Supramolecular prodrug-like nanotheranostics with dynamic and activatable nature for synergistic photothermal immunotherapy of metastatic cancer.

Synergistic photothermal immunotherapy has attracted widespread attention due to the mutually reinforcing therapeutic effects on primary and metastatic tumors. However, the lack of clinical approval nanomedicines for spatial, temporal, and dosage control of drug co-administration underscores the challenges facing this field. Here, a photothermal agent (Cy7-TCF) and an immune checkpoint blocker (NLG919) are conjugated via disulfide bond to construct a tumor-specific small molecule prodrug (Cy7-TCF-SS-NLG), which self-assembles into prodrug-like nano-assemblies (PNAs) that are self-delivering and self-formulating. In tumor cells, over-produced GSH cleaves disulfide bonds to release Cy7-TCF-OH, which re-assembles into nanoparticles to enhance photothermal conversion while generate reactive oxygen species (ROSs) upon laser irradiation, and then binds to endogenous albumin to activate near-infrared fluorescence, enabling multimodal imaging-guided phototherapy for primary tumor ablation and subsequent release of tumor-associated antigens (TAAs). These TAAs, in combination with the co-released NLG919, effectively activated effector T cells and suppressed Tregs, thereby boosting antitumor immunity to prevent tumor metastasis. This work provides a simple yet effective strategy that integrates the supramolecular dynamics and reversibility with stimuli-responsive covalent bonding to design a simple small molecule with synergistic multimodal imaging-guided phototherapy and immunotherapy cascades for cancer treatment with high clinical value.

Engineering Au44 Nanoclusters for NIR-II Luminescence Imaging-Guided Photoactivatable Cancer Immunotherapy.

Immunotherapy is an advanced therapeutic strategy of cancer treatment but suffers from the issues of off-target adverse effects, lack of real-time monitoring techniques, and unsustainable response. Herein, an ultrasmall Au nanocluster (NC)-based theranostic probe is designed for second near-infrared window (NIR-II) photoluminescence (PL) imaging-guided phototherapies and photoactivatable cancer immunotherapy. The probe (Au44MBA26-NLG for short) is composed of atomically precise and NIR-II emitting Au44MBA26 NCs (here MBA denotes water-soluble 4-mercaptobenzoic acid) conjugated with immune checkpoint inhibitor 1-cyclohexyl-2-(5H-imidazo[5,1-a]isoindol-5-yl)ethanol (NLG919) via a singlet oxygen (1O2)-cleavable linker. Upon NIR photoirradiation, the Au44MBA26-NLG not only enables NIR-II PL imaging of tumors in deep tissues for guiding tumor therapy but also allows the leverage of photothermal property for cancer photothermal therapy (PTT) and the photogenerated 1O2 for photodynamic therapy (PDT) and releasing NLG919 for cancer immunotherapy. Such a multiple effect modulated by Au44MBA26-NLG prompts the proliferation and activation of effector T cells, upshifts systemic antitumor T-lymphocyte (T cell) immunity, and finally suppresses the growth of both primary and distant tumors in living mice. Overall, this study may provide a promising theranostic nanoplatform toward NIR-II PL imaging-guided phototherapies and photoactivatable cancer immunotherapy.

Zwitterionic rhodamine-CPT prodrug nanoparticles with GSH/H2O2 responsiveness for cancer theranostics.

Rationale: Fluorescently traceable prodrugs, which can monitor their biodistribution in vivo and track the kinetics of drug delivery in living cells, are promising for constructing theranostic medicines. However, due to their charge and hydrophobicity, most of the fluorescently traceable prodrugs exhibit high protein binding and non-specific tissue retention affecting in vivo distribution and toxicity, with high background signals. Methods: Herein, the zwitterionic rhodamine (RhB) and camptothecin (CPT) were bridged with a disulfide bond to construct a tumorous heterogeneity-activatable prodrug (RhB-SS-CPT). The interaction of zwitterionic RhB-SS-CPT with proteins was detected by UV and fluorescence spectroscopy, and further demonstrated by molecular docking studies. Then, intracellular tracking and cytotoxicity of RhB-SS-CPT were determined in tumor and normal cells. Finally, the in vivo biodistribution, pharmacokinetics, and anticancer efficacy of RhB-SS-CPT were evaluated in a mouse animal model. Results: The tumorous heterogeneity-activatable RhB-SS-CPT prodrug can self-assemble into stable nanoparticles in water based on its amphiphilic structure. Particularly, the zwitterionic prodrug nanoparticles reduce the non-specific binding to generate a low background signal for better identification of cancerous lesions, achieve rapid internalization into cancer cells, selectively release bioactive CPT as a cytotoxic agent in response to high levels of GSH and H2O2, and exhibit high fluorescence that contributes to the visual chemotherapy modality. In addition, the RhB-SS-CPT prodrug nanoparticles show longer circulation time and better antitumor activity than free CPT in vivo. Interestingly, the zwitterionic nature allows RhB-SS-CPT to be excreted through the renal route, with fewer side effects. Conclusions: Zwitterionic features and responsive linkers are important considerations for constructing potent prodrugs, which provide some useful insights to design the next-generation of theranostic prodrugs for cancer.

