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. 2004 May;3(5):436-50.
doi: 10.1039/b311900a. Epub 2004 Feb 12.

Photodynamic therapy: a new antimicrobial approach to infectious disease?

Michael R Hamblin  1 , Tayyaba Hasan
Affiliations

Photodynamic therapy: a new antimicrobial approach to infectious disease?

Michael R Hamblin et al. Photochem Photobiol Sci. 2004 May.

Abstract

Photodynamic therapy (PDT) employs a non-toxic dye, termed a photosensitizer (PS), and low intensity visible light which, in the presence of oxygen, combine to produce cytotoxic species. PDT has the advantage of dual selectivity, in that the PS can be targeted to its destination cell or tissue and, in addition, the illumination can be spatially directed to the lesion. PDT has previously been used to kill pathogenic microorganisms in vitro, but its use to treat infections in animal models or patients has not, as yet, been much developed. It is known that Gram-(-) bacteria are resistant to PDT with many commonly used PS that will readily lead to phototoxicity in Gram-(+) species, and that PS bearing a cationic charge or the use of agents that increase the permeability of the outer membrane will increase the efficacy of killing Gram-(-) organisms. All the available evidence suggests that multi-antibiotic resistant strains are as easily killed by PDT as naive strains, and that bacteria will not readily develop resistance to PDT. Treatment of localized infections with PDT requires selectivity of the PS for microbes over host cells, delivery of the PS into the infected area and the ability to effectively illuminate the lesion. Recently, there have been reports of PDT used to treat infections in selected animal models and some clinical trials: mainly for viral lesions, but also for acne, gastric infection by Helicobacter pylori and brain abcesses. Possible future clinical applications include infections in wounds and burns, rapidly spreading and intractable soft-tissue infections and abscesses, infections in body cavities such as the mouth, ear, nasal sinus, bladder and stomach, and surface infections of the cornea and skin.

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Figures

Fig. 1
Fig. 1
Chemical structures of PS used for PDT in clinical trials.
Fig. 2
Fig. 2
Chemical structures of non-tetrapyrrole PS used for PDI of microbial species.
Fig. 3
Fig. 3
Diagrams illustrating differences in membrane structure between Gram-(+) and Gram-(−) bacteria.
Fig. 4
Fig. 4
Heme biosynthetic pathways of bacteria.
Fig. 5
Fig. 5
PDT of excisional wounds on the backs of mice infected with bioluminescent E. coli and treated by topical application of pL–ce6 conjugate, followed by irradiation with red light.
See this image and copyright information in PMC

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