Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Dual-Photosensitizer Nanoplatform Based on Near-Infrared Excitation Orthogonal Emission Nanomaterials for Enhanced Photodynamic Therapy of Tumors

Photodynamic therapy (PDT) is considered as a promising therapeutic approach for clinical cancer treatment. However, the hypoxia of the tumor microenvironment leads to the low effect of single PDT. Here, a dual-photosensitizer nanoplatform based on near-infrared excitation orthogonal emission nanomaterials is constructed by introducing two kinds of photosensitizers into the nanosystem. Orthogonal emission upconversion nanoparticles (OE-UCNPs) were used as light conversion reagents to generate red emission under 980 nm irradiation and green emission under 808 nm irradiation. On the one hand, merocyanine 540 (MC540) is introduced as a photosensitizer (PS), which can absorb green light to generate reactive oxygen species (ROS) and trigger PDT for tumor treatment. On the other hand, another photosensitizer, chlorophyll a (Chla), which can be excited by red light, has also been introduced into the system to build a dual PDT nanotherapeutic platform. The introduction of photosensitizer Chla can synergistically increase ROS concentration to accelerate cancer cell apoptosis. Our research shows that this dual PDT nanotherapeutic platform combined with Chla has better therapeutic effects and effectively destroys cancer.

Dissociation of Bipyridine and Coordination with Nitrosyl: Cyclometalated Ruthenium Nitrosyl Complex

A novel family of ruthenium nitrosyl complexes [Ru(bpy)(C^∧N)(MeCN)NO](PF₆)₂ (2a-2e, bpy = 2,2'-bipyridine, HC^∧N = 2-phenylpyridine and its derivatives) has been prepared by reacting cyclometalated ruthenium complexes [Ru(bpy)₂(C^∧N)][PF₆] (1a-1e) with NO⁺, which were comprehensively characterized by mass, IR, NMR, and UV-vis spectra as well as the single-crystal X-ray structure determinations. Herein, the coordination geometry of Ru atoms in 2a-2e is a distorted octahedron and {Ru^II-NO⁺}⁶ is present in these complexes. Theoretical calculations suggest that the reactions involving dissociation of one bipyridine and coordination with NO⁺ proceed spontaneously (ΔG < 0) and the transformation from 1a-1e to the intermediates is dominated by substituents (ΔG_RI varies from -1.19 to -1.53 eV), which influence the binding energy between Ru(II) and NO⁺ in complexes 2a-2e (-89.42 to -101.17 kcal/mol) and thus control the photorelease of NO on a certain scale. The weak absorption bands in the visible region could be attributed to the contribution of dπ(Ru^II) → π*(NO⁺), which were enhanced greatly under light, indicating the possible release of NO. The photoinduced NO, as well as singlet oxygen (¹O₂), was then confirmed by EPR spectra, and the amount of NO released from 2a-2e was estimated via Griess reagent assay. The cytotoxicity of these complexes with or without visible light irradiation was also investigated using an MTT assay.

Stimuli Responsive Nitric Oxide-Based Nanomedicine for Synergistic Therapy

Gas therapy has received widespread attention from the medical community as an emerging and promising therapeutic approach to cancer treatment. Among all gas molecules, nitric oxide (NO) was the first one to be applied in the biomedical field for its intriguing properties and unique anti-tumor mechanisms which have become a research hotspot in recent years. Despite the great progress of NO in cancer therapy, the non-specific distribution of NO in vivo and its side effects on normal tissue at high concentrations have impaired its clinical application. Therefore, it is important to develop facile NO-based nanomedicines to achieve the on-demand release of NO in tumor tissue while avoiding the leakage of NO in normal tissue, which could enhance therapeutic efficacy and reduce side effects at the same time. In recent years, numerous studies have reported the design and development of NO-based nanomedicines which were triggered by exogenous stimulus (light, ultrasound, X-ray) or tumor endogenous signals (glutathione, weak acid, glucose). In this review, we summarized the design principles and release behaviors of NO-based nanomedicines upon various stimuli and their applications in synergistic cancer therapy. We also discuss the anti-tumor mechanisms of NO-based nanomedicines in vivo for enhanced cancer therapy. Moreover, we discuss the existing challenges and further perspectives in this field in the aim of furthering its development.

