Perfluorocarbons in photodynamic and photothermal therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) belong to the category of phototherapy and are based on the photophysical generation of either noxious reactive oxygen species, thereby inducing oxidative stress, or rather cell-hostile environmental conditions (local hyperthermia) with the general aim to destroy abnormal tissues. A great advantage of both strategies is the fact that they are minimally invasive by low toxicity for the surrounding healthy tissue. In both cases, photosensitizers and light are inevitable. Furthermore, in PDT oxygen is a mandatory component for generating reactive oxygen species such as singlet oxygen. Perfluorocarbons (PFCs) can donate molecular oxygen tension in the target tissue of interest (tumor tissue) thereby improving PDT outcome in such a hypoxic region. Because applied PFCs can at the same monitored via both, ultrasonic and magnetic resonance imaging techniques, they increase the selectivity of PDT and PTT to target tissue while sparing healthy cells in the surroundings. This selectivity is especially important in tissues such as eye, brain or gastro-intestinal tract. During the last few years a lot of interesting approaches (clinical and preclinical) were developed to improve PDT and PTT with the aid of PFCs. This review informs the astute reader about actual approaches on the use of PFCs in PDT and PTT, respectively. The literature indicates that the use of PFCs can increase the efficiency of PDT and PTT thereby contributing to a more effective therapy of tumors and other diseases. ABBREVIATIONS: 5-ALA: δ-aminolevulinic acid; BCG: Bacillus Calmette Guerin; CT: computed tomography; DOX: doxorubicin; Gd: gadolinium-chelate; GO: graphene oxide; HP: Hollow mesoporous; ICG: indocyanine green; MRI: magnetic resonance imaging; NC: nanocapsule; NIR: noninvasive infrared-based; PB: Prussian Blue; PCV: polypoidal choroidal vasculopathy; PDT: photodynamic therapy; PEI: polyethyleneimine; PFC: perfluorocarbon; PFD: perfluorodecalin; HpD: hematoporphyrin derivate; PFH: perfluorohexane; PFOB: perfluoro octylbromide; PFP: perfluoropentane; PFTBA: perfluorotributylamine; PLGA: poly (lactide co-glycolide); PPy: polypyrrole; PTT: photothermal therapy; RA: rheumatoid arthritis; RBC: red blood cell; RES: reticuloendothelial system; TCC: transitional cell carcinoma; US: ultrasound imaging.