On the trail of the type i mechanism in photodynamic therapy using porphycenes and other porphyrin-like photosensitisers

• Autores: Noemí Rubio
• Directores de la Tesis: Santi Nonell Marrugat (dir. tes.)
• Lectura: En la Universitat Ramon Llull ( España ) en 2006
• Idioma: español
• Tribunal Calificador de la Tesis: Jordi Teixidó i Closa (presid.), Montserrat Agut Bonsfills (secret.), David Phillips (voc.), Lluïsa Sagristà Mª (voc.), Silvia E. Braslavsky (voc.)
• Materias:
  • Física
    • Óptica
      • Láseres
    • Química física
      • Fotoquímica
      • Radioquímica
  • Química
    • Bioquímica
      • Química microbiológica
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• Resumen

  • Two mechanisms are used to explain the cytotoxic effects of the photodynamic action, a photosensitisation process in the presence of oxygen, which are: Type I and Type II mechanisms. Type I mechanism is based on an electron or hydrogen transfer process between the excited photosensitiser and the biosubstrate to yield the reduced and the oxidised forms of the photosensitiser and the substrate, respectively. These species further react and start a free radical chain-type autooxidation process which yields the cytotoxic effect. The Type II mechanism is based of the energy transfer process from the triplet strate of the photosensitiser to molecular oxygen to yield singlet oxygen, the cytotoxic specie in this case.

    This Thesis is focused on the study of the Type I mechanism of action sinsitised by porphycenes and other porphyrin-like photosensitisers. For this purpose, and as a first step, the photophysical characterisation of potential candidates to be used in applications of the photodynamic action, such as photodynamic therapy of cancer (PDT) and photodynamic inactivation of bacteria (PDI), is performed. Among the studied sensitisers- 2,7,12,17-tetraphenylporphycene (TPPo) and its Pd(II) and Cu(II) complexes (PdTPPo and CuTPPo, respectively), holoboron(III) subnaphtalocyanine (SubNc) and 2,7,12,17-tetrakis(4-butylphenyl)-3,6,13,16-tetraazaporphycene (TAPo)- TPPo, PdTPPo and SubNc are those that show better photophysical properties to be used in PDT and PDI applications.

    The electron transfer reactivity of the previous compounds is studied in homogeneous organic solutions, in order to characterise the absortion spectra and kinetics of their radical ions. The proton transfer reactivity of TPPo and PdTPPo is also compared with that of TAPo. The study of the interaction of TPPo with several biomolecules shows that this photosensitiser is able to bind several biosubstrates, such as human serum albumin, gramicidin A and lipid A, fact which favo