NIR-Triggered Theranostic Bi2S3 Light Transducer for On-Demand NO Release and Synergistic Gas/Photothermal Combination Therapy of Tumors

Current trends in gas-synergized phototherapy for improved antitumor theranostics

Phototherapy, such as photothermal therapy (PTT) and photodynamic therapy (PDT), has been considered an elegant solution to eradicate tumors due to its minimal invasiveness and low systemic toxicity. Nevertheless, it is still challenging for phototherapy to achieve ideal outcomes and clinical translation due to its inherent drawbacks. Owing to the unique biological functions, diverse gases have attracted growing attention in combining with phototherapy to achieve super-additive therapeutic effects. Specifically, gases such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) have been proven to kill tumor cells by inducing mitochondrial damage in synergy with phototherapy. Additionally, several gases not only enhance the thermal damage in PTT and the reactive oxygen species (ROS) production in PDT but also improve the tumor accumulation of photoactive agents. The inflammatory responses triggered by hyperthermia in PTT are also suppressed by the combination of gases. Herein, we comprehensively review the latest studies on gas-synergized phototherapy for cancer therapy, including (1) synergistic mechanisms of combining gases with phototherapy; (2) design of nanoplatforms for gas-synergized phototherapy; (3) multimodal therapy based on gas-synergized phototherapy; (4) imaging-guided gas-synergized phototherapy. Finally, the current challenges and future opportunities of gas-synergized phototherapy for tumor treatment are discussed. STATEMENT OF SIGNIFICANCE: 1. The novelty and significance of the work with respect to the existing literature. (1) Strategies to design nanoplatforms for gas-synergized anti-tumor phototherapy have been summarized for the first time. Meanwhile, the integration of various imaging technologies and therapy modalities which endow these nanoplatforms with advanced theranostic capabilities has been summarized. (2) The mechanisms by which gases synergize with phototherapy to eradicate tumors are innovatively and comprehensively summarized. 2. The scientific impact and interest. This review elaborates current trends in gas-synergized anti-tumor phototherapy, with special emphases on synergistic anti-tumor mechanisms and rational design of therapeutic nanoplatforms to achieve this synergistic therapy. It aims to provide valuable guidance for researchers in this field.

L-Arginine self-delivery supramolecular nanodrug for NO gas therapy

NO gas therapy is a supplementary approach for tumor treatment due to the advantages of minimal invasion, little drug resistance, low side effect and amplified efficacy. l-Arginine (L-Arg), a natural NO source with good biocompatibility, can release NO under the stimulation of H2O2 in tumor microenvironment. However, the conventional l-Arg delivery systems via noncovalent loading usually lead to inevitable premature leakage of nano-cargos during blood circulation. In this work, an efficient l-Arg self-delivery supramolecular nanodrug (SDSND) for tumor treatment is demonstrated by combining Mannich reaction and π-π stacking. l-Arg links to (-)-epigallocatechin gallate (EGCG) with the assistance of formaldehyde through Mannich reaction, and then assembles into nanometer-sized particles via π-π stacking. The guanidine group of l-Arg and the phenolic hydroxyl groups of EGCG are preserved in the SDSNDs, which allows for accomplishing gas therapy by provoking tumor cell apoptosis and combining with EGCG to amplify apoptosis, respectively. In addition, the SDSNDs exhibit high biocompatibility and avoid the premature leakage of l-Arg in blood circulation, providing an alternative l-Arg delivery system for NO gas therapy. STATEMENT OF SIGNIFICANCE: NO gas therapy has attracted emerging interest in tumor treatment. However, the controlled NO release and the avoidance of premature leakage of NO donors remain challenging. In this work, L-Arginine (L-Arg) self-delivery supramolecular nanodrug for efficient tumor therapy is demonstrated through the Mannich reaction of L-Arg, (-)-epigallocatechin gallate (EGCG) and formaldehyde. Stimulated by tumor microenvironment, the guanidine groups of L-Arg allow for accomplishing NO release and thus provoking tumor cell apoptosis. The nanodrug also avoids the premature leakage of L-Arg in blood circulation. Moreover, the preserved phenolic hydroxyl groups of EGCG combine with L-Arg to amplify apoptosis. The nanodrug exhibits high biocompatibility and good therapeutic effect, providing an alternative L-Arg delivery system for NO gas therapy.