Advanced nitric oxide donors: chemical structure of NO drugs, NO nanomedicines and biomedical applications

Nitric oxide (NO), as an endogenous diatomic molecule, plays a key regulatory role in many physiological and pathological processes. This diatomic free radical has been shown to affect different physiological and cellular functions and participates in many regulatory functions ranging from changing the cardiovascular system to regulating neuronal functions. Thus, NO gas therapy as an emerging and promising treatment method has attracted increasing attention in the treatment of various pathological diseases. As is known, the physiological and pathological regulation of NO depends mainly on its location, exposure time and released dosage. However, NO gas lacks effective accumulation and controlled long-term gas releasing capacity at specific sites, resulting in limited therapeutic efficacy and potential side effects. Thus, researchers have developed various NO donors, but eventually found that it is still difficult to control the long-term release of NO. Inspired by the self-assembly properties of nanomaterials, researchers have realized that nanomaterials can be used to support NO donors to form nanomedicine to achieve spatial and temporal controlled release of NO. In this review, according to the history of the medicinal development of NO, we first summarize the chemical design of NO donors, NO prodrugs, and NO-conjugated drugs. Then, NO nanomedicines formed by various nanomaterials and NO donors depending on nanotechnology are highlighted. Finally, the biomedical applications of NO nanomedicine with optimized properties are summarized.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

An all-in-one theranostic nanoplatform based on upconversion dendritic mesoporous silica nanocomposites for synergistic chemodynamic/photodynamic/gas therapy

Gasotransmitters with high therapeutic efficacy and biosafety have been drawing the attention of researchers. Nevertheless, how to effectively deliver gases to and precisely control their generation at the lesion as well as integrate them with other therapies to realize precision therapy have remained elusive. Herein, we report a versatile Cu²⁺-initiated nitric oxide (NO) nanocomposite for multimodal imaging-guided synergistic chemodynamic/photodynamic/gas therapy. After the nanomedicine was ingested by tumor cells, the acidic tumor microenvironment accelerated the decomposition of CuO₂ and simultaneously triggered the Fenton-like catalytic reaction of Cu²⁺ and H₂O₂ to produce highly toxic ˙OH. By virtue of the NO generation and glutathione depletion, UMNOCC-PEG can relieve the antioxidant capacity and hypoxia of the tumor to improve the efficiency of chemodynamic therapy (CDT) and photodynamic therapy (PDT). Importantly, NO and reactive oxygen species (ROS) can generate reactive nitrogen species (RNS), which can result in DNA damage, further improving the therapeutic effect (cell apoptosis rate up to 93.4%). Moreover, the inherent properties of lanthanide ions endow UMNOCC-PEG with upconversion luminescence (UCL), CT and MRI trimodal imaging capability, achieving precise cancer treatment. By taking advantage of these features, the strategy developed here may provide a promising application foreground to conquer malignant tumors.

Activation Strategies in Image-Guided Nanotherapeutic Delivery

Therapeutic nanomaterials serve as an important platform for drug delivery under image guidance. Despite significant growth and broad applications, their design specifics remain a subject of continued interest primarily due to multifunctional factors involved, ranging from nanomaterial properties, imaging modalities, and therapeutic agents to activation strategies. This review article summarizes key findings on their design characteristics with a particular interest in strategies developed for therapeutic activation (release). First, their activation can be controlled using either an endogenous factor including low pH and glutathione or an external stimulation by light, ultrasound, or electromagnetic field. The former is passively controlled from a spatiotemporal aspect compared to the latter, which is otherwise actively controlled through drug linker photolysis, nanomaterial disassembly, or gate opening. Second, light stimulation serves a most notable strategy due to its essential role in controlled drug release, photothermal activation (hyperthermia), and photodynamic production of reactive oxygen species (ROS). Third, some of those activation strategies that rely on ultrasound, photothermal, photoacoustic, magnetic field, or X-ray radiation are dually functional due to their role in imaging modalities. In summary, this review article presents recent advances and new insights that pertain to nanotherapeutic delivery systems. It also addresses their technical limitations associated with tissue penetration (light), spatial resolution (ultrasound, hyperthermia), and occurrence of cellular resistance (ROS).

