Dissecting in vivo and in vitro redox responses using chemogenetics

Hydrogen peroxide (H2O2) is the most abundant reactive oxygen species (ROS) within mammalian cells. At low concentrations, H2O2 serves as a versatile cell signaling molecule that mediates vital physiological functions. Yet at higher concentrations, H2O2 can be a toxic molecule by promoting pathological oxidative stress in cells and tissues. Within normal cells, H2O2 is differentially distributed in a variety of subcellular locales. Moreover, many redox-active enzymes and their substrates are themselves differentially distributed within cells. Numerous reports have described the biological and biochemical consequences of adding exogenous H2O2 to cultured cells and tissues, but many of these observations are difficult to interpret: the effects of exogenous H2O2 do not necessarily replicate the cellular responses to endogenous H2O2. In recent years, chemogenetic approaches have been developed to dynamically regulate the abundance of H2O2 in specific subcellular locales. Chemogenetic approaches have been applied in multiple experimental systems, ranging from in vitro studies on the intracellular transport and metabolism of H2O2, all the way to in vivo studies that generate oxidative stress in specific organs in living animals. These chemogenetic approaches have exploited a yeast-derived d-amino acid oxidase (DAAO) that synthesizes H2O2 only in the presence of its d-amino acid substrate. DAAO can be targeted to various subcellular locales, and can be dynamically activated by the addition or withdrawal of its d-amino acid substrate. In addition, recent advances in the development of highly sensitive genetically encoded H2O2 biosensors are providing a better understanding of both physiological and pathological oxidative pathways. This review highlights several applications of DAAO as a chemogenetic tool across a wide range of biological systems, from analyses of subcellular H2O2 metabolism in cells to the development of new disease models caused by oxidative stress in vivo.

In Vitro Carcinoma Treatment Using Magnetic Nanocarriers under Ultrasound and Magnetic Fields

Nowadays, tumor hypoxia has become a more predominant problem for diagnosis as well as treatment of cancer due to difficulties in delivering chemotherapeutic drugs and their carriers to these regions with reduced vasculature and oxygen supply. In such cases, external physical stimulus-mediated drug delivery, such as ultrasound and magnetic fields, would be effective. In this work, the effect of simultaneous exposure of low-intensity pulsed ultrasound and static magnetic field on colon (HCT116) and hepatocellular (HepG2) carcinoma cell inhibition was assessed in vitro. The treatment, in the presence of anticancer drug, with and without magnetic carrier, significantly increased the reactive oxygen species production and hyperpolarized the cancer cells. As a result, a significant increase in cell inhibition, up to 86%, was observed compared to 50% inhibition with bare anticancer drug. The treatment appears to have relatively more effect on HepG2 cells during the initial 24 h than on HCT116 cells. The proposed treatment was also found to reduce cancer cell necrosis and did not show any inhibitory effect on healthy cells (MC3T3). Our in vitro results suggest that this approach has strong application potential to treat cancer at lower drug dosage to achieve similar inhibition and can reduce health risks associated with drugs.

In Situ Growth of Low-Dimensional Silver Nanoclusters with Their Tunable Plasmonic and Thermodynamic Behavior

Optical properties of noble metal nanostructures associated with localized surface plasmon resonance (SPR) are technically important for optical switches and plasmonic devices. In this work, silver nanoclusters are embedded inside the soda-lime glass matrix, followed by a thermal annealing process in an open air atmosphere for 1 h. The effects of thermal annealing on the plasmonic behavior of Ag nanoclusters embedded in the glass matrix are studied with UV-vis spectroscopy and photoluminescence. In the SPR spectra, a 14 nm blue shift is observed in the visible range under the influence of thermal annealing at a higher temperature. The thermal effects on Ag particle size and SPR have been illustrated for plasmonic properties. The structural and elemental investigation of as-grown Ag nanoclusters is confirmed by X-ray diffraction, high-resolution transmission electron microscope, and X-ray photoelectron spectroscopy. The structural, plasmonic, and thermodynamic properties associated with the growth mechanism of Ag nanoclusters have been explained under the thermal process. Enthalpy (ΔH), entropy (ΔS), and Gibbs energy (ΔG) for Ag nanoclusters growth and nucleation are significantly calculated and interpreted at different temperatures. An empirical relation among the ΔH, ΔS, and ΔG is developed vis-a-vis activation energy (97.70 J/mol), which is calculated by the Arrhenius linear equation.

D-amino acid oxidase-nanoparticle system: a potential novel approach for cancer enzymatic therapy

AIM

The authors propose a new magnetic nanoparticle-enzyme system for cancer therapy capable of targeting the enzyme and consequently decreasing the adverse effects, meanwhile improving the patient's life quality.

MATERIALS & METHODS

The authors have functionalized Fe3O4 nanoparticles with 3-amino-propyltriethoxysilane (APTES) and conjugated it to yeast D-amino acid oxidase (DAAO) by coupling this with glutaraldehyde.

RESULTS & CONCLUSION

The authors have tested the Fe3O4-APTES-DAAO system on three tumor cell lines. Exposed cells show, at the electron microscope level, nanoparticles on the surface of the plasma membrane and inside endocytic vesicles. Fe3O4-APTES-DAAO caused a substantial decrease of cell viability greatly augmented when D-alanine, a DAAO substrate, was added. Fe3O4-APTES-DAAO was demonstrated to be more effective than free DAAO, confirming the validity of the system in cancer therapy.