Polyaniline nanoparticles with controlled sizes using a cross-linked carboxymethyl chitin template

Polyaniline (PANI) nanoparticles were chemically synthesized in the presence of a cross-linked carboxymethyl chitin (CM-chitin) acting as a template. The reaction was performed under acidic conditions and the template was removed after the polymerization of aniline was completed. The morphology of the synthesized PANI was globular with a diameter in the nanometer range. The degree of cross-linking of the CM-chitin played an important role in determining the size of the obtained PANI nanoparticles, which decreased from approximately 392 to 160 nm with increase in concentration of the cross-linking agent, glutaraldehyde, from 0 to 9 μmol, respectively. At a higher glutaraldehyde concentration (18 μmol), an aggregated PANI network was observed due to the incomplete removal of the more highly cross-linked CM-chitin. Molecular characterization (including UV-Visible, FTIR, TGA, and XRD techniques) revealed that the structure of the synthesized PANI nanoparticles is identical to that of conventional PANI. A mechanism is proposed for the formation of PANI nanoparticles in the presence of the cross-linked CM-chitin template.     

Biocompatible polymeric implants for controlled drug delivery produced by MAPLE

Implants consisting of drug cores coated with polymeric films were developed for delivering drugs in a controlled manner. The polymeric films were produced using matrix assisted pulsed laser evaporation (MAPLE) and consist of poly(lactide-co-glycolide) (PLGA), used individually as well as blended with polyethylene glycol (PEG). Indomethacin (INC) was used as model drug. The implants were tested in vitro (i.e. in conditions similar with those encountered inside the body), for predicting their behavior after implantation at the site of action. To this end, they were immersed in physiological media (i.e. phosphate buffered saline PBS pH 7.4 and blood). At various intervals of PBS immersion (and respectively in blood), the polymeric films coating the drug cores were studied in terms of morphology, chemistry, wettability and blood compatibility. PEG:PLGA film exhibited superior properties as compared to PLGA film, the corresponding implant being thus more suitable for internal use in the human body. In addition, the implant containing PEG:PLGA film provided an efficient and sustained release of the drug. The kinetics of the drug release was consistent with a diffusion mediated mechanism (as revealed by fitting the data with Higuchi's model); the drug was gradually released through the pores formed during PBS immersion. In contrast, the implant containing PLGA film showed poor drug delivery rates and mechanical failure. In this case, fitting the data with Hixson-Crowell model indicated a release mechanism dominated by polymer erosion.     

Facile fabrication of mesoporous ZnO nanospheres for the controlled delivery of captopril

We numerically investigate the surface plasmon resonance (SPR) mode patterns in periodic silver-shell nanopearl arrays and its dimer arrays with the core relative permittivities filled inside the dielectric holes (DHs) by means of finite element method with three-dimensional calculations. Numerical results of resonant wavelengths corresponding to the effects of different period of unit cells, radii of DHs, illumination wavelengths, field propagation, electrical field stream lines, charge distributions, charge densities, half- body charge densities, and the DH core relative permittivities of periodic silver-shell nanopearls are also reported. It can be seen that the periodic silver-shell nanopearl arrays and its dimer arrays with DHs exhibit tunable SPR modes corresponding to the bonding and anti-bonding modes, respectively, that are not observed for the solid silver cases with the same volume. These results are crucial in designing localized SPR sensors and other optical devices based on periodic metal nanoparticle array structures.     

Enantiomeric PLA–PEG block copolymers and their stereocomplex micelles used as rifampin delivery

A novelty approach to self-assembling stereocomplex micelles by enantiomeric PLA–PEG block copolymers as a drug delivery carrier was described. The particles were encapsulated by enantiomeric PLA–PEG stereocomplex to form nanoscale micelles different from the microspheres or the single micelles by PLLA or PDLA in the reported literatures. First, the block copolymers of enantiomeric poly(l-lactide)–poly(ethylene–glycol) (PLLA–PEG) and poly(D-lactide)–poly(ethylene–glycol) (PDLA–PEG) were synthesized by the ring-opening polymerization of l-lactide and d-lactide in the presence of monomethoxy PEG, respectively. Second, the stereocomplex block copolymer micelles were obtained by the self-assembly of the equimolar mixtures of enantiomeric PLA–PEG copolymers in water. These micelles possessed partially the crystallized hydrophobic cores with the critical micelle concentrations (cmc) in the range of 0.8–4.8 mg/l and the mean hydrodynamic diameters ranging from 40 to 120 nm. The micelle sizes and cmc values obviously depended on the hydrophobic block PLA content in the copolymer. Compared with the single PLLA–PEG or PDLA–PEG micelles, the cmc values of the stereocomplex micelles became lower and the sizes of the stereocomplex micelles formed smaller. And lastly, the stereocomplex micelles encapsulated with rifampin were tested for the controlled release application. The rifampin loading capacity and encapsulation efficiency by the stereocomplex micelles were higher than those by the single polymer micelles, respectively. The drug release time in vitro was depending on the composites of the block copolymers and also could be controlled by the polymer molecular weight and the morphology of the polymer micelles.     

