Gas-Mediated Cancer Bioimaging and Therapy

Mesoporous silica nanoparticles: facile surface functionalization and versatile biomedical applications in oncology

Mesoporous silica nanoparticles (MSNs) have received increasing interest due to their tunable particle size, large surface area, stable framework, and easy surface modification. They are increasingly being used in varying applications as delivery vehicles including bio-imaging, drug delivery, biosensors and tissue engineering etc. Precise structure control and the ability to modify surface properties of MSNs are important for their applications. This review summarises the different synthetic methods for the preparation of well-ordered MSNs with tunable pore volume as well as the approaches of drugs loading, especially highlighting the facile surface functionalization for various purposes and versatile biomedical applications in oncology. Finally, the challenges of clinical transformation of MSNs-based nanomedicines are further discussed.

X-ray-triggered NO-released Bi-SNO nanoparticles: all-in-one nano-radiosensitizer with photothermal/gas therapy for enhanced radiotherapy

Hypoxia in tumor cells is regarded as the most crucial cause of clinical drug resistance and radio-resistance; thus, relieving hypoxia of tumor cells is the key to enhancing the efficacy of anticancer therapy. As a gas signal molecule of vasodilatation factors, nitric oxide (NO) can relieve the hypoxia status of tumor cells, thereby, enhancing the sensitivity of tumor cells to radiotherapy. However, considering complications of vascular activity, the level of NO required for radiotherapy sensitization cannot be obtained in vivo. In view of this, we design and fabricate a multifunctional bismuth-based nanotheranostic agent, which is functionalized with S-nitrosothiol and termed Bi-SNO NPs. X-rays break down the S-N bond and simultaneously trigger large amount of NO-releasing (over 60 μM). Moreover, the as-prepared Bi-SNO NPs not only possess the capability of absorbing and converting 808 nm NIR photons into heat for photothermal therapy, but also have the ability to increase X-ray absorption and CT imaging sensitivity. In addition, the collaborative radio-, photothermal-, and gas-therapy of Bi-SNO in vivo was further investigated and remarkable synergistic tumor inhibition was realized. Finally, no obvious toxicity of Bi-SNO NPs was observed in the treated mice within 14 days. Therefore, the Bi-SNO developed in this work is an effective nano-agent for cancer theranostics with well-controlled morphology and uniform size (36 nm), which could serve as a versatile CT imaging-guided combined radio-, photothermal- and gas-therapy nanocomposite with negligible side effects.

Nanostructured manganese dioxide for anticancer applications: preparation, diagnosis, and therapy

Nanostructured manganese dioxide (MnO₂) has attracted extensive attention in the field of anticancer applications. As we all know, the tumor microenvironment is usually characterized by a high glutathione (GSH) concentration, overproduced hydrogen peroxide (H₂O₂), acidity, and hypoxia, which affect the efficacy of many traditional treatments such as chemotherapy, radiotherapy, and surgery. Fortunately, as one kind of redox-active nanomaterial, nanostructured MnO₂ has many excellent properties such as strong oxidation ability, excellent catalytic activity, and good biodegradability. It can be used effectively in diagnosis and treatment when it reacts with some harmful substances in the tumor site. It can not only enhance the therapeutic effect but also adjust the tumor microenvironment. Therefore, it is necessary to present the recent achievements and progression of nanostructured MnO₂ for anticancer applications, including preparation methods, diagnosis, and treatment. Special attention was paid to photodynamic therapy (PDT), bioimaging and cancer diagnosis (BCD), and drug delivery systems (DDS). This review is expected to provide helpful guidance on further research of nanostructured MnO₂ for anticancer applications.

