MXenes with ordered triatomic-layer borate polyanion terminations.

Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2- species, which cap the MXene surface with an O-B-O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2 MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g-1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

STEM Tomography of Au Helical Assemblies.

Composite, helical nanostructures formed using cooperative interactions of liquid crystals and Au nanoparticles were studied using a scanning transmission electron microscopy (STEM) mode. The investigated helical assemblies exhibit long-range hierarchical order across length scales, as a result of the crystallization (freezing) directed growth mechanism of nanoparticle-coated twisted nanoribbons and their ability to form organized bundles. Here, STEM methods were used to reproduce the 3D structure of the Au nanoparticle double helix.

Single-step synthesis of Er3+ and Yb3+ ions doped molybdate/Gd2O3 core-shell nanoparticles for biomedical imaging.

Nanostructures as color-tunable luminescent markers have become major, promising tools for bioimaging and biosensing. In this paper separated molybdate/Gd2O3 doped rare earth ions (erbium, Er3+ and ytterbium, Yb3+) core-shell nanoparticles (NPs), were fabricated by a one-step homogeneous precipitation process. Emission properties were studied by cathodo- and photoluminescence. Scanning electron and transmission electron microscopes were used to visualize and determine the size and shape of the NPs. Spherical NPs were obtained. Their core-shell structures were confirmed by x-ray diffraction and energy-dispersive x-ray spectroscopy measurements. We postulated that the molybdate rich core is formed due to high segregation coefficient of the Mo ion during the precipitation. The calcination process resulted in crystallization of δ/ξ (core/shell) NP doped Er and Yb ions, where δ-gadolinium molybdates and ξ-molybdates or gadolinium oxide. We confirmed two different upconversion mechanisms. In the presence of molybdenum ions, in the core of the NPs, Yb3+-[Formula: see text] (∣2F7/2, 3T2〉) dimers were formed. As a result of a two 980 nm photon absorption by the dimer, we observed enhanced green luminescence in the upconversion process. However, for the shell formed by the Gd2O3:Er, Yb NPs (without the Mo ions), the typical energy transfer upconversion takes place, which results in red luminescence. We demonstrated that the NPs were transported into cytosol of the HeLa and astrocytes cells by endocytosis. The core-shell NPs are sensitive sensors for the environment prevailing inside (shorter luminescence decay) and outside (longer luminescence decay) of the tested cells. The toxicity of the NPs was examined using MTT assay.

Comparative Analysis of Metal Electrodeposition Rates towards Formation of High-Entropy WFeCoNiCu Alloy.

This study presents a calculation and comparison of Fe, Co, Ni and Cu deposition rates in the tungsten codeposition process based on the electrodeposition of numerous tungsten alloys. Eight different tungsten alloys containing from two to five metals were electrodeposited in constant conditions in order to compare the exact reduction rates. The calculated rates enabled control of the alloy composition precise enough to obtain a high-entropy WFeCoNiCu alloy with a well-balanced composition. The introduction of copper to form the quinternary alloy was found to catalyze the whole process, increasing the deposition rates of all the components of the high-entropy alloy.

Removal of doxorubicin hydrochloride and crystal violet from aqueous solutions using spray-dried niobium oxide coated with chitosan-activated carbon: Experimental and DFT calculations.

Spray-dried niobium oxide coated with chitosan-activated carbon (NIC) was synthesized and used to remove doxorubicin hydrochloride and crystal violet from aqueous solutions under different parameters such as solution pH (2, 4, 6, and 8), contact time (1 to 9 h), initial concentration (20 to 200 mg L-1), and competing ions (0.1 M of CaCl2 and NaCl). The addition of 5 % chitosan-activated carbon to the matrix of niobium oxide slightly increased the specific surface area from 26 to 30 m2 g-1, with the introduction of a carboxylic functional group. This led to an increase in the amount of adsorbed doxorubicin hydrochloride (DOH) from 30 to 44 mg g-1 and that of crystal violet (CV) from 15 to 32 mg g-1 from the initial respective 100 mg L-1 at pH 8. The data from the concentration study fitted into Liu isotherm having adsorption capacity of 128 and 57 mg g-1 for DOH and CV respectively, while pseudo first and second order are more suitable for adsorption kinetics. The additional functional groups on the IR spectrum of NIC after the adsorption of DOH and CV confirmed the interaction between NIC and the adsorbates' molecules. The mechanism of adsorption was supported by DFT calculations.

