Preface

Photodynamic medicine (therapy) (PDT) is a photochemistry-based approach involving the light activation (typically, near infrared) of a photosensitizer, which is somewhat preferentially localized into the target tissues, primarily by the enhanced permeability and retention phenomenon, aided by impaired biochemicals and lymphatics in tumors. Light activation of photosensitizers generates active molecular species, which are toxic to neighboring biological targets. There is inherent dual selectivity built into PDT because of the preferential localization of the photosensitizer and the confinement of light to specified volumes. With the advances in nanotechnology and drug delivery, PDT is also being transformed into a potential regional treatment, rather than being limited to localized treatment only.

Photodynamic medicine has been known of for 5000 years, when Egyptians and Indians used sunlight in combination with some “magic” plants and drugs for treating various somatic and physic disorders. “New-age” PDT began in 1900 and received its renaissance in 1970 thanks to Lipson, Diamond and Dougherty. Whereas the initial aim was the treatment of oncological disorders (bladder, brain, breast, gastric, lung and skin), the field shifted more and more towards diagnosis. The photosensitizers used as therapeutic agents in PDT often have a finite fluorescence, making it an inherently theranostic modality. In this context, photo-diagnostics—often referred to as photodynamic diagnosis (PDD)—is widely and routinely used. Most prominent is fluorescence diagnostic utilization in dermatology, urology, thoracic and brain surgery. Fluorescence-guided resection for brain tumors, bladder tumors or delineations for skin lesions are currently the gold standard in this diagnostic field. The logical next step is the theranostic approach following real-time, image-guided tumor resection and the combination with simultaneous therapy, all of which is on its way.

Photodynamic applications include a wide variety of fields and clinical indications. One of the driving and challenging forces is the close interaction and involvement of almost all known disciplines, starting from chemistry, physics, biology, pharmacy, light technology and lasers to almost all clinical oncological and non-oncological fields. In fact, one of the first-line indications for PDT is a non-oncological one in the treatment of age-related macular degeneration. Next to the oncological indications, the non-oncological indications are gaining wide attention and are contributing a great amount to human health and health economics. Recently, there has been a new emphasis on antimicrobial and environmental applications. Noteworthy among others is the successful field application of PDT for the control of malaria and Schistosoma or antimicrobial PDT in the fields of dentistry and chronic leg ulcers.

This book covers the highlights of progress in the fields of PDT and PDD. Thirty-three chapters cover a wide range of topics from basic photochemistry, photo-biotechnologies, targeted PDT, new photosensitizer delivery and nanotechnological applications to clinical oncological and non-oncological aspects. Included are also three chapters on nosocomial and environmental indications. There is an approximately equal distribution of basic and clinical chapters, reflecting the philosophy of the Brixen meetings, connecting bench to bedside and back. The biennial Brixen conferences were initiated in 1995 and continued to be organized for the subsequent two decades by Professors Giulio Jori (Padua, Italy) and Herwig Kostron (Innsbruck, Austria).

All of the authors are key persons and pioneers in their fields, discussing PDT in depth. Both basic scientists and clinicians are contributing to this book, bridging bench and clinic. Parallel to progress in the clinic, basic science has been much stimulated by clinicians, who ultimately wished to know more about the basic mechanisms of PDT and further future clinical indications. Therefore, understanding the needs of clinicians as well as the resulting stimulus for scientists is the driving force for exciting future developments in PDT.

The idea of writing this book was discussed by Professors Giulio Jori and Herwig Kostron during the very first Brixen meeting in 1995. After almost 20 years, the 10th and final so-called “Brixen meeting” (International Symposium in Photodiagnosis and Photodynamic Therapy in Clinical Practice, Brixen, 14–18 October 2014) was chosen in order to collect contributions from leading experts in the field, ranging from basic molecular biologists, chemists and technical suppliers to all clinical specialties. The intention was to represent milestones in the history of PDT by presenting reviews focusing on the present state and future progress in the various fields (basic and clinical) into which this technique has developed over the decades. Such an objective would be pursued through short reviews covering the latest information on advances, novel applications and, most importantly, future developments. In January 2014, Professor Jori wrote in his message asking the Royal Society of Chemistry to consider publishing this book within the Comprehensive Series in Photochemical and Photobiological Sciences, “We feel that such a book would have a large audience since it spans over a variety of applications and starts from basic arguments to clinics. Moreover, it should attract the attention of several people given the quality/authority of the speakers, hence the authors of the chapters.”

Unexpectedly, Professor Jori passed away in December 2014, leaving Professor Kostron to continue the book project. Fortunately, Professor Tayyaba Hasan readily provided help with collecting the contributions and provided valuable input into the content of this book.

This book will be of interest to both the scientific and medical communities, whether they are already practitioners of PDT or considering educational and research forays into this field, and may also be an evidence-based “handbook” for clinicians. We do hope that PDT gains wide acknowledgment and acceptance in the medical field as well as in health authorities, and finds the place that it deserves in medicine. PDT is not concurrent with but supplementary to existing medical techniques. Hopefully, this book will help others to understand PDT, and PDT will be acknowledged as the fourth mainstay in medical treatment alongside surgery, radiotherapy and chemotherapy.

Herwig Kostron

Tayyaba Hasan