Recent Advances in Applications of Fluorescent Perylenediimide and Perylenemonoimide Dyes in Bioimaging, Photothermal and Photodynamic Therapy

Single-Photon Deep-Red Light-Triggered Direct Release of an Anticancer Drug: An Investigative Tumor Regression Study on a Breast Cancer Spheroidal Tumor Model

Breast adenocarcinoma ranks high among the foremost lethal cancers affecting women globally, with its triple-negative subtype posing the greatest challenge due to its aggressiveness and resistance to treatment. To enhance survivorship and patients' quality of life, exploring advanced therapeutic approaches beyond conventional chemotherapies is imperative. To address this, innovative nanoscale drug delivery systems have been developed, offering precise, localized, and stimuli-triggered release of anticancer agents. Here, we present perylenemonoimide nanoparticle-based vehicles engineered for deep-red light activation, enabling direct chlorambucil release. Synthesized via the reprecipitation technique, these nanoparticles were thoroughly characterized. Light-induced drug release was monitored via spectroscopic and reverse-phase HPLC. The efficacy of the said drug delivery system was evaluated in both two-dimensional and three-dimensional spheroidal cancer models, demonstrating significant tumor regression attributed to apoptotic cell death induced by efficient drug release within cells and spheroids. This approach holds promise for advancing targeted breast cancer therapy, enhancing treatment efficacy and minimizing adverse effects.

Synthesis of Thionated Perylenediimides: State of the Art and First Investigations of an Alternative to Lawesson's Reagent

Perylenediimides (PDIs) are composed of a central perylene ring, on which are grafted two imide groups at the peri positions. Thionated PDIs are characterized by the substitution of one or more oxygen atoms of these imide functions with sulfur atoms. This structural modification alters the electronic properties with a redshift of the optical absorption accompanied by modification of the charge transport characteristics compared to their non-thionated counterparts. These properties make them suitable candidates for applications in optoelectronic devices, such as organic light-emitting diodes and organic photovoltaics. Moreover, the presence of sulfur atom(s) can favor the promotion of reactive oxygen species production for photodynamic and photothermal therapies. These thionated PDIs can be synthesized through the post-functionalization of PDIs by using a sulfurizing reagent. Nevertheless, the main drawbacks remain the difficulties in adjusting the degree of thionation and obtaining tri- and tetrathionated PDIs. Up to now, this thionation reaction has been described almost exclusively using Lawesson's reagent. In the current study, we present our first investigations into an alternative reagent to enhance selectivity and achieve a greater degree of thionation. The association of phosphorus pentasulfide with hexamethyldisiloxane (Curphey's reagent) clearly demonstrated higher reactivity compared with Lawesson's reagent to attain multi-thionated PDIs.

Nature and energetics of low-lying excited singlets/triplets and intersystem crossing rates in selone analogs of perylenediimide: A theoretical perspective

The structural rigidity and chemical diversity of the highly fluorescent perylenediimide (PDI) provide wide opportunities for developing triplet photosensitizers with sufficiently increased energy efficiency. Remarkably high intersystem crossing (ISC) rates with a complete fluorescence turn-off reported recently for several thione analogs of PDI due to substantially large spin-orbit coupling garners huge attention to develop other potential analogs. Here, several selone analogs of PDI, denoted as mSe-PDIs (m = 1-4) with varied Se content and positions, are investigated to provide a comprehensive and comparative picture down the group-16 using density functional theory (DFT) and time-dependent DFT implementing optimally tuned range-separated hybrid in toluene dielectric. All mSe-PDIs are confirmed to be dynamically stable and also thermodynamically feasible to synthesize from their oxygen and thione congeners. The first excited-state singlet (S1) of mSe-PDI with relatively low Se-content (m = 1, 2) is of nπ* character with an expected fluorescence turn-off. Whereas, the ππ* nature of the S1 for 3Se-PDI and 4Se-PDI suggests a possible fluorescence turn-on in the absence of any other active nonradiative deactivation pathways. However, ∼4-6 orders greater ISC rates (∼1012-1014 s-1) than the fluorescence ones (∼108 s-1) for all mSe-PDIs signify highly efficient triplet harvest. Importantly, significantly higher ISC rates for these mSe-PDIs than their thione congeners render them efficient triplet photosensitizers.

