Spectroscopic properties of potential sensitizers for new photodynamic therapy start mechanisms via two-step excited electronic states.
Three substituted tetraazaporphyrins, octa-(4-tert-butylphenyl)-tetrapyrazinoporphyrazine, tetra-(4-tert-butyl)phthalocyanine and tetra-(4-tert-butyl)phthalocyanatomagnesium(t4-PcMg), were spectroscopically checked in solutions and liposomes with respect to suitability as potential sensitizers of a possible new start mechanism for photodynamic therapy (PDT) from a stepwise excited higher singlet state. This PDT start mechanism was recently proposed to overcome the problem of O2 (1delta2)-caused cutaneous phototoxicity in PDT. By means of absorption and fluorescence measurements as well as nonlinear absorption investigation, transient spectroscopy and lasing experiments, compound t4-PcMg was found to have the most appropriate properties: Based on a high fluorescence quantum yield (phiF1 = 0.84) and a very low crossing to the triplet (phiISC = 0.05), two higher excited states can be effectively populated both by two stepwise absorption transitions at 674nm consecutive absorption transitions at 684 and and 710 nm. Moreover, t4-PcMg incorporates into liposomes very well with spectroscopic properties similar to those in solution.
Teuchner
K
K
Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berline, Germany.
Pfarrherr
A
A
Stiel
H
H
Freyer
W
W
Leupold
D
D
D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D008081:Liposomes; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D013329:Structure-Activity Relationship
D007211:Indoles; D054833:Isoindoles; D008081:Liposomes; D017319:Photosensitizing Agents; C013647:phthalocyanine