title: Pitfalls in evaluation of photosensitizing agents: an example with Q-switch II dye.
abstract: Photosensitizing agents potentiating laser therapy should have limited toxicity, no mutagenicity, stable spectral characteristics, and acceptable solubility when administered in vivo. Q-Switch II dye (QII) has been shown by others to be an effective chromophore for photodynamic therapy at 1051 nm in fibroblast cell culture. The objective of this study was to determine the spectral stability of QII in biological media and then to localize QII after administration in vivo. Spectral evaluation was performed between 250 and 1100 nm. QII dissolved in dimethyl sulfoxide (DMSO) rapidly lost its spectral characteristics, including its 1051-nm peak, when contacting water, minimal essential medium, human serum, organ surfaces, and intracellular fluid. One minute following intramuscular (IM) injection of 0.1 mg QII in 0.2 mL of DMSO, the dose precipitated as a discrete mass which was excised and reconstituted in DMSO. A new spectral pattern was seen, with no absorption between 850 and 1100 nm. Following intravenous (i.v.), (IM), or intraperitoneal (IP) injection, QII was not detected in any organ. Q-Switch II dye is not a suitable chromophore for in vivo photodynamic therapy at 1051 nm. Previous cell culture reports to the contrary did not account for the QII spectral change caused by biological media. Simple rapid assays are described to avoid this pitfall.
authors.affiliation: Department of Surgery, University of California at Los Angeles.
authors.forename: D
authors.initials: D
authors.lastname: Eton
authors.forename: S
authors.initials: S
authors.lastname: Ahn
authors.forename: S
authors.initials: S
authors.lastname: Kitada
authors.forename: V
authors.initials: V
authors.lastname: Shim
authors.forename: D G
authors.initials: DG
authors.lastname: Elis
authors.forename: D
authors.initials: D
authors.lastname: Lee
mesh_terms: D000042:Absorption; D000818:Animals; D001578:Benzopyrans / Q000008:administration & dosage / Q000493:pharmacokinetics; D004121:Dimethyl Sulfoxide; D005069:Evaluation Studies as Topic; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D066298:In Vitro Techniques; D007273:Injections, Intramuscular; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D053685:Laser Therapy; D051379:Mice; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D011817:Rabbits; D013053:Spectrophotometry
chemical_list: D001578:Benzopyrans; D005456:Fluorescent Dyes; D017319:Photosensitizing Agents; C054228:Q-switch II dye; D004121:Dimethyl Sulfoxide