Peroxynitrite (ONOO−, PON) is a powerful oxidizing agent generated in vivo by the diffusion-limited reaction of nitric oxide (NO) and superoxide (O₂˙⁻) radicals. Under oxidative stress, cumulated peroxynitrite levels are associated with chronic inflammatory disorders and other pathophysiological conditions. The accurate detection of peroxynitrite in biological systems is important, not only to understand the genesis and development of diseases, but also to explore and design potential therapeutics. Herein, a manganese oxide/hemin-modified graphene interface is explored as a platform for peroxynitrite amperometric detection. Hemin-functionalized reduced graphene oxide was further modified with manganese oxide nanoparticles to provide a composite material with catalytic activity toward the electrochemical oxidation of peroxynitrite. The morphology of the composite material was characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and UV-Vis absorption measurements. We investigated the electrocatalytic oxidation of peroxynitrite on graphite electrodes modified with the composite material using cyclic voltammetry and amperometry. The results showed that the incorporation of manganese oxide nanoparticles into graphene/hemin material enhances the catalytic detection of peroxynitrite compared to graphene/hemin alone.

Background: Investigation of the direct link between l -carnitine (LC), a quaternary ammonium compound that facilitates the passage of unsaturated fatty acids into the mitochondrial matrix, and free calcium (Ca ²⁺ ) is needed to explain a number of varying results obtained from different in vitro and in vivo studies of LC as a supplement. Methods: The chemical structure of LC, which contains oxygen ligand atoms, prompted to measure its activity as a Ca ²⁺ chelator. The measurement was carried out spectrophotometrically by measuring the reduction in the formation of Ca ²⁺ - o -cresolphthalein complexone (Ca-CPC) in the presence of different doses of LC (0.075, 0.75, and 7.5 mM) compared to the control (0.0 mM LC). Results: The effect of LC was measured as a free entity in solution and when added to human serum. Our results showed a significant decrease (p<0.05) in the average absorbance of Ca-CPC in the presence of LC compared to the control. Conclusions: In conclusion, LC exhibits a significant Ca ²⁺ chelating activity. As Ca ²⁺ is vital in the biochemical and physiological processes of living cells, LC could be affecting the calcium-dependent biological systems by limiting the levels of free Ca ²⁺ . Examples include decelerating the blood clotting process, amplifying the effect of anticoagulants, reducing nitric oxide synthase activity, inhibiting platelet aggregation, and decreasing sperm motility.

Introduction: Breast cancer is a significant cause of mortality in women globally, and current treatment approaches face challenges due to side effects and drug resistance. Nanotechnology offers promising solutions by enabling targeted drug delivery and minimizing toxicity to normal tissues.Methods: In this study, we developed a composite platform called (Alg-AgNPs-CisPt), consisting of silver nanoparticles coated with an alginate hydrogel embedding cisplatin. We examined the effectiveness of this nanocomplex in induce synergistic cytotoxic effects on breast cancer cells.Results and Discussion: Characterization using various analytical techniques confirmed the composition of the nanocomplex and the distribution of its components. Cytotoxicity assays and apoptosis analysis demonstrated that the nanocomplex exhibited greater efficacy against breast cancer cells compared to AgNPs or cisplatin as standalone treatments. Moreover, the nanocomplex was found to enhance intracellular reactive oxygen species levels, further validating its efficacy. The synergistic action of the nanocomplex constituents offers potential advantages in reducing side effects associated with higher doses of cisplatin as a standalone treatment. Overall, this study highlights the potential of the (Alg-AgNPs-CisPt) nanocomplex as a promising platform embedding components with synergistic action against breast cancer cells.

Nitric oxide (NO), a small free radical molecule, turned out to be pervasive in biology and was shown to have a substantial influence on a range of biological activities, including cell growth and apoptosis. This molecule is involved in signaling and affects a number of physiologic functions. In recent decades, several processes related to cancer, such as angiogenesis, programmed cell death, infiltration, cell cycle progression, and metastasis, have been linked with nitric oxide. In addition, other parallel work showed that NO also has the potential to operate as an anti-cancer agent. As a result, it has gained attention in cancer-related therapeutics. The nitric oxide synthase enzyme family (NOS) is required for the biosynthesis of nitric oxide. It is becoming increasingly popular to develop NO-releasing materials as strong tumoricidal therapies that can deliver sustained high concentrations of nitric oxide to tumor sites. In this paper, we developed NO-releasing materials based on sodium alginate hydrogel. In this regard, alginate hydrogel discs were modified by adsorbing layers of polyethyleneimine and iNOS-oxygenase. These NO-releasing hydrogel discs were prepared using the layer-by-layer film building technique. The iNOS-oxygenase is adsorbed on the positively charged polyethyleneimine (PEI) matrix layer, which was formed on a negatively charged sodium alginate hydrogel. We show that nitric oxide is produced by enzymes contained within the hydrogel material when it is exposed to a solution containing all the components necessary for the NOS reaction. The electrostatic chemical adsorption of the layer-by-layer process was confirmed by FTIR measurements as well as scanning electron microscopy. We then tested the biocompatibility of the resulting modified sodium alginate hydrogel discs. We showed that this NOS-PEI-modified hydrogel is overall compatible with cell growth. We characterized the NOS/hydrogel films and examined their functional features in terms of NO release profiles. However, during the first 24 h of activity, these films show an increase in NO release flux, followed by a gradual drop and then a period of stable NO release. These findings show the inherent potential of using this system as a platform for NO-driven modulation of biological functions, including carcinogenesis.

Purpose: Adsorption and uptake of heavy metals by polymeric nanoparticles is driven by a variety of physicochemical processes. In this work, we examined heavy metal uptake by synthetic melanin nanoparticles and analyzed physicochemical properties that affect the extent of metal uptake by the nanoparticles. Methods: Eumelanin nanoparticles were synthesized in a one-pot fast process from a 5,6-diacetoxy indole precursor that is hydrolyzed in situ into dihydroxy indole (DHI). The method allows the possibility of changing the level of sodium ions that ends up in the nanoparticles. Two variants of synthetic DHI–melanin (low-sodium and high sodium variants) were evaluated and demonstrated different relative adsorption efficiencies for heavy metal cations. Results and Discussion: For the low-sodium DHI–melanin and in terms of percentages of metal ion removal, the relative order of extraction from 50 ppm solutions was Zn²⁺ > Cd²⁺ > Ni²⁺ > Co²⁺ > Cu²⁺ > Pb²⁺, with the extraction percentages ranging from 90% down to 76%, for a 30-minute adsorption time before equilibrium. The lower-sodium DHI–melanin consistently removed more Zn²⁺ than the higher-sodium variant. Electron microscopy (SEM) showed an increase in melanin particle size after metal ions uptake. In addition, X-ray photoelectron spectroscopy (XPS) of DHI–melanin particles with depth profiling after Zn ions uptake supported particle swelling and ion transport within the particles. Conclusion: These initial studies showed the potential of this straightforward synthesis to obtain synthetic DHI–melanin nanoparticles similar to those from biological sources with the possibility to fine-tune their metal adsorption capacity. These synthetic nanoparticles can be used either for the removal of a variety of metal ions or to mimic and study mechanisms of metal uptake by melanin deriving from biological sources, with the potential to understand, for instance, differential heavy metal uptake by various melanic pigments.