Progress in targeting tumor cells by using drug-magnetic nanoparticles conjugate.

To limit cytotoxicity of anticancer drugs against healthy cells, an appropriate carrier should be synthesized to deliver the drug to the tumor tissue only. A good solution is to anchor a magnetic nanoparticle to the molecule of the drug and to use a properly directed external magnetic field. The synthesis of the conjugate of doxorubicin with magnetic nanoparticles (iron oxide) modified by us resulted in a substantial depression of the aggregation process of the nanoparticles and therefore allowed the correct examination of cytotoxicity of the modified drug. It has been shown, by performing the electrochemical microbalance measurements, that the use of magnetic field guaranteed the efficient delivery of the drug to the desired place. The change in the synthesis procedure led to an increase in the number of DOX molecules attached to one magnetic nanoparticle. The release of the drug took place at pH 5.8 (and below it), which pH characterizes the cancer cells. It has also been found that while the iron oxide magnetic nanoparticles were not cytotoxic toward human urinary bladder carcinoma cells UM-UC-3, the tumor cell sensitivity of the DOX-Np complex was slightly higher in comparison to the identical concentration of doxorubicin alone.

Exosomes derived from lung cancer cells: Isolation, characterization, and stability studies.

Recent advances in nanomedicine have paved the way for developing targeted drug delivery systems. Nanoscale exosomes are present in almost every body fluid and represent a novel mechanism of intercellular communication. Because of their membrane origin, they easily fuse with cells, acting as a natural delivery system and maintaining the bioactivity and immunotolerance of cells. To develop a reconstitutable exosome-based drug candidate for clinical applications, quality assurance by preserving its physical and biological properties during storage is necessary. Therefore, this study aimed to determine the best storage conditions for exosomes derived from lung cancer cells (A549). This study established that the phosphate-buffered saline buffer enriched with 25 mM trehalose is an optimal cryoprotectant for A549-derived exosomes stored at -80°C. Under these conditions, the concentration, size distribution, zeta potential, and total cargo protein levels of the preserved exosomes remained constant.

Application of biocompatible and ultrastable superparamagnetic iron(III) oxide nanoparticles doped with magnesium for efficient magnetic fluid hyperthermia in lung cancer cells.

Magnetic fluid hyperthermia (MFH) is a promising therapeutic strategy that targets malignant tissues by heating to 40-43 °C using magnetic nanoparticles (MNPs) subjected to an alternating magnetic field (AMF). In this study, novel magnetic iron(III) oxide nanoparticles doped with magnesium (Mg0.1-γ-Fe2O3(mPEG-silane)0.5) were synthesized, and their structural, chemical, and magnetic properties were analyzed using the following techniques: Fourier-transform infrared spectroscopy, Raman spectroscopy, vibrating magnetometer analysis, powder X-ray diffraction, inductively coupled plasma mass spectrometry, scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The as-synthesized MNPs were used as water ferrofluids for MFH under an AMF in two calorimetric setups, namely phantom and lung cancer cell (A549) models. The as-synthesized MNPs were hexagonal or rhombohedral shaped, with an average size of 27 nm. They showed a typical soft ferromagnetic behavior based on the hysteresis profile, with a magnetic saturation of 70 emu g-1 and remnant magnetization of 1.6 emu g-1. In phantom studies, the ferrofluid (3.0 mg mL-1) exposed to an AMF (18.3 kA m-1, 110.1 kHz) heated up extremely quickly, reaching more than 90 °C in the first 10 min of magnetization. In cell studies, the ferrofluid (0.25 mg mL-1) under an AMF (16.7 kA m-1, 110.1 kHz) showed a slight increase in temperature within the first 12 min, reaching a peak of ca. 43-45 °C, which was stable up to the end of the AMF exposure (45 min). Under these conditions, a pronounced cytotoxic effect on the lung cancer cells was observed (viability ca. 15-20%). No such deleterious effects were observed when the cells were treated with MNPs only without an AMF. Specific absorption rate (SAR) measurements were performed using three mathematical approaches, namely the initial slope method, the corrected slope method, and the Box-Lucas method, which ranged from ca. 429 to 596 W g-1 for phantom and cell studies. Iron(III) oxide MNPs doped with magnesium were found to be candidates for MFH in lung cancer treatments.

