Editorial
Recent Patents on Anti-Infective Drug Discovery, 2013, Vol. 8, No. 2
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Editorial Photosensitizers as an Alternative to Antibiotics Marina Nisnevitch Department of Chemical Engineering, Biotechnology and Materials, Ariel University, Ariel, Israel The history of mankind is rife with episodes of advancement and defeat, in the never-ending struggle between human beings and bacteria. The previous century can be considered a turning point in that struggle, which brought at last hope a winner may finally be determined. The year 1900 symbolizes the beginning of a new epoch of antimicrobial warfare, ushered in by the photodynamic inactivation of bacteria. The accidental discovery made by Oscar Raab that cells of Paramecium caudatum were inhibited by the dye acridine orange under illumination opened a new approach to the eradication of bacteria, which was instantly put into practice in the treatment of skin diseases [1, 2]. However, this technique was soon overshadowed by the discovery of penicillin by Sir Alexander Fleming in 1928 [3], and forgotten for decades. Since then, antibiotics from different sources, with different targets and modes of action were considered to be magic bullets, capable of combating any bacterial infection. The Golden Era of antibiotics however, did not last long, and a new obstacle, bacterial resistance to antibiotics destroyed hopes of a victory over bacteria. This phenomenon, caused by the massive and inappropriate use or misuse of antibiotics, poses a serious threat to patients due to development of bacterial strains resistant to conventional antibiotics and worse, the evolution of multi-drug resistance, leaving patients vulnerable to harmful diseases, with no treatment options left. This new situation has forced the scientific community to seek novel ways to defeat pathogenic bacteria, and has renewed interest in the photodynamic eradication of cells, called photodynamic antimicrobial chemotherapy (PACT). PACT’s mode of action is based on the lightactivation of dyes that are non-toxic or of low-toxicity in the dark, called photosensitizers. The electromagnetic radiation excites the photosensitizer into a higher energy state, making it activated. The excited photosensitizer can follow two pathways, either directly reacting with bio-organic molecules or transferring energy to molecular oxygen dissolved in the aqueous phase, resulting in the production of reactive oxygen species. In both cases, the active species cause damage to cellular components, inducing bacterial cell death [4]. PACT demonstrates a broad spectrum of activity against Gram-positive and Gram-negative bacteria, yeasts, fungi, protozoa and viruses, and exhibits a number of advantages over antibiotics: PACT apparently does not cause bacterial resistance or mutagenic effects; PACT is effective against antibiotic resistant bacterial strains and biofilm forming strains [5, 6]. At the moment it is considered to be a serious alternative to antibiotics. This issue is dedicated to the discussion of antimicrobial photodynamic treatment of Gram-positive and Gram-negative bacteria by photosensitizers in their free forms, encapsulated in liposomes, immobilized onto solid supports or conjugated with other molecules that amplify their efficiency or aide in targeting them to bacteria cells. ACKNOWLEDGEMENTS The editor would like to express her deepest gratitude to the authors for their highly professional contributions in the compilation of this issue, to the reviewers for their valuable and constructive comments and to the PRI editorial and publishing management for the help and support. REFERENCES [1] [2] [3] [4] [5] [6]
Raab O. Über die Wirkung, fluorezcierender Stoffe auf infusorien. Z Biol 1900; 39: 524-46. Von Tappeiner H, Jesionek A. Therapeutische Versuche mit fluorescierenden Stoffen. Munch Med Wochenschr 1903; 47: 2042-4. Flemming A. On the antibacterial action of cultures of a penicillium with special reference to their use in the isolation of B. influenza. Brit J Exp Pathol 1929; 10: 226-36. Malik Z, Hanania J, Nitzan Y. Bactericidal effects of photoactivated porphyrins - an alternative approach to antimicrobial drugs. J Photochem Photobiol B 1990; 5: 281-93. Soncin M, Fabris C, Busetti A, Dei D, Nistri D, Roncucci G, Jori G. Approches to selectivity in the Zn(II)- phthalocyanine-photosensitized inactivation of wild-type and antibiotic resistant Staphylococcus aureus. Photochem Photobiol Sci 2002; 1:815-9 Sharma M, Visai L, Bragheri F, Cristiani I, Gupta PK, Speziale P. Toluidine blue-mediated photodynamic effects on Staphylococci biofilms. Antimicrob Agents Chemoter 2008; 52: 299-305.
Marina Nisnevitch Department of Chemical Engineering, Biotechnology and Materials Ariel University, Israel Tel: +972-39066606/7 Fax: +972-39066323 E-mail:
[email protected]
