Chitosan-coated magnetic nanoparticles as carriers of 5-Fluorouracil: Preparation,characterization and cytotoxicity studies

The chitosan-coated magnetic nanoparticles (CS MNPs) were prepared as carriers of 5-Fluorouracil (CS–5-Fu MNPs) through a reverse microemulsion method. The characteristics of CS–5-Fu MNPs were determined by using transmission electron microscopy (TEM), FTIR spectroscopy and vibrating-sampling magnetometry (VSM). It was found that the synthesized CS–5-Fu MNPs were spherical in shape with an average size of 100 ± 20 nm, low aggregation and good magnetic responsivity. Meanwhile, the drug content and encapsulation rate of the nanoparticles was 16–23% and 60–92%, respectively. These CS–5-Fu MNPs also demonstrated sustained release of 5-Fu at 37 °C in different buffer solutions. The cytotoxicity of CS–5-Fu MNPs towards K562 cancer cells was investigated. The result showed that CS–5-Fu MNPs retained significant antitumor activities. Additionally, it was observed that the FITC-labeled CS–5-Fu MNPs could effectively enter into the SPCA-1 cancer cells and induced cell apoptosis.     

Spectroscopy of Ru(II) polypyridyl complexes used as intercalators in DNA: Towards a theoretical study of the light switch effect

The absorption spectroscopy of [Ru(phen)₂dppz]²⁺ and [Ru(tap)₂dppz]²⁺ (phen = 1,10-phenanthroline, tap = 1,4,5,8-tetraazaphenanthrene; dppz = dipyridophenazine) complexes used as molecular light switches by intercalation in DNA has been analysed by means of Time-Dependent Density Functional Theory (TD-DFT). The electronic ground state structures have been optimized at the DFT (B3LYP) level of theory. The absorption spectra are characterized by a high density of excited states between 500 nm and 250 nm. The absorption spectroscopy of [Ru (phen)₂dppz]²⁺ in vacuum is characterized by metal-to-ligand-charge-transfer (MLCT) transitions corresponding to charge transfer from Ru(II) either to the phen ligands or to the dppz ligand with a strong MLCT () absorption at 411 nm. In contrast, the main feature of the lowest part of the vacuum theoretical spectrum of [Ru(tap)₂dppz]²⁺ between 522 nm and 400 nm is the presence of various excited states such as MLCT (), ligand-to-ligand-charge-transfer LLCT () or intra-ligand IL () states. When taking into account solvent corrections within the polarizable continuum model (PCM) approach (H₂O, CH₃CN) the absorption spectrum of [Ru(tap)₂dppz]²⁺ is dominated by a strong absorption at 388 nm (CH₃CN) or 390 nm (H₂O) assigned to a ¹IL () corresponding to a charge transfer from the outside end of the dppz ligand to the site of coordination to Ru(II). These differences in the absorption spectra of the two Ru(II) complexes have dramatic effects on the mechanism of deactivation of these molecules after irradiation at about 400 nm. In particular, the electronic deficiency at the outside end of the dppz ligand created by absorption to the ¹IL state will favour electron transfer from the guanine to the Ru(II) complex when it is intercalated in DNA.     

Electroreduction of anions on chemically etched and electrochemically polished Bi(1 1 1) electrode

Electroreduction kinetics of to anions at chemically etched (CHE) and electrochemically polished (EP) Bi(1 1 1) electrodes has been studied using rotating disc electrode method. The surface nanostructure of CHE Bi(1 1 1) and EP Bi(1 1 1) electrodes has been studied by in situ STM and the very different values of root mean squared roughness (Rms) have been obtained (1000 times higher for CHE Bi(1 1 1) (Rms  143 nm) than for EP Bi(1 1 1) (Rms  0.145 nm)). The influence of the nanoroughness of CHE Bi(1 1 1) on the current density, heterogeneous reaction rate constant and corrected Tafel plots (cTp) has been demonstrated. For CHE Bi(1 1 1) the more pronounced inhibition of electroreduction reaction at moderate negative surface charge density has been observed in comparison with EP Bi(1 1 1), caused by the differences in surface charge density and also in diffuse layer ψ₀ potential drop values at crystallographically different homogeneous regions (planes) exposed at the surface of the macroheterogeneous polycrystalline CHE Bi(1 1 1) surface. The very low apparent transfer coefficient α_app obtained indicates the nearly activationless charge transfer mechanism for electroreduction at the CHE Bi(1 1 1) electrode similarly to EP Bi(1 1 1). However, α_app only very weakly depends on Rms for the Bi electrodes at high negative surface charge densities where the values of ψ₀ potential are nearly equal for different planes at fixed electrode potential. At very high negative surface charge densities the cationic catalysis through the adsorbed ion pairs is possible.     

