'Green' silver nanoparticles combined with tyrosol as potential oral antimicrobial therapy.

OBJECTIVES: This study aimed to evaluate silver nanoparticles (AgNPs) obtained by a 'green' route associated or not to tyrosol (TYR) against Streptococcus mutans and Candida albicans in planktonic and biofilms states. METHODS: AgNPs were obtained by a 'green' route using pomegranate extract. The minimum inhibitory concentration (MIC) against S. mutans and C. albicans was determined for AgNPs and TYR combined and alone, and fractional inhibitory concentration index (FICI) was calculated. Single biofilms of C. albicans and S. mutans were cultivated for 24 h and then treated with drugs alone or in combination for 24 h. RESULTS: AgNPs and TYR were effective against C. albicans and S. mutans considering planktonic cells alone and combined. The MIC values obtained for C. albicans was 312.5 µg/mL (AgNPs) and 50 mM (TYR) and for S. mutans was 78.1 µg/mL (AgNPs) and 90 mM (TYR). The combination of these antimicrobial agents was also effective against both microorganisms: 2.44 µg/mL/0.08 mM (AgNPs/TYR) for C. albicans and 39.05 µg/mL /1.25 mM (AgNPs/TYR) for S. mutans. However, synergism was observed only for C. albicans (FICI 0.008). When biofilm was evaluated, a reduction of 4.62 log10 was observed for S. mutans biofilm cells treated with AgNPs (p < 0.05, Tukey test). However, the addition of TYR to AgNPs did not improve their action against biofilm cells (p > 0.05). AgNPs combined with TYR demonstrated a synergistic effect against C. albicans biofilms. CONCLUSIONS: These findings suggest the potential use of AgNPs with or without TYR against C. albicans and S. mutans, important oral pathogens. CLINICAL SIGNIFICANCE: AgNPs obtained by a 'green' route combined or not with TYR can be an alternative to develop several types of oral antimicrobial therapies and biomaterials.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion.

OBJECTIVES: The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans. METHODS: Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100 ppm F, 225 ppm F, 100 ppm F + 0.2%TMP or 100 ppm F + 0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24 h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy. RESULTS: The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 µm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log10cm2) and structurally affected the biofilms. CONCLUSION: The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans. CLINICAL SIGNIFICANCE: The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

Antimicrobial Activity of Compounds Containing Silver Nanoparticles and Calcium Glycerophosphate in Combination with Tyrosol.

Nanocomposites containing antimicrobial agents and calcium phosphates have been developed. Thus, this study assessed the effects of two compounds containing silver nanoparticles (AgNPs) and ß-calcium glycerophosphate (CaGP), associated or not with tyrosol (TYR), against planktonic cells and biofilms of Candida albicans and Streptococcus mutans. The nanocompounds were synthesized through chemical and 'green' processes and characterized by scanning electron microscopy. The minimum and fractional inhibitory concentrations of each compound were determined for planktonic cells. Next, 24-h single biofilms of C. albicans and S. mutans were treated for 24 h with the nanocompounds alone or in combination with TYR, and the antibiofilm effect was assessed through enumeration of colony forming units. Biofilm data were statistically examined using one-way ANOVA and the Kruskal-Wallis test (α = 0.05). The chemically synthesized nanocompound in combination with TYR demonstrated a synergistic effect against planktonic cells of C. albicans and S. mutans. For the nanocompound obtained through the 'green' route associated with TYR, a synergistic effect was observed only against C. albicans. For biofilms, only the combination obtained through the 'green' route + TYR demonstrated a synergistic effect against C. albicans. Our results may contribute to the development of oral care products containing AgNPs-CaGP and TYR to combat oral infections.

Nanosynthesis of Silver-Calcium Glycerophosphate: Promising Association against Oral Pathogens.

Nanobiomaterials combining remineralization and antimicrobial abilities would bring important benefits to control dental caries. This study aimed to produce nanocompounds containing calcium glycerophosphate (CaGP) and silver nanoparticles (AgNP) by varying the reducing agent of silver nitrate (sodium borohydride (B) or sodium citrate (C)), the concentration of silver (1% or 10%), and the CaGP forms (nano or commercial), and analyze its characterization and antimicrobial activity against ATCC Candida albicans (10231) and Streptococcus mutans (25175) by the microdilution method. Controls of AgNP were produced and silver ions (Ag⁺) were quantified in all of the samples. X-ray diffraction, UV-Vis, and scanning electron microscopy (SEM) analysis demonstrated AgNP associated with CaGP. Ag⁺ ions were considerably higher in AgCaGP/C. C. albicans was susceptible to nanocompounds produced with both reducing agents, regardless of Ag concentration and CaGP form, being Ag10%CaGP-N/C the most effective compound (19.5⁻39.0 µg Ag mL−1). While for S. mutans, the effectiveness was observed only for AgCaGP reduced by citrate, also presenting Ag10%CaGP-N the highest effectiveness (156.2⁻312.5 µg Ag mL−1). Notably, CaGP enhanced the silver antimicrobial potential in about two- and eight-fold against C. albicans and S. mutans when compared with the AgNP controls (from 7.8 to 3.9 and from 250 to 31.2 µg Ag mL−1, respectively). The synthesis that was used in this study promoted the formation of AgNP associated with CaGP, and although the use of sodium borohydride (B) resulted in a pronounced reduction of Ag⁺, the composite AgCaGP/B was less effective against the microorganisms that were tested.

