title: LC-MS/MS determination in rabbit plasma of the main photoproduct of RLP068/Cl, a cationic sensitizer proposed for photodynamic therapy (PDT) of microbial infections.
abstract: The clinical development of a sensitizer for photodynamic therapy (PDT) requires the structural identification of the photoproducts and their quantification in biological fluids and tissues. We describe the LC-MS identification of the most important photoproducts of a cationic phthalocyanine sensitizer (RLP068/Cl) and a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of the main photoproduct (the cationic phthalimide derivative 3-[(1,3-dioxo-2,3-dihydro-1H-isoindol-4-yl)oxy]-N,N,N-trimethylbenzenaminium chloride) in rabbit plasma. The tri-deuterated product was used as co-eluting internal standard. The cationic photoproduct was isolated from plasma samples by protein precipitation with perchloric acid in methanol (7%, v/v). HPLC step was performed on a Phenomenex Synergi Hydro-RP column (20 mm x 2.0 mm, 2 microm particles) with a mobile phase of 0.5% (v/v) aqueous TFA/methanol (85:15, v/v). Flow rate was 0.2 mL/min and 40 microL injection were performed. Run time was 10 min. Detection was achieved by means of a Bruker Esquire 3000+ ion trap mass spectrometer equipped with an ESI source working in positive mode. A multiple reaction monitoring method following the transitions 297.1 --> 282.1 for the analyte and 300.1 --> 282.1+285.1 for the internal standard was used. The analytical method was validated over the concentration range 0.46-91.2 ng/mL and lower limits of detection (LLOD) and quantification (LLOQ) respectively of 0.2 and 0.5 ng/mL were found.
authors.affiliation: L. Molteni & C. S.p.A., S.S. 67 Toscoromagnola, 50018 Scandicci, Florence, Italy. g.chiti@moltenifarma.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Chiti
authors.forename: Moira
authors.initials: M
authors.lastname: Municchi
authors.forename: Valentina
authors.initials: V
authors.lastname: Paschetta
authors.forename: Gabrio
authors.initials: G
authors.lastname: Roncucci
mesh_terms: D000818:Animals; D001424:Bacterial Infections / Q000188:drug therapy*; D002138:Calibration; D002412:Cations; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007211:Indoles / Q000097:blood* / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000097:blood* / Q000627:therapeutic use; D010778:Photochemotherapy; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002412:Cations; D007211:Indoles; D009942:Organometallic Compounds; C477806:RLP068