title: Photosensitiser-loaded biodegradable polymeric micelles: preparation, characterisation and in vitro PDT efficacy.
abstract: The application of photosensitisers (PSs) in photodynamic therapy (PDT) is often hampered by their hydrophobicity, as this complicates their formulation and results in an unfavourable biodistribution. Consequently, there is an urgent need for novel delivery vehicles for PSs. In this paper, the loading and stability of thermosensitive mPEG-b-p(HPMAm-Lac2) micelles with a hydrophobic solketal-substituted phthalocyanine (Si(sol)2Pc) photosensitiser were studied. It was shown that the Si(sol)2Pc could be loaded efficiently in the micelles (diameter 75 nm) up to a concentration of approximately 2 mg/mL. UV/Vis and fluorescence spectroscopy showed that at low concentrations (< or =0.05 microM, 0.45 mg/mL polymer), the PS was molecularly dissolved in the micellar core, whereas it was present in an aggregated form at higher concentrations. In B16F10 and 14C cells, the photocytotoxicity of Si(sol)2Pc-loaded micelles (PS<0.05 microM) was similar to free PS, i.e. IC(50) of 3.0+/-0.2 nM (10% serum). The cellular uptake of high-loaded micelles (10 microM Si(sol)2Pc) was low and independent of the serum concentration. The nanoaggregates of Si(sol)2Pc loaded in the micellar core were only released upon hydrolysis-induced micellar dissociation, which was observed after 5.5 h at pH 8.7 at 37 degrees C. The stability of the high-loaded micellar Si(sol)2Pc formulation also in the presence of serum, the controlled release of the PS upon micellar disintegration and the high photodynamic activity of Si(sol)2Pc make these micelles interesting for future in vivo studies.
authors.affiliation: Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, PO Box 80082, 3508 TB Utrecht, The Netherlands.
authors.forename: Cristianne J F
authors.initials: CJ
authors.lastname: Rijcken
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Hofman
authors.forename: Femke
authors.initials: F
authors.lastname: van Zeeland
authors.forename: Wim E
authors.initials: WE
authors.lastname: Hennink
authors.forename: Cornelus F
authors.initials: CF
authors.lastname: van Nostrum
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D004355:Drug Stability; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008546:Melanoma, Experimental / Q000188:drug therapy / Q000473:pathology; D051379:Mice; D008823:Micelles; D008854:Microscopy, Electron; D008970:Molecular Weight; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D010316:Particle Size; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013997:Time Factors
chemical_list: D008823:Micelles; D009942:Organometallic Compounds; D017646:Organosilicon Compounds; D017319:Photosensitizing Agents; D011108:Polymers; D011092:Polyethylene Glycols