Bactericidal Efficacy of New Types of Magnesium Hydroxide and Calcium Carbonate Nanoparticles

Abstract—Objectives of the present study were to evaluate the antibacterial activity of the two types of inorganic magnesium hydroxide [Mg(OH)₂] and calcium carbonate [CaCO₃] nanoparticles (NPs) on the growth of three Gram-negative bacteria, e.g., Escherichia coli, Pseudomonas aeruginosa and Serratia marcescens and three Gram-positive bacteria, e.g., Streptococcus pyogenes, Staphylococcus aureus and Streptococcus bovis. The synthesis of these NPs was done by a microwave hydrothermal method. The structures and sizes of synthesized nanoparticles were investigated using X-ray diffractometer. Antimicrobial susceptibility of different NPs was determined at 20, 50 and 100 mg/mL by the agar-well diffusion method, growth reduction at the aqueous solution and time-kill assay. The antimicrobial effects across NPs and bacterial species were shown to be dose-dependent. The results of the different experiments indicated that smaller NP sizes have higher antibacterial effects. M29 [Mg(OH)₂-29] nanoparticles followed by silver (Ag) and C1 (CaCO₃-1) showed the highest influence on bacterial growth rates, while similar ability to kill bacteria across treatment time. In addition, Gram-negative bacteria were more affected in terms of the inhibition zone and reduction of growth rates after 24 h as well as in terms of the prolonged treatment of NPs up to 36 h due to the influence of different nanoparticles. We recommend to search the chance of further using M29 and C1 in medicine and industry.