Sialic acid–targeted drug delivery and imaging system for pH- and glutathione-triggered multiple anticancer drug release and enhanced oxidative stress

The emergence of multiple drug delivery systems can solve the disadvantages of single-drug therapy, such as high dose and easy generation of drug resistance. Here, we designed a sialic acid–targeted dextran-mercaptopurine prodrug linked by carbonyl vinyl sulfide for coordinate ZnO quantum dots to achieve multiple drug delivery (doxorubicin, 5-fluorouracil, 6-mercaptopurine), which can be released under the trigger of pH and glutathione. To enhance the antitumor effect, we used inorganic photosensitizer CdSe quantum dots to achieve photodynamic therapy, which can produce cytotoxic reactive oxygen species (hydroxyl radicals) under light conditions. Notably, we found that glutathione is consumed by the delivery of 6-mercaptopurine. It is able to efficiently amplify intracellular oxidative stress via increasing •OH generation. After chelating 99mTc4+ radioisotopes by diethylenetriamine pentaacetic acid, the drug delivery system could be tracked under in vivo single-photon emission computed tomography imaging. The results showed that the phenylboronic acid targeting substance can specifically recognize sialic acid, so that the drug system has a good accumulation in the tumor site, which can better increase the therapeutic effect. Compared to free doxorubicin, the drug system can reduce the IC50 value of cells 4.4-fold under light conditions and significantly inhibit tumor growth in vivo. These data indicate that the sialic acid–targeted nanomedicine system has achieved ideal antitumor effects and apparent photodynamic therapy effects and has broad application prospects.

Strategies for engineering advanced nanomedicines for gas therapy of cancer

As an emerging and promising treatment method, gas therapy has attracted more and more attention for treatment of inflammation-related diseases, especially cancer. However, therapeutic/therapy-assisted gases (NO, CO, H₂S, H₂, O₂, SO₂ and CO₂) and most of their prodrugs lack the abilities of active intratumoral accumulation and controlled gas release, resulting in limited cancer therapy efficacy and potential side effects. Therefore, development of nanomedicines to realize tumor-targeted and controlled release of therapeutic/therapy-assisted gases is greatly desired, and also the combination of other therapeutic modes with gas therapy by multifunctional nanocarrier platforms can augment cancer therapy efficacy and also reduce their side effects. The design of nanomedicines with these functions is vitally important, but challenging. In this review, we summarize a series of engineering strategies for construction of advanced gas-releasing nanomedicines from four aspects: (1) stimuli-responsive strategies for controlled gas release; (2) catalytic strategies for controlled gas release; (3) tumor-targeted gas delivery strategies; (4) multi-model combination strategies based on gas therapy. Moreover, we highlight current issues and gaps in knowledge, and envisage current trends and future prospects of advanced nanomedicines for gas therapy of cancer. This review aims to inspire and guide the engineering of advanced gas-releasing nanomedicines.

A Ruthenium Nitrosyl-Functionalized Magnetic Nanoplatform with Near-Infrared Light-Controlled Nitric Oxide Delivery and Photothermal Effect for Enhanced Antitumor and Antibacterial Therapy

