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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

A Simplified Jablonski Diagram.
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Figure 8: A Simplified Jablonski Diagram.

Mentions: When a chromophore, such as a porphyrin, absorbs a photon of electromagnetic radiation (EMR) in the form of light energy, an electron is promoted into a higher-energy molecular orbital; hence, the chromophore is elevated from the ground state (S0) into a short-lived, electronically excited state (Sn) composed of a number of vibrational sub-levels (Sn´) (figure 8). The excited chromophore can lose energy by rapidly decaying through these sub-levels via internal conversion (IC) to populate the first excited singlet state (S1), before quickly relaxing back to the ground state: the excited electron depopulates the excited singlet state (S1) and return back to the ground state (S0) by losing the absorbed energy via fluorescence (S1 → S0). Singlet state lifetimes of excited fluorophores are very short (τfl = 10-9 - 10-6 seconds) since transitions between the same spin states (S → S or T → T) conserve the spin multiplicity (spin) of the electron and are considered “allowed” transitions according to the Spin Selection Rules 27, 50. Alternatively, an excited singlet state electron (S1) can undergo spin inversion and populate the lower-energy first excited triplet state (T1) via intersystem crossing (ISC), a spin-forbidden process, since the spin of the electron is no longer conserved (S → Τ). The excited electron can then undergo a second spin-forbidden inversion and depopulate the excited triplet state (T1) by decaying back to the ground state (S0) via phosphorescence (T1 → S0). Owing to the spin-forbidden triplet to singlet transition, the lifetime of phosphorescence (τP = 10-3 - 1 second) is considerably longer than that of fluorescence.


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

Josefsen LB, Boyle RW - Theranostics (2012)

A Simplified Jablonski Diagram.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 8: A Simplified Jablonski Diagram.
Mentions: When a chromophore, such as a porphyrin, absorbs a photon of electromagnetic radiation (EMR) in the form of light energy, an electron is promoted into a higher-energy molecular orbital; hence, the chromophore is elevated from the ground state (S0) into a short-lived, electronically excited state (Sn) composed of a number of vibrational sub-levels (Sn´) (figure 8). The excited chromophore can lose energy by rapidly decaying through these sub-levels via internal conversion (IC) to populate the first excited singlet state (S1), before quickly relaxing back to the ground state: the excited electron depopulates the excited singlet state (S1) and return back to the ground state (S0) by losing the absorbed energy via fluorescence (S1 → S0). Singlet state lifetimes of excited fluorophores are very short (τfl = 10-9 - 10-6 seconds) since transitions between the same spin states (S → S or T → T) conserve the spin multiplicity (spin) of the electron and are considered “allowed” transitions according to the Spin Selection Rules 27, 50. Alternatively, an excited singlet state electron (S1) can undergo spin inversion and populate the lower-energy first excited triplet state (T1) via intersystem crossing (ISC), a spin-forbidden process, since the spin of the electron is no longer conserved (S → Τ). The excited electron can then undergo a second spin-forbidden inversion and depopulate the excited triplet state (T1) by decaying back to the ground state (S0) via phosphorescence (T1 → S0). Owing to the spin-forbidden triplet to singlet transition, the lifetime of phosphorescence (τP = 10-3 - 1 second) is considerably longer than that of fluorescence.

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