Exploring photoinactivation of microbial biofilms using laser scanning microscopy and confined 2-photon excitation

J Biophotonics. 2018 Oct;11(10):e201800018. doi: 10.1002/jbio.201800018. Epub 2018 Jun 19.


One pertinent complication in bacterial infection is the growth of biofilms, that is, communities of surface-adhered bacteria resilient to antibiotics. Photodynamic inactivation (PDI) has been proposed as an alternative to antibiotic treatment; however, novel techniques complementing standard efficacy measures are required. Herein, we present an approach employing multiphoton microscopy complemented with Airyscan super-resolution microscopy, to visualize the distribution of curcumin in Staphylococcus epidermidis biofilms. The effects of complexation of curcumin with hydroxypropyl-γ-cyclodextrin (HPγCD) were studied. It was shown that HPγCD curcumin demonstrated higher bioavailability in the biofilms compared to curcumin, without affecting the subcellular uptake. Spectral quantification following PDI demonstrates a method for monitoring elimination of biofilms in real time using noninvasive 3D imaging. Additionally, spatially confined 2-photon inactivation was demonstrated for the first time in biofilms. These results support the feasibility of advanced optical microscopy as a sensitive tool for evaluating treatment efficacy in biofilms toward improved mechanistic studies of PDI.

Keywords: Staphylococcus; curcumin; hydroxypropyl-γ-cyclodextrin; microbial biofilms; multiphoton microscopy; super-resolution microscopy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biofilms / drug effects*
  • Biofilms / radiation effects*
  • Curcumin / chemistry
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Intracellular Space / radiation effects
  • Microbial Viability / drug effects*
  • Microbial Viability / radiation effects*
  • Microscopy, Confocal*
  • Photochemotherapy
  • Photons*
  • Photosensitizing Agents / chemistry
  • Photosensitizing Agents / metabolism
  • Photosensitizing Agents / pharmacology
  • Staphylococcus epidermidis / cytology
  • Staphylococcus epidermidis / drug effects
  • Staphylococcus epidermidis / physiology*
  • Staphylococcus epidermidis / radiation effects
  • gamma-Cyclodextrins / chemistry
  • gamma-Cyclodextrins / metabolism
  • gamma-Cyclodextrins / pharmacology


  • Photosensitizing Agents
  • gamma-Cyclodextrins
  • hydroxypropyl-gamma-cyclodextrin
  • Curcumin