Antimicrobial Activity of Chlorhexidine and Gallium in ZIF-8 Against Enterococcus Faecalis

Objectives: This research aimed to synthesize nano zeolitic imidazolate framework (ZIF) materials embedded with chlorhexidine and gallium and evaluate their antimicrobial efficacy against Enterococcus faecalis.
Methods: Two systems were developed and analyzed: Gallium Incorporated into ZIF-8 (ZIF-8/Ga) and Chlorhexidine Incorporated into ZIF-8 (ZIF-8/CHX). The antimicrobial potential of these systems was initially assessed using disk diffusion test. Then, fifty uniradicular roots were exposed to Enterococcus faecalis and divided into five groups, each containing ten samples: Group 1: distilled water; Group 2: calcium hydroxide with polymyxin B, colistin, and cyclohexidine; Group 3: 35% calcium hydroxide paste in an aqueous solution; Group 4: 2% chlorhexidine gel; Group 5: ZIF-8/CHX gel. These specimens were treated with their respective substances for seven days and subsequently examined using a fluorescence confocal microscope. Statistical analysis involved the use of Student's t-test (P < 0.05).
Results: The results of the disk diffusion tests revealed E. faecalis sensitivity to ZIF-8/CHX, while ZIF-8/Ga did not exhibit antimicrobial effects. In terms of determining the Minimum Inhibitory Concentration (MIC), ZIF-8/CHX gel and 2% chlorhexidine gel completely inhibited bacterial growth when diluted up to 1024 times, whereas gallium demonstrated inhibition up to the fourth dilution, and vancomycin 0.1% exhibited inhibition up to a dilution of 256 times. Furthermore, ZIF-8/CHX gel demonstrated effective entry into the root canals, achieving the highest percentage of bacterial clearance. It was followed by 2% chlorhexidine gel, 35% calcium hydroxide paste in an aqueous solution, and calcium hydroxide with polymyxin B, colistin, and cyclohexidine.
Conclusions: In conclusion, gallium, whether integrated into ZIF-8 or not, displayed no antimicrobial activity against E. faecalis and is not recommended for medication. Conversely, chlorhexidine gluconate incorporated into the ZIF-8 system exhibited substantial antimicrobial efficacy against E. faecalis. Additionally, the combination of the gel and the ZIF-8/CHX system demonstrated effective antimicrobial action against E. faecalis within root canals.