Developing a spatiotemporal-controlled nitric oxide (NO) delivery nanoplatform is highly desirable for its biological applications as a tumor inhibitor and antibacterial agent. In this study, a novel multifunctional magnetic nanoplatform {Fe₃O₄@PDA@Ru-NO@FA} (1) was developed for the near-infrared (NIR) light-controlled release of NO in which a ruthenium nitrosyl (Ru-NO) donor and a folic acid (FA)-directing group were covalently functionalized onto Fe₃O₄@PDA. Nanoplatform 1 preferentially accumulated in folate receptor-overexpressing cancer cell lines and magnetic field-guided tumor tissue, instantly released NO, and simultaneously produced a prominent photothermal effect upon 808 nm NIR light irradiation, leading to remarkable in vitro and in vivo antitumor efficacy. When nanoplatform 1 was treated only once, the potential MRI contrast agent was sufficient to significantly inhibit or eliminate the tumor tissues in living mice, thus offering opportunities for future NO-involved multimodal cancer therapy. In addition, a NO delivery nanoplatform {Fe₃O₄@PDA@Ru-NO} was imbedded in the matrix of a chitosan (CS)-poly(vinyl alcohol) (PVA) material to develop a hybrid thermosensitive CS-PVA/NO hydrogel. The CS-PVA/NO hydrogels demonstrated mild (<150 mW cm^-2) NIR light-controlled NO delivery and thus produced an efficient antibacterial effect for both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Therefore, these hydrogels have potential as antibacterial dressings for wound bacterial infection treatment.

Visible light-controlled NO generation for photoreceptor-mediated plant root growth regulation

Nitric oxide (NO) is an essential redox-signaling molecule free radical, contributes a significant role in a diverse range of physiological processes. Photo-triggered NO donors have significant potential compared to other NO donors because it releases NO in the presence of light. Hence, an efficient visible light-triggered NO donor is designed and synthesized by coupling 2,6-dimethyl nitrobenzene moiety at the peri-position of 1, 8-naphthalimide. The NO-releasing ability is validated using various spectroscopic techniques, the photoproduct is characterized, and finally, the NO generation quantum yield is also determined. Furthermore, the photo-generated NO has been employed to Arabidopsis thaliana as a model plant to examine the effect of photoreceptor-mediated NO uptake on plant root growth regulation molecule.

Effects of copper ions on removal of nutrients from swine wastewater and on release of dissolved organic matter in duckweed systems

High concentration of Cu²⁺ in swine wastewater raises concerns about its potential adverse effects on nutrient removal by aquatic plants like duckweed. In this work, the effects of copper ions on nutrient removal and release of dissolved organic matter (DOM) were investigated in duckweed systems. Results showed that the removal performance of ammonia nitrogen (NH₃N) and total phosphorus (TP) increased at 0.1-1.0 mg/L of Cu²⁺, while dropped at 2.0-5.0 mg/L of Cu²⁺. A novel kinetic model in which Cu²⁺ was taken into account was then developed which was used to optimize Cu²⁺ concentration at 0.96 mg/L for nutrient removal in duckweed systems. NADH, detected in DOM by the parallel factor (PARAFAC) analysis, exhibited high capacities of binding copper ions, so it played an important role on the decrease of Cu²⁺ concentrations in duckweed systems. The principle component analysis (PCA) showed that the dominant DOM were lower molecular weight compounds at 1.0 mg/L of Cu²⁺ and higher molecular weight compounds at 2.0-5.0 mg/L of Cu²⁺. The bonds of CH (humic-like), NO (NO₃^-) and ArH (tyrosine) in DOM were responsible for not only the fastest binding with Cu²⁺ from the result of the two-dimensional Fourier transform infrared correlation spectroscopy (2D-FTIR-CoS) but also the variations of DOM conformations at a critical concentration of 0.5 mg/L Cu²⁺ from the perturbation correlation moving window two-dimensional (PCMW2D) analysis. These findings lead to a better understanding on the environmental behaviors and mechanisms of Cu²⁺ in duckweed systems.

Energy-Converting Nanomedicine

Serious side effects to surrounding normal tissues and unsatisfactory therapeutic efficacy hamper the further clinic applications of conventional cancer-therapeutic strategies, such as chemotherapy and surgery. The fast development of nanotechnology provides unprecedented superiorities for cancer therapeutics. Externally activatable therapeutic modalities mediated by nanomaterials, relying on highly effective energy transformation to release therapeutic elements/effects (cytotoxic reactive oxygen species, thermal effect, photoelectric effect, Compton effect, cavitation effect, mechanical effect or chemotherapeutic drug) for cancer therapies, categorized and termed as "energy-converting nanomedicine," have arouse considerable concern due to their noninvasiveness, desirable tissue-penetration depth, and accurate modulation of therapeutic dose. This review summarizes the recent advances in the engineering of intelligent functional nanotherapeutics for energy-converting nanomedicine, including photo-based, radiation-based, ultrasound-based, magnetic field-based, microwave-based, electric field-based, and radiofrequency-based nanomedicines, which are enabled by external stimuli (light, radiation, ultrasound, magnetic field, microwave, electric field, and radiofrequency). Furthermore, biosafety issues of energy-converting nanomedicine related to future clinical translation are also addressed. Finally, the potential challenges and prospects of energy-converting nanomedicine for future clinical translation are discussed.