An anti-freeze fluorescent organogel with rapid shape-forming properties for constructing artificial light harvesting systems used in extremely cold environments

Using polyvinyl alcohol (PVA) and perylene-3,9-dicarboxylic acid (PDA) as raw materials, a new anti-freeze (-50 °C) fluorescent organogel with rapid shape-forming (2 h) properties was synthesised based on a certain proportion of the binary solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Then, an artificial light-harvesting system (ALHS) used in extremely cold environments was successfully constructed by mixing fluorescent dyes sulphorhodamine101 (SR101) and rhodamine 6G (R6G) into them as acceptors.

Perylene diimide-based radical anions for the rapid detection of picomolar H2O2 in an aqueous medium

The formation of radical anions (PDI 1˙-) using H2S as a sacrificial electron donor in 50% HEPES buffer-THF solution is reported. PDI 1˙- was confirmed by optical, I-V plot, CV, DPV, NOBF4 and EPR studies. PDI 1˙- has a half-life of 96 minutes in solution and 11 days in the solid state without any additive. The formation of PDI 1˙- was confirmed by AFM and SEM. PDI 1˙- can be used for the detection of 26.6 pM of H2O2 supported by optical and CV data.

Regulating steric hindrances of perylenediimide to construct NIR photothermal J-aggregates with a large red-shift

Perylene diimide (PDI)-based photothermal agents (PTAs) possess excellent stability and high photothermal conversion efficiency. However, developing PDIs with strong near-infrared absorption under biological conditions remains a challenge. In this study, we introduce a novel approach to facilitate the formation of J-aggregate-based PTAs with significantly red-shifted absorption by modulating steric hindrances of PDIs. PDIA, featuring larger steric hindrances at the bay position and smaller steric hindrances at the imide position, self-assembles into J-aggregates which exhibit a remarkable red-shift of over 100 nm. After encapsulation by DPSE-PEG, PDIA nanoparticles (PDIA-NPs) demonstrated a uniform and stable size, while retaining their significant red-shift. In vitro experiments demonstrated the great potential of PDIA-NPs in photothermal therapies for tumors and thrombi under 808 nm laser irradiation. This research provides valuable insights into the design of stable J-aggregates based on PDIs suitable for biological applications, paving the way for the development of more effective PTAs.

Forcing Twisted 1,7-Dibromoperylene Diimides to Flatten in the Solid State: What a Difference an Atom Makes

Perylene diimides (PDI) are workhorses in the field of organic electronics, owing to their appealing n-semiconducting properties. Optimization of their performances is widely pursued by bay-atom substitution and diverse imide functionalization. Bulk solids and thin-films of these species crystallize in a variety of stacking configurations, depending on the geometry of the stable conformation of the polyaromatic core. We here demonstrate that 1,7-dibromo-substituted perylene diimides, PDI(H2 Br2 ), possessing a heavily twisted conformation in the gas phase, in solution and in the solids, can be easily flattened in the solid state into centrosymmetric molecules if the polyaromatic cores form π-π stabilized chains. This is achieved by using axial residues with low stereochemical hindrance, as guaranteed by a single CH2 /NH spacer directly linked to the imide function. Structural powder diffraction and DFT calculations on four newly designed species of the PDI(H2 Br2 ) class coherently show that, thanks to the flexibility of the N-X-Ar link (X=CH2 /NH), flat cores are indeed obtained by overcoming the interconversion barrier between twisted atropoisomers, of only 26.5 kJ mol-1 . This strategy may then be useful to induce "anomalously flat" polyaromatic cores of different kinds (substituted acenes/rylenes) in the solid state, towards suitable crystal packing and orbital interactions for improved electronic performances.