Ultrastable Near-Infrared Conjugated-Polymer Nanoparticles for Dually Photoactive Tumor Inhibition

Halogenated Aza-BODIPY for Imaging-Guided Synergistic Photodynamic and Photothermal Tumor Therapy

It is always a huge challenge to develop novel near-infrared (NIR) phototherapeutic agents suitable for imaging-guided cancer therapy. In order to clarify the positive heavy atom effects on the photodynamic and photothermal efficiencies of phototherapeutic agents, a series of chlorine-, bromide-, or iodine-substituted aza-BODIPYs (B2, B3, and B4, respectively) are designed and synthesized. Among them, B4 exhibits both excellent photodynamic and photothermal effects (singlet oxygen yield of B4 is 1.57 times more than that of B3) and excellent photothermal effects (1.3 °C higher than that of B3). Then, nanoparticles of B4 (IABNs) with excellent biocompatibility are prepared by coating hydrophobic B4 with hydrophilic polymer DSPE-mPEG₅₀₀₀ . IABN exhibits high photostability, excellent biocompatibility, and low dark toxicity both in vivo and in vitro. Furthermore, IABN shows the enhanced photodynamic effect and high photothermal conversion efficiency (34.8%). In addition, the strong fluorescence emission of IABN makes it suitable for fluorescence imaging-guided tumor therapy in vivo. Finally, IABN has successfully healed the Hela tumor-bearing mice under NIR fluorescence imaging- and photothermal imaging-guided synergistic photothermal and photodynamic therapy with low side effects, demonstrating that it is promising for future clinical applications.

Multifunctional Hybrid Liposome as a Theranostic Platform for Magnetic Resonance Imaging Guided Photothermal Therapy

Photothermal therapy (PTT) is an emerging modality for cancer treatment owing to its localized treatment of tumors and easy combination with other therapeutic approaches. An imaging guided tumor ablation will facilitate the implementation of the treatment to boost efficiency. A type of multifunctional hybrid liposome is synthesized by loading indocyanine green (ICG) into a hybrid liposome based on a mixture of hybrid lipid and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-diethylene triamine pentacetate acid-gadopentetate dimeglumine (DMPE-DTPA-Gd). The hybrid liposome exhibited high structure stability and narrow size distribution in aqueous media. According to magnetic resonance imaging (MRI), hybrid liposome after tail vein injection accumulated effectively in subcutaneous CT-26 tumor of mice. Moreover, photothermal therapy is able to ablate tumor effectively under MR imaging guidance. Thus, the MRI visible PTT agent-loaded theranostic nanoplatform is promising for effective cancer treatment.

Rational Design of Conjugated Photosensitizers with Controllable Photoconversion for Dually Cooperative Phototherapy

High-performance photosensitizers are highly desired for achieving selective tumor photoablation in the field of precise cancer therapy. However, photosensitizers frequently suffer from limited tumor suppression or unavoidable tumor regrowth due to the presence of residual tumor cells surviving in phototherapy. A major challenge still remains in exploring an efficient approach to promote dramatic photoconversions of photosensitizers for maximizing the anticancer efficiency. Here, a rational design of boron dipyrromethene (BDP)-based conjugated photosensitizers (CPs) that can induce dually cooperative phototherapy upon light exposure is demonstrated. The conjugated coupling of BDP monomers into dimeric BDP (di-BDP) or trimeric BDP (tri-BDP) induces photoconversions from fluorescence to singlet-to-triplet or nonradiative transitions, together with distinctly redshifted absorption into the near-infrared region. In particular, tri-BDP within nanoparticles shows preferable conversions into both primary thermal effect and minor singlet oxygen upon near-infrared light exposure, dramatically achieving tumor photoablation without any regrowth through their cooperative anticancer efficiency caused by their dominant late apoptosis and moderate early apoptosis. This rational design of CPs can serve as a valuable paradigm for cooperative cancer phototherapy in precision medicine.

Synthesis of carbon dots from Hypocrella bambusae for bimodel fluorescence/photoacoustic imaging-guided synergistic photodynamic/photothermal therapy of cancer

As phototheranostic agents, carbon dots (CDs), have recently drawn considerable attention due to their excellent physicochemical properties. However, the complex synthetic route and high-cost of CDs greatly limit their practical application. To address this issue, given their nearly infinite supply from nature, Hypocrella bambusae is used as the precursor for the preparation of CDs in this study. The obtained Hypocrella bambusae CDs (HBCDs) possess good water solubility, broad absorption (350-800 nm), red-light emission (maximum peak at 610 nm), and low biotoxicity. Moreover, HBCDs can highly generate ¹O₂ (0.38) and heat (27.6%) under 635 nm laser irradiation. These excellent properties of HBCDs capacitate them to be utilized for bimodal fluorescence/photoacoustic imaging-guided synergistic photodynamic therapy (PDT)/photothermal therapy (PTT). This work provides a new candidate for tumor treatment with the combination of PDT and PTT, and explores a novel approach for the preparation of CD-based phototheranostic agents with natural biomass as raw carbon sources.

