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Inactivation of Pathogens via Visible-Light Photolysis of Riboflavin-5′-Phosphate
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Inactivation of bacteria in plasma.

Ali Oguz Er1, Jie Chen, Thomas C Cesario

  • 1Department of Chemistry, University of California, Irvine, CA 92697, USA.

Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology
|July 27, 2012
PubMed
Summary
This summary is machine-generated.

Methylene blue (MB) shows a lower bacterial photo-inactivation rate in plasma due to faster MB photodegradation. This study explains why MB is less effective in plasma, impacting photodynamic therapy applications.

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Area of Science:

  • Photochemistry
  • Photobiology
  • Biophysics

Background:

  • Methylene blue (MB) is a photosensitizer used in various biomedical applications.
  • Its efficacy can be influenced by the surrounding medium.
  • Understanding these interactions is crucial for optimizing therapeutic outcomes.

Purpose of the Study:

  • To investigate the photo-inactivation rate of bacteria by methylene blue in plasma compared to other solutions.
  • To elucidate the photochemical mechanisms underlying the observed differences in MB efficacy.
  • To propose a mechanism explaining the reduced bacterial inactivation in plasma.

Main Methods:

  • Spectroscopic analysis of methylene blue in plasma, water, saline, and PBS.
  • Ultrafast time-resolved transient spectroscopy to study MB excited states.
  • Kinetics measurements of MB photodegradation under illumination.
  • Bacterial photo-inactivation assays under identical conditions.

Main Results:

  • The photo-inactivation rate of bacteria by MB was significantly lower in plasma than in water, saline, and PBS.
  • Methylene blue photodegraded faster and to a greater extent in plasma.
  • Excited singlet and triplet state populations of MB were substantially lower in plasma.
  • Optical density of MB in plasma decreased by ~50% after 1 minute of illumination, versus only 1% in PBS.

Conclusions:

  • Plasma proteins accelerate methylene blue photodegradation, leading to reduced excited state populations.
  • This accelerated photodegradation is the primary reason for the lower bacterial photo-inactivation rate observed in plasma.
  • The findings provide a mechanistic explanation for the reduced efficacy of MB-based photodynamic inactivation in plasma environments.