Effect of salts on the excited state of pyranine as determined by steady-state fluorescence

Pyranine is a pH-sensitive fluorescent probe useful in the pH range of 4.5–8, and it has been extensively employed to determine pH inside cells, membranes and membrane models. The fluorescent properties of pyranine are a consequence of the excited states ROH^* and RO^−*. The prototropic equilibrium of these excited species has a much lower than that of the ground state. In this paper we determined the (1.42 ± 0.06) and the relative quantum yield of pyranine in the pH range of 1–8 by analyzing the component peaks of the steady-state of the dye's emission spectrum. As pyranine is very sensitive to the medium we studied the influence of salts formed by mono-, di-, and trivalent ions on the apparent . In all cases, the presence of salts reduced the apparent to varying degrees depending on the valence of the cations. The strategy used to obtain this information was a dual emission ratiometric method at 441 and 511 nm after excitation at 350 nm. The results obtained demonstrate that pyranine is suitable to determine the pH of aqueous solutions in the range of 1–3.5.     

Magnetic nanoparticles modified with organic dendrimers containing methyl methacrylate and ethylene diamine for the microextraction of rosuvastatin

Magnetic nanoparticles (MNPs) modified with organic dendrimers are shown to be a viable sorbent of the microextraction of the drug rosuvastatin (RST; also known as Crestor). The MNPs were prepared from iron(II) chloride and iron(III) chloride and then coated with silicon dioxide. The coated MNPs produced by this method have diameters ranging from 10 to 60 nm according to scanning electron microscopy. The MNPs were further modified with organic dendrimers containing methyl methacrylate and ethylene diamine. The resulting MNPs were characterized by SEM, Fourier transform infra-red and thermal gravimetry analysis. Then, the efficacy of the modified MNPs with respect to the extraction of RST was studied. The adsorption of RST by MNPs can be best described by a Langmuir isotherm. Following elution with buffer, RST was quantified by HPLC. The method was applied to the determination of RST in (spiked) human blood plasma, urine, and in tablets. RST extraction efficiencies are 54.5% in plasma, 86.6% from the drug matrix, and 94.3% in urine. The highest adsorption capacity of the RST by the MNPs adsorbent was 61 mg?g^?1.

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Graphical abstract Co-precipitation was used to synthesize magnetic nanoparticles (MNPs). They were coated with a layer of SiO₂ and then branched by organic dendrimers containing methyl methacrylate (MMA) and ethylene diamine (EDA). Rosuvastatin (RST) drug was trapped between dendrimer branches, therefore adsorption capacity of the drug was strongly increased.

     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

Theoretical calculations of energetics, structures, and rate constants for the H + CH3OH hydrogen abstraction reactions

Barrier heights, structures, reaction energies, and rate constants are calculated with the DFT, MP2, and CCSD(T) methods for the first two channels of the H + CH₃OH reactions. The best estimate results based on CCSD(T) calculations give reaction enthalpies () for the first (−8.4 kcal/mol) and second (0.8 kcal/mol) reactive channels, which are comparable to the experimental values, −8.8 ± 0.9 and −0.3 ± 0.9 kcal/mol, respectively. Rate constants and activation energies calculated with the IVTST-0 method using CCSD(T)/cc-pVTZ geometries and frequencies are also in excellent agreement with experiment data.     

