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Special Issue "Advances in Photodynamic Therapy 2018"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Medicinal Chemistry".

Deadline for manuscript submissions: 30 July 2018

Special Issue Editor

Guest Editor
Assoc. Prof. Dr. Michael R. Hamblin

Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA
Website | E-Mail
Phone: +1-617 726 6182
Fax: +1 617 726 6643
Interests: photodynamic therapy (PDT); low-level light therapy (LLLT); wound healing and infectious disease; atherosclerotic vulnerable plaque; anti-tumor immunity; photochemical mechanisms

Special Issue Information

Dear Colleagues,

Photodynamic therapy (PDT) is now over 100 years old, but has yet to make a big impact in modern medical practice. Nevertheless, it remains an active area of research, with constant efforts being made to develop novel, ever more-active photosensitzers, to develop active targeting strategies to better direct the photosensitizers to the tumor (or other anatomical site), to understand the photochemical mechanisms involved and improve the photochemical efficiency. In recent years a new approach called antimicrobial photodynamic inactivation has been developed, using the same principles as PDT, but this time to treat localized infections, rather than malignant tumors. Photosensitizers can be designed to be specific for microbial cells and to leave surrounding host cells unharmed. PDT has a particular ability to activate the host immune system, and in the modern age of the renaissance of immuno-oncology may have a particular role to play.

Prof. Dr. Michael R. Hamblin
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • photodynamic therapy
  • antimicrobial photodynamic inactivation
  • new photosensitizers
  • anti-tumor immunity
  • photosensitizer targeting
  • photochemical mechanisms

Published Papers (2 papers)

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Research

Open AccessArticle Synthesis and Evaluation of New Potential Benzo[a]phenoxazinium Photosensitizers for Anticancer Photodynamic Therapy
Molecules 2018, 23(6), 1436; https://doi.org/10.3390/molecules23061436
Received: 16 May 2018 / Revised: 31 May 2018 / Accepted: 8 June 2018 / Published: 13 June 2018
PDF Full-text (2239 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The use of photodynamic therapy (PDT) and development of novel photosensitizers (PSs) for cancer treatment have received more and more attention nowadays. In the present work, five benzo[a]phenoxazinium derivatives have been prepared and evaluated for their in vitro anticancer photodynamic activity
[...] Read more.
The use of photodynamic therapy (PDT) and development of novel photosensitizers (PSs) for cancer treatment have received more and more attention nowadays. In the present work, five benzo[a]phenoxazinium derivatives have been prepared and evaluated for their in vitro anticancer photodynamic activity for the first time. They are red light absorbers and show low fluorescence quantum yield. Of these compounds, PS4 exhibited a higher quantum yield for reactive oxygen species (ROS) generation. The assays with cells in vitro showed that PS1 and PS4 were not significantly toxic in the dark, but was robustly toxic against the murine breast adenocarcinoma cells 4T1 and normal murine fibroblast cells NIH-3T3 upon photoactivation. More interestingly, PS5 was particularly selective towards 4T1 cancer cells and nearly non-phototoxic to non-cancerous NIH-3T3 cells. The results described in this report suggest that these new benzo[a]phenoxazinium derivatives are potential candidates as PSs for anticancer PDT. Further investigation of benzo[a]phenoxaziniums for anticancer PDT is warranted. Full article
(This article belongs to the Special Issue Advances in Photodynamic Therapy 2018)
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Graphical abstract