Hypoxia-Irrelevant Photonic Thermodynamic Cancer Nanomedicine

The hypoxic tumor microenvironment severely lowers the therapeutic efficacy of oxygen-dependent anticancer modalities because tumor hypoxia hinders the generation of toxic reactive oxygen species. Here we report a thermodynamic cancer-therapeutic modality that employs oxygen-irrelevant free radicals generated from thermo-labile initiators for inducing cancer cell death. A free radical nanogenerator was engineered via direct growth of mesoporous silica layer onto the surface of two-dimensional Nb₂C MXene nanosheets toward multifunctionality, where the mesopore provided the reservoirs for initiators and the MXene core acted as the photonic-thermal trigger at the near-infrared-II biowindow (NIR-II). Upon illumination by a 1064 nm NIR-II laser, the photothermal-conversion effect of Nb₂C MXene induced the fast release and quick decomposition of the encapsulated initiators (AIPH) to produce free radicals, which promoted cancer cell apoptosis in both normoxic and hypoxic microenvironment. Systematic in vitro and in vivo evaluations have demonstrated the synergistic-therapeutic outcome of this intriguing photonic nanoplatform-enabled thermodynamic cancer therapy for completely eradicating the 4T1 tumors without recurrence by NIR-II laser irradiation. This work pioneers the thermodynamic therapy for oxygen-independent cancer treatment by photonic triggering at the NIR-II biowindow.

Visible light-triggered NO generation from Naphthalimide-based probe for photoreceptor-mediated plant root growth regulation.. [DOI: 10.1101/550004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

An efficient visible light-triggered nitric oxide (NO) releasing fluorescent molecule is designed and synthesized by coupling 2,6-dimethyl nitrobenzene moiety at the peri-position of 1, 8-naphthalimide through an alkene bond. The NO-releasing ability is investigated in details using various spectroscopic techniques, and the photoproduct was also characterized. Further, the photo-generated NO has been employed to examine the effect of photoreceptor-mediated NO uptake on plant root growth regulation.

Targeted and NIR light-controlled delivery of nitric oxide combined with a platinum(iv) prodrug for enhanced anticancer therapy

This study reports a strategy of combining a Pt(iv) prodrug and a ruthenium nitrosyl (Ru-NO) donor into a single nanoplatform {N-GQDs@Ru-NO-Pt@FA} in which the platinum(iv) prodrug is conjugated onto a photoactivatable NO donor (Ru-NO) through a covalent bond and the nitric oxide-releasing platinum prodrug and folate groups are decorated on N-doped graphene quantum dots (N-GQDs). After cellular uptake of the nanoplatform, the platinum(iv) prodrug was reduced to an active anti-cancer Pt(ii) species inside the cancerous cells, and simultaneously, near-infrared (NIR) light illumination induced the release of NO, accompanied by a prominent photothermal effect. This nanoplatform is capable of targeting intracellular co-delivery of Pt(ii) and NO under 808 nm NIR light irradiation, accompanied by photothermal therapy, thereby leading to a significant synergistic therapeutic effect.

