Fe3O4-chitosan nanocomposite as a magnetic biosorbent for removal of nickel and cobalt heavy metals from polluted water.

Recently, natural polymers like chitosan have gained attention as promising adsorbents for water treatment. By combining chitosan with magnetic nanoparticles, their adsorption capabilities can be enhanced. In this study, chitosan-magnetite nanocomposite (CMNC) was synthesized via coprecipitation method to remove nickel and cobalt from aqueous solutions. The physicochemical properties of the synthesized CMNC were investigated by various techniques, including FESEM, TEM, XPS, FTIR, XRD, and VSM. The electron microscopy results confirmed the uniform dispersion of magnetite nanoparticles within CMNC nanocomposites, while VSM confirmed their significant magnetic properties. The adsorption experiments showed that at optimal conditions (pH = 6, contact time = 2 h, adsorbent dosage = 2 g/l), CMNC has high adsorption capacities of 30.03 mg/g for Ni2+ and 53.19 mg/g for Co2+. Furthermore, the adsorption data fitted best with the Langmuir isotherm, show that the active sites on CMNC are energetically homogenous. According to kinetic analysis, the experimental data were in good agreement with both pseudo-second-order and intra-particle diffusion models, which suggest that chemical sorption, along with mass transfer steps, influence the overall adsorption process. Finally, investigating the thermodynamic parameters (∆Gads, ∆Hads, ∆Sads) showed that the adsorption process on CMNC was endothermic and spontaneous, with stronger interactions observed between CMNC and Co2+ compared to Ni2+.

An electrochemical aptasensor for detection of prostate-specific antigen-based on carbon quantum dots-gold nanoparticles.

In this work, an electrochemical aptasensor was described for the determination of prostate-specific antigen (PSA). Aptamer chains were decorated on the surface of a glassy carbon electrode (GCE) via carbon quantum dots/Au nanoparticles (Au/CQD). Structural analysis that was used to characterize the prepared materials shows that Au/CQD nanoparticles synthesized in a spherical shape with an average size of 70 nm. Furthermore, the combination of Au nanoparticles with CQD resulted in formation of crystalline the structure of the Au/CQD composite. To study the electrochemical performance of the prepared aptasensor, cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy were used. The results show that the aptasensor has a good selectivity to PSA over other biomaterials with the time optimized about 30 min. K4 [Fe(CN)6 ] was used as an electrochemical probe with the limit of detection about 2 fg⋅mL-1 . To avoid the hazardous nature of K4 [Fe(CN)6 ], a label-based aptasensor was prepared using methylene blue as an electrochemical signal producer. They provide the capability of electrochemical detection in buffer phosphate solution with high sensitivity.

Inhibition Of Tau Protein Aggregation By a Chaperone-like ß-Boswellic Acid Conjugated To Gold Nanoparticles.

A potential therapeutic strategy to inhibit tau protein aggregation in neurons has substantial effects on preventing or controlling Alzheimer's disease (AD). In this work, we designed a covalent and noncovalent conjugation of ß-boswellic acid (BA) to gold nanoparticles (GNPs). We provided the opportunity to investigate the effect of the surface composition of BA-GNPs on the aggregation of the tau protein 1N/4R isoform in vitro. HR-TEM and FESEM micrographs revealed that GNPs were spherical and uniform, smaller than 25 nm. According to UV-visible and FTIR data, BA was successfully conjugated to GNPs. The finding illustrates the effect of the surface charge, size, and hydrophobicity of BA-GNPs on the kinetics of tau protein aggregation. The size and surface area of U-G-BA demonstrated that inhibited tau aggregation more effectively than covalently linked BA. The proposed method for preventing tau aggregation was monomer reduction. At the same time, a chaperone-like feature of GNP-BA while sustaining a tau native structure prevented the additional formation of fibrils. Overall, this study provides insight into the interaction of GNP-BAs with a monomer of tau protein and may suggest novel future therapies for AD.

Biological and structural properties of graphene oxide/curcumin nanocomposite incorporated chitosan as a scaffold for wound healing application.