Recent advances in stimuli-responsive nano-heterojunctions for tumor therapy

Stimuli-responsive catalytic therapy based on nano-catalysts has attracted much attention in the field of biomedicine for tumor therapy, due to its excellent and unique properties. However, the complex tumor microenvironment conditions and the rapid charge recombination in the catalyst limit catalytic therapy's effectiveness and further development. Effective heterojunction nanomaterials are constructed to address these problems to improve catalytic performance. Specifically, on the one hand, the band gap of the material is adjusted through the heterojunction structure to promote the charge separation efficiency under exogenous stimulation and further improve the catalytic capacity. On the other hand, the construction of a heterojunction structure can not only preserve the function of the original catalyst but also achieve significantly enhanced synergistic therapy ability. This review summarized the construction and functions of stimuli-responsive heterojunction nanomaterials under the excitation of X-rays, visible-near infrared light, and ultrasound in recent years, and further introduces their application in cancer therapy. Hopefully, the summary of stimuli-responsive heterojunction nanomaterials' applications will help researchers promote the development of nanomaterials in cancer therapy.

A multifunctional nanocomposite coated with a BSA membrane for cascaded nitric oxide therapy

Gas therapy based on nitric oxide (NO) has emerged as a potential therapeutic approach for cancer, and in conjunction with multi-mode combination therapy, offers new possibilities for achieving significant hyperadditive effects. In this study, an integrated AI-MPDA@BSA nanocomposite for diagnosis and treatment was constructed for PDA based photoacoustic imaging (PAI) and cascade NO release. Natural NO donor L-arginine (L-Arg) and photosensitizer (PS) IR780 were loaded into mesoporous polydopamine (MPDA). Bovine serum albumin (BSA) was conjugated to the MPDA to increase the dispersibility and biocompatibility of the nanoparticles, as well as to serve as a gatekeeper controlling IR780 release from the MPDA pores. The AI-MPDA@BSA produced singlet oxygen (¹O₂) and converted it into NO through a chain reaction based on L-Arg, enabling a combination of photodynamic therapy and gas therapy. Moreover, due to the photothermal properties of MPDA, the AI-MPDA@BSA performed good photothermal conversion, which allowed photoacoustic imaging. As expected, both in vitro and in vivo studies have confirmed that the AI-MPDA@BSA nanoplatform has a significant inhibitory effect on cancer cells and tumors, and no apparent systemic toxicity or side effects were detected during the treatment period.

Multifunctional Bi NSs@BSA Nanoplatform Guided by CT Imaging for Effective Photothermal Therapy

Photothermal therapy (PTT) has attracted great attention as an anticancer treatment strategy. With the rapid development of nanomedicine, multifunctional inorganic nanophotothermal agents provide a new way to improve the effect of PTT. Herein, bovine serum albumin (BSA)-modified Bi nanosheets (Bi NSs) with good biocompatibility were synthesized by a facile redox and ball milling method and applied as a photothermal agent for the enhancement of PTT. Owing to the strong near-infrared absorption, Bi NSs exhibit high photothermal conversion efficiency (η = 36.17%) under 808 nm laser irradiation and can serve as a nanotherapeutic agent for cancer therapy. In addition, in vitro cell safety analysis also suggests that the toxicity of BSA-modified Bi NSs is negligible. Upon 808 nm irradiation, the uptake ability of tumor cells to Bi NSs@BSA has been improved. Moreover, Bi NSs@BSA also can be used as a good contrast agent for CT imaging and then to observe the distribution of materials in the tumor site. Finally, Bi NSs@BSA-mediated PTT results show a high ablation rate of A549 tumor cells both in vitro and in vivo. All results reveal that Bi NSs@BSA is a promising nanotherapeutic platform for PTT.

