Antimicrobial effect of anacardic acid–loaded zein nanoparticles loaded on Streptococcus mutans biofilms

Abstract

Bacterial biofilms play a key role in the pathogenesis of major oral diseases. Nanoparticles open new paths for drug delivery in complex structures such as biofilms. This study evaluated the antimicrobial effect of zein nanoparticles containing anacardic acid (AA) extracted from cashew shells of Anacardium occidentale on in vitro Streptococcus mutans biofilm formation and mature biofilms. The minimum inhibitory concentration (MIC), minimum bacterial concentration (MBC), and antibiofilm assays were performed. Streptococcus mutans UA159 biofilms were formed on saliva-coated hydroxyapatite disk for 5 days. To evaluate the preventive effect on biofilm formation, before contact with the inoculum, the disks were immersed once for 2 min in (1) hydroethanolic solution; (2) blank zein nanoparticles; (3) zein nanoparticles containing AA; and (4) 0.12% chlorhexidine gluconate. To determine the effect against mature biofilms, the disks containing 5-day preformed biofilms were further treated using the same procedure. The bacterial viability and dry weight were determined for both assays and used to compare the groups using ANOVA followed by Tukey's test (p < 0.05). Both MIC and MBC for AA-loaded zein nanoparticles were 0.36 μg/mL. Groups 3 and 4 were very effective in inhibiting S. mutans biofilm formation, as no colony-forming units were detected. In contrast, for mature biofilms, no difference in bacterial viability (p = 0.28) or dry weight (p = 0.09) was found between the treatments. Therefore, the AA-based nanoformulation presented very high inhibitory and bactericidal activities against planktonic S. mutans, and the results indicate a strong antiplaque effect. However, the formulation showed no antimicrobial effect on the established biofilm.

The antimicrobial and antibiofilm effects of three herbal extracts on Streptococcus mutans compared with Chlorhexidine 0.2% (in vitro study)

“…The most efficient oral rinse for reducing dental plaque germs is Chlorhexidine, which is presently regarded as the gold standard antiplaque agent [ 5 ]. It has bactericidal and bacteriostatic characteristics with adequate oral cavity durability and is more efficient against S. mutans than Lactobacillus .…”

Sustainable multifunctional phenolic lipids as potential therapeutics in Dentistry

“…Lima et al (2020) demonstrated some anti- S. mutans biofilm activity of zein nanoparticles containing AA when used before the bacterial inoculation as a pre-treatment. However, they found no difference in bacterial viability for mature biofilms treated with their compound 16 . Another study tested the effect of the compound in early biofilm formation, showing a reduction in biomass 13 , however, similarly to the study by Lima et al (2020), the related "antibiofilm" effect might correspond to the AA potent antimicrobial activity, and not an antibiofilm effect itself as no cells were growing to form biofilms.…”

“…This effect may be triggered by inhibition of bacterial enzymes and complexation with metal ions 8 , 12 . Its activity against Streptococcus mutans has been extensively explored, with a consistent high sensitivity at low concentrations 9 , 12 , 16 . Due to this strong competence to kill S. mutans, AAs have inappropriately been defined as potential “anti-cavities” agents.…”

Toxicological and genotoxic evaluation of anacardic acid loaded-zein nanoparticles in mice

“…The formulations were obtained by nanoprecipitation of the protein according to our previously described method [ 13 ], using zein protein as a carrier and anacardic acid at 9.375 μg/mL (ZAa), the maximum loading reached. This concentration demonstrated the antibiofilm activity of ZAa against S. mutans in vitro [ 27 ]. Blank nanoparticles (ZB) were prepared in the same manner, except for the absence of drug, and used as control.…”

“…The cumulative effect of a short-term course treatment was assessed by a subacute toxicity assay for 7 consecutive days, according to the OECD 407 protocol [ 28 ] with some modifications, justified by the low doses administered, compatible to its effective dose [ 27 ] and the potential use as mouthwash in oral biofilm diseases prevention and control. ZAa nanoparticles were administered by oral gavage daily in two doses (ZAad 1 : 2.25 μg/kg and ZAad 2 : 112.5 μg/kg) (5 animals per group), while blank zein nanoparticles (ZB) and saline solution 0.9 % were administered in a volume equivalent to the highest dose to groups of four animals, each.…”