Photophysical, electrochemical characteristics and cross-linking of STAT-3 protein by an efficient bifunctional agent for fluorescence image-guided photodynamic therapy

Photochem Photobiol Sci. 2007 Dec;6(12):1257-67. doi: 10.1039/b710395f. Epub 2007 Sep 24.


The photophysical, electrochemical and spectroscopic characteristics of a conjugate of 3-devinyl-3-(1'-hexyloxyethyl)pyropheophorbide-a (HPPH) and a cyanine dye have been investigated both as a linked conjugate and as individual components. A photoexcitation of the HPPH moiety of the conjugate results in electron transfer from the singlet excited state of HPPH (1HPPH*) to the cyanine dye as well as that from the cyanine dye to 1HPPH* and is followed in both cases by facile back electron transfer to the ground state as indicated by time-resolved fluorescence and transient absorption measurements. Intersystem crossing to the triplet excited state (3HPPH*) competes with the electron transfer and 3HPPH* is quenched by oxygen to produce singlet oxygen (1O2), leading to specific covalent cross-linking of the nonactivated signal transducer and activator of transcription (STAT-3). In contrast to excitation of the HPPH moiety, photoexcitation of the cyanine dye unit results in a strong emission at 875 nm, which can be used for efficient tumor imaging. Compared to HPPH alone, the presence of the cyanine dye moiety in the conjugate produces a significantly higher uptake in tumors than in skin. Thus, the HPPH-cyanine dye conjugate can be used as a dual tumor imaging and photodynamic therapy agent.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carbocyanines / chemistry
  • Carbocyanines / pharmacology
  • Chlorophyll / analogs & derivatives
  • Chlorophyll / chemistry
  • Chlorophyll / pharmacology
  • Cross-Linking Reagents / chemistry*
  • Electrochemistry
  • Fluorescence
  • Glioma / diagnosis
  • Glioma / drug therapy
  • Mice
  • Mice, Nude
  • Molecular Structure
  • Neoplasm Transplantation
  • Oxidation-Reduction
  • Photochemotherapy / methods*
  • Photosensitizing Agents / chemistry
  • Photosensitizing Agents / pharmacology
  • STAT3 Transcription Factor / chemistry*
  • Singlet Oxygen / chemistry


  • Carbocyanines
  • Cross-Linking Reagents
  • Photosensitizing Agents
  • STAT3 Transcription Factor
  • Stat3 protein, mouse
  • Chlorophyll
  • 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a
  • Singlet Oxygen