Measurements on the depth of penetration of light (0.35?1.0 �m) in tissue

Abstract

Preliminary results on the spectral dependence of the absorption of light in tissue are presented and discussed with respect to medical laser application.

Photophysical properties and intracellular imaging of water-soluble porphyrin dimers for two-photon excited photodynamic therapy

“…This indicates that P 2 -SO 3 NH 4 aggregates to a lesser degree in water than the other dimers, which is explained by its structure. P 2 -SO 3 NH 4 has twice the number of charges compared to P 2 -NMeI, P 2 -NMe 3 OAc, P 2 C 2 -NMeI and P 2 -Suc, and its sulfonate groups are much weaker bases 185 than the carboxylate groups of P 2 C 2 -CO 2 NH 4 , therefore, at neutral pH, it will be fully ionised. Thus P 2 -SO 3 NH 4 appears to be the most water-soluble photosensitiser in the series.…”

“…5 and Table 2. The characteristic quadratic dependence of the emission intensity on the laser power was detected at wavelengths 215 longer than 830 nm for P 2 -NMeI, P 2 -NMe 3 OAc and P 2 -Suc, >850 nm for P 2 C 2 -CO 2 NH 4 and > 900 nm for P 2 C 2 -NMeI. Dimers P 2 -NMeI, P 2 -NMe 3 OAc and P 2 -Suc have peak TPA cross-sections of around 9000 GM between 830-838 nm, whilst the extended $-systems of P 2 C 2 -NMeI and P 2 C 2 -CO 2 NH 4 result in a further 220 increase to 17000 GM at 916 nm and 14000 GM at 878 nm respectively.…”

“…1 The structure of the conjugated porphyrin dimers under study. NMe 3 OAc, P 2 -SO 3 NH 4 and P 2 -Suc possess polar aromatic substituents directly bonded to the porphyrin meso-positions, thus steric interactions force these aryl substituents to twist out of conjugation with the porphyrin. In the second group, dimers P 2 C 2 -NMeI and P 2 C 2 -CO 2 NH 4 , the terminal aromatic groups are instead conjugated via an acetylene bridge, thereby increasing the length of the $-system.…”

“…Their lowest energy absorption maxima, Q-bands, lie between 650 and 800 nm and are intense compared to those of monomeric porphyrins. 5,30 The greater degree of conjugation in P 2 C 2 -NMeI and P 2 C 2 -CO 2 NH 4 , is clearly reflected in the shift of their Q-band absorption and fluorescence maxima to lower energy. The absorption of the 145 conjugated dimers favourably compares with the existing second generation PDT sensitisers, e.g. "…”

“…An efficient PDT photosensitiser requires a favourable combination of the following factors: (i) light absorption at 35 wavelengths which penetrate effectively into biological tissue (700-950 nm), 4 (ii) a high quantum yield for singlet oxygen generation (! !…”