Light-Activated Biodegradable Covalent Organic Framework-Integrated Heterojunction for Photodynamic, Photothermal, and Gaseous Therapy of Chronic Wound Infection.

Chronic wound healing, impeded by bacterial infections and drug resistance, poses a threat to global human health. Antibacterial phototherapy is an effective way to fight microbial infection without causing drug resistance. Covalent organic frameworks (COFs) are a class of highly crystalline functional porous carbon-based materials composed of light atoms (e.g., carbon, nitrogen, oxygen, and borane), showing potential applications in the biomedical field. Herein, we constructed porphyrin-based COF nanosheets (TP-Por CON) for synergizing photodynamic and photothermal therapy under red light irradiation (e.g., 635 nm). Moreover, a nitric oxide (NO) donor molecule, BNN6, was encapsulated into the pore volume of the crystalline porous framework structure to moderately release NO triggered by red light irradiation for realizing gaseous therapy. Therefore, we successfully synthesized a novel TP-Por CON@BNN6-integrated heterojunction for thoroughly killing Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus in vitro. Our research identified that TP-Por CON@BNN6 has favorable biocompatibility and biodegradability, low phototoxicity, anti-inflammatory properties, and excellent mice wound healing ability in vivo. This study indicates that the TP-Por CON@BNN6-integrated heterojunction with multifunctional properties provides a potential strategy for COF-based gaseous therapy and microorganism-infected chronic wound healing.

A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity.

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl2 (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t1/2) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl2 complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.

Photorelease Dynamics of Nitric Oxide from Cysteine-Bound Roussin's Red Ester.

Nitric oxide (NO) can either boost or impede the growth of cancer cells depending on its concentration. Therefore, any anticancer treatment using NO requires precisely controlled NO administration to the target cells in terms of dosage and timing. In this context, photochemically activated NO donors were actively explored, but their detailed NO-releasing dynamics, which is crucial for their use, is not known yet. We determined detailed photoexcitation dynamics of a stable, nontoxic, and water-soluble NO precursor, cysteine-bound Roussin's Red Ester (Cys-RRE), including secondary reactions of the nascent photoproducts. The primary quantum yields of the NO dissociation from the photoexcited Cys-RRE were found to be 24-54% depending on the excitation wavelength; however, the geminate rebinding of NO with the nascent radical reduced the level of biologically available NO to as low as 12%. Such information is useful to achieve efficient NO delivery to practical chemical and biological targets.

Review of a Potential Novel Approach for Erectile Dysfunction: Light-Controllable Nitric Oxide Donors and Nanoformulations.

INTRODUCTION: Nitric oxide (NO) is known as the key factor involved in initiating and maintaining an erection. Therefore, NO supplementation may be a target for erectile dysfunction. However, the use of NO donors carries the risk of systemic side effects. Recently, novel NO donors, such as a light-controllable NO donor or NO donor in nanoparticles, have been developed. In this review, we introduce such novel compounds and methods. AIM: To review light-controllable and nanotechnological NO donors for the treatment of erectile dysfunction. METHODS: We conducted a review of relevant articles via PubMed in December 2018. MAIN OUTCOME MEASURES: In this study, we reviewed novel NO donors, such as light-controllable NO donors and nanotechnological NO donors. RESULTS: Some light-controllable NO donors have been already reported. A light-controllable NO donor without metal has also been recently developed. Light-controllable NO donors and light irradiation can control the release of NO spatiotemporally. In an isometric tension study, a relaxing response of the aortic tissue and penile corpus cavernosum was observed under light irradiation with a light-controllable NO donor. In addition, the effects of nanoparticles and nanoemulsions containing sodium nitrate on erectile function have been reported. The nanoformulation containing an NO donor can likely be absorbed percutaneously and, thus, enhance erectile function. CONCLUSIONS: A light-controllable NO donor might be useful for treating erectile dysfunction because light irradiation is a convenient method to be applied for patients. However, light permeability might be an issue that needs to be solved. Nanoformulation is also likely to be a useful, non-invasive approach. The application of these procedures and compounds may help in the development of future treatments for erectile dysfunction. Hotta Y, Kataoka T, Taiki Mori T, et al. Review of a Potential Novel Approach for Erectile Dysfunction: Light-Controllable Nitric Oxide Donors and Nanoformulations. Sex Med Rev 2020;8:297-302.