Conditional femtosecond pulse collapse for white-light and plasma delivery to a controlled distance

Collisions between ultrashort pulses with different wavelengths are studied numerically. The relative delay, wavelength difference, focusing geometry, and chirp are used to accurately control the distance at which pulses undergo conditional collapse and generate plasma and white light. A wide supercontinuum spectrum is achievable even with pulses that by themselves do not have sufficient power for filament formation.     

Dual-capillary electroencapsulation of mesoporous silicon drug carrier particles for controlled oral drug delivery

The feasibility of electroencapsulation of mesoporous silicon (PSi) micro- and nanoparticles as a method to seal the PSi particles in mechanically processable solid units, and to facilitate time and site specific drug release from the pores of PSi particles, is of interest in the present work. Suitable microcapsules and micromatrix particles were produced in a single-step process using a setup with two electrospraying nozzles kept at high electric potentials of opposite polarities. The structures of the produced particles were analyzed by microscope and X-ray micro- and nanotomography imaging, and optimization of the electroencapsulation process production efficiency is discussed.     

Biodegradable self-assembled PEG-PCL-PEG micelles for hydrophobic drug delivery,part 2: in vitro and in vivo toxicity evaluation

Polymeric micelles, prepared by self-assembly of biodegradable poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG–PCL–PEG, PECE) copolymer in aqueous solution, were proved to be a potential carrier for hydrophobic drug honokiol in our previous contribution. In this study, the safety of blank PECE micelles was evaluated in vitro and in vivo before its further application in biomedical field. The average particle size of obtained micelle was 83.47 ± 0.44 nm, and polydisperse index was 0.27 ± 0.01. Also, the zeta potential of prepared micelles was about −0.41 ± 0.02 mV. Otherwise, cytotoxicity of PECE micelles was evaluated by cell viability assay using L929 cells, and in vitro hemolytic test was also performed. In vivo acute toxicity evaluation and histopathological study of PECE micelles were conducted in BALB/c mice by intravenous administration. Furthermore, serum chemistry profile and complete blood count test were performed. In acute toxicity test, the mice were observed continuously for 7 days. For histopathological study, samples including heart, liver, spleen, lung, and kidneys were histochemical prepared and stained with hematoxylin-eosin (H&E). No mortality or significant signs of acute toxicity was observed during the whole observation period, and there is no significant lesion to be shown in histopathological study of major organs. The maximal tolerance dose of PECE micelles (100 mg/mL) by intravenous administration was calculated to be higher than 10 g/kg body weight (b.w.). The results indicated that the obtained PECE micelles was non-toxic after intravenous administration, and could be a safe candidate for hydrophobic drug delivery system.     

Form-factors for different aggregation models of micelles

Spherical micelles in ionic micellar solutions, often aggregate to form spherical, cylindrical or chain-like aggregates on addition of salt to the solution. It is known that the technique of small angle neutron scattering (SANS) can be used to distinguish spherical and cylindrical aggregates. To examine if SANS can be used to distinguish the latter two aggregation processes, we have calculated the angular distribution of scattered neutrons from 0.002 M CTAB solutions. These calculations show that aggregation of CTAB micelles results in large changes in SANS spectra. The shapes of SANS spectra are different for the above three types of aggregates, suggesting that technique of SANS can indeed be used to distinguish the three aggregation processes. The size of the aggregate can also be obtained from such studies.     

Characterization of sonochemically prepared human serum albumin nanocapsules using different plant oils as core component for targeted drug delivery

The focus of this study is the preparation of proteinaceous human serum albumin (HSA) nanocapsules with biocompatible plant oil cores avoiding toxic cross-linker and noxious non-aqueous liquids. The sonochemical preparation of HSA capsules with different plant oils yields particles with narrow size distribution forming suspensions stable for at least 14 days and enabling long-term storage by freezing. Furthermore, wheat germ agglutinin (WGA) as a targeting molecule was successfully embedded into the proteinaceous particle shell at a molar ratio of 7:1 (HSA/WGA). As urothelial cell binding studies revealed up to 55% higher cell binding potential of WGA-grafted particles than those without a targeter, targeted protein nanocapsules represent the first step towards new and innovative formulations.     

Fluorescence study of the core/shell interface in polyelectrolyte micelles. Binding of fluorescent surfactants in the interfacial region

Properties of the interfacial region between the nonpolar core and the polar shell in polystyreneblock-poly (methacrylic acid) micelles were studied by fluorescence techniques using 5-(N-octadecanoyl) aminofluorescein (OAF) as a probe for microfluidity and local pH. The block copolymer used was tagged between blocks by one 9, 10-diphenylanthracene (DPA) group, which allowed us to study binding of OAF at the interface by means of nonradiative energy transfer between DPA and OAF. A shift in the pK _a of OAF and appreciable changes in anisotropy and quenching efficiency due to immobilization of the fluorophore head-group in hydrophobic poly(methacrylic acid) domains were observed after binding of the probe at the interface.     