Gas-Generating Nanoplatforms: Material Chemistry, Multifunctionality, and Gas Therapy

The fast advances of theranostic nanomedicine enable the rational design and construction of diverse functional nanoplatforms for versatile biomedical applications, among which gas-generating nanoplatforms (GGNs) have emerged very recently as unique theranostic nanoplatforms for broad gas therapies. Here, the recent developments of the rational design and chemical construction of versatile GGNs for efficient gas therapies by either exogenous physical triggers or endogenous disease-environment responsiveness are reviewed. These gases involve some therapeutic gases that can directly change disease status, such as oxygen (O₂ ), nitric oxide (NO), carbon monoxide (CO), hydrogen (H₂ ), hydrogen sulfide (H₂ S) and sulfur dioxide (SO₂ ), and other gases such as carbon dioxide (CO₂ ), dl-menthol (DLM), and gaseous perfluorocarbon (PFC) for supplementary assistance of the theranostic process. Abundant nanocarriers have been adopted for gas delivery into lesions, including poly(d,l-lactic-co-glycolic acid), micelles, silica/mesoporous silica, organosilica, MnO₂ , graphene, Bi₂ Se₃ , upconversion nanoparticles, CaCO₃ , etc. Especially, these GGNs have been successfully developed for versatile biomedical applications, including diagnostic imaging and therapeutic use. The biosafety issue, challenges faced, and future developments on the rational construction of GGNs are also discussed for further promotion of their clinical translation to benefit patients.

Combination of PDT photosensitizers with NO photodononors

Combination of photodynamic therapy (PDT) with other treatment modalities is emerging as one of the most suitable strategies to increase the effectiveness of therapeutic action on cancer and bacterial diseases and to minimize side effects. This approach aims at exploiting the additive/synergistic effects arising from multiple therapeutic species acting on different mechanistic pathways. The coupling of PDT with photocontrolled release of nitric oxide (NO) through the appropriate assembly of PDT photosensitizers (PSs) and NO photodonors (NOPDs) may open up intriguing avenues towards new and still underexplored multimodal therapies not based on "conventional" drugs but entirely controlled by light stimuli. In this contribution, we present an overview of the most recent advances in this field, illustrating several strategies to assemble PSs and NOPDs allowing them to operate independently without reciprocal interferences and describing the potential applications with particular emphasis on their impact in anticancer and antibacterial research.

Precision gas therapy using intelligent nanomedicine

Gas therapy is an emerging and promising field, utilizing the unique therapeutic effects of several kinds of gases (NO, CO, H₂S and H₂) towards many major diseases, including cancer and cardiovascular diseases, and it is also facing challenges relating to enhancing gas therapy efficacy and avoiding gas poisoning risks. Here, we have proposed a new concept for precision gas therapy using a nanomedicine strategy to overcome the challenges. In this perspective, we have addressed a series of existing and potential solutions from the point of view of nanomedicine, and conveyed a collection of opinions about future expandable research into precision gas therapy.

Cu2- xS Nanocrystals Cross-Linked with Chlorin e6-Functionalized Polyethylenimine for Synergistic Photodynamic and Photothermal Therapy of Cancer

Achieving an integrated system for combinational therapy of cancer with enhanced efficacy is always a challenge. A multifunctional system (CCeT nanoparticles (NPs)) for a synergistic photodynamic and photothermal cancer therapy was successfully developed. This system is composed of Cu_{2- x}S nanoclusters functionalized with chlorin e6 (Ce6)-conjugated branched polyethylenimine (PEI-Ce6) and mitochondria-targeting 3-(carboxypropyl)triphenylphosphonium bromide (TPP-COOH). The colocalization of the resulted CCeT NPs inside the mitochondria of cancer cells was proven. The CCeT NPs exhibited significant photodynamic therapy (PDT) efficacy due to efficient singlet oxygen (¹O₂) generation triggered by a 630 nm laser. This system also showed excellent photothermal conversion capability upon the irradiation of 808 nm laser for photothermal therapy (PTT). In particular, the platform achieved nearly 100% inhibitory rate of the tumor growth in vivo through combinational PDT and PTT. Thus, the CCeT NPs could efficiently inhibit the tumor growth in vitro and in vivo by combinational PDT and PTT, offering synergistic therapeutic efficiency as compared to PTT or PDT alone.