A lysosome specific theranostic NO donor inhibits cancer cells by stimuli responsive molecular self-decomposition with an on-demand fluorescence pattern.

The anticancer mechanism of NO is difficult to study owing to its short lifetime and high reactivity. Thus, a theranostic anticancer NO donor assembled with NO on-demand release abilities, accurate lysosome location capabilities and signal feedback behavior was developed. Profiting from the theranostic properties, the specific mechanism was comprehensively studied. Spectral and cell imaging studies revealed that the as prepared NO donors could release NO in solution or within cancer cells. Fluorescence co-dyeing experiments demonstrated that Mo-Nap-NO entered lysosomes specifically and disrupted them after being triggered by light. Upon irradiation with 460 nm visible light, both the donors demonstrated considerable in vitro anticancer effects. A further mechanistic study showed that after entering the lysosome and being triggered by 460 nm irradiation, NO ruptured the lysosome, resulting in the release of cathepsin D into the cytosol, which activated the caspase3 mediated apoptosis pathway.

Comprehensive study of nitrofuroxanoquinolines. New perspective donors of NO molecules.

The goal of present work is the study of NO releasing mechanisms in nitrofuroxanoquinoline (NFQ) derivatives. Mechanisms of their structural non-rigidity and pathways of NO donation - spontaneous or under the action of sulfanyl radicals or photoirradiation - were considered in details, both experimentally and quantum chemically. Furoxan-containing systems of the discussed type are not capable of spontaneous or photoinduced decomposition under mild conditions, and sulfanyl (radical) induced processes are the most preferable. It was shown that appropriate modification of NFQ through [3 + 2] cycloaddition and subsequent aromatization is a powerful tool to design new prospective donors of NO molecule. Two newly obtained NFQ derivatives were proven to have unusually high NO activity in full accordance with the theoretical model. We hope that these examples will encourage community to seek for new NO active molecules among cycloadducts and modified furoxanes.

Contact Lenses Delivering Nitric Oxide under Daylight for Reduction of Bacterial Contamination.

Ocular infection due to microbial contamination is one of the main risks associated with the wearing of contact lens, which demands novel straightforward strategies to find reliable solutions. This contribution reports the preparation, characterization and biological evaluation of soft contact lenses (CL) releasing nitric oxide (NO), as an unconventional antibacterial agent, under daylight exposure. A tailored NO photodonor (NOPD) was embedded into commercial CL leading to doped CL with an excellent optical transparency (transmittance = 100%) at λ ≥ 450 nm. The NOPD results homogeneously distributed in the CL matrix where it fully preserves the photobehavior exhibited in solution. In particular, NO release from the CL and its diffusion in the supernatant physiological solution is observed upon visible light illumination. The presence of a blue fluorescent reporting functionality into the molecular skeleton of the NOPD, which activates concomitantly to the NO photorelease, allows the easy monitoring of the NO delivery in real-time and confirms that the doped CL work under daylight exposure. The NO photoreleasing CL are well-tolerated in both dark and light conditions by corneal cells while being able to induce good growth inhibition of Staphylococcus aureus under visible light irradiation. These results may pave the way to further engineering of the CL with NOPD as innovative ocular devices activatable by sunlight.

Controlled light-induced gas phase nitric oxide release from S-nitrosothiol-doped silicone rubber films.