Sodium trimetaphosphate and hexametaphosphate impregnated with silver nanoparticles: characteristics and antimicrobial efficacy.

This study aimed to synthesize and characterize materials containing silver nanoparticles (AgNP) with polyphosphates (sodium trimetaphosphate (TMP) or sodium hexametaphosphate (HMP), and evaluate their effect against Candida albicans and Streptococcus mutans. The minimum inhibitory concentration (MIC) was determined, which was followed by the quantification of the biofilm by counting colony-forming units (CFUs), the amount of metabolic activity, and the total biomass. The MICs revealed greater effectiveness of composites containing 10% Ag (TMP + Ag10% (T10) and HMP + Ag10% (H10)) against both microorganisms. It was observed that T10 and H10 reduced the formation of biofilms by 56-76% for C. albicans and by 52-94% for S. mutans for total biomass and metabolic activity. These composites promoted significant log reductions in the number of CFUs, between 0.45-1.43 log10 for C. albicans and 2.88-3.71 log10 for S. mutans (p < .001). These composites demonstrated significant antimicrobial activity, especially against S. mutans, and may be considered a potential alternative for new dental materials.

Effects of polyphosphates and fluoride on hydroxyapatite dissolution: A pH-stat investigation.

OBJECTIVES: This study investigated the immediate and sustained effect of sodium trimetaphosphate (TMP) and sodium hexametaphosphate (HMP) associated or not with fluoride (F) on hydroxyapatite (HA) dissolution using an erosion-like model, considering as well as the influence of salivary coating. DESIGN: Baseline dissolution rates were determined for HA discs using a pH-stat system. In the first set of experiments, HA discs were treated with 1100µgF/mL, 1% or 8% of HMP, 1% or 8% of TMP and 1100µgF/mL associated with 1% or 8% of HMP or TMP, totaling 9 groups (n=8). In a second phase, HA discs were kept in pooled human saliva at 37°C for 2h before treatment with deionised water and 1100µgF/mL associated with 1% or 8% of HMP or TMP, totaling 5 groups (n=8). The post-treatment dissolution rate was determined from three consecutive 30-min assays. Data were analysed using 2 and 3-way ANOVA followed by Fisher and Holm-Sidak methods, respectively (α=0.05). RESULTS: All test solutions promoted reduction in HA dissolution rate when compared to baseline control in the first post-treatment run (p<0.001). However, a synergistic effect was only observed between fluoride and 1% HMP. Moreover, the duration of inhibitory effect was greater when 8% HMP and 1 or 8% HMP associated with F were assessed (p<0.001). The presence of salivary coating led to higher protection for all groups when compared to discs without coating (p<0.001). CONCLUSION: The reduction of HA dissolution rate, as well as the duration of this effect were influenced by fluoride, type and concentration of phosphate salt and the presence of a salivary coating.

Effect of low-fluoride dentifrices supplemented with calcium glycerophosphate on enamel demineralization in situ.

PURPOSE: To evaluate whether a low-fluoride dentifrice with calcium glycerophosphate (CaGP) reduced the demineralization process in situ. METHODS: A cross-over design with four treatment phases of 7 days each was used. Ten volunteers wore palatal devices containing four blocks of bovine dental enamel. The enamel was treated (ex-vivo) with a placebo, 500 microg-F/g (500), 500 microg-F/g with 0.25%CaGP (500 CaGP), and 1,100 microg-F/g (1,100) dentifrices (twice a day/1 minute) under cariogenic challenge from sucrose solution. To evaluate mineral loss, surface and cross-sectional hardness were performed. The fluoride, calcium, and phosphorus ion concentrations from enamel and dental plaque were determined. The insoluble extracellular polysaccharide (EPS) concentrations were also analyzed. The data were submitted to ANOVA (1-way) followed by the Student-Newman-Keuls test (P < 0.05). RESULTS: The mineral loss and EPS concentration were lowest in the 500 CaGP and 1,100 dentifrice groups. The use of the 500 CaGP and 1,100 dentifrices resulted in similar fluoride, calcium, and phosphorus concentrations in the enamel and in dental plaque (P > 0.05). The ionic activities of calcium phosphate phases for the 500 CaGP and 1,100 dentifrices were similar (P > or = 0.492). The low-fluoride dentifrice with 0.25%CaGP demonstrated efficacy similar to that of the positive control (1,100 dentifrice) with respect to in situ demineralization.