Reducing thermal damage to adjacent normal tissue with dual thermo-responsive polymer via thermo-induced phase transition for precise photothermal theranosis.

Photothermal therapy has been extensively studied to improve the light-to-heat efficiency for tumor ablation, but could cause severe damage to adjacent healthy tissue due to the thermal transfer, the random distribution of photothermal agents (PTAs), or combination hereof. Herein, we solve this dilemma with a material design strategy to develop a P(AAm-co-AN)-b-P(NIPAM-co-DMAa)-b-P(AAm-co-AN) ABA triblock copolymer by RAFT polymerization, which exhibits both UCST and LCST dual thermo-responsive behaviors in aqueous solution. The P(AAm-co-AN) block with appropriate AN content allows to finely tune its UCST to ∼ 43°C, which can effectively co-assemble with camptothecin (CPT) and Cy7-TCF, a near-infrared (NIR) PTA, realizing the photo-activated "on-demand" release of CPT and Cy7-TCF. The LCST of P(NIPAM-co-DMAa) segment is adjusted to ∼ 53°C by varying DMAa content, enabling an irreversible sol-to-gel transition. The heat transfer in hydrogel and heat dissipation at the interface of hydrogel-adjacent tissue are limited, resulting in selectively cell killing in tumor, with little hyperthermia in adjacent tissues. Moreover, the hydrogel continues to release CPT to enhance the synergistic efficacy of PTT with chemotherapy. These results suggest that dual thermo-responsive polymer can contribute PTT with high selectivity and negligible side effects for precise medicine. STATEMENT OF SIGNIFICANCE: Photothermal therapy exploits the susceptibility of tumor cells toward external light-induced hyperthermia, but can cause severe damage to adjacent healthy tissue due to thermal transfer, random distribution of photothermal agents (PTAs), or combination hereof. Here, we solve this dilemma by developing a P(AAm-co-AN)-b-P(NIPAM-co-DMAa)-b-P(AAm-co-AN) triblock copolymer with UCST and LCST dual thermo-responsive behaviors, realizing the sequential micelle-unimer-hydrogel phase transitions. The polymer can effectively encapsulate PTA/drug, achieve long systemic circulation, accumulate in tumor through EPR effect, regulate drug release by controlling tumor temperature above UCST via irradiation, and finally exhibit a sol-gel transition, eradicating the heat transfer to adjacent tissue. This represents a practicable strategy to guide the design of next-generation polymeric vector that can contribute PTT with negligible side effects.

Lighting up Self-Quenching Nanoaggregates with Protein Corona for Simultaneous Intraoperative Imaging and Photothermal Theranostics of Metastatic Cancer.

Near-infrared (NIR) photothermal transduction agents (PTAs) with large rigid π-extended and planar structures are prone to aggregate in a physiological environment where their emission is often quenched due to the strong intermolecular dipole-dipole or π-π interactions. This aggregation-caused quenching effect greatly impedes their applications in image-guided photothermal theranostics. Herein, we made an interesting finding that engineering a bioinspired protein corona (PC), once thermodynamically stabilized in preferred orientations on PTA nanoaggregates, can produce brilliant NIR fluorescence with a high quantum yield (∼6.2%) without compromising their photothermal properties. Both experimental data and computational modeling suggest that the mechanism of fluorescence enhancement is due to the high-affinity binding of nano-sized PTA to albumin, which regulates the molecular conformation and aggregation state of PTA. High spatial and temporal resolution imaging of albumin PC-coated PTA aggregates enables image-guided photothermal therapy for cancer cells in sentinel lymph nodes to remarkably inhibit pulmonary metastasis. Such a treatment combined with the surgical removal of the primary tumor can prolong animal survival, which is a promising candidate for clinical applications in the treatment of advanced metastatic cancers.