The light induced nitric oxide (NO) release properties of S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO) NO donors doped within polydimethylsiloxane (PDMS) films (PDMS-SNAP and PDMS-GSNO respectively) for potential inhaled NO (iNO) applications is examined. To achieve photolytic release of gas phase NO from the PDMS-SNAP and PDMS-GSNO films, narrow-band LED light sources are employed and the NO concentration in a N2 sweep gas above the film is monitored with an electrochemical NO sensor. The NO release kinetics using LED sources with different nominal wavelengths and optical power densities are reported. The effect of the NO donor loading within the PDMS films is also examined. The NO release levels can be controlled by the LED triggered release from the NO donor-doped silicone rubber films in order to generate therapeutic levels in a sweep gas for suitable durations potentially useful for iNO therapy. Hence this work may lay the groundwork for future development of a highly portable iNO system for treatment of patients with pulmonary hypertension, hypoxemia, and cystic fibrosis.

A molecular hybrid producing simultaneously singlet oxygen and nitric oxide by single photon excitation with green light.

Combination of photosensitizers (PS) for photodynamic therapy with NO photodonors (NOPD) is opening intriguing horizons towards new and still underexplored multimodal anticancer and antibacterial treatments not based on "conventional" drugs and entirely controlled by light stimuli. In this contribution, we report an intriguing molecular hybrid based on a BODIPY light-harvesting antenna that acts simultaneously as PS and NOPD upon single photon excitation with the highly biocompatible green light. The presented hybrid offers a combination of superior advantages with respect to the other rare cases reported to date, meeting most of the key criteria for both PSs and NOPDs in the same molecular entity such as: (i) capability to generate 1O2 and NO with single photon excitation of biocompatible visible light, (ii) excellent 1O2 quantum yield and NO quantum efficiency, (iii) photogeneration of NO independent from the presence of oxygen, (iv) large light harvesting properties in the green region. Furthermore, this compound together with its stable photoproduct, is well tolerated by both normal and cancer cells in the dark and exhibits bimodal photomortality of cancer cells under green light excitation due to the combined action of the cytotoxic 1O2 and NO.

Mannoside and 1,2-mannobioside ß-cyclodextrin-scaffolded NO-photodonors for targeting antibiotic resistant bacteria.

Two ß-cyclodextrin derivatives randomly appended on the primary face with both the nitric oxide (NO) photodonor 4-nitro-3-(trifluoromethyl)aniline and a mannose or α(1→2)mannobioside residue are reported to construct targeted NO photoreleasing nanocarriers. 2D ROESY and PGSE NMR suggested supramolecular homodimerization in water by inclusion of the nitroaniline group into the facing macrocycle cavities. Isothermal titration calorimetry on their concanavalin A lectin binding showed an exothermic binding event to the lectin and an endothermic process during the dilution of the conjugates. Both α(1→2)mannobioside and the nitroaniline moieties significantly enhanced the binding to the lectin. These effects might arise from a better fit within the carbohydrate-recognition site in the former case and a multivalent effect caused by homodimerization in the latter. Direct detection of NO by amperometric technique shows that both ß-cyclodextrin derivatives release this radical upon excitation with visible light with higher efficiency than the unfunctionalized NO photodonor.

Tuning the Hydrophobicity of a Mitochondria-Targeted NO Photodonor.

A few compounds in which the nitric oxide (NO) photodonor N-[4-nitro-3-(trifluoromethyl)phenyl]propane-1,3-diamine is joined to the mitochondria-targeting alkyltriphenylphosphonium moiety via flexible spacers of variable length were synthesized. The lipophilicity of the products was evaluated by measuring their partition coefficients in n-octanol/water. The obtained values, markedly lower than those calculated, are consistent with the likely collapsed conformation assumed by the compounds in solution, as suggested by molecular dynamics simulations. The capacity of the compounds to release NO under visible light irradiation was evaluated by measuring nitrite production by means of the Griess reaction. The accumulation of compounds in the mitochondria of human lung adenocarcinoma A549 cells was assessed by UPLC-MS. Interestingly, compound 13 [(9-((3-((4-nitro-3-(trifluoromethyl)phenyl)amino)propyl)amino)-9-oxononyl) triphenylphosphonium bromide] displayed both the highest accumulation value and high toxicity toward A549 cells upon irradiation-mediated NO release in mitochondria.

