Optimal photosensitizers for photodynamic therapy of infections should kill bacteria but spare neutrophils

Masamitsu Tanaka, Manabu Kinoshita, Yasuo Yoshihara, Nariyoshi Shinomiya, Shuhji Seki, Koichi Nemoto, Takahiro Hirayama, Tianhong Dai, Liyi Huang, Michael R. Hamblin, Yuji Morimoto

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)


Photodynamic therapy (PDT) for localized microbial infections exerts its therapeutic effect both by direct bacterial killing and also by the bactericidal effects of host neutrophils stimulated by PDT. Therefore, PDT-induced damage to neutrophils must be minimized, while direct photoinactivation of bacteria is maintained to maximize the therapeutic efficacy of antimicrobial PDT in vivo. However, there has been no study in which the cytocidal effect of PDT on neutrophils was investigated. In this study, the cytocidal effects of PDT on neutrophils were evaluated using different antimicrobial photosensitizers to find suitable candidate photosensitizers for antimicrobial PDT. PDT on murine peripheral-blood neutrophils was performed in vitro using each photosensitizer at a concentration that exerted a maximum bactericidal effect on methicillin-resistant Staphylococcus aureus, and morphological alteration and viability of neutrophils were studied. Most neutrophils were viable (>80%) after PDT using toluidine blue-O (TB) or methylene blue (MB), while neutrophils showed morphological change and their viabilities were decreased (<70%) after PDT using other photosensitizers (erythrosine B, rose bengal, crystal violet, Photofrin, new methylene blue and Laserphyrin). These results suggest that PDT using TB or MB can preserve host neutrophils while exerting a significant therapeutic effect on in vivo localized microbial infection.

Original languageEnglish
Pages (from-to)227-232
Number of pages6
JournalPhotochemistry and Photobiology
Issue number1
Publication statusPublished - Jan 2012
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry


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