Photodynamic inactivation (PDI) as a promising alternative to current pharmaceuticals for the treatment of resistant microorganisms

Abstract

Although the whole world is currently observing the global battle against COVID-19, it should not be underestimated that in the next 30 years, approximately 10 million people per year could be exposed to infections caused by multi-drug resistant bacteria. As new antibiotics come under pressure from unpredictable resistance patterns and relegation to last-line therapy, immediate action is needed to establish a radically different approach to countering resistant microorganisms. Among the most widely explored alternative methods for combating bacterial infections are metal complexes and nanoparticles, often in combination with light, but strategies using monoclonal antibodies and bacteriophages are increasingly gaining acceptance. Photodynamic inactivation (PDI) uses light and a dye termed a photosensitizer (PS) in the presence of oxygen to generate reactive oxygen species (ROS) in the field of illumination that eventually kill microorganisms. Over the past few years, hundreds of photomaterials have been investigated, seeking ideal strategies based either on single molecules (e.g., tetrapyrroles, metal complexes) or in combination with various delivery systems. The present work describes some of the most recent advances of PDI, focusing on the design of suitable photosensitizers, their formulations, and their potential to inactivate bacteria, viruses, and fungi. Particular attention is focused on the compounds and materials developed in our laboratories that are capable of killing in the exponential growth phase (up to seven logarithmic units) of bacteria without loss of efficacy or resistance, while being completely safe for human cells. Prospectively, PDI using these photomaterials could potentially cure infected wounds and oral infections caused by various multidrug-resistant bacteria. It is also possible to treat the surfaces of medical equipment with the materials described, in order to disinfect them with light, and reduce the risk of nosocomial infections.

A visible-light activated ROS generator multilayer film for antibacterial coatings

“…However, the intracellular ROS generated in both bacteria under dark conditions could lead to cell death predominantly in E. coli compared to S. aureus . 56,57 The number of cells remained mostly constant in untreated vials (both dark and light conditions). Subsequently, the MIC method was used to validate the previous results.…”

Amphiphilic AIE Fluorescent Probe: A Dual-Functionality Strategy for Efficient Antibacterial Therapy Fluorescence Bioimaging against Staphylococcus aureus

“…7 However, photodynamic therapy (PDT) has emerged as a promising alternative to antibacterial drugs, garnering significant attention. 8,9 PDT offers several advantages, including its noninvasive nature, excellent selectivity, low toxicity, and limited side effects. 10−12 PDT involves the use of photosensitizers (PSs) and specific light sources to interact with intracellular oxygen, generating reactive oxygen species (ROS).…”

Poly(oxanorbornene)s bearing triphenylphosphonium and PEGylated zinc(ii) phthalocyanine with boosted photobiological activity and singlet oxygen generation

“…32 Among the explored alternative methods, antimicrobial photodynamic therapy (aPDT) has gained importance for combating bacterial infections in recent years. [33][34][35][36][37] This method involves the use of photosensitizers to generate reactive oxygen species (ROS) upon light exposure at an appropriate wavelength and these ROS can cause damage to microbial cells, including oxidation of membrane lipids, nucleic acids, and amino acids, and cross-linking of proteins. 38,39 ZnPc has significant properties such as a relatively high extinction coefficient, excellent visible/near-infrared absorption and the ability to generate ROS to act as a photosensitizer.…”