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18 May 2010Real time optical coherence tomography monitoring of Candida albicans biofilm in vitro during photodynamic treatment
The biofilm formed by Candida albicans is the mainly cause of infections associated to medical devices such as
catheters. Studies have shown that photodynamic antimicrobial therapy (PAT) has lethal effect on C. albicans, and it is
based on photosensitizer (PS) in the presence of low intensity light to generate reactive oxygen species in biological
systems. The aim of this study was to analyze in real time, by Optical Coherence Tomography (OCT), the alterations in
C. albicans biofilm in vitro during PAT using methylene blue (MB) as a PS and red light. An OCT system with working
at 930nm was used, sequential images of 2000×512 pixels were generated at the frame rate of 2.5frames/sec. The
dimension of the analyzed sample was 6000μm wide by 1170μm of depth corrected by refraction index of 1.35. We
recorded 1min. before and after the irradiation with LED for PAT, generating 8min. of video. For biofilm formation,
discs were made from elastomeric silicone catheters. The PS was dissolved in PBS solution, and a final concentration of
1mM MB was applied on biofilm, followed by a red LED irradiation (λ=630nm±20nm) during 6min. We performed a
curve of survival fraction versus time of irradiation and it was reduced by 100% following 6min. of irradiation. OCT was
performed for measurement of biofilm thickness of 110μm when biofilm was formed. During irradiation, the variation of
biofilm thickness was ~70μm. We conclude that OCT system is able to show real time optical changes provided by PAT
in yeasts organized in biofilm.
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Luis Cláudio Suzuki, Renato Araujo Prates, Marcus Paulo Raele, Anderson Zanardi di Freitas, Martha Simões Ribeiro, "Real time optical coherence tomography monitoring of Candida albicans biofilm in vitro during photodynamic treatment," Proc. SPIE 7715, Biophotonics: Photonic Solutions for Better Health Care II, 771524 (18 May 2010); https://doi.org/10.1117/12.854305