Synthesis, structure characterization and fluorescence property of a new fluoride borate crystal, CdZn2KB2O6F

A new fluoride borate crystal, CdZn₂KB₂O₆F, has been synthesized by flux-supported solid-state reaction. The crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the trigonal space group with a=5.0381(6) Å, b=5.0381(6) Å, c=15.1550(19) Å, α=90.00°, β=90.00°, γ=120.00°, Z=2. The crystal represents a new structure type in which ZnBO₃ layers are connected through bridging fluorine and cadmium atoms alternately along the c-axis. K⁺ cations are filled in the intralayer open channels to balance charge. IR and Raman spectra further confirm the crystal structure. Photoluminescent measurement reveals that CdZn₂KB₂O₆F exhibits blue fluorescence at room temperature in the solid-state.     

Crystal structure, magnetic susceptibility and Mössbauer spectroscopy of the mixed-valence iron phosphate Na1/2Cu4/3Fe2(PO4)3

Single crystals of a new mixed-valent iron phosphate Na_1/2Cu_4/3Fe₂(PO₄)₃ have been synthesized by a flux method and structurally characterized from X-ray diffraction data. Crystal data: space group ; ; ; ; α=105.881(1)°; β=107.202(1)°; γ=101.467(1)°; Z=2; R₁=0.03; wR₂=0.093. The three-dimensional structure was found to be closely related to that of the well known Howardevansite structural type. It results from infinite chains of CuO₅ and FeO₆ polyhedra, joined together by (Cu,□)O₆ octahedra and PO₄ tetrahedra by corner-sharing. The large cavities in framework are occupied by Na⁺ ions. The magnetic susceptibility study revealed an antiferromagnetic behavior with Neel temperature of approximately 40 K. The Mössbauer spectroscopy confirmed the presence of iron in both +2 and +3 oxidation states.     

Hexachloroiridate(IV) as a redox probe for the electrochemical discrimination of B-DNA and M-DNA monolayers on gold

This paper demonstrates the effectiveness of using the redox couple to investigate DNA monolayers, and compares the potential advantages of this system to the standard redox couple. B-DNA monolayers were converted to M-DNA by incubation in buffer containing 0.4 mM Zn²⁺ at pH 8.6 and studied by cyclic voltammetry (CV), impedance spectroscopy (IS) and chronoamperometry (CA) with . Compared to B-DNA, M-DNA showed significant changes in CV, IS and CA spectra. However, only small changes were observed when the monolayers were incubated in Mg²⁺ at pH 8.6 or in Zn²⁺ at pH 6.0. The heterorgeneous electron-transfer rate (k_ET) between the redox probe and the surface of a bare gold electrode was determined to be 5.7 × 10⁻³ cm/s. For a B-DNA modified electrode, the k_ET through the monolayer was too slow to be measured. However, under M-DNA conditions, a k_ET of 1.5 × 10⁻³ cm/s was reached. As well, the percent change in resistance to charge transfer, measured by IS, was used to illustrate the dependence of M-DNA formation on pH. This result is consistent with Zn²⁺ ions replacing the imino protons on thymine and guanine residues. The redox couple was also effective in differentiating between single-stranded and double-stranded DNA during de-hybridization and rehybridization experiments.     

Unique charge ordering of manganese in a new mixed valent phosphate

A new mixed-valent manganese phosphate, , has been synthesized using hydrothermal method. Its monoclinic C2/c structure (a=12.5506(16) Å, b=10.4816(18) Å, c=13.6723(10) Å, β=103.758(11)°) forms a 3D framework of MnO₆ octahedra, MnO₅ trigonal bipyramids, PO₄ and PO₃OH tetrahedra. The main structural feature of this phosphate deals with its [Mn₄O₁₆]_∞ chains running along , which are interconnected through PO₄ and PO₃OH tetrahedra, forming intersecting tunnels running along [110], and [001]. The geometry of the [Mn₄O₁₆]_∞ chains and the charge ordering of manganese in the latter are unique: they consist of trimeric units of divalent manganese “” alternating with single trivalent Mn^IIIO₆ octahedra along . In each “” unit one central Mn^IIO₆ octahedron shares two opposite edges with two Mn^IIO₅ trigonal bipyramids. Along , one Mn(II) octahedron alternates with one Mn(III) octahedron by sharing one corner. The relationships between the structure of this unique charge ordered phosphate and other manganese phosphates are discussed.     

