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Proceedings Paper

Cryptococcus neoformans capsule protects cell from oxygen reactive species generated by antimicrobial photodynamic inactivation
Author(s): Renato Araujo Prates; Michael R. Hamblin; Ilka T. Kato; Beth Fuchs; Eleytherios Mylonakis M.D.; Martha Simões Ribeiro; George Tegos
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Paper Abstract

Antimicrobial photodynamic inactivation (APDI) is based on the utilization of substances that can photosensitize biological tissues and are capable of being activated in the presence of light. Cryptococcus neoformans is an yeast surrounded by a capsule composed primarily of glucoronoxylomannan that plays an important role in its virulence. This yeast causes infection on skin, lungs and brain that can be associated with neurological sequelae and neurosurgical interventions, and its conventional treatment requires prolonged antifungal therapy, which presents important adverse effects. The aim of this study was to evaluate the protective effect of Cryptococcus neoformans capsule against reactive oxygen species generated by APDI. Cryptococcus neoformans KN99α, which is a strain able to produce capsule, and CAP59 that does not present capsule production were submitted to APDI using methylene blue (MB), rose bengal (RB), and pL-ce6 as photosensitizers (PS). Then microbial inactivation was evaluated by counting colony form units following APDI and confocal laser scanning microscopy (CLSM) illustrated localization as well as the preferential accumulation of PS into the fungal cells. C. neoformans KN99α was more resistant to APDI than CAP59 for all PSs tested. CLSM showed incorporation of MB and RB into the cytoplasm and a preferential uptake in mitochondria. A nuclear accumulation of MB was also observed. Contrarily, pL-ce6 appears accumulated in cell wall and cell membrane and minimal florescence was observed inside the fungal cells. In conclusion, the ability of C. neoformans to form capsule enhances survival following APDI.

Paper Details

Date Published: 17 February 2011
PDF: 8 pages
Proc. SPIE 7887, Mechanisms for Low-Light Therapy VI, 788709 (17 February 2011); doi: 10.1117/12.876593
Show Author Affiliations
Renato Araujo Prates, Instituto de Pesquisas Energéticas e Nucleares (Brazil)
Michael R. Hamblin, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Medical School (United States)
Harvard-MIT Division of Health Sciences and Technology (United States)
Ilka T. Kato, Instituto de Pesquisas Energéticas e Nucleares (Brazil)
Beth Fuchs, Massachusetts General Hospital (United States)
Eleytherios Mylonakis M.D., Massachusetts General Hospital (United States)
Martha Simões Ribeiro, Instituto de Pesquisas Energéticas e Nucleares (Brazil)
George Tegos, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Medical School (United States)
The Univ. of New Mexico Health Sciences Ctr. (United States)

Published in SPIE Proceedings Vol. 7887:
Mechanisms for Low-Light Therapy VI
Michael R. Hamblin; Ronald W. Waynant; Juanita Anders, Editor(s)

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