Porphyrin Dyes for Nonlinear Optical Imaging of Live Cells

Abstract

SummarySecond 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.

Bioactivity studies of porphyrinoids against microsporidia isolated from honeybees

“…The water-soluble amphiphilic and cationic porphyrins are able to permeate cell walls and membranes of yeast and exhibit more pronounced photoactivity 43 . Compared to neutral (zwitterionic) porphyrins or porphyrins with non-charged head groups (e.g., ethylene glycol-based groups), cationic porphyrin dyes have a higher affinity for plasma membranes 44 . Since the studied cationic porphyrins (without amine functional groups) are also active against Nosema spores, the number and position of the charges, as well as the optimal ratio between hydrophilic and hydrophobic regions, should be considered when designing an ideal porphyrin-based antimicrosporidial agent; hydrophilicity facilitates distribution, and lipophilicity facilitates better cellular uptake 45 .…”

Singlet oxygen generation by porphyrins and metalloporphyrins revisited: A quantitative structure-property relationship (QSPR) study

“…Porphyrins represent a unique class of organic photosensitizers due to a combination of easily controllable photophysical properties and synthetic accessibility [3]. Porphyrins have multiple applications including drug delivery [4,5], bioimaging [6,7], and non-linear optics [8,9] to name a few. One of the most intriguing properties of porphyrins is their ability to produce singlet oxygen with high quantum yield under visible light irradiation, which is used for the treatment of skin diseases such as psoriasis [10], port-wine stains [11], as well as different types of cancer like mycosis fungoides (a type of a cutaneous T-cell lymphoma) [12], malignant mesothelioma [13], glioma [14], brain tumor [15], fibrosarcoma [16], colorectal cancer [17], osteosarcoma [18].…”

Label-free and Multimodal Second Harmonic Generation Light Sheet Microscopy

“…SHG emission direction changes depending on harmonophore alignment relative to the excitation electric field, and SHG signal is observed when there is alignment of the orientation of a harmonophore with the polarisation state of illumination 56,57 . The FM4-64 dye molecules are orientated parallel to the plasma membrane at every position on the oocyte surface, covering all possible orientations of the dye molecule, and thus are ideal for investigating the orientation dependence of the SHG signal from a simple harmonophore 58,59 . The signal dependence on input polarisation state agrees with Malkinson and co-workers on SHG-SPIM, who found that nanocrystal orientation and illumination polarisation both affect the orthogonally-detected SHG signal distributions measured from randomly orientated KTP and BaTiO3 nanocrystals suspended in agarose 57 .…”