Auger recombination dynamics in clusters

Electronic relaxation dynamics following interband excitation from the 6s to the 6p band in mass selected clusters are measured through femtosecond time-resolved photoelectron imaging (TRPEI). This interband transition is pumped at 4.65 eV and probed at 1.55 eV. Auger decay of occurs on a timescale of 490 ± 100 fs, and a similar time constant is seen for the transient excited state population created by the pump pulse. These time constants are an order of magnitude faster than those seen in previous experiments in which the lone p-electron in was excited within the p-band. The results presented here imply that substantial relaxation of either electrons in the p-band or the hole in the s-band takes place prior to Auger emission, with electron–electron scattering playing a key role in the fast observed dynamics.     

Ab initio electronic and rovibrational structure of

The electronic structure of the ground state of has been investigated using relativistically-corrected CCSD(T) in conjunction with ANO-RCC (Mg) and aug-cc-pVQZ (H) basis sets. The molecular potential energy surface possessed minima corresponding to both ¹A₁ and equilibrium structures (with a ¹Σ⁺ transition state). The ¹A₁ structure possessed R_e and θ_e values of 2.0297 Å and of 22.09°, respectively. The higher-energy structure exhibited an R_e value of 2.1658 Å. Property surfaces were constructed to calculate rovibrational energies and spectral line intensities for the ground states of , (¹A′) MgHD²⁺ and . For the vibration ground state of , the vibration-averaged R_e and θ_e values were calculated to be 2.0209 Å and 22.53°, respectively. The A, B and C rotational constants were calculated to be 58.0, 2.21 and 2.11 cm⁻¹, respectively.     

Low-temperature heat capacities and standard molar enthalpy of formation of the solid-state coordination compound trans-Cu(Ala)2(s) (Ala = l-α-alanine)

Low-temperature heat capacities of the solid coordination compound trans-Cu(Ala)₂(s) have been measured by a precision automated adiabatic calorimeter over the temperature range from T = 78 K to 390 K. The experimental values of the molar heat capacities in the temperature region were fitted to a polynomial equation of heat capacities (C_p,m) with the reduced temperatures (X), [X = f (T)], by a least square method. The smoothed molar heat capacities and thermodynamic functions of the complex trans-Cu(Ala)₂(s) were calculated based on the fitted polynomial. The smoothed values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated with an interval of 5 K. Enthalpies of dissolution of {Cu(Ac)₂·H₂O(s) + 2Ala (s)} and 2:1 HAc (aq) in 100 ml of 2 mol dm⁻³ HCl, respectively, and trans-Cu(Ala)₂(s) in the solvent [2:1 HAc (aq) + 2 mol dm⁻³ HCl] at T = 298.15 K were determined to be , , and by means of an isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the compound was determined as from the enthalpies of dissolution and other auxiliary thermodynamic data using a Hess thermochemical cycle.     

Preparation and crystal structure of binuclear chloro{6-[[chloro(triphenylphosphine)platinum](mesitylimino)methyl]pyridin-2-yl}bis(triphenylphosphine)platinum(II)

Treatment of N,N′-bis(mesityl)pyridine-2,6-carboxyimidoyl dichloride, 1, in toluene solution with [Pt(PPh₃)₄] at 100 °C afforded a novel platinacyclic compound, 3, in 63% yield, instead of the expected compound 2. The molecular and crystal structures of the title compound, 3, have been determined by the single crystal X-ray diffraction technique. The coordination geometries around the Pt atoms are distorted square-planar. In the crystal structure, the molecules are linked by a pair of C–H···N hydrogen bonds into a centrosymmetric dimer with an ring, centred at (1/2,1/2,1/2).     

