Bright Near-Infrared Aggregation-Induced Emission Luminogens with Strong Two-Photon Absorption, Excellent Organelle Specificity, and Efficient Photodynamic Therapy Potential

Abstract

Far-red and near-infrared (NIR) fluorescent materials possessing the characteristics of strong two-photon absorption and aggregation-induced emission (AIE) as well as specific targeting capability are much-sought-after for bioimaging and therapeutic applications due to their deep penetration depth and high resolution. Herein, a series of dipolar far-red and NIR AIE luminogens with a strong push-pull effect are designed and synthesized. The obtained fluorophores display bright far-red and NIR solid-state fluorescence with a high quantum yield of up to 30%, large Stokes shifts of up to 244 nm, and large two-photon absorption cross-sections of up to 887 GM. A total of three neutral AIEgens show specific lipid droplet (LD)-targeting capability, while the one with cationic and lipophilic characteristics tends to target the mitochondria specifically. All of the molecules demonstrate good biocompatibility, high brightness, and superior photostability. They also serve as efficient two-photon fluorescence-imaging agents for the clear visualization of LDs or mitochondria in living cells and tissues with deep tissue penetration (up to 150 μm) and high contrast. These AIEgens can efficiently generate singlet oxygen upon light irradiation for the photodynamic ablation of cancer cells. All of these intriguing results prove that these far-red and NIR AIEgens are excellent candidates for the two-photon fluorescence imaging of LDs or mitochondria and organelle-targeting photodynamic cancer therapy.

Effect of Conjugation Mode on Intramolecular Charge Transfer in Fabricating Acid‐Responsive Fluorophores

“…The molecular orbitald ensity in HOMO was located on the entirem olecular skeleton, whereas the LUMO level was primarily localized on the acceptorf ramework, indicating the charge transfer characteristics (Figure 3df). [17,18] The positive solvatochromismo ft he fluorescencee mission further verifiedt he ICT feature. It is noted that the compounds exhibited different solvatochromic effects.…”

In Situ Methylation Transforms Aggregation‐Caused Quenching into Aggregation‐Induced Emission: Functional Porous Silsesquioxane‐Based Composites with Enhanced Near‐Infrared Emission

“…For example, TPE decorated HOF derived from silesquioxane cages exhibits specific sensitivity to Cu 2 + , [34] whereas, TPE-silesquioxane based porous composites respond to Fe 3 + , Ru 3 + and Cu 2 + , effectively. [25] With increasing Ru 3 + , the fluorescence emission signal decreases gradually and even 8-fold decrements were observed at quenching equilibrium when C Ru 3 + achieved 10 À 3 mol L À 1 (Figure 6(c)). Meanwhile, The linear function between Ln (I) and C Ru 3 + ranging from 0 mol L À 1 to 6 × 10 À 4 mol L À 1 was plotted (K = À 2479, σ = 0.9930) to reveal the potential of TPAIE-2 for quantitatively monitoring Ru 3 + , especially at low C Ru 3 + [Figure 6(d)].…”

“…The multiple intermolecular interactions in M-TPA lock the molecular conformation and constrain rotation of phenyls effectively, which causes enhanced and unshifted emission in aggregated state. [25]…”

A Fluorescent Probe with Aggregation‐Induced Emission for Detecting Alkaline Phosphatase and Cell Imaging

“…[16,17] Molecules with aggregation-induced emission (AIE)f eature have beneficial advantages for serving as fluorescent probe. [18][19][20][21][22][23][24] AIE fluorescent probes usually exhibit large Stokes shifts with almost no overlap between their excitation and emissions pectra,w hich is conducive to fluorescence detection. [25][26][27][28] Moreover,t he AIE probes have better optical stability which is especially advantageous for long-time cell imaging and tracking.…”

“…[29] As for AIE probes, usuallys ufficientw ater solubility can ensure the probe's good solubility in aqueous solution with almost no emission;w hile upon the probe's reaction with the analyte, the resultant product has low water solubility, thus leadingt oa ggregation with enhanced emission. [19][20][21][22][23][24][25][26][27][28][29] At present,s ome AIE-active probes for ALP detection have been reported; [30][31][32][33][34][35][36][37] for most of these probes, they are based on TPE molecule with relativelyl ow conjugation degree,h ence they usually require short excitation wavelength (e.g. UV light) and exhibit relatively short emission wavelength,w hich could erode the detection accuracy due to autofluorescence of biological samples (which usually involves blue emission).…”