Modification of electrode surfaces: deposition of thin layers of polypyrrole--Au nanoparticle materials using a combination of interphase synthesis and dip-in method.

Formation of thin layers of the composite material by a method based on interphase polymerization induced by a transport-controlled redox reaction is described. The obtained films were of 0.2-1 microm thickness, consisted of polypyrrole and gold nanoparticles (up to 13.5 at. %), strongly adhered to the substrate surface, and were uniform. Different carbon materials and glass wool were employed as the substrates. The first step in the synthesis was deposition of an organic layer on the substrate. This was followed by dipping the substrate in an aqueous solution containing an oxidizer and appropriate washing and drying the composite film.

Polyacrylate microspheres composite for all-solid-state reference electrodes.

A novel concept is proposed for the encapsulation of components within polyacrylate microspheres, prior to their incorporation into a membrane phase. Thus finer and better controlled dispersion of heterogeneous membrane components can be achieved. This concept was verified by using a poly(n-butyl acrylate) membrane-based reference electrode as an example. In this example the proper dispersion of solid constituents of the heterogeneous membrane and prevention of their leakage are both of primary importance. Potassium chloride-loaded poly(n-butyl acrylate) microspheres were prepared and then left in contact with silver nitrate to convert some of the KCl into AgCl. The material obtained was introduced into a poly(n-butyl acrylate) membrane. The reference electrode membranes obtained in this way were characterized with much more stable potential (both in different electrolytes and over time) compared with electrodes prepared by the direct introduction of KCl and AgCl to the membrane.

Enantioselective sensing of (S)-Thalidomide in blood plasma with a chiral naphthalene diimide derivative.

Fast, simple in use and highly effective voltammetric enantiosensor dedicated for determination of thalidomide (TD) enantiomers (especially towards the toxic (S)-enantiomer) in blood plasma is still desirable. Here we have proven that newly synthesized chiral naphthalene diimide (NDI) derivatives are excellent electroactive materials for TD enantiosensors. The recognition process relies on the specific interaction between the chiral NDI receptor and the thalidomide enantiomer of the opposite configuration. This unique specific interaction between (S)-thalidomide and (R)-NDI derivative counterparts, evident in the DPV voltammograms, was confirmed by molecular modeling. The demonstrated voltammetric enantiosensors are characterized by the low detection limit at the level of µg·L-1, wide analytical range from 5·10-4 - 10 mg·L-1, high selectivity and long lifetime. The results of the recovery rates showed a very good degree of accuracy towards the determination of (S)-thalidomide in the blood samples, so it can be successfully used in the analysis of clinical samples.

Influence of a magnetic nanoparticle as a drug carrier on the activity of anticancer drugs: interactions of double stranded DNA and doxorubicin modified with a carrier.

Magnetic drug targeting executed by nanoparticles as carriers is a promising cancer treatment which avoids the side effects of conventional chemotherapy. We have modified doxorubicin with magnetic nanoparticles. Doxorubicin (adriamycin) is a potential anticancer drug yet nonspecific in its antibiotic action. Therefore, carriers for tissue-specific, targeted drug delivery are of utmost importance. We report here on the interaction of doxorubicin covalently bound via tether molecules to colloidal magnetic nanoparticles (ferrofluid) with calf thymus double stranded DNA (dsDNA). By means of spectroscopic and electrochemical techniques, we have shown that appropriate length and flexibility of tether molecules allows the preservation of essentially intact intercalation capabilities of free doxorubicin in the solution. In order to evaluate these capabilities, we have studied the binding constant of doxorubicin attached to nanoferrites with dsDNA as well as the binding site size on the dsDNA molecule. The binding constant decreased slightly compared to that of free doxorubicin while the binding site size, describing the number of consecutive DNA lattice residues involved in the binding, increased. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images were also obtained to support the conclusion on the interactions between doxorubicin-modified magnetic nanoparticles and dsDNA.

