Photochemical interactions of methylene blue and analogues with DNA and other biological substrates

Chemistry Department, Trinity College, Dublin, Ireland.
Journal of Photochemistry and Photobiology B Biology (Impact Factor: 2.96). 01/1993; 21(2-3):103-124.


The light-induced reactions of methylene blue and related phenothiazinium dyes with biological substrates are described. The properties of the excited states of the dyes, their reactions with nucleic acids and their photosensitised chemical modifications of nucleic acid bases are examined. Reports on phenothiazinium dye-induced damage to proteins, lipids, biological membranes, organelles, viruses, bacteria, mammalian cells and carcinomas are reviewed.

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    • "TH and its derivatives have the capability of generating singlet oxygen and it is widely used in many areas such as photodynamic therapy (PDT) [16] [17], development of biosensors [18] [19], as polymerization photoinitiators [20] [21], in the decontamination of blood products [22], as nucleic acid probes [23] and against bacteria [24e27], viruses and yeasts [28]. TH also used to induce photodynamic inactivation of bladder cancer cells, Escherichia coli, and Saccharomyces cerevisiae [23]. Previous studies have revealed that TH showed mutagenic activity towards eukaryotic cells [29]. "
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    ABSTRACT: In this article, an attempt is made to explore the binding mechanism of thionine with lysozyme by using multi-spectroscopic and molecular docking methods. The results from emission and time resolved fluorescence studies revealed that the emission quenching of lysozyme with thionine is initiated by static quenching mechanism. The binding constant and number of binding site of lysozyme-thionine complex was evaluated as 4.01 × 105 dm 3 mol-1 and ≈1, respectively. Furthermore, the results from absorption, constant wavelength synchronous fluorescence, three dimensional emission and circular dichroism spectral studies showed that thionine induced conformational changes in the secondary structure of lysozyme. Molecular docking study confirmed that the probable binding site of thionine is located near trptophan-63 residue of lysozyme and it is further revealed that the existence of hydrogen bonding along with hydrophobic interaction are the primary forces responsible for the complexation of thionine with lysozyme.
    Full-text · Article · Jan 2015 · Dyes and Pigments
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    • "Among them, methylene blue is very popular because it is highly photo-stable, easily eliminated from the body, and has minimum toxicity [7]. Hence, methylene blue has also been approved as a potential PDT drug for the local treatment of periodontal disease because of its relative low toxicity and high generation yield of singlet oxygen [8,9,10]. However, methylene blue also has some drawbacks, because its activity decreases in vivo. "
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    ABSTRACT: Purpose: Photodynamic therapy (PDT) is gaining increasing recognition for breast cancer treatment because it offers local selectivity and reduced toxic side effects compared to radiotherapy and chemotherapy. In PDT, photosensitizer drugs are loaded in different nanomaterials and used in combination with light exposure. However, the most representative issue with PDT is the difficulty of nanomaterials to encapsulate anticancer drugs at high doses, which results in low efficacy of the PDT treatment. Here, we proposed the development of the poly(N-isopropylacrylamide) (PNIPAM) microgel for the encapsulation of methylene blue, an anticancer drug, for its use as breast cancer treatment in MCF-7 cell line. Methods: We developed biocompatible microgels based on nonfunctionalized PNIPAM and its corresponding anionically functionalized PNIPAM and polyacrylic acid (PNIPAM-co-PAA) microgel. Methylene blue was used as the photosensitizer drug because of its ability to generate toxic reactive oxygen species upon exposure to light at 664 nm. Core PNIPAM and core/shell PNIPAM-co-PAA microgels were synthesized and characterized using ultraviolet-visible spectroscopy and dynamic light scattering. The effect of methylene blue was evaluated using the MCF-7 cell line. Results: Loading of methylene blue in core PNIPAM microgel was higher than that in the core/shell PNIPAM-co-PAA microgel, indicating that electrostatic interactions did not play an important role in loading a cationic drug. This behavior is probably due to the skin layer inhibiting the high uptake of drugs in the PNIPAM-co-PAA microgel. Core PNIPAM microgel effectively retained the cationic drug (i.e., methylene blue) for several hours compared to core/shell PNIPAM-co-PAA and enhanced its photodynamic efficacy in vitro more than that of free methylene blue. Conclusion: Our results showed that the employment of core PNIPAM and core/shell PNIPAM-co-PAA microgels enhanced the encapsulation of methylene blue. Core PNIPAM microgel released the drug more slowly than did core/shell PNIPAM-co-PAA, and it effectively inhibited the growth of MCF-7 cells.
    Full-text · Article · Mar 2014 · Journal of Breast Cancer
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    • "Especially lipid peroxidation, induced by MB photosensitization, has detrimental effects on membrane integrity, leading to a loss of fluidity and alterations on the functions of several ion channels, receptors, and transporters (see section 8). This damage is thought to be triggered both by type I and type II mechanisms and has been comprehensively described in earlier reviews (Tuite and Kelly, 1993; Tardivo et al., 2005). "
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    ABSTRACT: Methylene Blue (MB), following its introduction to biology in the 19th century by Ehrlich, has found uses in various areas of medicine and biology. At present, MB is the first line of treatment in methemoglobinemias, is used frequently in the treatment of ifosfamide-induced encephalopathy, and is routinely employed as a diagnostic tool in surgical procedures. Furthermore, recent studies suggest that MB has beneficial effects in Alzheimer's disease and memory improvement. Although the modulation of the cGMP pathway is considered the most significant effect of MB, mediating its pharmacological actions, recent studies indicate that it has multiple cellular and molecular targets. In the majority of cases, biological effects and clinical applications of MB are dictated by its unique physicochemical properties including its planar structure, redox chemistry, ionic charges, and light spectrum characteristics. In this review article, these physicochemical features and the actions of MB on multiple cellular and molecular targets are discussed with regard to their relevance to the nervous system.
    Full-text · Article · Apr 2011 · Medicinal Research Reviews
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