Functional mimics of superoxide dismutase enzymes as therapeutic agents

Effects of Strawberry Tree Water Leaf Extract and Arbutin on Biochemical Markers and DNA Integrity in Brain Cells of Lewis Rats

There is growing evidence that arbutin and plant extracts rich in arbutin, such as extracts of the strawberry tree (Arbutus unedo L.), exert a range of beneficial effects, including cyto- and genoprotective properties. This study evaluated the effects of strawberry tree water leaf extract (STE) and arbutin in the brain tissue of Lewis rats. STE or arbutin were administered per os to male and female rats at a dose of 200 mg/kg body weight/day for 14 or 28 days. Treatment outcomes were evaluated using biochemical markers (lipid peroxidation and the activities of the antioxidative enzymes catalase and superoxide dismutase). The effects of the tested substances on DNA integrity in brain cells were evaluated using the alkaline comet assay. The results suggest a high biocompatibility of both tested substances with rat brain tissue. No significant harmful disturbances were observed in the oxidative/antioxidative status or impairments of DNA integrity in the rat brain cells. Nearly all post-treatment values were within tolerable limits as compared to the matched control rats. Such encouraging findings support further research using other subtle biomarkers to clarify the safety aspects of arbutin and STE prior to the development of specific nutraceutical products.

Balanced Duality: H2O2-Based Therapy in Cancer and Its Protective Effects on Non-Malignant Tissues

Conventional cancer therapy strategies, although centered around killing tumor cells, often lead to severe side effects on surrounding normal tissues, thus compromising the chronic quality of life in cancer survivors. Hydrogen peroxide (H2O2) is a secondary signaling molecule that has an array of functions in both tumor and normal cells, including the promotion of cell survival pathways and immune cell modulation in the tumor microenvironment. H2O2 is a reactive oxygen species (ROS) crucial in cellular homeostasis and signaling (at concentrations maintained under nM levels), with increased steady-state levels in tumors relative to their normal tissue counterparts. Increased steady-state levels of H2O2 in tumor cells, make them vulnerable to oxidative stress and ultimately, cell death. Recently, H2O2-producing therapies-namely, pharmacological ascorbate and superoxide dismutase mimetics-have emerged as compelling complementary treatment strategies in cancer. Both pharmacological ascorbate and superoxide dismutase mimetics can generate excess H2O2 to overwhelm the impaired H2O2 removal capacity of cancer cells. This review presents an overview of H2O2 metabolism in the physiological and malignant states, in addition to discussing the anti-tumor and normal tissue-sparing mechanism(s) of, and clinical evidence for, two H2O2-based therapies, pharmacological ascorbate and superoxide dismutase mimetics.

Polymeric Nanozyme with SOD Activity Capable of Inhibiting Self- and Metal-Induced α-Synuclein Aggregation

Despite decades of research, Parkinson's disease is still an idiopathic pathology for which no cure has yet been found. This is partly explained by the multifactorial character of most neurodegenerative syndromes, whose generation involves multiple pathogenic factors. In Parkinson's disease, two of the most important ones are the aggregation of α-synuclein and oxidative stress. In this work, we address both issues by synthesizing a multifunctional nanozyme based on grafting a pyridinophane ligand that can strongly coordinate CuII, onto biodegradable PEGylated polyester nanoparticles. The resulting nanozyme exhibits remarkable superoxide dismutase activity together with the ability to inhibit the self-induced aggregation of α-synuclein into amyloid-type fibrils. Furthermore, the combination of the chelator and the polymer produces a cooperative effect whereby the resulting nanozyme can also halve CuII-induced α-synuclein aggregation.

Bioinspired Photoactive Cu-Halide Coordination Polymers for Reduction Activation and Oxygen Conversion

Natural copper oxygenases provide fundamental principles for catalytic oxidation with kinetically inert molecular oxygen, but it remains a marked challenge to mimic both their structure and function in an entity. Inspired by the CuA enzymatic sites, herein we report two new photoactive binuclear copper-iodine- and bisbenzimidazole-comodified coordination polymers to reproduce the natural oxo-functionalization repertoire in a unique photocatalytic pathway. Under light irradiation, the Cu-halide coordination polymers effectively reduce NHP esters and complete oxygen reduction activation via photoinduced electron transfer for the aerobic oxidative coupling of hydroquinone with terminal alkynes, affording hydroxyl-functionalized ketones with high efficiency and selectivity. This supramolecular approach to developing bioinspired artificial oxygenases that merge transition metal- and photocatalysis supplies a new way to fabricate distinctive photocatalysts with desirable catalytic performances and controllable precise active sites.