Substantial difference between temperature dependencies of dsDNA predenaturation process obtained by voltammetry and spectroscopy.

The electrooxidation of double stranded DNA has been studied in a wide temperature range by cyclic and square wave voltammetries and the results were compared with UV-Vis and CD spectroscopies. A twofold increase of dsDNA voltammetric peaks related to the conformation changes preceding the denaturation process was found to begin at a temperature lower than the well known increase of dsDNA absorbance upon denaturation (the melting point) by circa 20 degrees C. Since the dsDNA voltammetric peaks are related directly to the electrooxidation of guanine and adenine, early conformational changes in guanine-cytosine (G-C) and adenine-thymine (A-T) pairs in dsDNA are possible reasons for the increase of the voltammetric peaks. The above observations prove that the voltammetric methods are much more sensitive to the changes in guanine and adenine base-pairs conformations and indicate increased exposition of guanine and adenine in the reversible stages that precede the denaturation process of dsDNA. Interestingly, two distinct ranges of change in ellipticity in CD spectra correlate well to the changes obtained by voltammetry and UV spectroscopy, respectively. We also checked the influence of an intercalator on the dsDNA denaturation (temperature) plots. The spectroscopic measurements indicated an increase in the stability of the structure of the double stranded helix upon the addition of the intercalator, while voltammetry showed also that the exposition of guanine and adenine for the electrooxidation drops substantially in the region preceding the denaturation process.

Preparation of Pt-skin PtRhNi Nanoframes Decorated with Small SnO2 Nanoparticles as an Efficient Catalyst for Ethanol Oxidation Reaction.

Pt-based nanoframes are one of the most promising catalysts for ethanol oxidation reaction in direct ethanol fuel cells. It is important to understand the mechanisms responsible for creating these hollow nanoframe-based catalysts. Herein, for the first time, Pt-skin PtRhNi rhombic dodecahedral nanoframes were decorated with small SnO2 nanoparticles and were used as an efficient catalyst for the ethanol oxidation reaction. Moreover, by combining the ex situ scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy observations at various stages of synthesis, along with density functional theory calculations, it was possible to track the synthesis route of solid rhombic dodecahedral PtRhNi nanoparticles, which are the precursors of PtRhNi nanoframes. After the chemical etching of the Ni core from solid PtRhNi nanoparticles, the obtained nanoframes were decorated with SnO2 nanoparticles. The resulting SnO2@PtRhNi heteroaggregates were deposited on high-surface-area carbon and electrochemically tested, showing a 6-fold higher mass activity and 10-fold higher specific activity toward ethanol oxidation reaction than commercially available Pt catalysts.

Reduced graphene oxide doping with nanometer-sized ferrocene moieties - New active material for glucose redox sensors.

Herein, we present that the reduced graphene oxide (rGO) doped with nanometer-sized ferrocene moieties is a new, excellent active material for redox sensors. Two distinct approaches were utilized for the modification of rGO. The first method was based on the covalent decoration of rGO via the addition of azomethine ylide generated from the ferrocenecarboxaldehyde oxime. The second approach utilized the adsorption of 1,1'-ferrocenedicarboxylic acid on the graphene sheet via the π-π stacking. The morphology of the synthesized graphene materials was studied by application of microscopic techniques, whereas the Raman data allowed the characteristics of the tested materials in terms of their structural properties. The tested graphene materials doped with ferrocene moieties were used as a bioactive platform for glucose oxidase (GOx) immobilization. The enzyme was immobilized onto the rGO materials in two ways: (i) using a crosslinking agent - glutaraldehyde (GA) and (ii) by formation of the amide bonds between carboxylic groups of rGO-Fc(COOH)2 and amine groups from enzyme. Ferrocene moieties present at the graphene surface play the role of mediator in the electron transfer between the redox center of GOx and the electrode surface. The functionality of the constructed biosensors has been tested on real samples. The results of the recovery rates showed a satisfying degree of accuracy toward determination of glucose concentration. Examination of the potential interfering species has demonstrated favorable sensitivity and selectivity of the designed biosensor for the detection of glucose.