Open AccessFeature PaperArticle Assessing Photosensitizer Targeting Using Meso-Tetra(Carboxyphenyl) Porphyrin
Molecules 2018, 23(4), 892; https://doi.org/10.3390/molecules23040892
Received: 6 March 2018 / Revised: 28 March 2018 / Accepted: 10 April 2018 / Published: 12 April 2018
PDF Full-text (7752 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Mesotetra(4-carboxyphenyl)porphyrin (mTCPP) is a commercially available small molecule fluorophore and photosensitizer with four free carboxylic acid groups. mTCPP can readily be conjugated with amines for facile attachment of functional groups. In this work, we synthesized and assessed tetravalent, lysine-conjugated mTCPP, for its potential
[...] Read more.
Mesotetra(4-carboxyphenyl)porphyrin (mTCPP) is a commercially available small molecule fluorophore and photosensitizer with four free carboxylic acid groups. mTCPP can readily be conjugated with amines for facile attachment of functional groups. In this work, we synthesized and assessed tetravalent, lysine-conjugated mTCPP, for its potential applications in targeted imaging and photodynamic therapy. Fmoc-protected d-lysine or l-lysine was conjugated to mTCPP via amide coupling with the epsilon amine group of lysine, followed by Fmoc deprotection. The resulting compounds did not dissolve well in aqueous solvent, but could be solubilized with the assistance of surfactants, including cholic acid. The l-amino acid transporter (LAT1) can uptake diverse neutral l-amino acids. In vitro studies with U87 cells revealed a non-specific uptake of the hydrophobic Fmoc-protected lysine-conjugated mTCPP precursors, but not d- or l-lysine mTCPP. Likewise, only the Fmoc-protected compounds induced substantial phototoxicty in cells following incubation and irradiation with blue light. These experimental results do not provide evidence to suggest that lysine-mTCPP is able to specifically target cancer cells. However, they do highlight mTCPP as a convenient and accessible framework for assessing molecular targeting of photosensitizers. Full article
(This article belongs to the Special Issue Advances in Photodynamic Therapy 2018)
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Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Inorganic salts and photodynamic therapy: mechanistic mysteries?
Author: 
Michael R Hamblin
Abstract: 
We have recently discovered that many different photosensitizes (PS) can be dramatically potentiated by addition of a solution containing a range of different inorganic salts. Most of these studies have centered around antimicrobial photodynamic inactivation that kills Gram-negative and Gram-positive bacteria in suspension. Addition of non-toxic water-soluble salts during illumination can kill up to six additional logs of bacterial cells. The PS investigated range from those that undergo mainly type 1 photochemical mechanisms (electron transfer to produce superoxide, hydrogen peroxide, and hydroxyl radicals) to those that are type 2 (energy transfer to produce singlet oxygen). At one extreme is the salt sodium azide that quenches singlet oxygen, but can produce azide radical (presumed to be highly reactive) via electron transfer from photoexcited phenothiazinium dyes. Potassium iodide is oxidized to molecular iodine by both type 1 and type 2 PS, but may also form reactive iodine species. Potassium bromide is oxidized to hypobromite, but only by titanium dioxide photocatalysis (type 1). Potassium thiocyanate appears to require a mixture of type 1 and type 2 photochemistry to first produce sulfite that can then form the sulfur trioxide radical anion. Potassium selenocyanate can react with either type 1 or type 2 (or indeed with other oxidizing agents) to produce the semi-stable selenocyanogen (SCN)2. Finally, sodium nitrite may react with either type 1 or type 2 PS to produce peroxynitrate (again semi-stable) that can kill bacteria and nitrate tyrosine. Many of these salts (except azide) are non-toxic and may be clinically applicable.

Title: Selective Photokilling of Human Pancreatic Adenocarcinoma Cells Using EGFR Antibody-Labelled Mesoporous Silica Nanoparticles
Author: Santi Nonell
Affiliation: Institut Químic de Sarrià, Universitat Ramon Llull, Vía Augusta, 390, 08017 Barcelona, Spain

Title: Effects of blue-light-induced free radicals formation from catechin on the inactivation of Acinetobacter baumannii
Author: Ji-Yuan Liang
Abstract: In this article, we have described a finding that catechin is unstable in an alkaline solution treated with blue-light irradiation. The transformation of catechins under blue-light irradiation was investigated by chromatography and photospectrometry. Catechin dimer is formed by catechin photolysis and decreased in the presence of ascorbic acid. Detection of superoxide anion radical (O2•−) and the inactivation of Acinetobacter baumannii were examined during the photoreaction of catechin. The photochemical treatment of catechin under blue light irradiation via electron transfer generated O2•− that inactivated Acinetobacter baumannii, due primarily to reactive oxygen species (ROS) produced via photon-induced electron transfer from catechin photolysis.

Title: Cyclodextrins for passive targeting in cancer treatment by PDT
Author: Celine Frochot
Abstract: Photodynamic therapy (PDT) is a minimally invasive photochemical-based treatment with a promising clinical track record for oncological and some other diseases. Most PDT-drugs (photosensitizers) are highly hydrophobic and require delivery systems. To improve their solubility and pharmacokinetic properties, cyclodextrins derivatives were proposed. In this review, the use of cyclodextrins in PDT for treatment against cancer by passive targeting is described, as well as their characteristics and molecular mechanism of action when associated to photosensitizers.

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