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Proceedings Paper

Photodynamic therapy can kill Cryptococcus neoformans in in vitro and in vivo models
Author(s): Renato A. Prates; Eriques G. da Silva; Priscila F. Chaves; Antônio José S. Santos; Claudete R. Paula; Martha S. Ribeiro
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Paper Abstract

Cryptococcosis is an infection caused by the encapsulated yeast Cryptococcus neoformans and the most afflicted sites are lung, skin and central nervous system. A range of studies had reported that photodynamic therapy (PDT) can inactivate yeast cells; however, the in vivo experimental models of cryptococcosis photoinactivation are not commonly reported. The aim of this study was to investigate the ability of methylene blue (MB) combined with a low-power red laser to inactivate Cryptococcus neoformans in in vitro and in vivo experimental models. To perform the in vitro study, suspension of Cryptococcus neoformans ATCC-90112 (106cfu/mL) was used. The light source was a laser (Photon Lase III, DMC, São Carlos, Brazil) emitting at λ660nm with output power of 90mW for 6 and 9min of irradiation, resulting fluences at 108 and 162J/cm². As photosensitizer, 100μM MB was used. For the in vivo study, 10 BALB/c mice had the left paw inoculated with C. neoformans ATCC-90112 (107cfu). Twenty-four hours after inoculation, PDT was performed using 150μM MB and 100mW red laser with fluence at 180J/cm2. PDT was efficient in vitro against C. neoformans in both parameters used: 3 log reduction with 108J/cm² and 6 log reduction with 162J/cm². In the in vivo experiment, PDT was also effective; however, its effect was less expressive than in the in vitro study (about 1 log reduction). In conclusion, PDT seems to be a helpful alternative to treat dermal cryptococcosis; however, more effective parameters must be found in in vivo studies.

Paper Details

Date Published: 18 February 2009
PDF: 7 pages
Proc. SPIE 7165, Mechanisms for Low-Light Therapy IV, 71650H (18 February 2009); doi: 10.1117/12.809734
Show Author Affiliations
Renato A. Prates, IPEN-CNEN/SP (Brazil)
Eriques G. da Silva, ICB/USP (Brazil)
Priscila F. Chaves, IPEN-CNEN/SP (Brazil)
Antônio José S. Santos, IPEN-CNEN/SP (Brazil)
Claudete R. Paula, ICB/USP (Brazil)
Martha S. Ribeiro, IPEN-CNEN/SP (Brazil)

Published in SPIE Proceedings Vol. 7165:
Mechanisms for Low-Light Therapy IV
Michael R. Hamblin; Ronald W. Waynant; Juanita Anders, Editor(s)

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