Potentiation by potassium iodide using TPPS4 for antimicrobial photodynamic inactivation

Liyi Huang, Michael R. Hamblin

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Potassium iodide can potentiate antimicrobial photodynamic inactivation (aPDI) of a broad-spectrum of microorganisms, producing many extra logs of killing. We compared two charged porphyrins, TPPS4 (thought to be anionic and not able to bind to Gram-negative bacteria) and TMPyP4 (considered cationic and well able to bind to bacteria). As expected TPPS4 + light did not kill Gram-negative Escherichia coli, but surprisingly when 100 mM KI was added, it was highly effective at mediating aPDI (eradication at 200 nM + 10 J/cm2 of 415 nm light). TPPS4 was more effective than TMPyP4 in eradicating the Gram-positive bacteria, methicillin-resistant Staphylococcus aureus and the fungal yeast Candida albicans (regardless of KI). TPPS4 was also highly active against E. coli after a centrifugation step when KI was added, suggesting that the supposedly anionic porphyrin bound to bacteria and Candida. We conclude that TPPS4 behaves as if it has some cationic character in the presence of bacteria, which may be related to its supply from vendors in the form of a dihydrochloride salt.

Original languageEnglish
Title of host publicationLight-Based Diagnosis and Treatment of Infectious Diseases
EditorsTianhong Dai
ISBN (Electronic)9781510614437
Publication statusPublished - 2018
Externally publishedYes
EventLight-Based Diagnosis and Treatment of Infectious Diseases 2018 - San Francisco, United States
Duration: 29 Jan 201831 Jan 2018

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceLight-Based Diagnosis and Treatment of Infectious Diseases 2018
Country/TerritoryUnited States
CitySan Francisco


  • TMPyP4
  • TPPS4
  • anionic porphyrin
  • antimicrobial photodynamic inactivation
  • cationic porphyrin
  • potassium iodide

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology, Nuclear Medicine and Imaging


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