Porphyrin Dyes for Nonlinear Optical Imaging of Live Cells

Anjul Khadria; Jan Fleischhauer; Igor Boczarow; James D Wilkinson; Michael M Kohl; Harry L Anderson

doi:10.1016/j.isci.2018.05.015

Porphyrin Dyes for Nonlinear Optical Imaging of Live Cells

iScience. 2018 Jun 29:4:153-163. doi: 10.1016/j.isci.2018.05.015. Epub 2018 May 26.

Authors

Anjul Khadria¹, Jan Fleischhauer¹, Igor Boczarow¹, James D Wilkinson¹, Michael M Kohl², Harry L Anderson³

Affiliations

¹ Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
² Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
³ Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK. Electronic address: harry.anderson@chem.ox.ac.uk.

Abstract

Second harmonic generation (SHG)-based probes are useful for nonlinear optical imaging of biological structures, such as the plasma membrane. Several amphiphilic porphyrin-based dyes with high SHG coefficients have been synthesized with different hydrophilic head groups, and their cellular targeting has been studied. The probes with cationic head groups localize better at the plasma membrane than the neutral probes with zwitterionic or non-charged ethylene glycol-based head groups. Porphyrin dyes with only dications as hydrophilic head groups localize inside HEK293T cells to give SHG, whereas tricationic dyes localize robustly at the plasma membrane of cells, including neurons, in vitro and ex vivo. The copper(II) complex of the tricationic dye with negligible fluorescence quantum yield works as an SHG-only dye. The free-base tricationic dye has been demonstrated for two-photon fluorescence and SHG-based multimodal imaging. This study demonstrates the importance of a balance between the hydrophobicity and hydrophilicity of amphiphilic dyes for effective plasma membrane localization.

Keywords: Chemistry; Imaging Methods in Chemistry; Nonlinear Optics; Organic Synthesis.