Super-Resolution Monitoring of Mitochondrial Dynamics upon Time-Gated Photo-Triggered Release of Nitric Oxide.

Nitric oxide (NO) potentially plays a regulatory role in mitochondrial fusion and fission, which are vital to cell survival and implicated in health, disease, and aging. Molecular tools facilitating the study of the relationship between NO and mitochondrial dynamics are in need. We have recently developed a novel NO donor (NOD550). Upon photoactivation, NOD550 decomposes to release two NO molecules and a fluorophore. The NO release could be spatially mapped with subdiffraction resolution and with a temporal resolution of 10 s. Due to the preferential localization of NOD550 at mitochondria, morphology and dynamics of mitochondria could be monitored upon NO release from NOD550.

Preparation of non-heme {FeNO}7 models of cysteine dioxygenase: sulfur versus nitrogen ligation and photorelease of nitric oxide.

We present the synthesis and spectroscopic characterization of [Fe(NO)(N3PyS)]BF4 (3), the first structural and electronic model of NO-bound cysteine dioxygenase. The nearly isostructural all-N-donor analogue [Fe(NO)(N4Py)](BF4)2 (4) was also prepared, and comparisons of 3 and 4 provide insight regarding the influence of S vs N ligation in {FeNO}(7) species. One key difference occurs upon photoirradiation, which causes the fully reversible release of NO from 3, but not from 4.

Fabrication and characterization of a nitric oxide-releasing nanofibrous gelatin matrix.

Nitric oxide (NO) plays an important role in cardiovascular homeostasis, immune responses, and wound repair. The pro-angiogenic and antimicrobial properties of NO has stimulated the development of NO-releasing materials for wound dressings. Gelatin, an abundant natural biodegradable polymer derived from collagen, is able to promote wound repair. S-Nitroso-N-acetylpenicillamine (SNAP) can release NO under physiological conditions and when exposed to light. The objective of this project was to fabricate a NO-releasing gelatin-based nanofibrous matrix with precise light-controllable ability. Results showed that under controlled phase separation fabrication conditions, the gelatin formed a highly porous matrix with the nanofiber diameter ranging from 50 to 500 nm. Importantly, the removal of the trace amount of divalent metal ions within gelatin generated a more stable nanofibrous structure. N-acetyl-D-penicillamine (NAP) was functionalized onto the matrix and nitrosated with t-butyl nitrite, yielding a SNAP-gelatin matrix. Analysis of the photoinitiated NO-release showed that the SNAP-gelatin matrices released NO in a highly controllable manner. Application of increasing light intensities yielded increased NO flux from the matrices. In addition, the dried matrices stored in dark at 4 °C maintained stable NO storage capacity, and the purified (ion-removed) gelatin preserved higher NO-releasing capacity than nonpurified gelatin. The antibacterial effect from the SNAP-gelatin matrices was demonstrated by exposing Staphylococcus aureus ( S. aureus ) to a light-triggered NO flux. This controllable NO-releasing scaffold provides a potential antibacterial therapeutic approach to combat drug resistant bacteria.

Photoactive ruthenium nitrosyls as NO donors: how to sensitize them toward visible light.

