Antimicrobial photodynamic therapy (aPDT) for biofilm treatments. Possible synergy between aPDT and pulsed electric fields

Abstract

Currently, microbial biofilms have been the cause of a wide variety of infections in the human body, reaching 80% of all bacterial and fungal infections. The biofilms present specific properties that increase the resistance to antimicrobial treatments. Thus, the development of new approaches is urgent, and antimicrobial photodynamic therapy (aPDT) has been shown as a promising candidate. aPDT involves a synergic association of a photosensitizer (PS), molecular oxygen and visible light, producing highly reactive oxygen species (ROS) that cause the oxidation of several cellular components. This therapy attacks many components of the biofilm, including proteins, lipids, and nucleic acids present within the biofilm matrix; causing inhibition even in the cells that are inside the extracellular polymeric substance (EPS). Recent advances in designing new PSs to increase the production of ROS and the combination of aPDT with other therapies, especially pulsed electric fields (PEF), have contributed to enhanced biofilm inhibition. The PEF has proven to have antimicrobial effect once it is known that extensive chemical reactions occur when electric fields are applied. This type of treatment kills microorganisms not only due to membrane rupture but also due to the formation of reactive compounds including free oxygen, hydrogen, hydroxyl and hydroperoxyl radicals. So, this review aims to show the progress of aPDT and PEF against the biofilms, suggesting that the association of both methods can potentiate their effects and overcome biofilm infections.

Treatment of Pseudomonas aeruginosa infectious biofilms: Challenges and strategies

“…Although some types of PSs only bind to the cell surface, most types of PSs can pass through the cytoplasmic membrane and enter the cytoplasm. PSs bound to the biofilm matrix generate reactive oxygen species (ROS) under light, thereby initiating multi-target damage (Hu et al, 2018), which attacks various biofilm components, leading to disintegration, including the disintegration of lipids, proteins, DNA, and exopolysaccharides in the matrix (Dosselli et al, 2012; Martins Antunes de Melo et al, 2021). Studies have reported many examples of aPDT used in the treatment of biofilm infections, and some have been used in clinical trials (Tahmassebi et al, 2015;Liang et al, 2020).…”

Pulsed Electric Fields Alter Expression of NF-κB Promoter-Controlled Gene

“…The quantity of highly reactive oxygen species depends on the parameters of the electric pulses applied to cells (field intensity, frequency, number and duration of the pulses, cell concentration). The generation of ROS after exposure to pulsed electric fields can be direct when free radicals form at the surface of the electrodes and indirect when free radicals form inside the cells in response to electrical stimulation [ 68 ]. We speculate that another mechanism could involve regulation by calcium ions—a preceding research revealed that microsecond-duration pulsed electric fields can permeabilize the endoplasmic reticulum membrane of mammalian cells, causing the leak of Ca 2+ [ 69 ].…”

Design and Properties of Antimicrobial Biomaterials Surfaces

“…Recently, photothermal dynamic or magnetic therapy have been integrated to synergistically enhance the antibiofilm effects rendered by an electric field. [ 395,108 ] For instance, Campli et al. [ 109 ] have found that bacteria exposed to 50 Hz and 1 mT electromagnetic field show modified morphology and adhesion.…”