Chapter 22 Future directions - photosensitizer targeting and new disease indications

This chapter will focus on some aspects of PDT that may be more speculative in nature and attempt to identify some applications that may become useful in the future both in dermatology and in wider clinical practice. We will attempt to outline areas of research underway in PS development and targeting strategies that have the aim of enhancing selectivity for specific cells in tumors or other tissues, This will include the use of noncovalent complexes and covalent conjugates between PS and macromolecular vehicles where the object is to allow the macromolecular vehicle to control the targeting and pharmacokinetics, and to choose the PS based only on its photophysical and photochemical properties. Although these targeted PS will usually be systemically injected, the possibility of topical or intralesional administration should not be overlooked. The development of methods to enhance the penetration of topical PS or PS precursors through the skin's permeability barrier, and the development of new light sources and dosimetry methods will be briefly covered. Finally some new possible indications for PDT in dermatology and related fields will be mentioned, many of which are still under pre-clinical investigation. These will be grouped under oncological, nononcologic and infectious disease headings.