Synthesis of novel chelating agents and their effect on cadmium decorporation

Polymer-Initiating Caveolae-Mediated Endocytosis and GSH-Responsive MiR-34a Gene Delivery System for Enhanced Orthotopic Triple Negative Breast Cancer Therapy

Gene therapy based on miRNAs has broad application prospects in the treatment of tumors. However, due to degradation and ineffective release during intracellular transport, current gene delivery vectors used for miRNAs limited their actual transfection efficiency. This study develops a novel nonviral vector PEI-SPDP-Man (PSM) that can simultaneously target cellular uptake pathways and intracellular responsive release for miR-34a. PSM is synthesized by connected mannitol (Man) to branched polyethylenimine (PEI) using a disulfide bond. The prepared PSM/miR-34a gene delivery system can induce and enter to tumor cells through caveolae-mediated endocytosis to reduce the degradation of miR-34a in lysosomes. The disulfide bond is sensed at high concentration of glutathione (GSH) in the tumor cells and miR-34a is released, thereby reducing the expression of Bcl-2 and CD44 to suppress the proliferation and invasion of tumor cells. In vitro and in vivo experiments show that through the targeted cellular uptake and the efficient release of miR-34a, an effective antitumor and antimetastasis profiles for the treatment of orthotopic triple negative breast cancer (TNBC) are achieved. This strategy of controlling intracellular transport pathways by targeting cellular uptake pathways in the gene therapy is an approach that could be developed for highly effective cancer therapy.

Colorimetric cadmium ion detection in aqueous solutions by newly synthesized Schiff bases

Two newly synthesized Schiff bases DMCA and DMBA were used for selective detection of Cd²⁺ over a wide range of other metal ions in acetonitrile (ACN)/ Tris-HCl buffer (10 mM, pH 7.32, v/v 2:1). The sensors can detect Cd²⁺ ions by colour changes from colourless to orange for DMBA and yellow to reddish for DMCA. Response of the probes towards metal ions was investigated by using UV-vis spectroscopy. The complex stoichiometry between the sensors, DMBA and DMCA, and Cd²⁺ was found to be 2:1 and the binding constants were calculated to be 2.65 ×10¹² M^-2 and 4.95 ×10¹² M^-2, respectively. The absorbance-based detection limits of DMBA and DMCA were calculated as 0.438 μM and 0.102 μM, respectively. The sensors were also successfully applied to real samples.

A unique dual sensor for the detection of DCNP (nerve agent mimic) and Cd2+ in water

A unique carbazole–pyrrole conjugate CPC dual sensor was successfully developed for the simultaneous detection of DCNP (nerve agent mimic) and Cd²⁺ – a heavy metal toxicant – in aqueous medium at very low concentrations.

Mobilization and removing of cadmium from kidney by GMDTC utilizing renal glucose reabsorption pathway

Chronic exposure to cadmium compounds (Cd(2+)) is one of the major public health problems facing humans in the 21st century. Cd(2+) in the human body accumulates primarily in the kidneys which leads to renal dysfunction and other adverse health effects. Efforts to find a safe and effective drug for removing Cd(2+) from the kidneys have largely failed. We developed and synthesized a new chemical, sodium (S)-2-(dithiocarboxylato((2S,3R,4R,5R)-2,3,4,5,6 pentahydroxyhexyl)amino)-4-(methylthio) butanoate (GMDTC). Here we report that GMDTC has a very low toxicity with an acute lethal dose (LD50) of more than 10,000mg/kg or 5000mg/kg body weight, respectively, via oral or intraperitoneal injection in mice and rats. In in vivo settings, up to 94% of Cd(2+) deposited in the kidneys of Cd(2+)-laden rabbits was removed and excreted via urine following a safe dose of GMDTC treatment for four weeks, and renal Cd(2+) level was reduced from 12.9μg/g to 1.3μg/g kidney weight. We observed similar results in the mouse and rat studies. Further, we demonstrated both in in vitro and in animal studies that the mechanism of transporting GMDTC and GMDTC-Cd complex into and out of renal tubular cells is likely assisted by two glucose transporters, sodium glucose cotransporter 2 (SGLT2) and glucose transporter 2 (GLUT2). Collectively, our study reports that GMDTC is safe and highly efficient in removing deposited Cd(2+) from kidneys assisted by renal glucose reabsorption system, suggesting that GMDTC may be the long-pursued agent used for preventive and therapeutic purposes for both acute and chronic Cd(2+) exposure.

