title: Tailoring protease-sensitive photodynamic agents to specific disease-associated enzymes.
abstract: We have developed novel polymeric photosensitizer prodrugs (PPPs) for improved photodynamic therapy. In PPPs, multiple photosensitizer units are covalently coupled to a polymeric backbone via protease-cleavable peptide linkers. These initially non-photoactive compounds become fluorescent and phototoxic after specific enzymatic cleavage of the peptide linkers and subsequent release of the photosensitizer moieties. Tethering the photosensitizer via a short and easily modified amino acid sequence to the polymeric backbone allows for the targeting of a wide variety of proteases. Model compounds, sensitive to trypsin-mediated cleavage, with different pheophorbide a-peptide loading ratios and backbone net charges were evaluated with respect to their solubility, "self-quenching" capacity of fluorescence emission, and reactive oxygen species (ROS) generation. In addition, linker sequence impaired selectivity toward enzymatic cleavage was demonstrated either by incubating PPPs with different enzymes having trypsin-like activity or by introducing a single d-arginine mutant in the peptide sequence. In vitro cell culture tests confirmed dose-dependent higher phototoxicity of enzymatically activated PPPs compared to the nonactivated conjugate after irradiation with white light. These data suggest that similar compounds adapted to disease-associated proteases can be used for selective photodynamic therapy.
authors.affiliation: Laboratory of Pharmaceutics and Biopharmaceutics, Section of Pharmaceutical Sciences, University Lausanne, University Genève, 30 Quai Ernest-Ansermet, CH-1211, Geneva, Switzerland.
authors.forename: Doris
authors.initials: D
authors.lastname: Gabriel
authors.forename: Marino A
authors.initials: MA
authors.lastname: Campo
authors.forename: Robert
authors.initials: R
authors.lastname: Gurny
authors.forename: Norbert
authors.initials: N
authors.lastname: Lange
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D010455:Peptides / Q000737:chemistry; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000494:pharmacology; D011107:Polylysine / Q000737:chemistry; D011355:Prodrugs / Q000138:chemical synthesis* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014357:Trypsin / Q000737:chemistry
chemical_list: D010455:Peptides; D017319:Photosensitizing Agents; D011355:Prodrugs; D017382:Reactive Oxygen Species; D002734:Chlorophyll; D011107:Polylysine; D014357:Trypsin; C032623:pheophorbide a