Palladium-based nanomaterials for cancer imaging and therapy

In recent decade, palladium-based (Pd-based) nanomaterials have shown significant potential for biomedical applications because of their unique optical properties, excellent biocompatibility and high stability in physiological environment. Compared with other intensively studied noble nanomaterials, such as gold (Au) and silver (Ag) nanomaterials, research on Pd-based nanomaterials started late, but the distinctive features, such as high photothermal conversion efficiency and high photothermal stability, have made them getting great attention in the field of nanomedicine. The goal of this review is to provide a comprehensive and critical perspective on the recent progress of Pd-based nanomaterials as imaging contrast agents and therapeutic agents. The imaging section focuses on applications in photoacoustic (PA) imaging, single-photon emission computed tomography (SPECT) imaging, computed tomography (CT) imaging and magnetic resonance (MR) imaging. For treatment of cancer, single photothermal therapy (PTT) and PTT combined with other therapeutic modalities will be discussed. Finally, the safety concerns, forthcoming challenges and perspective of Pd-based nanomaterials on biomedical applications will be presented.

ZnS@ZIF-8 core-shell nanoparticles incorporated with ICG and TPZ to enable H2S-amplified synergistic therapy

Abnormal tumor microenvironment, such as hypoxia, interstitial hypertension and low pH, leads to unexpected resistance for current tumor treatment. The development of versatile drug delivery systems which present responsive characteristics to tumor microenvironment (TME) has been extensively carried out, but remains challenging. In this study, zeolitic imidazolate framework-8 (ZIF-8) coated ZnS nanoparticles have been designed and prepared for co-delivery of ICG/TPZ molecules, denoted as ZSZIT, for H2S-amplified synergistic therapy. Methods: The ZSZ nanoparticles were characterized using SEM, TEM and XRD. The in vitro viabilities of cancer cells cultured with ZSZIT under normoxia/hypoxia conditions were evaluated by cell counting kit-8 (CCK-8) assay. In addition, in vivo anti-tumor effect was also performed using male Balb/c nude mice as animal model. Results: ZSZIT shows cascade PDT and hypoxia-activated chemotherapeutic effect under an 808nm NIR irradiation. Meanwhile, ZSZIT degrades under tumor acidic environment, and H2S produced by ZnS cores could inhibit the expression of catalase, which subsequently favors the hypoxia and antitumor effect of TPZ drug. Both in vitro and in vivo studies demonstrate the H2S-sensitized synergistic antitumor effect based on cascade PDT/chemotherapy. Conclusion: This cascade H2S-sensitized synergistic nanoplatform has enabled more effective and lasting anticancer treatment.

ATP Suppression by pH-Activated Mitochondria-Targeted Delivery of Nitric Oxide Nanoplatform for Drug Resistance Reversal and Metastasis Inhibition

Mitochondria, which are important mediators for cancer initiation, growth, metastasis, and drug resistance, have been considered as a major target in cancer therapy. Herein, an acid-activated mitochondria-targeted drug nanocarrier is constructed for precise delivery of nitric oxide (NO) as an adenosine triphosphate (ATP) suppressor to amplify the therapeutic efficacy in cancer treatments. By combining α-cyclodextrin (α-CD) and acid-cleavable dimethylmaleic anhydride modified PEG conjugated mitochondria-targeting peptide, the nanocarrier shows prolonged blood circulation time and enhanced cellular uptake together with selectively restoring mitochondria-targeting capability under tumor extracellular pH (6.5). Such specific mitochondria-targeted delivery of NO proves crucial in inducing mitochondria dysfunction through facilitating mitochondrial membrane permeabilization and downregulating ATP level, which can inhibit P-glycoprotein-related bioactivities and formation of tumor-derived microvesicles to combat drug resistance and cancer metastasis. Therefore, this pioneering acid-activated mitochondria-targeted NO nanocarrier is supposed to be a malignant tumor opponent and may provide insights for diverse NO-relevant cancer treatments.