Cascade-amplifying synergistic effects of chemo-photodynamic therapy using ROS-responsive polymeric nanocarriers

The simple integration of chemotherapeutic drugs and photosensitizers (PSs) into the same nanocarriers only achieves a combination of chemo-photodynamic therapy but may not confer synergistic effects. The boosted intracellular release of chemotherapeutic drugs during the photodynamic therapy (PDT) process is necessary to achieve a cascade of amplified synergistic therapeutic effects of chemo-photodynamic therapy. Methods: In this study, we explored an innovative hyperbranched polyphosphate (RHPPE) containing a singlet oxygen (SO)-labile crosslinker to boost drug release during the PDT process. The photosensitizer chlorin e6 (Ce6) and doxorubicin (DOX) were simultaneously loaded into RHPPE nanoparticles (denoted as ^SOHNP_Ce6/DOX). The therapeutic efficacy of ^SOHNP_Ce6/DOX against drug-resistant cancer was evaluated in vitro and in vivo. Results: Under 660-nm light irradiation, ^SOHNP_Ce6/DOX can produce SO, which not only induces PDT against cancer but also cleaves the thioketal linkers to destroy the nanoparticles. Subsequently, boosted DOX release can be achieved, activating a chemotherapy cascade to synergistically destroy the remaining tumor cells after the initial round of PDT. Furthermore, ^SOHNP_Ce6/DOX also efficiently detected the tumor area by photoacoustic/magnetic resonance bimodal imaging. Under the guidance of bimodal imaging, the laser beam was precisely focused on the tumor areas, and subsequently, ^SOHNP_Ce6/DOX realized a cascade of amplified synergistic chemo-photodynamic therapeutic effects. High antitumor efficacy was achieved even in a drug-resistant tumor model. Conclusion: The designed ^SOHNP_Ce6/DOX with great biocompatibility is promising for use as a co-delivery carrier for combined chemo-photodynamic therapy, providing an alternative avenue to achieve a cascade of amplified synergistic effects of chemo-photodynamic therapy for cancer treatment.

Purification of Semiconducting Polymer Dots by Size Exclusion Chromatography Prior to Cytotoxicity Assay and Stem Cell Labeling

Semiconducting polymer dots (Pdots) as fluorescent probes have shown promising applications because of their excellent optical properties. However, apparent differences were observed in cytotoxicity assays, which might originate from impurities introduced in polymer synthesis or nanoparticle preparation. A simple gel-filtration-based purification method was used to address this issue. Purified Pdots displayed obviously decreased cytotoxicity as compared with the same batch of unpurified Pdots. The purified Pdots were further examined in a cytotoxicity study on mesenchymal stem cells (MSCs), which are very sensitive to exogenous probes. The results indicated that purified Pdots did not affect the proliferation ability of MSCs, while unpurified Pdots could have obvious cytotoxicity. In addition, the purified Pdots did not show cytotoxicity even after 6 months of storage. Our results demonstrated that gel filtration is an effective method for obtaining Pdots with minimal cytotoxicity, which are more suitable for biological applications.

Multistimuli Responsive Core-Shell Nanoplatform Constructed from Fe3 O4 @MOF Equipped with Pillar[6]arene Nanovalves

An intelligent theranostic nanoplatform based on nanovalve operated metal-organic framework (MOF) core-shell hybrids, incorporating tumorous microenvironment-triggered drug release, magnetic resonance imaging (MRI) guidance, sustained release, and effective chemotherapy in one pot is reported. The core-shell hybrids are constructed by an in situ growth method, in which Fe₃ O₄ particles with superior abilities of MRI and magnetic separation form the core and UiO-66 MOF with high loading capacity compose the shell, and then are surface-installed with pillararene-based pseudorotaxanes as tightness-adjustable nanovalves. This strategy endows the system with the ability of targeted, multistimuli responsive drug release in response to pH changes, temperature variations, and competitive agents. Water-soluble carboxylatopillar[6]arene system achieved sustained drug release over 7 days due to stronger host-guest binding, suggesting that the nanovalve tightness further reinforces the desirable release of anticancer agent over a prolonged time at the lesion site.

Organic molecule-based photothermal agents: an expanding photothermal therapy universe

Over the last decade, organic photothermal therapy (PTT) agents have attracted increasing attention as a potential complement for, or alternative to, classical drugs and sensitizers involving inorganic nanomaterials. In this tutorial review, we provide a structured description of the main classes of organic photothermal agents and their characteristics. Representative agents that have been studied in the context of photothermal therapy since 2000 are summarized and recent advances in using PTT agents to address various cancers indications are highlighted.

