The Antimicrobial Activity of Curcumin and Xanthohumol on Bacterial Biofilms Developed over Dental Implant Surfaces

Abstract

In search for natural products with antimicrobial properties for use in the prevention and treatment of peri-implantitis, the purpose of this investigation was to evaluate the antimicrobial activity of curcumin and xanthohumol, using an in vitro multi-species dynamic biofilm model including Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. The antimicrobial activities of curcumin (5 mM) and xanthohumol (100 μM) extracts, and the respective controls, were evaluated with 72-h biofilms formed over dental implants by their submersion for 60 seconds. The evaluation was assessed by quantitative polymerase chain reaction (qPCR), confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). For the data analysis, comparisons were tested applying ANOVA tests with post-hoc Bonferroni corrections to evaluate the antimicrobial activity of both extracts. With qPCR, statistically significant reductions in bacterial counts were observed for curcumin and xanthohumol, when compared to the negative control. The results with CLSM and SEM were consistent with those reported with qPCR. It was concluded that both curcumin and xanthohumol have demonstrated antimicrobial activity against the six bacterial species included in the dynamic in vitro biofilm model used.

Keywords: antibacterial; antibiofilm; confocal laser microscopy; curcumin; in vitro; oral biofilms; peri-implantitis; polymerase chain reaction; scanning electron microscopy; xanthohumol.

Figure 1

Chemical structure of curcumin.

Figure 2

Chemical structure of xanthohumol.

Figure 3

Images obtained by confocal laser scanning microscopy (CLSM) at 72 h over implants treated with phosphate buffer saline (PBS) (A), 0.2% chlorhexidine (CHX) (B), 2.5% dimethyl sulfoxide (DMSO) (C), µM xanthohumol 100 (D) and 5 mM curcumin (E) (scale bar = 100 µm). LIVE/DEAD^® BackLight Kit was used. Live bacteria (green), dead bacteria (red) and implant surface (white) can be differentiated.

Figure 4

Images obtained by scanning electron microscope (SEM) with 2500× magnification of biofilm developed at 72 h over implants treated with phosphate buffer saline (PBS) (A), 0.2% chlorhexidine (CHX) (B), 2.5% dimethyl sulfoxide (DMSO) (C), 100 µM xanthohumol (D) and 5 mM curcumin (E) (scale bar = 20 µm).

Figure 5

(a) Robbins device hosting the (b) nylon anchoring screws that carry the implants.

Figure 6

Schematic representation of Robbins devices placed in series hosting the implants.

Figure 7

Modified model to generate biofilm over implants with the Robbins devices in series. (a) Culture medium—modified BHI; (b) Peristaltic pumps; (c) Incubation recipient; (d) Bioreactor (temperature control, pH, pO₂, agitation and weight); (e) Robbins devices in series hosting the implants.

Figure 8

Microplate wells with the decontamination groups (a) phosphate-buffered saline (PBS), (b) chlorhexidine (CHX), (c) dimethyl sulfoxide (DMSO), (d) xanthohumol and (e) curcumin.