In vitro effect of antimicrobial photodynamic therapy with phycocyanin on Aggregatibacter actinomycetemcomitans biofilm on SLA titanium discs.

Abstract

The aim of this in vitro study was to evaluate antimicrobial photodynamic therapy (aPDT) with phycocyanin on Aggregatibacter actinomycetemcomitans biofilm formed on sandblasted, large-grit, and acid-etched (SLA) titanium discs. In this in vitro experimental study, the minimum inhibitory concentration (MIC), sublethal dose of diode laser irradiation time, and sublethal dose of aPDT were first determined. Next, 30 SLA titanium discs with 8 mm diameter and 2 mm thickness were incubated with A. actinomycetemcomitans in order for the bacterial biofilm to form, and were randomly divided into 5 groups (n = 6): (I) negative control with no treatment, (II) positive control, immersed in 0.2 % chlorhexidine (CHX) for 5 min, (III) phycocyanin alone with ×2 MIC concentration for 5 min, (IV) diode laser alone (635 nm wavelength, 220 mW power), and (V) PDT with diode laser and phycocyanin. The samples were then sonicated, and the number of colony-forming units (CFUs) on each disc was calculated. Data were analyzed using one-way ANOVA, t-test, and a post-hoc test. aPDT with 125 μg/mL phycocyanin and 4 min irradiation of 635 nm diode laser decreasedA. actinomycetemcomitans biofilm by 40.07 %. The lowest mean colony count (CFUs/mL) was noted in 0.2 % CHX group (0.0 × 105 CFU/mL) while the highest mean was observed in the negative control group (4.55 ± 0.08 × 105 CFUs/mL). Using phycocyanin alone significantly decreased the A. actinomycetemcomitans count by 27.54 % (3.29 ± 0.06 × 105 CFUs/mL) compared with the negative control group (P < 0.0001). Significant differences were noted between the negative control and other groups (P < 0.0001). aPDT with phycocyanin and diode laser can decrease the A. actinomycetemcomitans biofilm on SLA titanium implant surfaces and can be used as a safe and non-invasive decontamination method for reduction of A. actinomycetemcomitans biofilm on implant surfaces.