Efficient Binding of Heavy Metals by Black Sesame Pigment: Toward Innovative Dietary Strategies To Prevent Bioaccumulation

Black sesame pigment (BSP) was shown to bind lead, cadmium, and mercury at pH 7.0 and to a lower extent at pH 2.0. BSP at 0.05 mg/mL removed the metals at 15 μM to a significant extent (>65% for cadmium and >90% for mercury and lead), with no changes following simulated digestion. The maximum binding capacities at pH 7.0 were 626.0 mg/g (lead), 42.2 mg/g (cadmium), and 69.3 mg/g (mercury). In the presence of essential metals, such as iron, calcium, and zinc, BSP retained high selectivity toward heavy metals. Model pigments from caffeic acid, ferulic acid, and coniferyl alcohol showed lower or comparable binding ability, suggesting that the marked properties of BSP may result from cooperativity of different sites likely carboxy groups and o-diphenol and guaiacyl functionalities. Direct evidence for the presence of such units was obtained by structural analysis of BSP by solid-state Fourier transform infrared spectroscopy and (13)C nuclear magnetic resonance spectroscopy.

Effective removal of cadmium ions from a simulated gastrointestinal fluid by Lentinus edodes

Lentinus edodes, a functional food, was evaluated as a potential antidote for adsorption/removal of cadmium ion from simulated gastrointestinal fluids. An adsorption/removal capacity of 65.12 mg/g was achieved by L. edodes in solutions with a pH ranging from 2.5 to 6.0, while little if any adsorption was observed in solutions with a pH under 2.5. In solutions with pH 6.0, 84% of the cadmium adsorption by L. edodes occurred in the first minute. Scanning electronic microscopic examination showed that the cell wall polysaccharides of L. edodes provided a rough sponge-like surface for effective cadmium adsorption. FTIR indicated that the carboxyl, hydroxyl and –NH groups of the cell wall polysaccharides and proteins were the primary functional groups that chemically bind with cadmium ions. The energy dispersive spectrometry further revealed that cation exchange might be attributed to cadmium biosorption. These results suggested that L. edodes was effective for cadmium detoxication, especially in low concentration.

Improving the visible light photoactivity of In2S3-graphene nanocomposite via a simple surface charge modification approach

We report an efficient and easily accessible self-assembly route to synthesize In2S3-GR nanocomposites via electrostatic interaction of positively charged In2S3 nanoparticles with negatively charged graphene oxide (GO) followed by a hydrothermal process for reduction of GO to graphene (GR). The as-synthesized In2S3-GR nanocomposites exhibit much higher visible light photocatalytic activity toward selective reduction of nitroaromatic compounds in water than bare In2S3 nanoparticles and In2S3-GR-H that is obtained from the simple "hard" integration of GR nanosheets with solid In2S3 nanoparticles without modification of surface charge. On the basis of the joint characterizations and structure-photoactivity correlation it is disclosed that the enhanced photocatalytic performance of In2S3-GR is mainly ascribed to the more efficient interfacial contact between In2S3 and the GR nanosheets than In2S3-GR-H, which would amplify the use of electron conductivity and mobility of GR to improve the lifetime and transfer of photogenerated charge carriers more efficiently and thus boost the photoactivity more effectively. This work highlights the significant effect of preparation methods on the photoactivity of GR-semiconductor nanocomposites. It is expected that such a simple electrostatic self-assembly strategy could aid to rationally fabricate more efficient GR-semiconductor nanocomposites with improved interfacial contact and photocatalytic performance toward various photocatalytic selective transformations.

In vitro removal of toxic heavy metals by poly(γ-glutamic acid)-coated superparamagnetic nanoparticles

Background:

Chelation therapy involving organic chelators for treatment of heavy metal intoxication can cause cardiac arrest, kidney overload, mineral deficiency, and anemia.

Methods:

In this study, superparamagnetic iron oxide nanoparticles (SPIONs) modified with an edible biopolymer poly(γ-glutamic acid) (PGA) were synthesized by coprecipitation method, characterized and evaluated for their removal efficiency of heavy metals from a metal solution, and simulated gastrointestinal fluid (SGIF).

Results:

Instrumental characterization of bare- and PGA-SPIONs revealed 7% coating of PGA on SPIONs with a spherical shape and an iron oxide spinel structure belonging to magnetite. The particle sizes as determined from transmission electron microscopy images were 8.5 and 11.7 nm for bare- and PGA-SPIONs, respectively, while the magnetization values were 70.3 and 61.5 emu/g. Upon coating with PGA, the zeta potentials were shifted from positive to negative at most of the environmental pH (3–8) and biological pH (1–8), implying good dispersion in aqueous suspension and favorable conditions for heavy metal removal. Batch studies showed rapid removal of lead and cadmium with the kinetic rates estimated by pseudo-second-order model being 0.212 and 0.424 g/mg·min, respectively. A maximum removal occurred in the pH range 4–8 in deionized water and 5–8 in SGIF corresponding to most gastrointestinal pH except for the stomach. Addition of different ionic strengths (0.001–1 M sodium acetate) and essential metals (Cu, Fe, Zn, Mg, Ca, and K) did not show any marked influence on lead removal by PGA-SPIONs, but significantly reduced the binding of cadmium. Compared to deionized water, the lead removal from SGIF was high at all pH with the Langmuir monolayer removal capacity being 98.70 mg/g for the former and 147.71 mg/g for the latter. However, a lower cadmium removal capacity was shown for SGIF (23.15 mg/g) than for deionized water (31.13 mg/g).