Nitric oxide (NO) can induce apoptosis (programmed cell death) at micromolar or higher doses. Although cell death via NO-induced apoptosis has been studied quite extensively, the targeted delivery of such doses of NO to infected or malignant tissues has not been achieved. The primary obstacle is indiscriminate NO release from typical systemic donors such as glycerin trinitrate: once administered, the drug travels throughout the body, and NO is released through a variety of enzymatic, redox, and pH-dependent pathways. Photosensitive NO donors have the ability to surmount this difficulty through the use of light as a localized stimulus for NO delivery. The potential of the method has prompted synthetic research efforts toward new NO donors for use as photopharmaceuticals in the treatment of infections and malignancies. Over the past few years, we have designed and synthesized several metal nitrosyls (NO complexes of metals) that rapidly release NO when exposed to low-power (milliwatt or greater) light of various wavelengths. Among them, the ruthenium nitrosyls exhibit exceptional stability in biological media. However, typical ruthenium nitrosyls release NO upon exposure to UV light, which is hardly suitable for phototherapy. By following a few novel synthetic strategies, we have overcome this problem and synthesized a variety of ruthenium nitrosyls that strongly absorb light in the 400-600-nm range and rapidly release NO under such illumination. In this Account, we describe our progress in designing photoactive ruthenium nitrosyls as visible-light-sensitive NO donors. Our research has shown that alteration of the ligands, in terms of (i) donor atoms, (ii) extent of conjugation, and (iii) substituents on the ligand frames, sensitizes the final ruthenium nitrosyls toward visible light in a predictable fashion. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations provide guidance in this "smart design" of ligands. We have also demonstrated that direct attachment of dye molecules as light-harvesting antennas also sensitize ruthenium nitrosyls to visible light, and TDDFT calculations provide insight into the mechanisms of sensitization by this technique. The fluorescence of the dye ligands makes these NO donors "trackable" within cellular matrices. Selected ruthenium nitrosyls have been used to deliver NO to cellular targets to induce apoptosis. Our open-design strategies allow the isolation of a variety of these ruthenium nitrosyls, depending on the choices of the ligand frames and dyes. These designed nitrosyls will thus be valuable in the future endeavor of synthesizing novel pharmaceuticals for phototherapy.

Nitric oxide photogeneration from trans-Cr(cyclam)(ONO)(2)(+) in a reducing environment. activation of soluble guanylyl cyclase and arterial vasorelaxation.

The chromium(III) nitrito complex trans-Cr(cyclam)(ONO)(2)(+) (1) is a very promising photochemical precursor for nitric oxide delivery to physiological targets. Here, we demonstrate that visible wavelength excitation of 1 in solutions containing thiol reductants such as the biological antioxidant glutathione (GSH) leads to permanent reaction even under anaerobic conditions, resulting in high quantum yield NO release. The nitric oxide formed under such conditions is sufficient, even at muM concentrations of 1 and using a low-intensity light source, to activate the enzyme soluble guanylyl cyclase (sGC). We also demonstrate that photolysis of 1 in the nM concentration range with a portable blue LED leads to vasorelaxation of porcine coronary arterial rings, a process also attributed to the NO activation of sGC.

Sensitization of ruthenium nitrosyls to visible light via direct coordination of the dye resorufin: trackable NO donors for light-triggered NO delivery to cellular targets.

Three nitrosyl-dye conjugates, namely, [(Me 2bpb)Ru(NO)(Resf)] ( 1-Resf), [(Me 2bQb)Ru(NO)(Resf)] ( 2-Resf), and [((OMe) 2bQb)Ru(NO)(Resf)] ( 3-Resf) have been synthesized via direct replacement of the chloride ligand of the parent {Ru-NO} (6) nitrosyls of the type [(R 2byb)Ru(NO)(L)] with the anionic tricyclic dye resorufin (Resf). The structures of 1-Resf- 3-Resf have been determined by X-ray crystallography. The dye is coordinated to the ruthenium centers of these conjugates via the phenolato-O atom and is trans to NO. Systematic red shift of the d pi(Ru) --> pi*(NO) transition of the parent nitrosyls [(R 2byb)Ru(NO)(L)] due to changes in R and y in the equatorial tetradentate ligand R 2byb (2-) results in its eventual merge with the intense absorption band of the dye around 500 nm in 3-Resf. Unlike the UV-sensitive parent [(R 2byb)Ru(NO)(L)] nitrosyls, these dye-sensitized nitrosyls rapidly release NO when exposed to visible light (lambda >/= 465 nm). Comparison of the photochemical parameters reveals that direct coordination of the light-harvesting chromophore to the ruthenium center in the present nitrosyls results in a significantly greater extent of sensitization to visible light compared to nitrosyls with appended chromophore (linked via alkyl chains). 1-Resf has been employed as a "trackable" NO donor to promote NO-induced apoptosis in MDA-MB-231 human breast cancer cells under the control of light. The results of this work demonstrate that (a) the d pi(Ru) --> pi*(NO) transition (photoband) of {Ru-NO} (6) nitrosyls can be tuned into visible range via careful alteration of the ligand frame(s) and (b) such nitrosyls can be significantly sensitized to visible light by directly ligating a light-harvesting chromophore to the ruthenium center. The potential of these photosensitive nitrosyl-dye conjugates as (i) biological tools to study the effects of NO in cellular environments and (ii) "trackable" NO donors in photodynamic therapy of malignancies (such as skin cancer) has been discussed.

