Photodynamic treatment of pathogens

Abstract

The current viral pandemic has highlighted the compelling need for effective and versatile treatments, that can be quickly tuned to tackle new threats, and are robust against mutations. Development of such treatments is made even more urgent in view of the decreasing effectiveness of current antibiotics, that makes microbial infections the next emerging global threat. Photodynamic effect is one such method. It relies on physical processes proceeding from excited states of particular organic molecules, called photosensitizers, generated upon absorption of visible or near infrared light. The excited states of these molecules, tailored to undergo efficient intersystem crossing, interact with molecular oxygen and generate short lived reactive oxygen species (ROS), mostly singlet oxygen. These species are highly cytotoxic through non-specific oxidation reactions and constitute the basis of the treatment. In spite of the apparent simplicity of the principle, the method still has to face important challenges. For instance, the short lifetime of ROS means that the photosensitizer must reach the target within a few tens nanometers, which requires proper molecular engineering at the nanoscale level. Photoactive nanostructures thus engineered should ideally comprise a functionality that turns the system into a theranostic means, for instance, through introduction of fluorophores suitable for nanoscopy. We discuss the principles of the method and the current molecular strategies that have been and still are being explored in antimicrobial and antiviral photodynamic treatment.

Novel Oxygen- and Curcumin-Laden Ionic Liquid@Silica Nanocapsules for Enhanced Antimicrobial Photodynamic Therapy

“…The results are shown in Table 3. The 1 O 2 lifetime in solution strongly depends on its surroundings, namely the solvent [15]. For example, the 1 O 2 lifetime in water is about 3-4 µs while in deuterated water it is 57 µs [15].…”

“…The 1 O 2 lifetime in solution strongly depends on its surroundings, namely the solvent [15]. For example, the 1 O 2 lifetime in water is about 3-4 µs while in deuterated water it is 57 µs [15]. The lifetimes of 1 O 2 in the bulk ILs were found to be much higher than in water: Note: Due to the highly scattering medium of the solutions/suspensions and although a Newport long band-pass RG1000 filter was used, the initial part of the decays presented a spike that is attributed to scatter light.…”

“…Although most applications of PDT are essentially focused on anticancer therapies, and therefore most PS-loaded NPs have been developed for these purposes, the photodynamic effect has also been explored for the inactivation of microorganisms [14,15], being referred to as antimicrobial photodynamic therapy (aPDT). In this context the use of PS-loaded NPs has also found relevant applications [16], particularly for infected wound management, where light-activated nanoparticles with photodynamic and/or photothermal properties have been combined with polymeric materials to produce antimicrobial multifunctional wound dressings [17,18].…”

Innovative Phosphorene Nanoplatform for Light Antimicrobial Therapy

“…Since many exhaustive reviews have recently described the latest updates on aPDT or PDI [ 6 , 7 , 8 , 17 , 18 , 19 , 20 , 21 ], herein, we will only recall some basic concepts that are useful for understand how aPDT works. The fundamental mechanism of aPDT is based on the simultaneous presence of three main actors: (1) a photosensitizer (PS), a molecule or a complex that is physiologically harmless and able to absorb light in spectral regions ranging from the visible to near-infrared wavelengths; (2) a light source emitted in the spectral range absorbed by PS; and (3) molecular oxygen, i.e., O 2 [ 22 ] ( Figure 1 ).…”

Métodos físicos, químicos e biológicos de controle de biofilmes bacterianos

“…Dentre muitos os métodos de controle de microrganismos, a terapia fotodinâmica tem se destacado como forma alternativa e de grande excelência nos setores industrial, hospitalar e ambiental (PRADO-SILVA et al, 2022). A terapia fotodinâmica consiste na administração de um agente fotossensibilizante em uma determinada superfície e ao sofrer a irradiação de um certo comprimento de onda, concomitante à presença do Brazilian Journal of Development, Curitiba, v.8, n.12, p. 78646-78664, dec., 2022 oxigênio, o fotossensibilizante sofre excitação, pela absorção da energia emitida da fonte luminosa e promove ação fototóxica, devido hiperprodução de Espécies Reativas de Oxigênio, como superóxido, peróxido de hidrogênio e oxigênio singlete (DELCANALE et al, 2022;SARGAZI et al, 2022). Tais constituintes ocasionam danos às células microbianas, reduzindo ou potencializando reações bioquímicas, as quais resultam sua destruição POURHAJIBAGHER et al, 2019).…”