Sulfur dioxide signaling molecule-responsive polymeric nanoparticles

Stimuli-responsive polymer nano-capsules toward a specific signaling molecule show great potential in the fabrication of smart and efficient controlled/targeted drug vehicles. Herein, we design and synthesize a PEG45-b-PVPOP14 diblock copolymer (PEG = poly(ethylene glycol) and PVPOP = poly(4-vinylphenyl 4-oxopentanoate), the subscripts representing the number of repeat units of each block) with levulinate-protected phenol side groups. The PEG45-b-PVPOP14 diblock copolymer could self-assemble to form large compound micelles in aqueous media. Since the core of the large compound micelles formed contains both hydrophilic PEG and hydrophobic PVPOP domains, this kind of micelle is able to load both hydrophobic and hydrophilic species within the core. The ester moiety of levulinate-protected phenol can be selectively cleaved upon incubation with a sulfite, a derivative of SO2 in aqueous media, to give phenol groups. Thus, the sulfite exhibits the ability to alter the amphiphilicity and further the self-assembled behavior of PEG45-b-PVPOP14. The release of payloads in the core of micelles can be accelerated by triggering of the sulfite. Significantly, the nano-capsule of PEG45-b-PVPOP14 shows specific response to the sulfite (SO2) with slight interference of other bio-species, such as Cys, GSH and Hcy. As far as we are aware, this is the first example of a nano-capsule with sulfite (SO2) specific responsiveness. We envisage that this polymer model could broaden the scope of biological signaling molecule responsive macromolecular systems and provide a new platform to fabricate SO2-responsive biomedicine materials.

Nitric oxide-induced stromal depletion for improved nanoparticle penetration in pancreatic cancer treatment

Abundant desmoplastic stroma, which typically exists in pancreatic ductal adenocarcinoma (PDAC), can act as a natural protective physical barrier rendering insufficient drug delivery and penetration. To address this issue, we herein report a two-step sequential delivery strategy for enhanced pancreatic cancer therapy. In this sequential strategy, the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) loaded liposomes (Lip-SNAP) were firstly delivered to pancreatic stellate cells (PSCs) in tumor tissue to inhibit the production of dense stroma, by inhibiting the expression of TGF-β1 and its downstream profibrotic signal transduction. Therefore, the PSC-mediated desmoplastic reaction could be suppressed by inhibiting the expression of fibronectin, α-SMA and collagen. The gemcitabine (GEM) loaded liposomes (Lip-GEM) were administrated subsequently. The enhanced intratumoral penetration of Lip-GEM was then achieved due to the stromal disruption in consequence of NO treatment, thus significantly improving the drug delivery efficiency. The tumor growth inhibition of the two-step sequential delivery of Lip-SNAP and Lip-GEM was investigated on both subcutaneous and orthotopic tumor mouse models, to show the remarkably improved therapeutic efficacy of GEM. Such NO-induced stromal depletion provides a general strategy to overcome the blockage of desmoplastic stroma on other therapeutic agents.

Porous materials as carriers of gasotransmitters towards gas biology and therapeutic applications

This review highlights the strategies employed to load and release gasotransmitters such as NO, CO and H₂S from different kinds of porous materials, including zeolites, mesoporous silica, metal–organic frameworks and protein assemblies.

pH/glutathione-responsive release of SO2 induced superoxide radical accumulation for gas therapy of cancer

A pH/glutathione (GSH)-responsive SO₂ generation nanoplatform (BODS NPs) is established to achieve lysosomal escape and GSH depletion in tumors to sensitize the SO₂-mediated oxidative stress.

Photo-degradable micelles for co-delivery of nitric oxide and doxorubicin

Photo-degradable triblock copolymers enable the co-delivery of nitric oxide and doxorubicin exerting an improved therapeutic effect.

A green, efficient and precise hydrogen therapy of cancer based on in vivo electrochemistry

By combined use of traditional Chinese acupuncture Fe needle electrode and in vivo electrochemistry, we achieved in vivo H₂ generation in tumors in a controllable manner and exploited it for effective and green therapy of tumors for the first time. The cathodic acupuncture electrodes working under an applied voltage of ∼3 V (with minimal damage to the living body) undergo effective electrochemical reactions in the acidic tumor area that produce sufficient H₂ locally to cause cancer cells to burst and die. Due to puncture positioning, the acidic tumor microenvironment and gas diffusion effect, the developed H₂ generation electrochemotherapy (H₂-ECT) strategy enables precise and large-scale tumor therapy, as demonstrated by in vivo treatment of diseased mice (glioma and breast cancers). Such green H₂-ECT is simple, highly efficient and minimally invasive, requiring no expensive medical equipment or nano materials and medication, and is therefore very promising for potential clinical applications.