The effect of antimicrobial photodynamic therapy using different concentrations of phycocyanin against Streptococcus mutans

Background

The aim of this study is to investigate the effect of antimicrobial photodynamic therapy (aPDT) using three different concentrations of phycocyanin and two different laser powers on Streptococcus mutans.

Materials and methods

In this study, Streptococcus mutans was investigated using three different concentrations of phycocyanin (2.5, 5, and 10 mg/mL), in the presence and absence of 635 nm diode laser at two power levels (400 and 500 mW). The treatments were as follows: the control group received no treatment. The next 3 groups received only the phycocyanin at 2.5, 5, and 10 mg/mL. The remaining groups received both phycocyanin and laser treatment. Finally, bacteria were counted using the colony forming units (CFUs)/mL method. Data analysis was performed using IBM SPSS 26 software and ANOVA statistical test.

Results

All groups except for the phycocyanin group at a concentration of 10 mg/mL showed a statistically significant difference compared to the control group (p-Value < 0.05). Additionally, the least effect was observed in the control and the phycocyanin at a concentration of 10 mg/mL groups, while the greatest effect was found in the group receiving phycocyanin at 2.5 mg/mL concentration and laser with a power of 500 mW (2.5 + DL500).

Conclusion

aPDT can be used as a complementary and non-invasive method to reduce bacterial load. The effectiveness of aPDT decreased with increasing phycocyanin concentration. Moreover, higher laser irradiation power resulted in reduced Streptococcus mutans bacterial load. Thus, the most pronounced effects were observed in the group receiving phycocyanin at 2.5 mg/mL concentration and 635 nm diode laser with a power of 500 mW (2.5 + DL500).