxicity results tends to be complicated. Six different molar ratios Ag-TiO2 composites were synthesized by a reduction method using two different commercial TiO2 particles as base materials and were used to find the aggregate size in distilled water and Mueller-Hinton Broth, and to obtain the minimum inhibitory concentrations (MIC) against E. coli and E. faecalis. To evaluate the evolution of the Ag-TiO2 particle size (z-average) three dilutions of each of the synthesized composites 100 µg/ml, 250 µg/mL and 500 µg/ml were realized in deionized water and Mueller Hinton broth. It was found that Ag-TiO2 composites increased in size after being diluted in Mueller-Hinton Broth, but once they grew in size, they remained constant for 24 minutes, and after this time, did not affect the MIC for the microorganisms involved.
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