Polarity Mapping of Cells and Embryos by Improved Fluorescent Solvatochromic Pyrene Probe

Abstract

Solvatochromic dyes enable sensing and imaging of biomolecular organization in living systems by monitoring local polarity (lipophilicity), but most such dyes suffer from limited brightness, photostability, lack of a convenient spectral range and limited sensitivity to polarity. Moreover, the presence of an electron acceptor group, typically a carbonyl, in their push-pull structure raises concerns about their potential chemical reactivity within the biological environment. In order to achieve robust bioimaging, we synthesized a push-pull pyrene probe bearing a ketone acceptor group (PK) and compared it with a recently developed aldehyde analogue (PA). We found that in live cells the aldehyde analogue PA transforms slowly (in ~100 min) into blue-emissive species, assigned to in situ formation of an imine analogue, whereas the PK probe is stable in the presence of primary amines and inside cells. Like the parent PA, the new probe shows strong solvatochromism and an emission color response to lipid order in membranes (ordered vs. disordered liquid phases), while its blue-shifted absorption is more optimal for excitation with 400-nm light sources. In live cells, the PK probe enables high-contrast polarity mapping of organelles using two-color ratiometric detection, suggesting that polarity increases in the following order: lipid droplets < plasma membranes < endoplasmic reticulum. In the zebrafish embryo, polarity imaging with the PK probe reveals a new dimension in visualizing the organization of tissueslipophilicity distribution, where biomembranes, lipid droplets, cells, yolk, extracellular space and newly formed organs are revealed by specific emission wavelengths of the probe. The newly developed probe and the proposed approach of polarity mapping open new opportunities for bioimaging at the cellular and animal level.

Spying on the Polarity Dynamics during Wound Healing of Zebrafish by Using Rationally Designed Carbon Dots

“…As shown in the adult zebrafish image, PPh‐CDs selectively gathered in the yolk sac of zebrafish, probably due to the abundance of lipids and lipoproteins in the yolk, causing it to be least polar. [ 40,41 ]…”

High-quality Fluorescence Imaging of the Human Acrosyringium Using a Transparency: Enhancing Technique and an Improved, Fluorescent Solvatochromic Pyrene Probe

“…Solvatochromic dyes sense and image the biomolecular organization of living systems by monitoring local polarity (lipophilicity). pyrene probe is superior to other solvatochromic dyes in terms of brightness, photostability, and sensitivity to environmental polarity [15]. The dye is ideal for staining the lipid components of skin tissue, detecting cell walls, peripheral nerve sheaths, and sebaceous glands.…”

“…Samples were optically cleared using the LUCID method [7]. The pyrene probe has been previously described [15]. We prepared a 2-μM pyrene probe solution in LUCID; this served as the master mix solution (MMS) and was stored at room temperature.…”

“…The pyrene probe was also employed to study the organization of tissue lipophilicity in zebrafish embryo. Biomembranes, lipid droplets, cells, yolk, the extracellular space, and newly formed organs were associated with specific probe emission wavelengths [15]. Here, we combined use of the solvatochromic pyrene probe with a transparency-enhancing technology when examining skin tissues, especially epidermal structures of clinical importance such as the acrosyringium.…”

π‐Extended Push‐Pull‐Type Bicyclic Fluorophores Based on Quinoline and Naphthyridine Frameworks with an Iminophosphorane Fragment

“…[1] In particular, the large Stokes shifts, solvatochromic behavior, and red-shifted emissions have enabled the utilization of these molecules as bioimaging tools in biochemistry, enabling identification of the polarity of localized areas. [2,3] However, in push-pull-type fluorophores, emission quenching often occurs in the polar environment because of the formation of a TICT state, [4] making it difficult to develop effective fluorescent compounds using the push-pull-type fluorophore. Previously, we have developed push-pull-type aminoquinoline (TFMAQ) and aminonaphthyridine (1, derivatives composed of a bicyclic framework, [5][6][7][8] as well as aminobenzo[X]quinoline (X = g or f) derivatives composed of a tricyclic framework (Scheme 1).…”