Computational Analysis of the Superoxide Dismutase Mimicry Exhibited by a Zinc(II) Complex with a Redox-Active Organic Ligand

Previously, we found that a Zn(II) complex with the redox-active ligand N-(2,5-dihydroxybenzyl)-N,N',N'-tris(2-pyridinylmethyl)-1,2-ethanediamine (H2qp1) was able to act as a functional mimic of superoxide dismutase, despite its lack of a redox-active transition metal. As the complex catalyzes the dismutation of superoxide to form O2 and H2O2, the quinol in the ligand is believed to cycle between three oxidation states: quinol, quinoxyl radical, and para-quinone. Although the metal is not the redox partner, it nonetheless is essential to the reactivity since the free ligand by itself is inactive as a catalyst. In the present work, we primarily use calculations to probe the mechanism. The calculations support the inner-sphere decomposition of superoxide, suggest that the quinol/quinoxyl radical couple accounts for most of the catalysis, and elucidate the many roles that proton transfer between the zinc complexes and buffer has in the reactivity. Acid/base reactions involving the nonmetal-coordinating hydroxyl group on the quinol are predicted to be key to lowering the energy of the intermediates. We prepared a Zn(II) complex with N-(2-hydroxybenzyl)-N,N',N'-tris(2-pyridinylmethyl)-1,2-ethanediamine (Hpp1) that lacks this functional group and found that it could not catalyze the dismutation of superoxide; this confirms the importance of the second, distal hydroxyl group of the quinol.

Unimolecular Cascaded Multienzyme Conjugates Modulate the Microenvironment of Diabetic Wound to Promote Healing

An abnormal microenvironment underlies poor healing in chronic diabetic chronic wounds. However, effectively modulating the microenvironment of the diabetic wound remains a great challenge due to sustained oxidative stress and chronic inflammation. Here, we present a unimolecular enzyme-polymer conjugate that demonstrates excellent multienzymatic cascade activities. The cascaded enzyme conjugates (CECs) were synthesized by grafting poly(N-acryloyl-lysine) (pLAAm) from the glycan moieties of glucose oxidase (GOx) via glycan-initiated polymerization. The resulting CECs exhibited multiple enzymatic properties of GOx, superoxide dismutase mimic, and catalase mimic activities simultaneously. The CECs facilitated the depletion of high blood glucose, ROS scavenging, bacteria-killing, anti-inflammatory effects, and sustained oxygen generation, which restored the microenvironment in diabetic wounds. In vivo results from a diabetic mouse model confirmed the capacity and efficiency of the cascade reaction for diabetic wound healing. Our findings demonstrate that the three-in-one enzyme-polymer conjugates alone can modulate the diabetic microenvironment for wound healing.

A macrocyclic quinol-containing ligand enables high catalase activity even with a redox-inactive metal at the expense of the ability to mimic superoxide dismutase

Previously, we found that linear quinol-containing ligands could allow manganese complexes to act as functional mimics of superoxide dismutase (SOD). The redox activity of the quinol enables even Zn(ii) complexes with these ligands to catalyze superoxide degradation. As we were investigating the abilities of manganese and iron complexes with 1,8-bis(2,5-dihydroxybenzyl)-1,4,8,11-tetraazacyclotetradecane (H4qp4) to act as redox-responsive contrast agents for magnetic resonance imaging (MRI), we found evidence that they could also catalyze the dismutation of H2O2. Here, we investigate the antioxidant behavior of Mn(ii), Fe(ii), and Zn(ii) complexes with H4qp4. Although the H4qp4 complexes are relatively poor mimetics of SOD, with only the manganese complex displaying above-baseline catalysis, all three display extremely potent catalase activity. The ability of the Zn(ii) complex to catalyze the degradation of H2O2 demonstrates that the use of a redox-active ligand can enable redox-inactive metals to catalyze the decomposition of reactive oxygen species (ROS) besides superoxide. The results also demonstrate that the ligand framework can tune antioxidant activity towards specific ROS.

A novel hybrid protein composed of superoxide-dismutase-active Cu(II) complex and lysozyme

A novel hybrid protein composed of a superoxide dismutase-active Cu(II) complex (CuST) and lysozyme (CuST@lysozyme) was prepared. The results of the spectroscopic and electrochemical analyses confirmed that CuST binds to lysozyme. We determined the crystal structure of CuST@lysozyme at 0.92 Å resolution, which revealed that the His15 imidazole group of lysozyme binds to the Cu(II) center of CuST in the equatorial position. In addition, CuST was fixed in position by the weak axial coordination of the Thr89 hydroxyl group and the hydrogen bond between the guanidinium group of the Arg14 residue and the hydroxyl group of CuST. Furthermore, the combination of CuST with lysozyme did not decrease the superoxide dismutase activity of CuST. Based on the spectral, electrochemical, structural studies, and quantum chemical calculations, an O₂^- disproportionation mechanism catalyzed by CuST@lysozyme is proposed.

