Chapter 13
Photodynamic Therapy
Keiichi Imato and Yousuke Ooyama
Abstract Photosensitizing dyes with the ability to produce singlet oxygen (
1 O 2 )
under light irradiation can be used for photodynamic therapy (PDT), a treatment of
early-stage cancer with less stress on bodies, where the photogenerated
1 O 2 destroys
cancer cells. For PDT use, photosensitizing dyes require several capabilities such
as strong photoabsorption in the phototherapeutic window (650–900 nm), high
1 O 2
generation quantum yield (Φ ), good water solubility, and low toxicity without
light irradiation. Therefore, the effects of chemical structures and substituents of
photosensitizing dyes on these properties have been investigated, which enables to
create new photosensitizing dyes with excellent performance for PDT. This chapter
overviews recent studies and developments in photosensitizing dyes with a focus on
porphyrin, phthalocyanine, boron-dipyrromethene (BODIPY), xanthene, phenothiazinium, heteropolycycle, pyrylium, azinium, squalin, and transition metal (Ru, Ir,
Pt) complex skeletons.
Keywords Photosensitizing dyes · Photodynamic therapy · Singlet oxygen ·
Intersystem crossing · Photoabsorption
13.1 Introduction
Photodynamic therapy (PDT) using photosensitizing dyes with the ability to produce
singlet oxygen (
1 O 2 ) and low-power laser light has attracted much attention as a treatment for cancer in an early stage with less stress on bodies (Fig. 13.1a) (DeRosa and
Crutchley 2002; Patrice 2003; Pawlicki et al. 2009; Lovell et al. 2010; D˛ abrowski
and Arnaut 2015; Zhou et al. 2016; Callaghan and Senge 2018). The mechanism of
PDT is shown in Fig. 13.1b. Photosensitizing dyes (
1 Dye) adsorbed to cancer cells
are excited to photoexcited singlet states (
1 Dye*) by light irradiation, undergo intersystem crossing (ISC) to be excited triplet states (
3 Dye*), and generate reactive
1 O 2
via ISC and energy transfer from
3 Dye* to ground-state triplet oxygen (
3 O 2 ) (Type
K. Imato · Y. Ooyama (B)
Hiroshima University, Higashihiroshima, Japan
e-mail: yooyama@hiroshima-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_13
445
Photodynamic Therapy
Keiichi Imato and Yousuke Ooyama
Abstract Photosensitizing dyes with the ability to produce singlet oxygen (
1 O 2 )
under light irradiation can be used for photodynamic therapy (PDT), a treatment of
early-stage cancer with less stress on bodies, where the photogenerated
1 O 2 destroys
cancer cells. For PDT use, photosensitizing dyes require several capabilities such
as strong photoabsorption in the phototherapeutic window (650–900 nm), high
1 O 2
generation quantum yield (Φ ), good water solubility, and low toxicity without
light irradiation. Therefore, the effects of chemical structures and substituents of
photosensitizing dyes on these properties have been investigated, which enables to
create new photosensitizing dyes with excellent performance for PDT. This chapter
overviews recent studies and developments in photosensitizing dyes with a focus on
porphyrin, phthalocyanine, boron-dipyrromethene (BODIPY), xanthene, phenothiazinium, heteropolycycle, pyrylium, azinium, squalin, and transition metal (Ru, Ir,
Pt) complex skeletons.
Keywords Photosensitizing dyes · Photodynamic therapy · Singlet oxygen ·
Intersystem crossing · Photoabsorption
13.1 Introduction
Photodynamic therapy (PDT) using photosensitizing dyes with the ability to produce
singlet oxygen (
1 O 2 ) and low-power laser light has attracted much attention as a treatment for cancer in an early stage with less stress on bodies (Fig. 13.1a) (DeRosa and
Crutchley 2002; Patrice 2003; Pawlicki et al. 2009; Lovell et al. 2010; D˛ abrowski
and Arnaut 2015; Zhou et al. 2016; Callaghan and Senge 2018). The mechanism of
PDT is shown in Fig. 13.1b. Photosensitizing dyes (
1 Dye) adsorbed to cancer cells
are excited to photoexcited singlet states (
1 Dye*) by light irradiation, undergo intersystem crossing (ISC) to be excited triplet states (
3 Dye*), and generate reactive
1 O 2
via ISC and energy transfer from
3 Dye* to ground-state triplet oxygen (
3 O 2 ) (Type
K. Imato · Y. Ooyama (B)
Hiroshima University, Higashihiroshima, Japan
e-mail: yooyama@hiroshima-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_13
445