A small molecule for theraNOstic targeting of cancer cells

Thera/NO - a small molecule that is activated by hydrogen peroxide to generate nitric oxide (NO) and a fluorescence signal is reported. Using cancer and primary cells, we show that Thera/NO preferentially releases NO in cancer cells, which can trigger DNA damage and cell death in them. The coupled fluorescence signal facilitated tracking the NO release in living cells without collateral consumption of NO.

Novel Sigma Receptor Ligand-Nitric Oxide Photodonors: Molecular Hybrids for Double-Targeted Antiproliferative Effect

This contribution reports the synthesis and evaluation of novel hybrid compounds that conjugate a sigma (σ) receptor pharmacophore and a nitric oxide (NO) photodonor. All compounds preserve their capability to generate NO under visible light and possess overall σ receptor nanomolar affinity, with one of them (8b) exhibiting remarkable σ₂ receptor selectivity. Compounds 8b, 11a, and 11b were tested on tumorigenic MCF-7 and A2058 cells expressing high levels of σ₂ and σ₁ receptor, respectively. Considerable loss of cell viability was detected under light excitation, while negligible effects in the dark were detected. Moreover, they did not show any significant cytotoxicity in the dark or under irradiation on nontumorigenic NCTC-2544 keratinocytes. NO-induced reduction of cellular viability was demonstrated by in-cell NO detection and total nitrite estimation. For the first time, a combination of σ receptor moieties and a NO photodonor is reported, providing distinctive ligands potentially useful for cancer management.

A unified understanding of the direct coordination of NO to first-transition-row metal centers in metal-ligand complexes

The binding of nitric oxide (NO) to heme-proteins is an important biochemical process involved in a variety of physiological functions. Here, using hybrid density-functional calculations, we systematically investigate the adsorption of NO to first-transition-row metal centers in metal-ligand complexes. Through the comparative study for different transition metal (TM) centers, we provide a unified understanding of the microscopic interactions of NO with the TM centers and related chemical trends. We found that as the atomic number of the TM center increases, the binding strength of NO is largely reduced from 207 kJ mol^-1 to near zero due to the low d-orbital energies for late TM centers. The intermolecular spin coupling between the localized spins at the TM center and the NO molecule is generally antiferromagnetic, except for the case of Sc. The spin-spin coupling is determined in such a way to avoid the energy penalty associated with the electron occupation in the antibonding states of the NO-bound complex. The adsorption strength of NO is generally larger than of CO because the unpaired electron of NO occupies the associated bonding state.

Self-assembling soft structures for intracellular NO release and promotion of neurite outgrowth

Nitric oxide (NO), an endogenously produced free radical species, is an extremely important signalling molecule in several biochemical processes related to neurotransmission, neuronal communication, and vasodilation, to name a few. Other than relying on endogenous synthesis, intracellular NO delivery presents an interesting challenge to fully exploit the therapeutic potential of this gaseous molecule. We have applied a self-assembling peptide conjugate strategy to devise a construct carrying a NO-release arm, which can be activated under standard redox conditions. Consequently, a tryptophan-based peptide carrier was designed, which self-assembled in the solution phase to afford soft nanospherical structures, and released NO in Neuro2a cell line, resulting in neurite outgrowth.

Cyclometalated Iridium(III)-Complex-Based Micelles for Glutathione-Responsive Targeted Chemotherapy and Photodynamic Therapy

The integration of chemotherapy and photodynamic therapy (PDT) in a single delivery system is highly desirable for enhancing anticancer therapeutic efficacy. Herein, two cyclometalated Ir(III) complex-constructed micelles FIr-1 and FIr-2 were demonstrated for glutathione (GSH) activated targeted chemotherapy and PDT. The cyclometalated Ir(III) complexes were prepared by conjugating phosphorescent Ir(III) compounds with chemotherapeutic drug camptothecin (CPT) through GSH responsive disulfide bond linkages, and the Ir(III) complexes were then assembled with amphiphilic surfactant pluronic F127 via noncovalent encapsulation to afford micelles. The surfaces of the micelles were further decorated with folic acid as a targeting group. The micelles showed intense fluorescence that renders them with excellent real-time imaging capability. The release of free anticancer drug CPT from the micelles was realized through GSH-activated disulfide bond cleavage in tumor cells. In addition, the micelles were capable of generating singlet oxygen used for PDT upon visible light irradiation. On account of having folic acid targeting ligand, the micelles displayed greater cellular accumulation in folate receptor (FR) overexpressed HeLa cells than FR low-expressed MCF-7 cells, leading to selective cancer cell killing effect. As compared with solo therapeutic systems, the micelles with targeted combinational chemotherapy and PDT presented superior potency and efficacy in killing tumor cells at a low dosage. On the basis of these findings, the multifunctional micelles could serve as a versatile theranostic nanoplatform for cancer cell targeted imaging and combinational therapy.

