Approach toward characterizing the fraction of all oxidation events that attack a particular site within cells during PDT

Steven L. Jacques; Paulo R. Bargo

doi:10.1117/12.434688

9 July 2001 Approach toward characterizing the fraction of all oxidation events that attack a particular site within cells during PDT

Steven L. Jacques, Paulo R. Bargo

Author Affiliations +

Proceedings Volume 4257, Laser-Tissue Interaction XII: Photochemical, Photothermal, and Photomechanical; (2001) https://doi.org/10.1117/12.434688
Event: BiOS 2001 The International Symposium on Biomedical Optics, 2001, San Jose, CA, United States

Abstract

This paper considers the fraction PDT-induced oxidizing radicals that react with a specific oxidizable target within a cell rather than with all possible oxidizable sites. There are many oxidizable sites within the cell, each with a different efficiency of oxidation (Y_ox_j) and a different in vivo concentration (C_iv_j). One measures the efficiency of oxidation of a single ith chemical species in vitro (Y_it_i), then measures the oxidation of the same species in vivo (Y_iv_i). The concentration of this ith species in vivo must be measured (C_iv_i). A convenient test chemical species is chosen, such as a photobleachable fluorophore. Then the in vivo yield is approximately: Y_iv_i = (C_iv_i*Y_it_i)/sum_all_j(C_iv_j*Y_iv_j) (eq.1). Rearranging to solve for the total oxidation: Sum_all_j(C_iv_j*Y_iv_j) = (C_iv_i*Y_it_i)/Y_iv_I (Eq.2) Once the sum_all_j() in Eq.2 is specified, one can measure the in vitro oxidation efficiency and the in vivo concentration of any ith species and use Eq.1 to predict the fraction of PDT_generated singlet oxygen that will attack that ith species in vivo. Of course, the above is only a first approximation toward a complex problem but is a beginning. This paper illustrates the experimental specification of the Y_ox_j for NADPh oxidation in a cuvette using the photosensitizer Photofrin.

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Steven L. Jacques and Paulo R. Bargo "Approach toward characterizing the fraction of all oxidation events that attack a particular site within cells during PDT", Proc. SPIE 4257, Laser-Tissue Interaction XII: Photochemical, Photothermal, and Photomechanical, (9 July 2001); https://doi.org/10.1117/12.434688

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