AIMS: The purpose of this research is to fabricate chitosan (CS)/graphene oxide (GO)/curcumin (Cur) 3D scaffolds through the freeze-drying method for wound dressing applications. MAIN METHODS: GO is produced by Hammer's method; then, it is characterized by X-ray diffraction and TEM analysis. Fabricated scaffolds are characterized by FTIR, FESEM, AFM, water vapor transmission rate, PBS absorption, contact angle, tensile strength, porosity measurement, biodegradability, and drug release methods. The cell viability and morphology of NIH/3 T3 cells are investigated by WST assay kit and FESEM analysis, and the antibacterial activity of scaffolds is determined by the optical density (OD) method. The photothermal antibacterial activity is characterized by NIR irradiation, too. KEY FINDINGS: The mean pore diameter of scaffolds adjusted by the incorporation of about 0-1.5%wt. of GO/Cur nanocomposite into CS matrix, decreasing from 87 to 40 µm that can be attributed to the intermolecular bonds between CS and GO/Cur nanocomposite. Besides, the PBS absorption of scaffolds enhances by the addition of GO/Cur, especially 1% of it. Furthermore, the overall average of cell viability of nanocomposite scaffolds is about 95%, and the FESEM images show that NIH/3T3 fibroblasts well spread on the nanocomposite scaffolds. GO/Cur has a significant influence on the antibacterial activity of CS scaffolds as CS/GO/Cur 0.5 scaffold diminishes the bacterial growth to about 52% of the control sample's growth. SIGNIFICANCE: The results evidence the antibacterial CS/GO/Cur scaffolds are excellent supports for cell growth and proliferation, and they could be promising candidates for wound dressing applications.

Electrospun poly-caprolactone/graphene oxide/quercetin nanofibrous scaffold for wound dressing: Evaluation of biological and structural properties.

AIMS: In this study, for the first time, the effect of quercetin (Q) on the characteristic properties, antimicrobial activity, and cell viability of polycaprolactone (PCL)/graphene oxide (GO) electrospun scaffold was investigated. MAIN METHODS: Quercetin loaded graphene oxide nanoparticles have been incorporated into the poly-caprolactone solution, and their mixture has been electrospun to be applied as a nanofibrous scaffold for wound dressing and tissue engineering applications. The properties of scaffolds, like their morphology, tensile strength, hydrophilicity, and in vitro biological performance, are investigated. KEY FINDINGS: The SEM micrographs reveal the uniform bead-free nanofibers with smooth structures have been successfully fabricated via the electrospinning procedure. The overall average of cell viability of NIH/3 T3 fibroblast cells on scaffolds is 95% that means the scaffolds have no toxicity, and FESEM shows cells attach and proliferate on scaffolds. Moreover, among all the fabricated scaffolds, the maximum release of quercetin belongs to PCL/GO/Q 0.5 with about 70% after 15 days, and this scaffold reduces bacterial growth by about 50% after 12 h shows the excellent effect of GO/Q on the antibacterial activity of PCL nanofibers. SIGNIFICANCE: The results confirm that more than 1% of GO has some cytotoxicity, which limits its concentration; therefore, a second antibacterial agent is essential to improve the antibacterial activity of PCL/GO scaffold, and quercetin shows that it is an excellent candidate for this purpose.

Vanadium oxide decorated carbon nanotubes as a promising support of Pt nanoparticles for methanol electro-oxidation reaction.

VO(x)-MWCNTs nanocomposite was prepared via deposition-precipitation method followed by microwave treatment. Platinum nanoparticles were dispersed via polyol process over the nanocomposite support, and thus, prepared electro-catalyst was employed in methanol electro-oxidation reaction. The electro-catalysts were characterized by means of TGA, XRD, EDS, FESEM, TEM, and H(2)-TPR analysis. The electro-catalytic activity and stability of the electrodes toward methanol oxidation reaction in acidic medium were studied by using cyclic voltammetry (CV), CO-stripping, and electrochemical impedance spectroscopy (EIS) techniques. Compared to the Pt/MWCNTs, the Pt/VO(x)-MWCNTs electro-catalyst not only exhibits high electro-catalytic activity, but also shows very good stability during methanol electro-oxidation reaction. In addition, the presence of VO(x) in the composite support dramatically increases the electrochemical active surface area of platinum nanoparticles. The results of electrochemical impedance spectroscopy reveal that formation kinetics of adsorbed hydroxyl group on surface of the electro-catalysts is improved upon vanadium oxide addition to the support. This phenomenon is very helpful to facilitate oxidative removal of adsorbed CO group through bifunctional mechanism on Pt/VO(x)-MWCNTs.