Increased Efficiency of a Functional SOD Mimic Achieved with Pyridine Modification on a Pyclen-Based Copper(II) Complex

A series of Cu(II) complexes with the formula [CuRPyN3]2+ varying in substitution on the pyridine ring were investigated as superoxide dismutase (SOD) mimics to identify the most efficient reaction rates produced by a synthetic, water-soluble copper-based SOD mimic reported to date. The resulting Cu(II) complexes were characterized by X-ray diffraction analysis, UV-visible spectroscopy, cyclic voltammetry, and metal-binding (log β) affinities. Unique to this approach, the modifications to the pyridine ring of the PyN3 parent system tune the redox potential while exhibiting high binding stabilities without changing the coordination environment of the metal complex within the PyN3 family of ligands. We were able to adjust in parallel the binding stability and the SOD activity without compromising on either through simple modification of the pyridine ring on the ligand system. This goldilocks effect of high metal stabilities and high SOD activity reveals the potential of this system to be explored in therapeutics. These results serve as a guide for factors that can be modified in metal complexes using pyridine substitutions for PyN3, which can be incorporated into a range of applications moving forward.

Diquinol Functionality Boosts the Superoxide Dismutase Mimicry of a Zn(II) Complex with a Redox-Active Ligand while Maintaining Catalyst Stability and Enhanced Activity in Phosphate Solution

In the current work, we demonstrate ligand design concepts that significantly improve the superoxide dismutase (SOD) activity of a zinc complex; the catalysis is enhanced when two quinol groups are present in the polydentate ligand. We investigate the mechanism through which the quinols influence the catalysis and determine the impact of entirely removing a chelating group from the original hexadentate ligand. Our results suggest that SOD mimicry with these compounds requires a ligand that coordinates Zn(II) strongly in both its oxidized and reduced forms and that the activity proceeds through Zn(II)-semiquinone complexes. The complex with two quinols displays greatly enhanced catalytic ability, with the activity improving by as much as 450% over a related complex with a single quinol. In the reduced form of the diquinol complex, one quinol appears to coordinate to the zinc much more weakly than the other. We believe that superoxide can more readily displace this portion of the ligand, facilitating its coordination to the metal center and thereby hastening the SOD reactivity. Despite the presence of two redox-active groups that may communicate through intramolecular hydrogen bonding and redox tautomerism, only one quinol undergoes two-electron oxidation to a para-quinone during the catalysis. After the formation of the para-quinone, the remaining quinol deprotonates and binds tightly to the metal, ensuring that the complex remains intact in its oxidized state, thereby maintaining its catalytic ability. The Zn(II) complex with the diquinol ligand is highly unusual for a SOD mimic in that it performs more efficiently in phosphate solution.

Antioxidant colloids via heteroaggregation of cerium oxide nanoparticles and latex beads

Antioxidant colloids were developed via controlled heteroaggregation of cerium oxide nanoparticles (CeO₂ NPs) and sulfate-functionalized polystyrene latex (SL) beads. Positively charged CeO₂ NPs were directly immobilized onto SL particles of opposite surface charge via electrostatic attraction (SL/Ce composite), while negatively charged CeO₂ NPs were initially functionalized with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte and then, aggregated with the SL particles (SPCe composite). The PDADMAC served to induce a charge reversal on CeO₂ NPs, while the SL support prevented nanoparticle aggregation under conditions, where the dispersions of bare CeO₂ NPs were unstable. Both SL/Ce and SPCe showed enhanced radical scavenging activity compared to bare CeO₂ NPs and were found to mimic peroxidase enzymes. The results demonstrate that SL beads are suitable supports to formulate CeO₂ particles and to achieve remarkable dispersion storage stability. The PDADMAC functionalization and immobilization of CeO₂ NPs neither compromised the peroxidase-like activity nor the radical scavenging potential. The obtained SL/Ce and SPCe artificial enzymes are foreseen to be excellent antioxidant agents in various applications in the biomedical, food, and cosmetic industries.

Ascorbic Acid Ameliorates Cardiac and Hepatic Toxicity Induced by Azithromycin-Etoricoxib Drug Interaction

The complexity of prescribing safe and effective drug therapy is still challenging. Due to the increased number of medications taken by patients, the potential for drug-drug interactions has clinically important consequences. This study focuses on the potential drug-drug interaction between azithromycin and etoricoxib and the possibility of counteracting this adverse reaction by giving ascorbic acid intraperitoneally to male albino rats. Sixty adult male albino rats weighing 150–180 g were used. The rats were allocated into six equal groups. One group was a control, and the others were given azithromycin, etoricoxib, either alone or combination, with one group treated with ascorbic acid and the last group treated with the drug combination and ascorbic acid. Blood samples were collected for measuring AST, ALT, LDH, CK-MB, and troponin alongside antioxidant enzymes and histopathological examination for both liver and heart tissue. The results showed both hepatic and cardiac damage in azithromycin and etoricoxib groups represented by increasing levels of heaptoc enzymes (ALT, AST, LDH, CK-MB, and troponin) with declining antioxidant enzymes and elevation of malondialdehyde and the appearance of hepatic and cardiac toxicities. Upon administration, ascorbic acid ameliorated all the mentioned biochemical parameters. In conclusion, ascorbic acid has great antioxidant capacities and hepatic and cardiac ameliorative effects and can alleviate drug interaction toxicity.