Near infrared light triggered nitric oxide releasing platform based on upconversion nanoparticles for synergistic therapy of cancer stem-like cells

Near infrared (NIR) light-driven nitric oxide (NO) release nano-platform based on upconversion nanoparticles (UCNPs) and light sensitive NO precursor Roussin's black salt (RBS) was fabricated to generate NO upon 808nm irradiation. The application of 808nm laser as the excitation source could achieve better penetration depth and avoid overheating problem. The combination of UCNPs and RBS could realize the on-demand release of NO at desired time and location by simply controlling the output of NIR laser. Cellular uptake results showed that more nanoparticles were internalized in cancer stem-like cells (CSCs) rather than non-CSCs. Therefore, a synergistic cancer therapy strategy to eradicate both CSCs and non-CSCs simultaneously was developed. Traditional chemo-drug could inhibit non-CSCs but has low killing efficiency in CSCs. However, we found that the combination of NO and chemotherapy could efficiently inhibit CSCs in bulk cells, including inhibiting mammosphere formation ability, decreasing CD44⁺/CD24^- subpopulation and reducing tumorigenic ability. The mechanism studies confirmed that NO could not only induce apoptosis but also increase drug sensitivity by declining drug efflux in CSCs. This UCNPs-based platform may provide a new combinatorial strategy of NO and chemotherapy to improve cancer treatment.

Protein Nanocage-Based Photo-Controlled Nitric Oxide Releasing Platform

A photoactive NO releasing system was constructed by incorporation of NO-bound Fe-S clusters into horse spleen apoferritin cavities with high loading efficacy. The composites retained intact core-shell structure and indicated advantages such as enhanced stability, reduced cytotoxicity, efficient cellular uptake, and photocontrolled NO releasing property.

Ruthenium nitrosyl functionalized graphene quantum dots as an efficient nanoplatform for NIR-light-controlled and mitochondria-targeted delivery of nitric oxide combined with photothermal therapy

A mitochondria-targeting nanoplatform for near-infrared-light-controlled release of nitric oxide accompanied by photothermal therapy was developed, which consists of ruthenium nitrosyl functionalized N-doped graphene quantum dots and a triphenylphosphonium moiety. The nanoplatform demonstrated both in vitro and in vivo anti-tumor efficacy upon irradiation with 808 nm light.

A ruthenium-nitrosyl-functionalized nanoplatform for the targeting of liver cancer cells and NIR-light-controlled delivery of nitric oxide combined with photothermal therapy

A multifunctional nanoplatform is capable of targeting liver cancer cells for NIR-light-controlled NO-release, and achieving both photodynamic and photothermal therapies.

Tumor cell specific and lysosome-targeted delivery of nitric oxide for enhanced photodynamic therapy triggered by 808 nm near-infrared light

A novel cancer cell lysosome-targetable multifunctional NO-delivery nanoplatform (Lyso-Ru-NO@FA@C-TiO₂) (1) was developed.

A multifunctional nanoplatform for lysosome targeted delivery of nitric oxide and photothermal therapy under 808 nm near-infrared light

NIR light induced spatiotemporal delivery of NO to lysosome accompanied by hyperthermia was realized.

trans- and cis-(Cl,Cl)-[RuII(FT)Cl2(NO)](PF6): promising candidates for NO release in the NIR region

Efficient NO photodelivery from cis- and trans-(Cl,Cl)-[Ru^II(FT)Cl₂(NO)](PF₆) complexes upon two-photon excitation in the NIR region.