Singlet oxygen mediated photodynamic effects

Abstract

This special issue of Photonics & Lasers in Medicine on singlet molecular oxygen and photodynamic effects is divided into two sections. The first deals with 38 short reports submitted to the First Sino-German Symposium on “Singlet molecular oxygen and photodynamic effects”, which was held in Fuzhou (the capital city of Fujian province), China, from 23 to 28 March 2015. The second part includes two original contributions related to singlet oxygen (O2) mediated photodynamic effects. Singlet oxygen, the lowest excited electronic state of molecular oxygen, is a highly oxidative reactive oxygen species (ROS) that plays an important role in numerous chemical and photochemical reactions in different biological systems [1–3]. In particular, O2 is widely accepted as being the key reactive species mediating the photodynamic effect via type-II of photosensitization [4, 5]. This effect is the basic mechanism of photodynamic therapy (PDT) and is used for treatment of superficial tumors, agerelated macular degeneration, localized infection, and several benign skin conditions [6, 7]. Currently PDT is the subject of research as an alternative method for replacing antibiotics or biocides in the deactivation of harmful microorganisms such as antibiotic-resistant bacteria or mold fungi on surfaces [8–10]. The aim of the Sino-German Symposium was to highlight not only the molecular mechanisms of photosensitized O2 generation and quenching in biological systems but also to show possible ways of enhancing the luminescence signal. The symposium was also dedicated to giving an overview of the whole spectrum of possible applications of photodynamic effects. Also quantified techniques for O2 production during photosensitization are of immense importance for research and clinical practice. With regard to the photodynamic effects induced by the O2, the 10 main topics of this symposium were: O2 generation and detection, newly-emerging multifunctional photosensitizers and targeting carrier systems, photodynamic inactivation of microorganisms, enhancement of O2 generation, general aspects and new approaches of PDT, novel sensitive techniques for monitoring PDT, dosimetry and predicting the biological responses, clinical PDT and recent advances in PDT [11]. One main objective of the symposium was to bringing together experts from diverse areas such as chemistry, physics, optical engineering, materials, biological sciences and clinical medicine, and to create a productive platform for brainstorming. During the symposium, a round-table discussion was organized to establish a possible long-term academic collaboration including scientific aspects and student exchange between Chinese and German research groups, with a special emphasis on the clinical translation research on the detection of O2 luminescence. This issue also includes two original contributions related to O2 mediated photodynamic effects. In order to enhance the photodynamic effects, Kasimova et al. [12] reported about in-vitro studies in lung cancer cells combining either cisplatin or etoposide with indocyanine greenmediated PDT, and the synergistic gain that was achieved. In the second study, Lademann et al. [13] demonstrated that high antioxidant concentrations in human skin might be an efficient mechanism to reduce ROS and thus prevent skin aging. This was non-invasively determined using resonance Raman spectroscopy and reflectance spectroscopy. In addition to the scientific contributions you will find an announcement of the Deutsche Gesellschaft für Lasermedizin (DGLM) e.V. [14] and the protocol of the general meeting of the DGLM e.V. [15]. Our international readers will hopefully excuse the fact that the protocol is written in German as it specifically addresses the members of the DGLM e.V. Finally, we wish to express our gratitude to the participants of the First Sino-German Symposium on “Singlet molecular oxygen and photodynamic effects”. In particular, we would like to thank all the authors for their excellent contributions and last but not least, Dr. Ronald Sroka, one of the editors-in-chief of Photonics & Lasers in Medicine, for his initiative and support for this special issue. On behalf of all participants, we also would like to thank the Sino-German Center for Research Promotion for making this great event possible. We hope that this special issue will not only serve as an overview but also provide readers with a comprehensive source of information on the latest developments in this interesting field.