Tetrahedral Keggin Core Tunes the Visible Light-Assisted Catalase-Like Activity of Icosahedral Keplerate Shell

In this work, the effect of Keggin polyoxometalates encapsulated in Keplerate {Mo₇₂Fe₃₀} shell (K shell) on the visible light-assisted catalase-like activity (H₂O₂ dismutation) of the resulting core-shell clusters PMo₁₂@K, SiMo₁₂@K, and BW₁₂@K was investigated. Superior photodismutation activity of PMo₁₂@K compared to that of K shell and two other core-shell clusters was discovered. The homogeneity of PMo₁₂@K and its improved oxidative stability, increased redox potential, and reduced band gap caused by a synergistic effect between the Keplerate shell and Keggin core seem reasonable to explain such a superiority. The light-dependent photocatalytic performance of PMo₁₂@K evaluated by action spectra revealed a maximum apparent quantum efficiency (AQY) at 400 nm, demonstrating the visible light-driven photocatalytic reaction. A first-order rate constant of 2 × 10^-4 s^-1 and activation energy of 108.8 kJ mol^-1 alongside a turnover frequency of 0.036 s^-1 and a total turnover number of up to ∼3800 approved the effective photocatalytic activity and improved the oxidative stability of PMo₁₂@K. A nonradical photocatalytic mechanism through a Fe-OOH intermediate was proposed. Thus, the structure, optical activity, and oxidative stability of a host Keplerate-type nanocluster can be tuned significantly by encapsulation of a guest, like "cluster-in-cluster" structures, which opens the scope for introducing new visible light-sensitive hierarchical nanostructures.

Antidiabetic Drug Sitagliptin with Divalent Transition Metals Manganese and Cobalt: Synthesis, Structure, Characterization Antibacterial and Antioxidative Effects in Liver Tissues

Metals and their complexes have an increasing number of medical applications. Sitagliptin (STG) acts as an antidiabetic drug. Mn(II) and Co(II) complexes were studied and characterized based on physical characterization, FT-IR, DG/TG, XRD, ESM, and TEM. Data revealed that STG acts as a bidentate ligand through the oxygen atom of a carbonyl group and the nitrogen atom of an amino group. Magnetic measurement data revealed that the Mn/STG metal complex has a square planner geometry. The experiment was performed on 40 male albino rats who were divided into four groups: the control group, STG group, group treated with STG/Mn, and group treated with Co/STG. Biomarkers for hepatic enzymes and antioxidants were found in the blood, and hepatic tissue histology was evaluated. STG in combination with Mn and Co administration showed potent protective effects against hepatic biochemical alterations induced by STG alone, as well as suppressing oxidative stress and structural alterations. These complexes prevented any stress and improved hepatic enzymatic levels more than STG alone. The STG/Mn complex was highly effective against Bacillus subtilis and Streptococcus pneumonia, while STG/Co was highly effective against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureas. Therefore, STG combined with Mn and Co produced a synergistic effect against oxidative stress and improved the histological structure of the liver tissues. STG metal complexes with Mn and Co showed the most potential ameliorative antioxidant and hepatoprotective effects.

An antioxidant boehmite amino-nanozyme able to disaggregate Huntington's inclusion bodies

A novel amino-nanozyme, based on boehmite nanoparticles (BNPs) functionalised with a tetra-azapyridinophane (L1), has been designed to undermine some of the key issues underlying Huntington disease. L1 forms Cu²⁺ complexes with a striking SOD activity, while when grafted to the BNPs displays mitoROS scavenging properties and ability to disaggregate mutant huntingtin deposits in cells.

Exceptional Manganese(II) Stability and Manganese(II)/Zinc(II) Selectivity with Rigid Polydentate Ligands

While MnII complexes meet increasing interest in biomedical applications, ligands are lacking that enable high MnII complex stability and selectivity vs. ZnII , the most relevant biological competitor. We report here two new bispidine derivatives, which provide rigid and large coordination cavities that perfectly match the size of MnII , yielding eight-coordinate MnII complexes with record stabilities. In contrast, the smaller ZnII ion cannot accommodate all ligand donors, resulting in highly strained and less stable six-coordinate complexes. Combined theoretical and experimental data (X-ray crystallography, potentiometry, relaxometry and 1 H NMR spectroscopy) demonstrate unprecedented selectivity for MnII vs. ZnII (KMnL /KZnL of 108 -1010 ), in sharp contrast to the usual Irving-Williams behavior, and record MnII complex stabilities and inertness with logKMnL close to 25.

