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Photomechanical wave-assisted molecular delivery in oral biofilms


Photomechanical waves (PW), the product of an intense light beam interaction with a target material, enhance molecular delivery across biological membranes and skin. The ability to deliver methylene blue (MB), a fluorescent probe and photosensitizer, into bacterial biofilms was demonstrated by applying PW on saliva-derived multi-species biofilms that were developed on agar surfaces in 24-well plates. PW were generated with a Q-switched Nd:YAG laser and were directed into the biofilms in the presence of 25 μg/ml MB. The biofilms were then irradiated with red light at 665 nm. After illumination, adherent bacteria were scraped and spread over the surface of blood agar plates. Survival fractions were calculated by counting bacterial colonies. Microbial analysis was performed via a colony lift method and a DNA checkerboard assay using whole genomic probes to 40 oral microorganisms. Visual analysis by confocal scanning laser microscopy demonstrated that the application of PW enhanced the penetration depth of MB in biofilms. Exposure to MB, PW and light led to a significant reduction of the mean levels of log10 CFU counts compared with the group that received MB and light (P = 0.006). The DNA checkerboard assay showed some benefit from PW-assisted phototargeting in 25 biofilm microorganisms relative to phototreatment alone. Our data provide a basis for further exploration and optimization of PW parameters for complete eradication of microorganisms in oral microcosm biofilms.

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This work was supported by the NIDCR grant RO1-DE-14360. Dr. Ogura acknowledges support by the Ministry of Education, Science, Sports and Culture, Grant-in Aid for JSPS Fellows, 7596, 2004. Dr. Doukas acknowledges support by the DoD Medical Free Electron Laser Program (FA9550-04-1-0079). We thank the Palomar Corp., Lexington, MA for the loan of the Nd:YAG laser. We thank Dr. Rick Rogers, Harvard School of Public Health, Boston for his help with the confocal scanning laser microscopy. We thank Dr. Phil Stewart, The Center for Biofilm Engineering, Montana State University-Bozeman, and Drs. Federico Foschi and Carla Fontana, Applied Molecular Photomedicine Laboratory, The Forsyth Institute for critically reading the manuscript. Dr. Ogura thanks Dr. Monoru Obara, Keio University, and Dr. Shunichi Sato, National Defense Medical College Research Institute, for helpful discussions.

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Correspondence to Nikolaos S. Soukos.

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Ogura, M., Abernethy, A.D., Blissett, R.D. et al. Photomechanical wave-assisted molecular delivery in oral biofilms. World J Microbiol Biotechnol 23, 1637–1646 (2007).

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  • Confocal scanning laser microscopy
  • Drug delivery
  • Oral biofilms
  • Photodynamic therapy
  • Photomechanical waves
  • Stress waves
  • Ultrasound