Second Near-Infrared Conjugated Polymer Nanoparticles for Photoacoustic Imaging and Photothermal Therapy

Photothermal conversion in the second near-infrared (NIR-II) window allows deeper penetration and higher exposure to lasers, but examples of NIR-II photothermal agents are mainly formulated by inorganic compounds. In view of the underlying influence of inorganic materials, a novel NIR-II photothermal nanoagent based on a narrow band gap D-A conjugated polymer (TBDOPV-DT) with 2,2-bithiophene as the donor and thiophene-fused benzodifurandione-based oligo( p-phenylenevinylene) as the acceptor has been developed. More importantly, TBDOPV-DT nanoparticles (TBDOPV-DT NPs) are demonstrated to combine excellent photoacoustic imaging (PAI) and photothermal therapy (PTT) ability. TBDOPV-DT NPs exhibit dramatic photostability and heating reproducibility with a photothermal conversion efficiency of 50%. Especially, the NPs possess a remarkable PTT effect toward cancer cells in vitro and can eliminate tumor cells completely in vivo under 1064 nm laser irradiation, while no appreciable side effects have been observed. This study achieves PAI-guided cancer therapy and sheds light on the future of using organic polymer NPs for the NIR-II PTT of cancer.

Highly Stable Conjugated Polymer Dots as Multifunctional Agents for Photoacoustic Imaging-Guided Photothermal Therapy

Theranostic nanomedicines involved in photothermal therapy (PTT) have received constant attention as promising alternatives to traditional therapies in clinic. However, most photothermal agents are limited by their instability and low photothermal conversion efficiency. In this study, we report new conjugated polymer dots (Pdots) as multifunctional agents for photoacoustic (PA) imaging-guided PTT. The novel 4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b']dithiophene-6,6'-dibromo-N,N'-(2-ethylhexyl)isoindigo (BDT-IID) Pdots are readily fabricated though nanoreprecipitation and can absorb strongly in the 650-700 nm region. Furthermore, the BDT-IID Pdots possess a stable nanostructure and an extremely low biotoxicity. In particular, its photothermal conversion efficiency can be up to 45%. More importantly, our in vivo results exhibit that the BDT-IID Pdots are able to offer concurrently enhanced PA contrast and sufficient photothermal effect. Consequently, the BDT-IID Pdots can be exploited as a unique theranostic nanoplatform for PA imaging-guided PTT of tumors, holding great promise for their clinical translational development.

Polypyrrole-coated UCNPs@mSiO2@ZnO nanocomposite for combined photodynamic and photothermal therapy

Under 980 nm light irradiation, polypyrrole-coated UCNPs@mSiO₂@ZnO nanocomposites can convert NIR light to achieve both photodynamic therapy (PDT) and photothermal therapy (PTT).

Zwitterionic diketopyrrolopyrrole for fluorescence/photoacoustic imaging guided photodynamic/photothermal therapy

Water-soluble zwitterionic diketopyrrolopyrrole (DPP-SPMA) for fluorescence/photoacoustic imaging guided photodynamic/photothermal therapy with favorable renal excretion and ultralow cytotoxicity.

Triphenylamine flanked furan-diketopyrrolopyrrole for multi-imaging guided photothermal/photodynamic cancer therapy

The combination of photodynamic therapy (PDT) and photothermal therapy (PTT) is highly desired to improve the cancer phototherapeutic effect. However, most reported multicomponent therapeutic agents need complex preparation processes and must be excited by using multiple light sources. Herein, triphenylamine flanked furan-diketopyrrolopyrrole (FDPP-TPA) with a donor-acceptor-donor structure has been synthesized and used as a sole-component agent for fluorescence, photoacoustic and photothermal imaging guided photodynamic and photothermal synergistic therapy. FDPP-TPA nanoparticles (NPs) obtained by re-precipitation exhibit a high molar extinction coefficient (ε = 2.13 (±0.2) × 10⁴ M^-1 cm^-1), excellent photothermal conversion efficiency (η = 47%) and favorable singlet oxygen quantum yield (Φ_Δ(X) = 40%). In vitro, the half-maximal inhibitory concentration (IC₅₀) is 13 μg mL^-1 determined by cytotoxicity assay. And the apoptosis rate is 67.3% according to flow cytometry analysis. In vivo, the tumor can be completely ablated without recurrence, which suggests that FDPP-TPA NPs can generate considerable poisonous singlet oxygen and hyperthermia for tumor treatment.

Controlled synthesis of upconverting nanoparticles/CuS yolk–shell nanoparticles for in vitro synergistic photothermal and photodynamic therapy of cancer cells

A chemical solution method involving multistep process has been developed to fabricate UCNPs@CuS yolk–shell nanoparticles for synergistic photothermal and photodynamic therapy of cancer cells.