Photobleaching kinetics of optically trapped multilamellar vesicles containing verteporfin using two-photon excitation section sign.

Abstract

Two-photon excitation photodynamic therapy (TPE-PDT) is being developed as an improved treatment for retinal diseases. TPE-PDT has advantages over one-photon PDT, including lower collateral damage to healthy tissue and more precise delivery of PDT. As with one-photon PDT, there can be local photochemical depletion of oxygen during TPE-PDT. Here, we investigate model systems and live cells to measure local photosensitizer photobleaching and through it, infer local oxygen consumption in therapeutic volumes of the order 1 microm3. Multilamellar vesicles (MLV) and African green monkey kidney (CV-1) cells were used to study the TPE photobleaching dynamics of the photosensitizer, Verteporfin. It was found that in an oxygen-rich environment, photobleaching kinetics could not be modeled using a mono-exponential function, whereas in hypoxic conditions a mono-exponential decay was adequate to represent photobleaching. A biexponential was found to adequately model the oxygen-rich conditions and it is hypothesized that the fast part of the decay is oxygen-dependent, whereas the slower rate constant is largely oxygen-independent. Photobleaching recovery studies in the CV-1 cells support this hypothesis.

• Authors: Kimberley S Samkoe, Matthew S Fecica, Rebecca L Goyan, Jennifer L Buchholz, Chantel Campbell, Nicole M Kelly, David T Cramb
• Journal: Photochemistry and photobiology (Photochem Photobiol) 2006 Jan-Feb Vol. 82 Issue 1 Pg. 152-7 ISSN: 0031-8655 [Print] United States
• PMID: 16149861 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Liposomes
• Porphyrins
• Verteporfin
• Oxygen

Topics

• Humans
• Kinetics
• Liposomes
• Oxygen
• Photochemotherapy
• Photons
• Porphyrins (chemistry)
• Retinal Diseases (therapy)
• Verteporfin