Enhanced degradation of tetracycline by Cu(II) complexation in the FeS/sulfite system

This study applied a mineral material of FeS to activate sulfite for efficient degradation of TTC in the presence of Cu(II) based on the identified complexation mechanism through UV-Vis spectra, FTIR spectroscopy and DFT calculation. pH plays an important role in TTC degradation and the initial pH of 6 and 7 were the divide in the contributions of FeS/sulfite oxidation and complex-precipitation. TTC-Cu(II) exhibits a superior promoting effect on the TTC degradation in FeS/sulfite system due to the improvement of TTC electron transfer reactivity and Fe(II) dissolution from FeS. Moreover, the formation of Cu(I) improved the recycling of Fe(II) from Fe(III). Dissolved oxygen-dependent free radicals' generation was confirmed, and TTC degradation was mainly attributed to SO₄^·- and ·OH. The characterization of FeS surface through XPS, XRD, SEM-EDS, Fe(II) deactivation tests, together with the comparison of pseudo-first-order rate constants for TTC degradation by FeS and ferrous ion supported the important role of surface and dissolved Fe(II) in sulfite activation. Furthermore, reasonable degradation pathways of TTC have been proposed according to the detected products by LC-MS. This work highlights the important role of pH, DO and Cu(II) complexation in sulfite activation and TTC degradation, furnishing theoretical support for further relevant studies.

Albumin-mediated “Unlocking” of supramolecular prodrug-like nanozymes toward selective imaging-guided phototherapy

An adaptive nanozyme without producing off-target toxicity has been successfully applied in phototherapy.

An antioxidant system through conjugating superoxide dismutase onto metal-organic framework for cardiac repair

Acute myocardial infarction (AMI) remains a dominant origin of morbidity, mortality and disability worldwide. Increases in reactive oxygen species (ROS) are key contributor to excessive cardiac injury after AMI. Here we developed an immobilized enzyme with Superoxide Dismutase (SOD) activity cross-link with Zr-based metal-organic framework (ZrMOF) (SOD-ZrMOF) for mitigate ROS-caused injury. In vitro and in vivo evidence indicates that SOD-ZrMOF exhibits excellent biocompatibility. By efficiently scavenging ROS and suppressing oxidative stress, SOD-ZrMOF can protect the function of mitochondria, reduce cell death and alleviate inflammation. More excitingly, long-term study using an animal model of AMI demonstrated that SOD-ZrMOF can reduce the infarct area, protect cardiac function, promote angiogenesis and inhibit pathological myocardial remodeling. Therefore, SOD-ZrMOF holds great potential as an efficacious and safe nanomaterial treatment for AMI.

Quinol-containing ligands enable high superoxide dismutase activity by modulating coordination number, charge, oxidation states and stability of manganese complexes throughout redox cycling

Reactivity assays previously suggested that two quinol-containing MRI contrast agent sensors for H₂O₂, [Mn(H2qp1)(MeCN)]²⁺ and [Mn(H4qp2)Br₂], could also catalytically degrade superoxide. Subsequently, [Zn(H2qp1)(OTf)]⁺ was found to use the redox activity of the H2qp1 ligand to catalyze the conversion of O₂˙⁻ to O₂ and H₂O₂, raising the possibility that the organic ligand, rather than the metal, could serve as the redox partner for O₂˙⁻ in the manganese chemistry. Here, we use stopped-flow kinetics and cryospray-ionization mass spectrometry (CSI-MS) analysis of the direct reactions between the manganese-containing contrast agents and O₂˙⁻ to confirm the activity and elucidate the catalytic mechanism. The obtained data are consistent with the operation of multiple parallel catalytic cycles, with both the quinol groups and manganese cycling through different oxidation states during the reactions with superoxide. The choice of ligand impacts the overall charges of the intermediates and allows us to visualize complementary sets of intermediates within the catalytic cycles using CSI-MS. With the diquinolic H4qp2, we detect Mn(iii)-superoxo intermediates with both reduced and oxidized forms of the ligand, a Mn(iii)-hydroperoxo compound, and what is formally a Mn(iv)-oxo species with the monoquinolate/mono-para-quinone form of H4qp2. With the monoquinolic H2qp1, we observe a Mn(ii)-superoxo ↔ Mn(iii)-peroxo intermediate with the oxidized para-quinone form of the ligand. The observation of these species suggests inner-sphere mechanisms for O₂˙⁻ oxidation and reduction that include both the ligand and manganese as redox partners. The higher positive charges of the complexes with the reduced and oxidized forms of H2qp1 compared to those with related forms of H4qp2 result in higher catalytic activity (k_cat ∼ 10⁸ M⁻¹ s⁻¹ at pH 7.4) that rivals those of the most active superoxide dismutase (SOD) mimics. The manganese complex with H2qp1 is markedly more stable in water than other highly active non-porphyrin-based and even some Mn(ii) porphyrin-based SOD mimics.

Manganese complexes with polydentate quinol-containing ligands are found to catalyze the degradation of superoxide through inner-sphere mechanisms. The redox activity of the ligand stabilizes higher-valent manganese species.

