Microelectrode measurements of photochemical oxygen depletion in multicell tumor spheroids during photodynamic therapy

Michael G. Nichols; Thomas H. Foster

doi:10.1117/12.179983

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Microelectrode measurements of photochemical oxygen depletion in multicell tumor spheroids during photodynamic therapy

Conference paper

Peer reviewed

Microelectrode measurements of photochemical oxygen depletion in multicell tumor spheroids during photodynamic therapy

Michael G. Nichols and Thomas H. Foster

Proceedings of SPIE - The International Society for Optical Engineering, Vol.2133, pp.260-271

2133

Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy III 1994 (Los Angeles, United States, 01/23/1994 - 01/29/1994)

07/19/1994

DOI: https://doi.org/10.1117/12.179983

Abstract

Electronic, Optical and Magnetic Materials

Condensed Matter Physics

Computer Science Applications

Applied Mathematics

Electrical and Electronic Engineering

We have previously reported results of experiments in which EMT6/Ro spheroids were subjected to Photofrin®-PDT consisting of a fixed incident fluence (60 J-cm-2) delivered at 200, 50, and 25 mW-cm-2. Surviving fractions from treated spheroids decreased as the incident fluence rate was lowered over this range. We have interpreted these data using a model wherein the cells comprising the surviving fractions are assumed to originate from within a therapy-induced anoxic volume resulting from Type-il photochemistry. In this paper, we demonstrate direct measurements of the phenomenon in individual photosensitized EMT6 spheroids. Steadystate measurements of 3O2 gradients in and around metabolizing spheroids allow determination of the 3O2 diffusion constant and the rate of metabolic 3O2 consumption within a spheroid. Timedependent measurements obtained at a single spatial location during laser irradiation are fit to numerical solutions of a pair of time-dependent diffusion with consumption equations. Fits allow a determination of the rate of PDT-induced 3O2 consumption. Based on these fits, it is possible to calculate the spatial and temporal distributions of oxygen within a spheroid undergoing PDT.

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Title: Microelectrode measurements of photochemical oxygen depletion in multicell tumor spheroids during photodynamic therapy
Creators: Michael G. Nichols (Author) - University of Rochester
Thomas H. Foster (Author) - University of Rochester
Publication Details: Proceedings of SPIE - The International Society for Optical Engineering, Vol.2133, pp.260-271
Conference: Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy III 1994 (Los Angeles, United States, 01/23/1994 - 01/29/1994)
Series: 2133
Number of pages: 12
Grant note: The work reported here has been supported by USPHS grant CA36856 and by a grant from the American Lung Association of NY State. M.G.N. gratefully acknowledges a grant-in-aid of research from Sigma Xi. The authors wish to thank Donna Hartley for technical assistance, Shari Harwell for preparation of Figure 1 , and Russell Hilf and Scott Gibson for helpful discussions on many aspects of photodynamic therapy. Finally, we thank Mr. Stewart Levine of the Diamond General Development Corp. for his expertise and patience in guiding us through the mysterious world of oxygen-sensitive microelectrodes.
Identifiers: 991005929665502656
Academic Unit: Creighton University
Language: English
Resource Type: Conference paper

Microelectrode measurements of photochemical oxygen depletion in multicell tumor spheroids during photodynamic therapy

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