Ultrasmall PEI-Decorated Bi2Se3 Nanodots as a Multifunctional Theranostic Nanoplatform for in vivo CT Imaging-Guided Cancer Photothermal Therapy

Bi-based nanomaterials, such as Bi2Se3, play an important part in biomedicine, such as photothermal therapy (PTT) and computed tomography (CT) imaging. Polyethylenimine (PEI)-modified ultrasmall Bi2Se3 nanodots were prepared using an ultrafast synthetic method at room temperature (25°C). Bi2Se3 nanodots exhibited superior CT imaging performance, and could be used as effective photothermal reagents owing to their broad absorption in the ultraviolet-visible-near infrared region. Under irradiation at 808 nm, PEI-Bi2Se3 nanodots exhibited excellent photothermal-conversion efficiency of up to 41.3%. Good biocompatibility and significant tumor-ablation capabilities were demonstrated in vitro and in vivo. These results revealed that PEI-Bi2Se3 nanodots are safe and a good nanotheranostic platform for CT imaging-guided PTT of cancer.

How do bismuth-based nanomaterials function as promising theranostic agents for the tumor diagnosis and therapy?

The complexity of tumor microenvironment and the diversity of tumors seriously affect the therapeutic effect, the focus, therefore, has gradually been shifted from monotherapy to combination therapy in clinical research in order to improve the curative effect. The synergistic enhancement interactions among multiple monotherapies majorly contribute to the birth of the multi-mode cooperative therapy, whose effect of the treatment is clearly stronger than that of any single therapy. In addition, the accurate diagnosis of the tumour location is also crucial to the treatment. Bismuth-based nanomaterials (NMs) hold great properties as promising theranostic platforms based on their many unique features that include low toxicity, excellent photothermal conversion efficiency as well as high ability of X-ray computed tomography imaging and photoacoustic imaging. In this review, we will introduce briefly the main features of tumor microenvironment first and its effect on the mechanism of nanomedicine actions and present the recent advances of bismuth-based NMs for diagnosis and photothermal therapy-based combined therapies using bismuth-based NMs are presented, which may provide a new way for overcoming drug resistance and hypoxia. At the end, further challenges and outlooks regarding this promising field are discussed accompanied with some design tips for bismuth-based NMs, hoping to provide researchers some inspirations to design safe and effective nanotherapeutic agents for the clinical treatments of cancers.

Multishell Nanoparticles with "Linkage Mechanism" for Thermal Responsive Photodynamic and Gas Synergistic Therapy

The strategies of combining photodynamic therapy (PDT) with other therapeutics are considered to be the most suitable methods in improving the antitumor therapeutic efficiency. Herein, a "Linkage Mechanism" strategy based on thermal controllable multishell nanoparticles (CuS@SiO₂ -l-Arg (l-arginine)@PCM (phase-change material)-Ce6 (chiorin e6)) is proposed for combing PDT and NO-based gas therapy. Upon 1060 nm laser irradiation, the PCMs will melt under the photothermal effect induced by CuS and the loaded Ce6 and l-Arg can accurately release from the nanoparticles. Under further 660 nm laser irradiation, the released Ce6 will produce plenty of singlet oxygen (¹ O₂ ) for PDT, while the generated ¹ O₂ can oxidize l-Arg to release NO for the synergy of PDT and gas therapy. The "Linkage Mechanism" can achieve precise release of the payloads under the control of photothermal effect at tumor site, and the chain reaction of PDT and gas therapy overcomes the problem of premature release of gas during transportation. Benefiting from the guidance of fluorescence imaging and second near infrared photoacoustic imaging by Ce6 and CuS, both in vitro and in vivo experiments present effective antitumor efficiencies. The nanoparticles provide new ideas for controllable release of drugs and the synergistic effect of multiple treatments, possessing great application prospects.