Conclusion:

These results suggest that PGA-SPIONs could be used as a metal chelator for clinical treatment of metal poisoning.

Lead detoxification activity and ADMET hepatotoxicity of N-(alpha-L-arabino-furanos-1-yl)-L-cysteine

N-(alpha-L-Arabinofuranos-1-yl)-L-cysteine was stereoselectively prepared from L-arabinose and l-cysteine. Its in vivo detoxification action was evaluated on lead loaded mice at the doses of 0.1, 0.2, and 0.4 mmol/kg. The results show that lead accumulation in the livers, kidneys, brains, and femurs of the treated mice could be efficiently decreased by N-(alpha-L-arabinofuranos-1-yl)-L-cysteine, even at the dose of 0.1 mmol/kg. Compared with the lead detoxification efficacy, 0.4 mmol/kg of N-(alpha-L-arabinofuranos-1-yl)-L-cysteine did not affect the essential metals in the treated mice, such as Fe, Cu, Zn, and Ca. In the apparent permeability coefficient test, the values of P(app)(A-->B), P(app)(B-->A), and P(app)(A-->B)/P(app)(B-->A) indicated that N-(alpha-L-arabinofuranos-1-yl)-L-cysteine was transported actively across the Caco-2 cell monolayer. Silico molecular modeling results predicted that N-(alpha-L-arabinofuranos-1-yl)-L-cysteine had no hepatotoxicity.

In vitro binding of heavy metals by an edible biopolymer poly(gamma-glutamic acid)

An edible biopolymer poly(gamma-glutamic acid) (gamma-PGA) was evaluated for possible use as an chelating/binding agent in the treatment of metal intoxication in humans. In vitro binding of the toxic heavy metals lead and cadmium as affected by pH, contact time, metal concentration, gamma-PGA dose, and essential metals was carried out in a batch mode. A maximum binding occurred in the pH range 5-7, corresponding to the gastrointestinal pH values except for the stomach. Binding isotherms at pH 5.5 were well described by the heterogeneous models (Freundlich and Toth), while the lead isotherm at pH 2.5 showed a S-type curve, which was fitted as multiple curves with the Langmuir model and a shifted-squared Langmuir model. However, no adsorption occurred for cadmium at pH 2.5. The maximum binding capacities of lead and cadmium at pH 5.5 were 213.58 and 41.85 mg/g, respectively. A curvilinear biphasic Scatchard plot signified a multisite interaction of metals. Binding was extremely rapid with 70-100% of total adsorption being attained in 2 min. Kinetics at low and high metal concentrations obeyed pseudo-first-order and pseudo-second-order models, respectively. The gamma-PGA dose-activity relationship revealed a low dose of gamma-PGA to be more efficient in binding a large amount of metals. Incorporation of Cu, Zn, Fe, Mg, Ca, and K showed only a minor influence on lead binding but significantly reduced the binding of cadmium.

Naked eye sensor on polyvinyl chloride platform of chromo-ionophore molecular assemblies: A smart way for the colorimetric sensing of toxic metal ions

We demonstrate the possibility of fabricating a simple, naked eye colorimetric sensor miniature, using chromo-ionophore molecular assemblies anchored on polyvinyl chloride (PVC) surface. The ion-sensing probe (4-n-dodecyl-6-(2-thiazolylazo)-resorcinol) provides a better efficiency with PVC platform in developing a series of colour transitions, while targeting trace levels of Cd(2+), Pb(2+) and Hg(2+). The physical properties of the film sensor are controlled by measuring the probe isotherm plot. The surface morphology and molecular composition of the solid-state optical sensor are characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The changes in sensor's optical intensity and its response time for the target analytes are followed by absorption spectroscopy. High speed of response (t</=5 min) and confidence in determination of analytes from chemically complex matrices has been achieved, using simulated synthetic mixtures and spiked real environmental samples, with a relative standard deviation of <3.9%. The proposed method offers consistent data reproducibility and reliability, with a detection limit of 0.031, 0.025 and 0.034 microM, for Cd(2+), Pb(2+) and Hg(2+) ions, respectively. The sensor strips are reversible and reusable without any change in the sensing efficiency, up to four cycles. The signal response observed with the proposed method is consistent between sensors, and also are stable over time.