Antimicrobial, anti-biofilm and cytotoxic activities of silver nanoparticles and farnesol solutions to root canal disinfection

Author(s)

Gisselle Moraima Chávez Andrade

• Document type: Doctoral Thesis
• Press: Araraquara. 2016-10-25.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara
• Defense date: 2016-09-19
• Advisor: Juliane Maria Guerreiro Tanomaru

Abstract

Silver nanoparticles (AgNPs) have potential for applications in dentistry due to bactericidal action and biocompatibility. Farnesol (FAR) is an alcohol found in essential oils of citrus fruits and it has antibacterial/antibiofilm activity. The aim of this study was to evaluate the antimicrobial, antibiofilm activities and the cytotoxicity of AgNPs and FAR solutions used as root canal disinfectant. The study was divided into two publications. In Publication 1, antimicrobial activity was evaluated against Enterococcus faecalis, Candida albicans or Pseudomonas aeruginosa, by determining the minimum inhibitory concentration (MIC) and the minimum microbicidal concentration (MMC) by microdilution method and rezasurin staining. The anti-biofilm activity was performed by crystal violet assay. The anti-biofilm adhesion ability was evaluated using bovine root dentine blocks after treating them with tested solutions for 3 min. Scanning electron microscopy (SEM) analysis and CFU mL-1 log 10 counting were performed. Data were statistically analyzed (α=0.05). The antibacterial test against planktonic cells of E. faecalis showed MIC/MMC values of 42.5/50μM and 0.85/1.0% for AgNPs and FAR, respectively. The values of MIC/MMC of AgNPs and FAR for C. albicans were 27.5/37.5μM and 1.75/2.5% and for P. aeruginosa were 32.5/32.5μM and 2.5/2.75%, respectively. The anti-adhesion biofilm capacity assay showed smaller amount of biofilm adhered to the substrate treated with AgNPs and FAR when compared to control group (saline solution - SS), but there was no statistical difference between the two solutions (p>0.05), except for C. albicans. The log 10 UFC mL-1 counting showed no statistical difference between AgNPs and FAR solutions (p>0.05), which were similar to the control group (SS) for all strains. In publication 2, the cytotoxicity and genotoxicity of the solutions were evaluated in culture cell of fibroblast L929 by MTT and Comet assays, respectively. To evaluate the ex vivo antibacterial effectiveness, different irrigation protocols were performed in the final stage of root canal instrumentation on extracted human teeth infected with E. faecalis for 21 days. The number of log 10 CFU mL-1 in each group was determined in microbiological samples collected at different periods (initial, post-irrigation and final). Data were statistically analyzed (α=0.05). In the MTT assay, AgNPs and FAR were less cytotoxic than NaOCl. In the Comet assay, both solutions showed lower % of DNA in the tail, compared to positive control (H2O2). In the antimicrobial assay, all the irrigating protocols were more effective than C+ (without irrigation), with exception of SS/FAR. NaOCl and their combinations with AgNPs or FAR led to complete bacterial elimination (p>0.05). In comparison with initial sample, both the post-irrigation and final samples showed significant microbial reduction (p<0.05). AgNPs-PVA and FAR showed low cytotoxicity and genotoxicity, contribute to E. faecalis reduction and exhibit potential for use as a final irrigation protocols of the RCS. (AU)

• FAPESP's process: 12/11362-8 - Antimicrobial, antibiofilm and cytotoxic activity of silver nanoparticles and farnesol solutions for root canals desinfection.
• Grantee: Gisselle Moraima Chávez Andrade
• Support Opportunities: Scholarships in Brazil - Doctorate