A simple colorimetric sensor for biologically important anions based on intramolecular charge transfer (ICT)

A sensitive colorimetric sensor (1) based on 4,5-dinitrobenzene-1,2-diamine was designed and synthesized. Binding of anions such as AcO⁻, F⁻ and results in a notable change in the visible region of spectrum (an approximately 90 nm red shift), which can be detected by the ‘naked-eye’. Furthermore, the binding ability was evaluated by UV–vis titration experiments as following: AcO⁻ > F⁻ >   Cl⁻, Br⁻, I⁻. The nature of the color change of 1 induced by AcO⁻ was due to the intramolecular charge transfer (ICT) which was confirmed by X-ray crystal structure and ¹H NMR titration spectra.     

Low-temperature flux synthesis of a novel one-dimensional copper (II) chlorophosphate: crystal structure and magnetic property of Na3[CuO(HPO4)Cl]

A novel one-dimensional copper (II) chlorophosphate, Na₃[CuO(HPO₄)Cl] has been prepared by using the low-temperature flux method. It crystallizes in the orthorhombic system, space group Pnma, a=11.096(2), b=6.5703(13) and , , Z=4. Its crystal structure presents a one-dimensional character in such a way that the edge-sharing CuO₄Cl₂ building blocks yield a novel linear octahedral chains via Cu-O-Cu and Cu-Cl-Cu bridges. The HPO₄ groups, as the modifier, are grafted onto these chains and sodium ions are located between the chains to satisfy the charge balance. The magnetic susceptibility obeys a Curie-Weiss law above 120 K with C=0.38 (emu K)/mol and , showing the Cu²⁺ character and antiferromagnetic interactions.     

Preparation and characterization novel polymer-coated magnetic nanoparticles as carriers for doxorubicin

The poly(lactide-co-glycolide)-coated magnetic nanoparticles (PLGA MNPs) were prepared as carriers of doxorubicin (PLGA-DOX MNPs) through water-in-oil-in-water (W/O/W) emulsification method. The characteristics of PLGA-DOX MNPs were measured by using transmission electron microscopy (TEM) and vibrating-sampling magnetometry (VSM). It was found that the synthesized nanoparticles were spherical in shape with an average size of 100 ± 20 nm, low aggregation and good magnetic responsivity. Meanwhile, the drug content and encapsulation efficiency of nanoparticles can be achieved by varying the feed weight ratios of PLGA and DOX particles. These PLGA-DOX MNPs also demonstrated sustained release of DOX at 37 °C in buffer solution. Besides, influence of drug-loaded nanoparticles on in vitro cytotoxicity was determined by MTT assay, while cellular apoptosis was detected by Annexin V-FITC apoptosis detection kit. The results showed that PLGA-DOX MNPs retained significant antitumor activities. Therefore, PLGA-DOX MNPs might be considered a promising drug delivery system for cancer chemotherapy.     

Synthesis, structure, magnetic susceptibility and Mössbauer and Raman spectroscopies of the new oxyphosphate Fe0.50TiO(PO4)

A new iron titanyl oxyphosphate Fe_0.50TiO(PO₄) was synthesized by both solid-state reaction and Cu²⁺-Fe²⁺ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer spectroscopy, magnetic susceptibility measurements and Raman spectroscopy. The crystal structure of the compound was refined, using X-ray powder diffraction data, by Rietveld profile method; it crytallizes in the monoclinic system, space group P2₁/c (No.14), with , , , β=120.36°(1), and Z=4. The volume of the title compound is comparable to those of the M_0.50^IITiO(PO₄) series, where M^II=Mg, Co, Ni and Zn. The framework is built up from [TiO₆] octahedra and [PO₄] tetrahedra. [TiO₆] octahedra are linked together by corners and form infinite chains along the c-axis. Ti atoms are displaced from the center of octahedral units showing an alternating short distance (1.73 Å) and a long one (2.22 Å). These chains are linked together by [PO₄] tetrahedra. Fe²⁺ cations occupy a triangle-based antiprism sharing two faces with two [TiO₆] octahedra. Mössbauer and magnetic measurements show the existence of iron only in divalent state, located exclusively in octahedral sites with high spin configuration (t_2g⁴e_g²). Raman study confirms the existence of Ti-O-Ti chains.