Physical and chemical changes in Alhydrogel™ damaged by freezing.

Accidental freezing of aluminum-based vaccines occurs during their storage and transportation, in both developed and developing countries. Freezing damages the freeze-sensitive aluminum adjuvanted vaccines, through separation of lattice between aluminum adjuvant and antigen, leading to formation of aluminum aggregates, and loss of potency. In this study, we examined Alhydrogel™ ([AlO(OH)]xnH2O, aluminum hydroxide, hydrated for adsorption) stored under recommended conditions, and exposed to freezing temperature until solid-frozen. The main purpose of our research was to determine the destruction areas of the solid-frozen Alhydrogel™ using selected methods of scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy working in diffraction mode. The Zeta potential evaluation, measurements of albumin adsorption power, thermogravimetric analysis and estimation of the mass loss after drying indicated significant structural (physical) and chemical differences between the freeze-damaged and non-frozen vaccine adjuvant. The presented results are important to better understand the type and nature of damages occurring in freeze-damaged aluminum-based vaccines. These results can be used in future studies to improve the temperature stability of aluminum adjuvanted vaccines.

Electrooxidation of dissolved dsDNA backed by in situ UV-Vis spectroscopy.

The electrooxidation of double-stranded DNA (dsDNA) from calf thymus was carried by using cyclic voltammetry. A glassy carbon disk-, a platinum disk-, a platinum mesh- and a carbon vapor-deposited platinum mesh electrodes were used. It is shown that the appropriate chemical and biological (steam treatment) purification of the complete cell allows, for the graphite electrode, formation of a wide anodic dsDNA signal with two visible anodic peaks. There was no necessity of preaccumulation of dsDNA on the electrode surface and of use of mediators to get well defined voltammetric signals. These peaks apparently reflect electrooxidation of the DNA's guanine and adenine. The spectrophotometric data obtained during the electrooxidation indicate that the absorbance increases with an increase in potential and electrooxidation current of dsDNA. However, the absorption band maximum either does or does not change its position depending on the mesh material. This different spectroscopic behavior may mean that the changes in the dsDNA structure upon electrooxidation are different in the case of Pt and C electrodes.

Electrodeposition of poly(N-vinylcarbazole) at the three-phase junction. Formation of very different polymer structures.

Poly(N-vinylcarbazole) films can be deposited at the three-phase boundary when the organic phase contains only monomer, N-vinylcarbazole, while the aqueous phase contains supporting electrolyte. A cylindrical platinum microelectrode is immersed into the two-liquid system in such a way that a part of it is located in one liquid and the other part resides in the second liquid. The thickness of the reaction layer, or the width of the microelectrode zone where the polymer grows, depends on the kind of ions present in the aqueous phase and the time of the experiment. The structure of the deposited polymer may be very different and depends on the distance from the three-phase boundary and the type of the anion present in the aqueous phase. The key parameters here are the local electrode potential and the local concentration of the anions. The list of obtained polymer structures includes, among others, arrays of perfectly arranged deep oval channels and groups of microcrystals. The porosity of the polymer deposits increases with the distance from the aqueous phase.

Electrochemical examination of ability of dsDNA/PAM composites for storing and releasing of doxorubicin.

Composites consisting of ss- and ds-DNA strands and polyacrylamide (PAM) hydrogel have been synthesized. DNA was entrapped non-covalently. The obtained DNA biomaterial exhibited a strong increase in guanine and adenine anodic currents when temperature reached the physiological level. This increase was related to the unique oligonucleotide structural changes in the composite. The structural alterations in the PAM lattices were employed for the release of the drug accumulated in the composite. Doxorubicin (Dox) was selected as the drug; it was accumulated by intercalation to dsDNA and was slowly released from the dsDNA/PAM system by using a minor temperature increase (up to 40÷45 °C) as it is routinely done in hyperthermia. The applied release temperature was either constant or oscillating. The binding strength, the rate of Dox release and the properties of the composite were examined using voltammetry, SEM and ICP-MS.