Conjugate of chitosan nanoparticles with chloroaluminium phthalocyanine: synthesis, characterization and photoinactivation of Streptococcus mutans biofilm

Background Antimicrobial photodynamic therapy (aPDT) using chloroaluminium phthalocyanine (ClAlPc) has high oxidative power allowing for the control of biofilms, especially when the photosensitizer is administered in an appropriate release vehicle. This study aimed to develop/characterize the ClAlPc encapsulated in chitosan nanoparticles (CSNPs), and evaluate its antimicrobial properties against S. mutans biofilms. Methods CSNPs were prepared by ion gelation, and characterization studies included particle size, polydispersion index (IPd), zeta potential, accelerated stability, absorption spectrum and ClAlPc quantification. The S. mutans biofilms were formed in bovine dentin blocks at 37 °C for 48 h under microaerophilic conditions. 8 μM ClAlPc was combined with a diode laser (InGaAlP) at 660 nm and 100 J/cm2. The aPDT toxicity was verified by dark phototoxicity. The antimicrobial activity was verified by CFU/mL and biofilm was analyzed by scanning electron microscopy (SEM). The number of viable bacteria was analyzed by ANOVA and Tukey HSD tests (α = 0.05). Results The characterization revealed that the ClAlPc nanoparticles were found in nanometer-scale with adequate photophysical and photochemical properties. The aPDT mediated by ClAlPc + CSNPs nanoconjugate showed a significant reduction in the viability of S. mutans (1log10 CFU/mL) compared to the negative control (PBS, p 0.05). SEM revealed change in biofilm morphology following the treatment of bacteria with aPDT ClAlPc + CSNPs. Cells were arranged as single or in shorted chains. Irregular shapes of S. mutans were found. Conclusion ClAlPc nanoparticles are considered stable and aPDT mediated by ClAlPc + CSNPs nanoconjugate was effective against S. mutans biofilm.