Oxygen diffusion and reaction kinetics in the photodynamic therapy of multicell tumour spheroids

Michael G. Nichols, T. H. Foster

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

Effects of oxygen diffusion and reaction kinetics in photodynamic therapy are considered in the context of a multicell tumour spheroid model. Steady-state measurements of oxygen made with a Clark-style microelectrode (4 mu m diameter tip) enable the authors to determine the rate of metabolic oxygen consumption and the oxygen diffusion coefficient in 500 mu m diameter EMT6/Ro spheroids. These values are 5.77 mu mol 1-1 s-1 and 1460 mu m 2 s-1, respectively. Time-dependent electrode measurements of oxygen concentration during laser irradiation of individual Photofrin-sensitized spheroids are fitted to numerical solutions of a pair of diffusion-with-reaction equations. The analysis yields the rate of photodynamic oxygen consumption and a parameter that governs the oxygen sensitivity of photodynamic therapy. These experimentally derived quantities are used to calculate the temporal and spatial distributions of oxygen and the rate of oxygen consumption in a spheroid during irradiation at several fluence rates. The spatial distribution of photodynamic oxygen consumption is strongly fluence rate dependent. Using the experimental and theoretical results developed in this report, previously published survival data are analysed. The analysis indicates that the threshold dose of reacting singlet oxygen in the EMT6/Ro spheroid is 323+or-38 mu mol 1-1 (mean+or-SEM).

Original languageEnglish
Article number003
Pages (from-to)2161-2181
Number of pages21
JournalPhysics in Medicine and Biology
Volume39
Issue number12
DOIs
StatePublished - 1994
Externally publishedYes

Fingerprint

Photodynamic therapy
spheroids
Photochemotherapy
Reaction kinetics
Tumors
therapy
reaction kinetics
tumors
oxygen consumption
Oxygen
Oxygen Consumption
kinetics
oxygen
Neoplasms
Dihematoporphyrin Ether
spatial distribution
fluence
Singlet Oxygen
Microelectrodes
temporal distribution

All Science Journal Classification (ASJC) codes

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy (miscellaneous)
  • Biomedical Engineering

Cite this

Oxygen diffusion and reaction kinetics in the photodynamic therapy of multicell tumour spheroids. / Nichols, Michael G.; Foster, T. H.

In: Physics in Medicine and Biology, Vol. 39, No. 12, 003, 1994, p. 2161-2181.

Research output: Contribution to journalArticle

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