Polymeric Nanoparticle-Based Photodynamic Therapy for Chronic Periodontitis in Vivo

Abstract

Antimicrobial photodynamic therapy (aPDT) is increasingly being explored for treatment of periodontitis. Here, we investigated the effect of aPDT on human dental plaque bacteria in suspensions and biofilms in vitro using methylene blue (MB)-loaded poly(lactic-co-glycolic) (PLGA) nanoparticles (MB-NP) and red light at 660 nm. The effect of MB-NP-based aPDT was also evaluated in a clinical pilot study with 10 adult human subjects with chronic periodontitis. Dental plaque samples from human subjects were exposed to aPDT-in planktonic and biofilm phases-with MB or MB-NP (25 µg/mL) at 20 J/cm² in vitro. Patients were treated either with ultrasonic scaling and scaling and root planing (US + SRP) or ultrasonic scaling + SRP + aPDT with MB-NP (25 µg/mL and 20 J/cm²) in a split-mouth design. In biofilms, MB-NP eliminated approximately 25% more bacteria than free MB. The clinical study demonstrated the safety of aPDT. Both groups showed similar improvements of clinical parameters one month following treatments. However, at three months ultrasonic SRP + aPDT showed a greater effect (28.82%) on gingival bleeding index (GBI) compared to ultrasonic SRP. The utilization of PLGA nanoparticles encapsulated with MB may be a promising adjunct in antimicrobial periodontal treatment.

Keywords: PLGA; biofilms; methylene blue; nanoparticles; periodontitis; photodynamic therapy.

Figure 1

Recovered CFU/mL after antimicrobial photodynamic therapy (aPDT) treatment of planktonic bacteria with free methylene blue (MB) (25 µg/mL) and MB-NP (25 µg/mL equivalent to MB) and visible light at 660 nm with an energy fluence of 20 J/cm². Each bar is the mean values of the means from 10 samples (data from each sample were representative of four independent suspensions). Error bars denote the standard deviation of the mean. The asterisks represent the statistical difference between the groups and the control (one-way ANOVA with Tukey’s post hoc). *** p < 0.001; ns: not significant; MB: methylene blue; MB-NP: MB-loaded PLGA nanoparticles; CFU: colony forming units.

Figure 2

Recovered CFU/mL after aPDT treatment of bacteria growing in biofilms with free MB (25 µg/mL) and MB-NP (25 µg/mL equivalent to MB) and visible light at 660 nm with an energy fluence of 20 J/cm². Each bar is the mean values of the means from 10 samples (data from each sample were representative of four independent biofilms). The asterisks represent the statistical difference between the groups and the control (one-way ANOVA with Tukey’s post hoc). *** p < 0.001; ns: not significant; MB: methylene blue; MB-NP: MB-loaded PLGA nanoparticles; CFU: colony forming units.

Figure 3

Probing pocket depths. Probing was accessed at baseline, one week, one month, and three months after treatments. Shapes represent mean values from 10 patients at each time point. Error bars represent the standard deviation. US + SRP: ultrasonic scaling and scaling and root planing; US + SRP + aPDT: US + SRP followed by antimicrobial photodynamic therapy.

Figure 4

Visible plaque and Gingival bleeding indexes. VPI (a) and GBI (b) scores were accessed at baseline, one week, one month, and three months after treatments. Shapes represent mean values from 10 patients at each time point. Error bars represent the standard deviation. US + SRP: ultrasonic scaling and scaling and root planing; US + SRP + aPDT: US + SRP followed by antimicrobial photodynamic therapy.

Figure 5

Bleeding on probing and Clinical attachment level. BOP (a) and CAL (b) scores were accessed at baseline, one week, one month, and three months after treatments. Shapes represent mean values from 10 patients at each time point. Error bars represent the standard deviation. US + SRP: ultrasonic scaling and scaling and root planing; US + SRP + aPDT: US + SRP followed by antimicrobial photodynamic therapy.

Figure 6

Scanning electron micrograph (SEM) of PLGA nanoparticles. Figure shows an SEM image of higher magnification with spherical nanoparticles of 150–250 nm in diameter.