Near-infrared light activated release of nitric oxide from designed photoactive manganese nitrosyls: strategy, design, and potential as NO donors.

Two new manganese complexes derived from the pentadentate ligand N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-quinoline-2-carboxamide, PaPy2QH, where H is dissociable proton), namely, [Mn(PaPy2Q)(NO)]ClO4 (2) and [Mn(PaPy2Q)(OH)]ClO4 (3), have been synthesized and structurally characterized. The Mn(III) complex [Mn(PaPy2Q)(OH)]ClO4 (3), though insensitive to dioxygen, reacts with nitric oxide (NO) to afford the nitrosyl complex [Mn(PaPy2Q)(NO)]ClO4 (2) via reductive nitrosylation. This diamagnetic {Mn-NO}6 nitrosyl exhibits nuNO at 1725 cm-1 and is highly soluble in water, with lambdamax at 500 and 670 nm. Exposure of solutions of 2 to near-infrared (NIR) light (810 nm, 4 mW) results in bleaching of the maroon solution and detection of free NO by an NO-sensitive electrode. The quantum yield of 2 (Phi = 0.694 +/- 0.010, lambdairr = 550 nm, H2O) is much enhanced over the first generation {Mn-NO}6 nitrosyl derived from analogous polypyridine ligand, namely, [Mn(PaPy3)(NO)]ClO4 (1, Phi = 0.385 +/- 0.010, lambdairr = 550 nm, H2O), reported by this group in a previous account. Although quite active in the visible range (500-600 nm), 1 exhibits very little photoactivity under NIR light. Both 1 and 2 have been incorporated into sol-gel (SG) matrices to obtain nitrosyl-polymer composites 1.SG and 2.SG. The NO-donating capacities of the polyurethane-coated hybrid materials 1.HM and 2.HM have been determined. 2.HM has been used to transfer NO to reduced myoglobin with 780 nm light. The various strategies for synthesizing photosensitive metal nitrosyls have been discussed to establish the merits of the present approach. The results of the present study confirm that proper ligand design is a very effective way to isolate photoactive manganese nitrosyls that could be used to deliver NO to biological targets under the control of NIR light.

The macrocyclic effect and vasodilation response based on the photoinduced nitric oxide release from trans-[RuCl(tetraazamacrocycle)NO](2+).

Irradiation of trans-[RuCl(cyclam)(NO)](2+), cyclam is 1,4,8,11-tetraazacyclotetradecane, at pHs 1-7.4, with near UV light results in the release of NO and formation of trans-[Ru(III)Cl(OH)(cyclam)](+) with pH dependent quantum yields (from approximately 0.01 to 0.16 mol Einstein(-1)) lower than that for trans-[RuCl([15]aneN(4))(NO)](2+), [15]aneN(4) is 1,4,8,12-tetaazacyclopentadecane, (0.61 mol Einstein(-1)). After irradiation with 355 nm light, the trans-[RuCl([15]aneN(4))(NO)](2+) induces relaxation of the aortic ring, whereas the trans-[RuCl(cyclam)(NO)](2+) complex does not. The relaxation observed with trans-[RuCl([15]aneN(4))(NO)](2+) is consistent with a larger quantum yield of release of NO from this complex.