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Unique diagnostic and therapeutic roles of porphyrins and phthalocyanines in photodynamic therapy, imaging and theranostics.

Josefsen LB, Boyle RW - Theranostics (2012)

Bottom Line: Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types.Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms.The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, The University Of Hull, Kingston-Upon-Hull, HU6 7RX, U.K.

ABSTRACT
Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

No MeSH data available.


Related in: MedlinePlus

Copper Octaethylbenzochlorin.
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Figure 9: Copper Octaethylbenzochlorin.

Mentions: Excited state porphyrins (1Psen*, S>0 or 3Psen*, T>0) are relatively efficient at undergoing ISC and can have a high triplet-state (quantum) yields (ΦT 0.62 (tetraphenylporphyrin (TPP), methanol), 0.75 (TPP, liposome, D2O) and 0.71 (tetrasulphonated TPP, D2O) 49, 50. The longer lifetime is sufficient to allow the excited triplet state photosensitiser to interact with the surrounding biomolecules 4, 5. Excited triplet-state photosensitisers can react in two ways defined as Type I and Type II processes. Type I processes involve the excited triplet photosensitiser (3Psen*, T1) interacting with readily oxidizable or reducible substrates; whereas, Type II processes involve the interaction of the excited triplet photosensitiser (3Psen*, T1) with molecular oxygen (3O2, 3Σg) (figure 8) 4, 5, 9, 25-29, 49-59. The highly-reactive oxygen species (1O2) produced via the Type II process act near to their site of generation with a typical lifetime of approximately 40ns in biological systems 3, 5, 14, 53. These interactions cause damage and potential destruction to cellular membranes and enzyme deactivation, culminating in cell death 35-37, 50, 53. It is highly probable that in the presence of molecular oxygen, both Type I and II pathways play a pivotal role in disrupting both cellular mechanisms and cellular structure as a direct result of the photoirradiation of the photosensitiser molecule. Nevertheless, there is considerable evidence to suggest that the Type II photo-oxygenation process predominates in the role of cell damage, a consequence of the interaction between the irradiated photosensitiser and molecular oxygen 3, 4, 24, 40, 50, 59, 60. It has however, been suggested that cells in vitro are partially protected against the effects of pdt by the presence of singlet oxygen scavengers, such as histidine, and that certain skin cells are somewhat resistant to pdt in the absence of molecular oxygen; further supporting the proposal that the Type II process is at the heart of photo-initiated cell death 5, 46, 59-62. The efficiency of Type II processes is dependent upon the triplet state lifetime (τT) and the triplet quantum yield (ΦT) of the photosensitiser, both parameters have been implicated in the effectiveness of a photosensitiser in phototherapeutic medicine; further supporting the distinction between Type I and Type II mechanisms. However, it is worth noting that the success of a photosensitiser is not exclusively dependent upon a Type II process taking place - there are a number of photosensitisers whose excited triplet lifetimes are too short to permit a Type II process to occur, for example, the copper metallated octaethylbenzochlorin photosensitiser (figure 9) has a triplet state lifetime of less than 20ns and is still deemed to be an efficient photodynamic agent 46.


Unique diagnostic and therapeutic roles of porphyrins and phthalocyanines in photodynamic therapy, imaging and theranostics.

Josefsen LB, Boyle RW - Theranostics (2012)

Copper Octaethylbenzochlorin.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3475217&req=5

Figure 9: Copper Octaethylbenzochlorin.
Mentions: Excited state porphyrins (1Psen*, S>0 or 3Psen*, T>0) are relatively efficient at undergoing ISC and can have a high triplet-state (quantum) yields (ΦT 0.62 (tetraphenylporphyrin (TPP), methanol), 0.75 (TPP, liposome, D2O) and 0.71 (tetrasulphonated TPP, D2O) 49, 50. The longer lifetime is sufficient to allow the excited triplet state photosensitiser to interact with the surrounding biomolecules 4, 5. Excited triplet-state photosensitisers can react in two ways defined as Type I and Type II processes. Type I processes involve the excited triplet photosensitiser (3Psen*, T1) interacting with readily oxidizable or reducible substrates; whereas, Type II processes involve the interaction of the excited triplet photosensitiser (3Psen*, T1) with molecular oxygen (3O2, 3Σg) (figure 8) 4, 5, 9, 25-29, 49-59. The highly-reactive oxygen species (1O2) produced via the Type II process act near to their site of generation with a typical lifetime of approximately 40ns in biological systems 3, 5, 14, 53. These interactions cause damage and potential destruction to cellular membranes and enzyme deactivation, culminating in cell death 35-37, 50, 53. It is highly probable that in the presence of molecular oxygen, both Type I and II pathways play a pivotal role in disrupting both cellular mechanisms and cellular structure as a direct result of the photoirradiation of the photosensitiser molecule. Nevertheless, there is considerable evidence to suggest that the Type II photo-oxygenation process predominates in the role of cell damage, a consequence of the interaction between the irradiated photosensitiser and molecular oxygen 3, 4, 24, 40, 50, 59, 60. It has however, been suggested that cells in vitro are partially protected against the effects of pdt by the presence of singlet oxygen scavengers, such as histidine, and that certain skin cells are somewhat resistant to pdt in the absence of molecular oxygen; further supporting the proposal that the Type II process is at the heart of photo-initiated cell death 5, 46, 59-62. The efficiency of Type II processes is dependent upon the triplet state lifetime (τT) and the triplet quantum yield (ΦT) of the photosensitiser, both parameters have been implicated in the effectiveness of a photosensitiser in phototherapeutic medicine; further supporting the distinction between Type I and Type II mechanisms. However, it is worth noting that the success of a photosensitiser is not exclusively dependent upon a Type II process taking place - there are a number of photosensitisers whose excited triplet lifetimes are too short to permit a Type II process to occur, for example, the copper metallated octaethylbenzochlorin photosensitiser (figure 9) has a triplet state lifetime of less than 20ns and is still deemed to be an efficient photodynamic agent 46.

Bottom Line: Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types.Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms.The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, The University Of Hull, Kingston-Upon-Hull, HU6 7RX, U.K.

ABSTRACT
Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

No MeSH data available.


Related in: MedlinePlus