PMID- 27942676
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20180322
LR  - 20180322
IS  - 1474-9092 (Electronic)
IS  - 1474-905X (Linking)
VI  - 16
IP  - 4
DP  - 2017 Apr 12
TI  - Singlet oxygen feedback delayed fluorescence of protoporphyrin IX in organic 
      solutions.
PG  - 507-518
LID - 10.1039/c6pp00298f [doi]
AB  - Delayed fluorescence (DF) of protoporphyrin IX (PpIX) has been recently proposed 
      as a tool for monitoring of mitochondrial oxygen tension in vivo as well as for 
      observation of the effectiveness of photodynamic therapy (PDT) [E. G. Mik, 
      Anesth. Analg., 2013, 117, 834-346; F. Piffaretti et al., J. Biomed. Opt., 2012, 
      17, 115007]. However, the efficiency of the mechanism of thermal activation 
      (E-type DF), which was considered in the papers, is limited due to a large energy 
      gap between the first excited singlet and the first triplet state of PpIX at room 
      or body temperatures. Moreover, the energy gap is roughly equal to other 
      porphyrinoid photosensitizers that generate DF mostly through the Singlet Oxygen 
      Feedback-Induced mechanism (SOFDF) under certain conditions [M. Scholz and R. 
      Dedic, Singlet Oxygen: Applications in Biosciences and Nanosciences, 2016, vol. 
      2, pp. 63-81]. The mechanisms of delayed fluorescence of PpIX dissolved either in 
      dimethylformamide (DMF) or in the mixture of DMF with ethylene glycol (EG) were 
      investigated at atmospheric partial pressure of oxygen by means of a simultaneous 
      time-resolved detection of (1)O(2) phosphorescence and PpIX DF which makes a 
      direct comparison of the kinetics and lifetimes of both the luminescence channels 
      possible. Samples of PpIX (100 muM) exhibit concave DF kinetics, which is a 
      typical footprint of the SOFDF mechanism. The dramatic decrease in the DF 
      intensity after adding a selective (1)O(2) quencher sodium azide (NaN(3), 10 mM) 
      proves that >90% of DF is indeed generated through SOFDF. Moreover, the analysis 
      of the DF kinetics in the presence of NaN(3) implies that the second significant 
      mechanism of DF generation is the triplet-triplet annihilation (P-type DF). The 
      bimolecular mechanism of DF was further confirmed by the decrease of the DF 
      intensity in the more viscous mixture DMF/EG and by the increase of the ratio of 
      DF to the prompt fluorescence (PF) intensity with the increasing excitation 
      intensity. These results show the significant role of the SOFDF mechanism in the 
      DF of PpIX at high concentrations and at atmospheric partial pressure of oxygen 
      and should be considered when developing diagnostic tools for clinical 
      applications.
FAU - Vinklarek, Ivo S
AU  - Vinklarek IS
AD  - Charles University, Faculty of Mathematics and Physics, Department of Chemical 
      Physics and Optics, Ke Karlovu 3, 121 16, Prague, The Czech Republic. 
      vinklarekivo@gmail.com.
FAU - Scholz, Marek
AU  - Scholz M
FAU - Dedic, Roman
AU  - Dedic R
FAU - Hala, Jan
AU  - Hala J
LA  - eng
PT  - Journal Article
PL  - England
TA  - Photochem Photobiol Sci
JT  - Photochemical & photobiological sciences : Official journal of the European 
      Photochemistry Association and the European Society for Photobiology
JID - 101124451
EDAT- 2016/12/13 06:00
MHDA- 2016/12/13 06:01
CRDT- 2016/12/13 06:00
PHST- 2016/12/13 06:00 [pubmed]
PHST- 2016/12/13 06:01 [medline]
PHST- 2016/12/13 06:00 [entrez]
AID - 10.1039/c6pp00298f [doi]
PST - ppublish
SO  - Photochem Photobiol Sci. 2017 Apr 12;16(4):507-518. doi: 10.1039/c6pp00298f.