Suspensão de partículas de quitosana carregadas com fluoreto de sódio: síntese, caracterização e efeito no esmalte dental após biofilme de S. mutans

Abstract

The aim of this study was to evaluate the in vitro effect of application of chitosan particles loaded with sodium fluoride (NaF/Chit) on tooth enamel after cariogenic challenge with S. mutans (UA159). The suspension of NaF/Chit particles were synthesized by ionic gelation and the characterization of the suspension was evaluated by titration in a dynamic rheometer evaluating viscosity (η), molecular interaction by infrared absorption spectroscopy (FTIR). The stability of particles in suspension was evaluated using ZP, Dh and pH for one month, with an interval of one week between measurements. After obtaining the molar/stoichiometric ratio of the NaF/Chitmonomers complex by titration in a rheometer, the suspensions of Quit/NaF particles with a fluoride concentration of 0.05% and 0.2% were prepared by mixing the chitosan solutions (0 .0118 mol/L and 0.0475 mol/L) and NaF (0.0118 mol/L and 0.0475 mol/L) in 1% v/v acetic acid solution. Subsequently, the minimal inhibitory concentration (MIC) and minimal bactericidal (MBC) tests were performed for the nine groups: 1) Chit 0.05%; 2) NaF 0.05%; 3) suspension NaF/Chit 0.05%; 4) Control 0.05% (acetic acid); 5) Chit 0.2%; 6) NaF 0.2%; 7) suspension NaF/Chit 0.2%; 8) Control 0.2%; and 9) 0.12% Chlorhexidine Digluconate (CLX) - positive control. The effect on biofilm formation under the surface of human tooth enamel was evaluated by surface hardness (Knoop) and colonyforming unit count (CFU/mL). Twenty-three enamel blocks (4 x 4 mm) were obtained from third molars and embedded in acrylic resin. Nine groups were formed (n=5) as mentioned above. Microhardness data were analyzed by repeated measures ANOVA, One Way ANOVA and Tukey (α= 0.05) and the results of CFU/mL were analyzed by Shapiro-Wilk, Levene and repeated measures ANOVA. At the beginning of the titration, chitosan showed higher values of η. With the addition of NaF, there was a reduction in the viscosity up to the molar ratio of [NaF]/ = [Chit] ≈ 0.64, which was attributed to polymer chain neutralization. The FTIR spectra showed interaction between NaF-Chit, evidencing the formation of microparticles. Stability tests showed the formation of stable microparticles. The MIC of the 0.05% and 0.2% NaF/Chit particle suspension was 0.65 mg/mL and the MBC was 0.65 mg/mL and 1.3 mg/mL, respectively. The suspension of particles of NaF/Chit 0.2% showed a reduction in CFU/mL of S. mutans when compared to compounds isolated at the same concentration (Chit 0.2% and NaF 0.2%). The NaF/Chit groups at both concentrations (0.05% and 0.2%) and CLX had higher hardness values and lower hardness loss after cariogenic challenge with S. mutans. The suspension of NaF/Chit at concentrations of 0.05% and 0.2% showed antimicrobial activity against S. mutans and minimized enamel demineralization after cariogenic challenge showing potential for use in mouthwashes to control caries.