Development of a nano antibiotic paste for lesion sterilization and tissue repair technique in pediatric dentistry

This is an in vitro study aimed to develop a nano-antibiotic paste containing chloramphenicol, tetracycline, and silver and zinc oxide nanoparticles, evaluating its microbiological efficacy against four bacterial strains, determining its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against a commercial CTZ paste. Silver and zinc oxide nanoparticles (1 × 10^- 2 M) were synthesized and characterized by UV-Vis and DLS. A paste of tetracycline and chloramphenicol was prepared to a known concentration (10%), adding the synthesized nanoparticles and reducing the antibiotic percentage from the original proportions (- 4%). The commercial CTZ paste was then prepared following the manufacturer's instructions (13% concentration). Microdilution method and Kirby-Bauer assessment were used at three different concentrations to evaluate antimicrobial activity for both pastes against Enterococcus faecalis, Staphylococcus aureus, Streptococcus mutans, and Escherichia coli. MBC for the nano antibiotic paste (10%) and commercial CTZ paste (13%) were 4.8 µg/ml and 12 µg/ml for S. aureus, 19.5 µg/ml and 12.8 µg/ml for E. coli, 19.5 µg/ml and 12.8 µg/ml for E. faecalis, 39 µg/ml and 25 µg/ml for S. mutans, respectively. For Kirby Bauer statistical difference was shown, favoring nano paste for C1 E. coli (p = 0.000262) and C2 E. coli (p = 0.000388), and for C3 S. mutans (p = 0.00749), and commercial CTZ paste, for C2 S. aureus (p = 0.0146) and C2 E. faecalis (p = 0.00033). Microbiological assays revealed that the commercial CTZ de Mexico™ paste (13%) exhibited superior bactericidal activity, with lower MBCs, than the Nano formulation (10%) containing 4% less antibiotic. Results offer in vitro doses for the strains.