Antimicrobial sonodynamic and photodynamic therapies againstCandida albicans

Abstract

Candida albicans biofilms exhibit unique characteristics and are highly resistant to antifungal agents. Antimicrobial photodynamic therapy (aPDT) is an alternative treatment limited to treating superficial infections due to the poor light penetration. In this manuscript, the antifungal properties of sonodynamic therapy (SDT) were assessed. SDT uses ultrasound instead of light, enabling the treatment of deeper infections. Planktonic cells and biofilms of C. albicans were treated with aPDT or SDT, in addition to combined aPDT/SDT, with cell survival determined using colony forming units. The total biomass and structural integrity of the biofilms were also investigated. The results demonstrated that while individual aPDT or SDT eradicated suspensions, they had little impact on biofilms. However, combined aPDT/SDT significantly reduced the viability and total biomass of biofilms. Microscopic images revealed that biofilms treated with aPDT/SDT were thinner and comprised mainly of dead cells. These results highlight the potential of combined aPDT/SDT for the inactivation of C. albicans biofilms.

An Insight into Advanced Approaches for Photosensitizer Optimization in Endodontics—A Critical Review

“…Presently, the most acceptable mechanism relies on ROS production which causes apoptosis [142]. An alternative theory advocates that the elevated temperatures lead to thermal destruction and might also result in the generation of free radicals directly from the sensitizers [140], with ROS being successively formed in an acoustic cavitation phenomenon-a similar approach to a PDT type I reaction [143]. When compared to aPDT, SDT's main advantage is that ultrasound propagates deeper than light, and therefore may be used to treat diseases mediated by complex and dense biofilms.…”

“…When compared to aPDT, SDT's main advantage is that ultrasound propagates deeper than light, and therefore may be used to treat diseases mediated by complex and dense biofilms. Moreover, SDT may facilitate the generation of transient pores in the biofilm matrix, enabling a greater diffusion of PSs, SSs, and light [143], or as a complement to aPDT [142] since the main advantage of SDT over aPDT is that ultrasound can be tightly focused with penetration in soft tissue up to several tens of centimeters.…”

“…An important aspect to mention is that PDZ was excited by a light with proper wavelength (660 nm) and RB (λ = 549 nm) was not, and this might influence the final aPDT efficacy. Still, aPDT + SDT showed a significant cell viability reduction, and reduced total biofilm biomass (thinner biofilms comprised mainly of dead cells) [143]. It was hypothesized that both approaches were able to disrupt the biofilms, enabling PS penetration deep into the biofilms since ultrasound increases the uptake of molecules through microorganisms' membranes' transient pores (via sonoporation).…”

Aspects of Photodynamic Inactivation of Bacteria

“…Alves et al have recently reported on effective destruction of Candida albicans by photodithazine and RB in the dark under the ultrasonic excitation. A significant synergistic effect of the combination between PDT and SACT for combatting C. albicans biofilms was also found [36]. Figure 2 demonstrates the effect of ultrasonic activation that we showed on the antibacterial activity of two PSs-RB (Figure 2a) and MB (Figure 2b)-against S. aureus compared to photodynamic activation.…”

“…It was found that some well-known PSs also have sonosensitizing properties. Among them are porphyrins [35], RB [36,37], chlorin e6 derivative, photodithazine [36], and curcumin [38]. Several studies found sonodynamic therapy (SDT) to be the promising treatment in various forms of cancerous tumors [39][40][41][42][43].…”