In Situ Neutral System Synthesis, Spectroscopic, and Biological Interpretations of Magnesium(II), Calcium(II), Chromium(III), Zinc(II), Copper(II) and Selenium(IV) Sitagliptin Complexes

Magnesium(II), calcium(II), chromium(III), zinc(II), copper(II), and selenium(IV) sitagliptin (STG) complexes—with the general formulas [Mg(STG)₂(Cl)₂]·6H₂O, [Ca(STG)₂(Cl)₂], [Cr(STG)₂(Cl)₂]Cl.6H₂O, [Zn(STG)₂(Cl)₂], [Cu(STG)₂(Cl)₂]·2H₂O, and [Se(STG)₂(Cl)₂]Cl₂, respectively—were designed and synthesized by the chemical reactions between metal(II, III, and IV) chloride salts with an STG ligand in situ methanol solvent in a 1:2 stoichiometric ratio (metal:ligand). Tentative structures of the complexes were proposed based on elemental analysis, molar conductance, magnetic moments, thermogravimetric analysis, and spectral (infrared, electronic, and ¹H NMR) data. The particle size and morphological investigation were checked on the bases of scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction analyses. All the Mg²⁺, Ca²⁺, Cr³⁺, Zn²⁺, Cu²⁺, and Se⁴⁺ complexes were found to be six-coordinated, wherein the STG ligands act as bidentate chelating agents. This study demonstrates that pancreatic tissues are affected by the induction of experimental diabetes mellitus and clarifies the potential of the synthesized STG complexes, which was found to more significantly improve insulin secretion and the pancreatic and glycometabolic complications of diabetic rats than STG alone.

Avasopasem manganese synergizes with hypofractionated radiation to ablate tumors through the generation of hydrogen peroxide

Avasopasem manganese (AVA or GC4419), a selective superoxide dismutase mimetic, is in a phase 3 clinical trial (NCT03689712) as a mitigator of radiation-induced mucositis in head and neck cancer based on its superoxide scavenging activity. We tested whether AVA synergized with radiation via the generation of hydrogen peroxide, the product of superoxide dismutation, to target tumor cells in preclinical xenograft models of non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma, and pancreatic ductal adenocarcinoma. Treatment synergy with AVA and high dose per fraction radiation occurred when mice were given AVA once before tumor irradiation and further increased when AVA was given before and for 4 days after radiation, supporting a role for oxidative metabolism. This synergy was abrogated by conditional overexpression of catalase in the tumors. In addition, in vitro NSCLC and mammary adenocarcinoma models showed that AVA increased intracellular hydrogen peroxide concentrations and buthionine sulfoximine- and auranofin-induced inhibition of glutathione- and thioredoxin-dependent hydrogen peroxide metabolism selectively enhanced AVA-induced killing of cancer cells compared to normal cells. Gene expression in irradiated tumors treated with AVA suggested that increased inflammatory, TNFα, and apoptosis signaling also contributed to treatment synergy. These results support the hypothesis that AVA, although reducing radiotherapy damage to normal tissues, acts synergistically only with high dose per fraction radiation regimens analogous to stereotactic ablative body radiotherapy against tumors by a hydrogen peroxide-dependent mechanism. This tumoricidal synergy is now being tested in a phase I-II clinical trial in humans (NCT03340974).

Novel predictor markers for early differentiation between transient tachypnea of newborn and respiratory distress syndrome in neonates

Neonatal Respiratory Distress Syndrome (RDS) and Transient Tachypnea of newborn (TTN) are common similar neonatal respiratory diseases. Study the early predictor markers in differentiation between TTN and RDS in neonates. A prospective case control study which was done in Neonatal Intensive Care Unit (NICU) of Tanta University Hospital (TUH) from September 2016 to March 2018. Three groups of neonates were included in the study: RDS group (45 neonates), TTN group (45 neonates), and control group (45 healthy neonates). There were statistically significant difference (SSD) between our studied three groups as regard serum Malondialdehyde (MDA), Superoxide dismutase SOD, Lactate dehydrogenase (LDH), and blood PH and P-values were 0.001* for these comparative parameters. The ROC curve of RDS cases revealed that the serum MDA Cut off, sensitivity and specificity were 1.87 mmol/L, 98%, 96%, respectively which had the highest sensitivity and specificity followed by the serum SOD then the serum LDH and lastly the blood PH while in TTN cases, the serum MDA Cut off, sensitivity and specificity were 0.74 mmol/L, 96%, 93%, respectively then the serum SOD then the serum LDH and lastly the blood PH. Serum MDA, SOD, LDH, and PH had a beneficial role as early predictors in differentiation between TTN and RDS in neonates.

Biomimetic Design of Mitochondria-Targeted Hybrid Nanozymes as Superoxide Scavengers

Development of enzyme mimics for the scavenging of excessive mitochondrial superoxide (O₂ ^•- ) can serve as an effective strategy in the treatment of many diseases. Here, protein reconstruction technology and nanotechnology is taken advantage of to biomimetically create an artificial hybrid nanozyme. These nanozymes consist of ferritin-heavy-chain-based protein as the enzyme scaffold and a metal nanoparticle core as the enzyme active center. This artificial cascade nanozyme possesses superoxide dismutase- and catalase-like activities and also targets mitochondria by overcoming multiple biological barriers. Using cardiac ischemia-reperfusion animal models, the protective advantages of the hybrid nanozymes are demonstrated in vivo during mitochondrial oxidative injury and in the recovery of heart functionality following infarction via systemic delivery and localized release from adhesive hydrogels (i.e., cardiac patch), respectively. This study illustrates a de novo design strategy in the development of enzyme mimics and provides a promising therapeutic option for alleviating oxidative damage in regenerative medicine.

