Pyrrolopyrrole aza-BODIPY-based NIR-II fluorophores for in vivo dynamic vascular dysfunction visualization of vascular-targeted photodynamic therapy

Cationic conjugated polymer coupled non-conjugated segments for dually enhanced NIR-II fluorescence and lower-temperature photothermal-gas therapy

The lack of a simple design strategy to obtain ideal conjugated polymers (CPs) with high absorbance and fluorescence (FL) in the near-infrared-II (NIR-II; 1000-1700 nm) region still hampers the success of NIR-II light-triggered phototheranostics. Herein, novel phototheranostic nanoparticles (PPN-NO NPs) were successfully prepared by coloading a cationic NIR-II CPs (PBC-co-PBF-NMe3) and a NO donor (S-nitroso-N-acetylpenicillamine, SNAP) onto a 1:1 mixture of DSPE-PEG5000 and dimyristoylphosphatidylcholine (DMPC) for NIR-II FL and NIR-II photoacoustic (PA) imaging-guided low-temperature NIR-II photothermal therapy (PTT) and gas combination therapy for cancer treatment. A precise NIR-II FL dually enhanced design tactic was proposed herein by integrating flexible nonconjugated segments (C6) into the CPs backbone and incorporating quaternary ammonium salt cationic units into the CPs side chain, which considerably increased the radiative decay pathway, resulting in desirable NIR-II FL intensity and balanced NIR-II absorption and NIR PTT properties. The phototheranostic PPN-NO NPs exhibited distinguished NIR-II FL and PA imaging performance in tumor-bearing mice models. Furthermore, the low-temperature photothermal effect of PPN-NO NPs could initiate NO release upon 980 nm laser irradiation, efficiently suppressing tumor growth owing to the combination of low-temperature NIR-II PTT and NO gas therapy in vitro and in vivo.

Supramolecular dye nanoassemblies for advanced diagnostics and therapies

Dyes have conventionally been used in medicine for staining cells, tissues, and organelles. Since these compounds are also known as photosensitizers (PSs) which exhibit photoresponsivity upon photon illumination, there is a high desire towards formulating these molecules into nanoparticles (NPs) to achieve improved delivery efficiency and enhanced stability for novel imaging and therapeutic applications. Furthermore, it has been shown that some of the photophysical properties of these molecules can be altered upon NP formation thereby playing a major role in the outcome of their application. In this review, we primarily focus on introducing dye categories, their formulation strategies and how these strategies affect their photophysical properties in the context of photothermal and non-photothermal applications. More specifically, the most recent progress showing the potential of dye supramolecular assemblies in modalities such as photoacoustic and fluorescence imaging, photothermal and photodynamic therapies as well as their employment in photoablation as a novel modality will be outlined. Aside from their photophysical activity, we delve shortly into the emerging application of dyes as drug stabilizing agents where these molecules are used together with aggregator molecules to form stable nanoparticles.

Strategies to address key challenges of metallacycle/metallacage-based supramolecular coordination complexes in biomedical applications

Owing to their capacity for dynamically linking two or more functional molecules, supramolecular coordination complexes (SCCs), exemplified by two-dimensional (2D) metallacycles and three-dimensional (3D) metallacages, have gained increasing significance in biomedical applications. However, their inherent hydrophobicity and self-assembly driven by heavy metal ions present common challenges in their applications. These challenges can be overcome by enhancing the aqueous solubility and in vivo circulation stability of SCCs, alongside minimizing their side effects during treatment. Addressing these challenges is crucial for advancing the fundamental research of SCCs and their subsequent clinical translation. In this review, drawing on extensive contemporary research, we offer a thorough and systematic analysis of the strategies employed by SCCs to surmount these prevalent yet pivotal obstacles. Additionally, we explore further potential challenges and prospects for the broader application of SCCs in the biomedical field.

pH-Responsive NIR-II phototheranostic agents for in situ tumor vascular monitoring and combined anti-vascular/photothermal therapy

Developing nanoplatforms integrating superior fluorescence imaging ability in second near-infrared (NIR-II) window and tumor microenvironment responsive multi-modal therapy holds great potential for real-time feedback of therapeutic efficacy and optimizing tumor inhibition. Herein, we developed a pH-sensitive pyrrolopyrrole aza-BODIPY-based amphiphilic molecule (PTG), which has a balanced NIR-II fluorescence brightness and photothermal effect. PTG is further co-assembled with a vascular disrupting agent (known as DMXAA) to prepare PTDG nanoparticles for combined anti-vascular/photothermal therapy and real-time monitoring of the tumor vascular disruption. Each PTG molecule has an active PT-3 core which is linked to two PEG chains via pH-sensitive ester bonds. The cleavage of ester bonds in the acidic tumor environment would tricker releases of DMXAA for anti-vascular therapy and further assemble PT-3 cores into micrometer particles for long term monitoring of the tumor progression. Furthermore, benefiting from the high brightness in the NIR-II region (119.61 M-1 cm-1) and long blood circulation time (t1/2 = 235.6 min) of PTDG nanoparticles, the tumor vascular disrupting process can be in situ visualized in real time during treatment. Overall, this study demonstrates a self-assembly strategy to build a pH-responsive NIR-II nanoplatform for real-time monitoring of tumor vascular disruption, long-term tracking tumor progression and combined anti-vascular/photothermal therapy.