Intramolecular Charge Transfer-Based Conjugated Oligomer with Fluorescence, Efficient Photodynamics, and Photothermal Activities

Abstract

To develop efficient photoactive agents with satisfactory fluorescence, photodynamic, and photothermal effects is crucial for a phototherapeutic strategy to combat cancer diseases and pathogenic microbes. Herein, a water-soluble donor−acceptor−donor (D−A−D) structured conjugated oligomer was designed and synthesized, consisting of two cyclopenta-dithiophene (CDT) units as the electron donor and boron dipyrromethene (BODIPY) as the electron acceptor. Upon excitation, dual emission was observed for CDT-BODIPY with blue and red fluorescence peaks at 463 nm and at 730 nm, respectively, which was ascribed to intramolecular charge transfer (ICT). Due to the ICT effect, the singlet-to-triplet intersystem crossing rate of CDT-BODIPY was also enhanced, leading to an outstanding photodynamic behavior to produce reactive oxygen species (ROS). Meanwhile, its low bandgap also enabled it a moderate photothermal capability with a conversion efficiency of 33.1%. Taking advantage of its phototriggered activities, this conjugated oligomer exhibited an effective inhibition behavior on the pathogenic growth of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans), which can be guided by dual-wavelength fluorescence imaging. This D−A−D type conjugated oligomer with balanced photophysical characteristics provides a promising strategy to imaging-guided photoactive therapy.

In Situ Synthesis of Gold Nanoclusters in Covalent Organic Frameworks with Enhanced Photodynamic Properties and Antibacterial Performance

“…To design novel photosensitizers that generate cytotoxic reactive oxygen species (ROS) triggered by light is an essential task for the development of photodynamic therapy (PDT) and antibacterial photodynamic therapy. − To date, a series of materials including organic molecules, conjugated oligomer/polymer, carbon-based material, and Au/Ag-based nanoclusters have been developed as photosensitizers. − Recently, covalent organic frameworks (COFs), a kind of organic crystalline polymer linked by dynamic covalent bonds in two or three dimensions, showed great potential in ROS-related biomedical applications. − Their unique framework and rich porosity are reported to be able to promote the diffusion of oxygen and ROS, which is especially important for ROS efficiency because of their extremely short lifetime (<3.5 μs) . To endow COFs with satisfactory photodynamic behaviors, two strategies are usually adopted, including incorporating photosensitive units as building blocks to construct the π-conjugated skeleton and grafting phototherapeutic agents by postmodification via covalent bonds. , However, the involved tedious synthetic processes with a high cost limit the further applications.…”

Red‐to‐Near‐Infrared Emitting PyrrolylBODIPY Dyes: Synthesis, Photophysical Properties and Bioimaging Application

“…Similarly, a significant decrease of the fluorescence quantum yields was observed for meso ‐mesityl substituted 3‐pyrrolylBODIPYs 3 ab , 3 bb , 3 ac and 3 bc when changing the solvent from hexane ( 3 ab and 3 bb : Φ=0.13, 3 ac and 3 bc : Φ=0.05) to dichloromethane (<0.01) and methanol (<0.01). This solvent‐dependent fluorescence emission may be attributed to the increased electron density on the uncoordinated 3‐pyrrolic moiety associated with the installation of electron‐rich alkyl substituents, which enhanced the intramolecular electron transfer process [22] within the chromophore. Similarly, decreasing the electron density on the BODIPY core with installation of Cl atoms also benefits this possible photoinduced electron transfer process.…”

BODIPY as a Multifunctional Theranostic Reagent in Biomedicine: Self‐Assembly, Properties, and Applications

“…Donor–Acceptor–Donor (D–A–D) Structure : Li and co‐workers [ 434 ] developed a novel D–A–D conjugated oligomer with BODIPY as the electron acceptor and two cyclopentanedithiophene (CDT) units as the electron donor, named CDT–BODIPY. The CDT components are covalent to the 3‐ and 5‐positions of BODIPY by vinyl π bridge bond.…”