Catalytic antioxidant nanocomposites based on sequential adsorption of redox active metal complexes and polyelectrolytes on nanoclay particles

An antioxidant nanocomposite was prepared by successive adsorption of redox active metal complexes (copper(ii)-bipyridyl and iron(iii)-citrate) and polyelectrolytes (poly(styrene sulfonate) and poly(diallyldimethyl ammonium)) on layered double hydroxide nanoclay. The experimental conditions were optimized in each preparation step and thus, the final composite formed highly stable colloids, i.e., excellent resistance against salt-induced aggregation was achieved. Due to the synergistic effect of the metal complexes, the developed composite showed remarkable activity in the dismutation of superoxide radicals, close to the one determined for the native superoxide dismutase enzyme. The obtained composite is highly selective for superoxide radical dismutation, while its activity in other antioxidant tests was close to negligible. Structural characterization of the composite revealed that the excellent superoxide radical scavenging ability originated from the advantageous coordination geometry around the copper(ii) center formed upon immobilization. The structure formed around the metal centers led to optimal redox features and consequently, to an improved superoxide dismutase-like activity. The catalytic antioxidant composite is a promising candidate to reduce oxidative stress in industrial manufacturing processes, where natural enzymes quickly lose their activity due to the harsh environmental conditions.

Manganese(II) complexes derived from acyclic ligands having flexible alcohol arms: structural chracterization and SOD and catalase mimetic studies

In this work, a series of seven MnII complexes of noncyclic flexible ligands derived from 2,6-diformylpyridine and ethanolamine or alkyl-substituted ethanolamines were prepared and characterized, six structurally by single-crystal X-ray diffraction studies. The complexes are dichlorido{2,2′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]diethanol}manganese(II), [MnCl2(C11H15N3O2)] or [MnCl2(L1)], (2), bis{μ-2,2′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]diethanol}bis[dithiocyanatomanganese(II)], [Mn2(NCS)4(C11H15N3O2)2] or [Mn2(NCS)4(L1)2], (3), chlorido{1,1′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]bis(propan-2-ol)}manganese(II) chloride monohydrate, [MnCl(C13H19N3O2)(H2O)]Cl·H2O or [MnCl(L2)(H2O)]Cl·H2O, (4), {1,1′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]bis(propan-2-ol)}dithiocyanatomanganese(II), [Mn(NCS)2(C13H19N3O2)] or [Mn(NCS)2(L2)], (5), aquadichlorido{2,2′-dimethyl-2,2′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]bis(propan-1-ol)}manganese(II) 0.3-hydrate, [MnCl2(C15H23N3O2)(H2O)]·0.3H2O or [MnCl2(L3)(H2O)]·0.3H2O, (6), (dimethylformamide){2,2′-dimethyl-2,2′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]bis(propan-1-ol)}dithiocyanatomanganese(II), [Mn(NCS)2(C15H23N3O2)(C3H7NO)] or [Mn(NCS)2(L3)(DMF)], (7), and (dimethylformamide){2,2′-[(pyridine-2,6-diyl)bis(nitrilomethanylylidene)]bis(butan-1-ol)}dithiocyanatomanganese(II) dimethylformamide monosolvate, [Mn(NCS)2(C15H23N3O2)(C3H7NO)]·C3H7NO or [Mn(NCS)2(L4)(DMF)]·DMF, (8). The crystal structure of ligand L1 is also reported, but that of (5) is not. All four ligands (L1–L4) have five potential donor atoms in an N3O2 donor set, i.e. three N (pyridine/diimine donors) and two alcohol O atoms, to coordinate the MnII centre. The N3O2 donor set coordinates to the metal centre in a pentagonal planar arrangement; seven-coordinated MnII complexes were obtained via coordination of two auxiliary ligands (anions or water molecules) at the axial positions. However, in some cases, the alcohol O-atom donors remain uncoordinated, resulting in five- or six-coordinated MnII complexes. The structurally characterized complexes were tested for their catalytic scavenging of superoxide and peroxide. The results indicated that the complexes with coordinated exogenous water or chloride ligands showed higher SOD activity than those with exogenous thiocyanate ligands.

In vitro measurement of superoxide dismutase-like nanozyme activity: a comparative study

Analyzing the SOD-like activity of nanozymes in vitro is of great importance for identifying new nanozymes and predicting their potential biological effects in vivo.

