The Potential Application of Natural Photosensitizers Used in Antimicrobial Photodynamic Therapy against Oral Infections

Abstract

Oral health problems and the emergence of antimicrobial resistance among pathogenic bacterial strains have become major global challenges and are essential elements that negatively affect general well-being. Antimicrobial photodynamic therapy (APDT) is based on a light source and oxygen that activates a nontoxic photosensitizer, resulting in microbial destruction. Synthetic and natural products can be used to help the APDT against oral microorganisms. The undesirable consequences of conventional photosensitizers, including toxicity, and cost encourage researchers to explore new promising photosensitizers based on natural compounds such as curcumin, chlorella, chlorophyllin, phycocyanin, 5-aminolevulinic acid, and riboflavin. In this review, we summarize in vitro studies describing the potential use of APDT therapy conjugated with some natural products against selected microorganisms that are considered to be responsible for oral infections.

Keywords: biofilms; dental infection control; drug resistance; nanoparticles; photochemotherapy; photosensitizing agents.

Figure 1

Mechanism of APDT. After absorption of single photon, the photosensitizer transfers from its ground singlet state to an excited singlet state. Next, the photosensitizer can lose energy, thereby returning to ground state, or it can turn to an excited triplet state. The long−lived triplet state can react with oxygen in two ways, as follows: In type I reactions, the charge is transferred to form ROS. In type II reactions, energy is transferred directly to the ground state molecular oxygen (³O₂), leading to the appearance of singlet oxygen (¹O₂). ¹PS*; photosensitizers in its singlet excited state, ³PS*; photosensitizers in its triplet excited state.