Effect of Ca2+ on the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria and the dye affinity for lipopolysaccharides

Marina N. Usacheva, Matthew C. Teichert, Chet E. Sievert, Merrill A. Biel

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Background and Objectives: Methylene blue (MB) and toluidine blue (TB) form metachromatic complexes with lipopolysaccharides (LPS). The greater photobactericidal efficacy of TB may be explained by its affinity for LPS. This study aims to elucidate the difference in photobactericidal efficacies between the dyes using Ca2+ as a competitor for dye-binding sites on the bacterial outer membrane. Study Design/Materials and Methods: Fixed dye concentration solutions with gram-negative bacteria and increasing concentrations of CaCl2 were exposed to red laser light. Bacterial survival and spectrophotometry were used to describe the effect of Ca 2+ on dye interaction with bacteria and LPS. Results: MB-mediated photokilling was inhibited more significantly than that of TB. CaCl2 inhibited dye photo-bleaching and suppressed the metachromatic reaction between the dyes and LPS, in particular TB. Conclusions: CaCl2 inhibits bacterial photokilling by binding with LPS, as well as other anionic polymers including outer membrane proteins. LPS is chiefly involved in TB-mediated photokilling, whereas outer membrane proteins probably are more involved in MB-mediated photokilling.

Original languageEnglish (US)
Pages (from-to)946-954
Number of pages9
JournalLasers in Surgery and Medicine
Volume38
Issue number10
DOIs
StatePublished - Dec 2006

Keywords

  • Bacterial damage
  • CaCl inhibition
  • Phenothiazine dyes
  • Photobleaching
  • Proteins of bacterial outer membrane
  • Red laser light

Fingerprint

Dive into the research topics of 'Effect of Ca<sup>2+</sup> on the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria and the dye affinity for lipopolysaccharides'. Together they form a unique fingerprint.

Cite this