Antioxidant metal oxide nanozymes: role in cellular redox homeostasis and therapeutics

Nanomaterials with enzyme-like activity, generally referred to as ‘nanozymes’, find myriad potential in various biomedical fields. More importantly, the nanoparticles that can functionally mimic the activity of cellular antioxidant enzymes attract tremendous interest owing to their possible therapeutic candidature in oxidative stress-mediated disorders. Oxidative stress culminating due to excess reactive oxygen species (ROS) level and dysregulated cellular antioxidant machinery is implicated in the development and progression of various pathophysiological disorders such as cancer, diabetes, cardiovascular and neurodegenerative diseases. Moreover, the optimum essentiality of ROS due to its pivotal role in cell signaling evokes the requirement of novel artificial antioxidant enzymes that can circumvent the detrimental effects of enhanced ROS levels without perturbing the basal redox status of cells. In recent years, the fast emanating artificial enzymes, i.e. nanozymes with antioxidant enzyme-like activity, has made tremendous progress with their broad applications in therapeutics, diagnostic medicine, bio-sensing, and immunoassay. Among various antioxidant nanoparticles reported till-date, the metal oxide nanozymes have emerged as the most efficient and successful candidates in mimicking the activity of first-line defense antioxidant enzymes, i.e. superoxide dismutase, catalase, and glutathione peroxidase. This review intends to exclusively highlight the development of representative metal oxide-based antioxidant nanozymes capable of maintaining the cellular redox homeostasis and their potential therapeutic significance.

Metal Complexes as Promising Agents for Biomedical Applications

Background::

In this review article, a brief overview of novel metallotherapeutic agents (with an emphasis on the complexes of essential biometals) promising for medical application is presented. We have also focused on the recent work carried out by our research team, specifically the development of redox-active antimicrobial complexes of sterically hindered diphenols with some essential biometals (copper, zinc, nickel).

Results::

The complexes of essential metals (manganese, iron, cobalt, nickel, copper, zinc) described in the review show diverse in vitro biological activities, ranging from antimicrobial and antiinflammatory to antiproliferative and enzyme inhibitory. It is necessary to emphasize that the type of organic ligands in these metal complexes seems to be responsible for their pharmacological activities. In the last decades, there has been a significant interest in synthesis and biological evaluation of metal complexes with redox-active ligands. A substantial step in the development of these redox-active agents is the study of their physicochemical and biological properties, including investigations in vitro of model enzyme systems, which can provide evidence on a plausible mechanism underlying the pharmacological activity. When considering the peculiarities of the pharmacological activity of the sterically hindered diphenol derivatives and their nickel(II), copper(II) and zinc(II) complexes synthesized, we took into account the following: (i) all these compounds are potential antioxidants and (ii) their antimicrobial activity possibly results from their ability to affect the electron-transport chain.

Conclusion::

We obtained novel data demonstrating that the level of antibacterial and antifungal activity in the series of the above-mentioned metal-based antimicrobials depends not only on the nature of the phenolic ligands and complexing metal ions, but also on the lipophilicity and reducing ability of the ligands and metal complexes, specifically regarding the potential biotargets of their antimicrobial action – ferricytochrome c and the superoxide anion radical. The combination of antibacterial, antifungal and antioxidant activity allows one to consider these compounds as promising substances for developing therapeutic agents with a broad spectrum of activities.

Unveiling the reaction mechanism of novel copper N-alkylated tetra-azacyclophanes with outstanding superoxide dismutase activity

Quantum chemical and multiscale calculations reveal the mechanistic pathway of two superoxide dismutase mimetic N-alkylated tetra-azacyclophane copper complexes with remarkable activity. The arrangement of the binding site afforded by the bulky alkyl substituents and the coordinated water molecule as a proton source play key roles in the reaction mechanism.

Rational De Novo Design of a Cu Metalloenzyme for Superoxide Dismutation

Superoxide dismutases (SODs) are highly efficient enzymes for superoxide dismutation and the first line of defense against oxidative stress. These metalloproteins contain a redox-active metal ion in their active site (Mn, Cu, Fe, Ni) with a tightly controlled reduction potential found in a close range around the optimal value of 0.36 V versus the normal hydrogen electrode (NHE). Rationally designed proteins with well-defined three-dimensional structures offer new opportunities for obtaining functional SOD mimics. Here, we explore four different copper-binding scaffolds: H3 (His3 ), H4 (His4 ), H2 DH (His3 Asp with two His and one Asp in the same plane) and H3 D (His3 Asp with three His in the same plane) by using the scaffold of the de novo protein GRα3 D. EPR and XAS analysis of the resulting copper complexes demonstrates that they are good CuII -bound structural mimics of Cu-only SODs. Furthermore, all the complexes exhibit SOD activity, though three orders of magnitude slower than the native enzyme, making them the first de novo copper SOD mimics.

Anti-inflammatory activity of superoxide dismutase mimics functionalized with cell-penetrating peptides

A superoxide dismutase mimic was functionalized with three peptides: -R9, -RRWWRRWRR or -F_x-r-F_x-K (MPP). They were studied in intestinal epithelial cells in an inorganic cellular chemistry approach: quantification, distribution and bio-activity.

Unusual chemistry of Cu(ii) salan complexes: synthesis, characterization and superoxide dismutase activity

Cu(ii)-salan complexes: structural and spectral characterization, solvent assisted ring cleavage and correlation of superoxide dismutase activity with cyclic voltammetry data and steric effects.