Mathematical modeling of microbubble cavitation at 70 kHz and the importance of the subharmonic in drug delivery from micelles

In order to gain insight into the experimental observation of ultrasound-induced release of drugs from micelles, we modeled the dynamic oscillations of a 10-μm-diameter bubble insonated at 70 kHz. The Parlitz modification of the Keller–Miksis model was employed to generate bubble dynamics over a wide range of mechanical index values. The resulting Poincaré maps and bifurcation diagram show that bubble oscillations bifurcate at a MI value of 0.32, then return apparently to a single mode before displaying a sudden onset of chaotic behavior at 0.35. The experimental release of drug from micelles occurs at a MI value of 0.37 and correlates with the intensity of the subharmonic in (μW/cm²) of the acoustic spectrum. The dynamic model shows the return to single mode at a MI value of 0.43, and bifurcation leading to chaos at values above 0.5. The correlation between the chaotic behavior predicted by the model and drug release hints at insonation conditions that could facilitate drug delivery.     

Pluronic F127-cyclodextrin conjugate micelles for encapsulation of honokiol

To overcome honokiol’s poor water solubility and investigate its antifungal activity and pharmacokinetic property, Pluronic® F-127 (F127)-cyclodextrin conjugate was synthesized and employed to prepare honokiol-loaded micelles through emulsion-solvent evaporation method. The drug-loaded micelles were obtained with 92.30?±?3.28% of encapsulation efficiency being higher than that obtained from F127 due to additional cyclodextrin inclusion. Fourier transformation infrared spectrometry and diffraction scanning calorimetry analysis tests demonstrated that honokiol was successfully encapsulated into the conjugate micelles in the amorphous or solid solution state because of their interactions. Meanwhile, in vitro antifungal activity experiment indicated that the MIC₉₀ of drug-loaded micelles was 64 μg/mL, showing the same antifungal activity as pure honokiol although it obviously retarded honokiol’s release. In vivo pharmacokinetic results confirmed that in vivo area under curve and apparent distribution volume of honokiol in drug-loaded micelles were 2- and 1.69-folds higher than that for pure honokiol, with its obvious prolonged mean retention time and half-life period, respectively. The clearance rate of honokiol was also shortened about 2-fold in comparison with pure honokiol when encapsulated into the micelles. These results suggest that the developed F127-cyclodextrin micellar formulation is a promising drug delivery system for antifungal drugs.

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Biodistribution of doxorubicin and nanostructured ferrocarbon carrier particles in organism during magnetically controlled drug delivery

Biodistribution of doxorubicin and ferrocarbon carrier particles in organism during and after magnetically controlled anti-tumor drug delivery and deposition was studied. Animal tests show high concentration of the cytostatic drug in the target zone, while its concentration is three orders of magnitude lower in bloodstream and other organs. A significant depot of the drug remains on the deposited particles days after the procedure. Macrophages actively phagocytose the ferrocarbon (FeC) particles and remain viable long enough to carry them to the lymph nodes.     

Synthesis and characterization of novel urethane cross-linked ormolytes for solid-state lithium batteries

A novel family of Li⁺-based organic/inorganic materials obtained by the sol–gel process is proposed. The compounds, named urethanesils, are obtained as thin, transparent, elastomeric and amorphous monolithic films. They incorporate solvating pendant methyl end-capped short poly(oxyethylene) chains which are covalently bonded to the silica backbone by means of urethane cross-links. The urethane linkages are formed by reacting 3-isocyanatepropyltriethoxysilane with hepta(ethylene glycol) methyl ether (HEGME). Li⁺ has been introduced in the urethanesils as lithium triflate (LiCF₃SO₃). Two compositions of salt have been considered: n=100 and 8, where n represents the molar ratio of (OCH₂CH₂) units per lithium ion. Infrared spectroscopy provides conclusive evidence that, although the oligopolyether chains of HEGME become less disordered upon formation of the inorganic network, the addition of salt induces disorder. The FTIR spectrum of the most concentrated urethanesil strongly suggests that the triflate ions are essentially coordinated in the material. The thermal and mechanical properties of the undoped and doped urethanesils have been investigated by DSC and DMTA. At 90°C, the highest ionic conductivity (approximately 10⁻⁶ Ω⁻¹ cm⁻¹) is observed for composition n=8. The electrochemical stability domain of the least concentrated urethanesil spans 5 V.     

A double core model for fission

A fission model formed of two cores of stable nuclei is proposed. Fission is viewed as a neutron excess problem. Suggested yield formula takes account of the core stabilities, the neutron excess and neutron acceptibility of the cores.