title: Localized thermal tumor destruction using dye-enhanced photothermal tumor therapy.
abstract: OBJECTIVE
  In an attempt to develop a new therapeutic approach for highly localized thermal destruction of tissue targets that lack natural pigmentation, the potential of in-vivo dye-enhanced photothermal therapy (PTT) was investigated. PTT involves the application of an exogenous absorber, which accumulates in metabolically active tissues, followed by non-invasive light irradiation, using appropriate wavelengths, exposure durations, and irradiances. The chromophore used, palladium(II) octabutoxynaphthalocyanine (PdNc(OBu)8 ), strongly absorbs in the near infrared wavelength range which thus permits good penetration depth of the exciting light. The predominant de-excitation routes of the chromophore are radiationless thermal processes.
  
  
  METHODS
  Using a BALB/c mouse model with a subcutaneously implanted syngeneic EMT6 adenocarcinoma, 96-100 hours after intraperitoneal application of PdNc(OBu)8 , tumor, and surrounding tissue were irradiated with a 830 nm continuous wave diode laser applying 30 Wcm(-2) for 10-20 seconds. Treatment parameters were based on theoretical calculations.
  
  
  RESULTS
  Histological evaluation of thermal effects on tumor and normal tissue showed that after PdNc(OBu)8 -enhanced photothermal treatment, highly localized and selective thermal damage of the tumors was achieved. The necrotic tumor area was invaded by inflammatory cells, including neutrophils, macrophages, mast cells, and lymphocytes, thus reflecting a prominent host immune response. In tumors treated with PTT for 15 or 20 seconds, respectively, only few surviving tumor cells were detected underneath the epidermis. Adjacent peripheral normal tissue including skin and muscle remained completely unaffected.
  
  
  CONCLUSIONS
  This study highlights the potential of achieving irreversible thermal tissue damage closely localized to the target tissue when PdNc(OBu)8 is used in combination with continuous-wave light.
authors.affiliation: Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany.
authors.forename: Heyke C
authors.initials: HC
authors.lastname: Diddens-Tschoeke
authors.affiliation: Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany.
authors.forename: Gereon
authors.initials: G
authors.lastname: Hüttmann
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
authors.forename: Achim D
authors.initials: AD
authors.lastname: Gruber
authors.affiliation: Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, Ontario, Canada.
authors.forename: Roy H
authors.initials: RH
authors.lastname: Pottier
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Hanken
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000601:surgery*; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D053685:Laser Therapy / Q000379:methods*; D054023:Lasers, Semiconductor; D051379:Mice; D008807:Mice, Inbred BALB C; D009942:Organometallic Compounds; D012878:Skin Neoplasms / Q000473:pathology / Q000601:surgery*
chemical_list: D009942:Organometallic Compounds; C428883:palladium 5,9,14,18,23,27,32,36-octabutoxynaphthalocyanine
keywords: dye-enhanced; in-vivo; laser; naphthalocyanine derivative; photothermal therapy