Jonáš Tokarský

Preparation and characterization of photoactive composite kaolinite/TiO2

Preparation of nanocomposite kaolinite/TiO(2), using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. A variable (kaolin)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO(2) content in prepared nanocomposites. Calcination of the composites at 600 °C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO(2) composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and diffuse reflectance spectroscopy in the UV-VIS region. Structural ordering of TiO(2) on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the Material Studio modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.

A simple molecular modeling method for the characterization of polymeric drug carriers

A simple molecular modeling method for the characterization of polymeric drug carriers is presented. Six biodegradable polymers have been investigated as drug carriers using molecular simulations: l-polylactide, d-polylactide, chitosan, polyglycolic acid, polyethylene glycol and cellulose. Cyclosporine A has been chosen as a model drug substance. Classical molecular dynamics and docking calculations were employed to model and predict polymer-drug interactions. These interactions have been analyzed by non-bond interaction energy and interaction parameter calculated using Flory-Huggins theory. Flexibility of polymer chains has been characterized by the change of gyration radius along the molecular dynamics trajectory. The relationship between mixing energy, chain length and chain flexibility has been revealed for each polymer/drug system.

Structure and stability of kaolinite/TiO2 nanocomposite: DFT and MM computations

AbstractThe adhesion of TiO2 (anatase structure) nanoparticles to kaolinite substrate was investigated using molecular modeling. Universal force field computation, density function theory computation, and a combination of both two approaches were used. This study enabled the adhesion energy for the TiO2/kaolinite nanocomposite to be estimated, and revealed the preferred orientation of the TiO2 nanoparticles on the kaolinite substrate. The results of all three levels of computation were compared in order to show that the accuracy of universal force field computations is sufficient in this context. The role of nanoparticle size and the importance of the nanoparticle–substrate bonding contribution are presented here and discussed. A comparison of the molecular modeling results with scanning electron microscopy observations showed that the results of the modeling were consistent with the experimental data, and that this approach can be used to help characterize nanocomposites of the nanoparticle/phyllosilicate substrate type. FigureDensity function theory computation, Universal force field computation and the combination of both two approaches are used to estimate adhesion energies for TiO2/kaolinite nanocomposite and to reveal the preferred orientation of TiO2 nanoparticles on the kaolinite substrate

Molecular modeling of gel nanoparticles with cyclosporine A for oral drug delivery

Structure and behavior of amphiphilogel nanoparticles as a drug carriers for cyclosporine A (CsA) have been studied by the molecular modeling using empirical force field. Five atomistic models of a gel-based emulsions (GEM) with various gel compositions have been investigated in order to find a system most similar to a sixth atomistic model of self-microemulsifying drug delivery system (SMEDDS) taken as an exemplar of CsA delivery system. Structural parameters and energy characteristics (i.e. non-bond interaction energy between CsA and whole remaining components of a gel nanoparticle, CsA/gel nanoparticle intermolecular non-bond interaction energy, CsA-gel molecule pair interaction energy, volume fraction, concentration profiles and number of pervaded water molecules) of these six models in a waterless form and in a water containing form have been studied in dependence on the composition. The Flory-Huggins theory as implemented in the Accelrys Materials Studio 4.2 modeling environment was used to study the pair interactions of cyclosporine A with various types of surfactants. Structural parameters and energy characteristics of all systems have been compared and one composition was selected as a very promising for further experimental study.

Structure and properties of kaolinite intercalated with potassium acetate and their nanocomposites with polyamide 1010

The intercalation complex marked as KAA was a modified kaolinite (KA) with potassium acetate as an intercalating agent, which was used as a reinforcement to prepare polyamide 1010 (PA1010) matrix nanocomposites (PKAA) by melt compounding. X-Ray diffraction results indicated that the interlayer basal spacing increased from 0.720 nm (KA) to 1.411 nm (KAA), after an intercalation process with an intercalation ratio of 99.7%. The nanocomposite with 2 wt% KAA exhibited the best comprehensive mechanical properties, including tensile strength, elongation at break, and notched impact strength. Furthermore, the thermal performance of these nanocomposites could be effectively improved, which manifested as the elevated glass transition temperature and thermal decomposition temperature in the test results of the dynamic mechanical thermal analysis and thermogravimetric analysis (TGA). The melting point and crystallization behavior of PKAA were also increased due to results from the differential scanning calorimetry. Besides, the bilayer inserting model was simulated by Materials Studios software to further understand the structure-function relationship of PKAA.

Functional nanostructures of montmorillonite with conducting polyaniline

Abstract The present work describes the effect of montmorillonite (MMT) particles on the alignment of conducting polyaniline (PANI) chains in a PANI/MMT composite. The composite was prepared both as a powder, pressed into pellets, and as thin films deposited on glass surfaces. For comparison, pure PANI was also prepared in these two forms. A combination of X-ray powder diffraction analysis and molecular modelling confirmed the successful intercalation of the PANI into theMMT, while Raman spectroscopy confirmed the presence of the conducting form of PANI (i.e. the emeraldine salt) in all samples. Scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to study the morphologies of all samples. Conductivity measurements showed that the presence of the MMT particles in the PANI/MMT composites contributes to a significant increase in the electrical conductivity in comparison with the pure PANI samples. Moreover, in the pressed pellets the presence of theMMT particles led to an extremely high electrical anisotropy. TheUV-VIS spectroscopy results showed that the PANI/MMT thin film exhibited a selective transmittance in the range 450-650 nm; therefore, the PANI/MMT thin film is not only conductive, but also suitable for use in various optical applications.

Structure and properties of polyaniline/montmorillonite nanocomposites prepared under various conditions

Abstract Three different methods have been used for the preparation of polyaniline/montmorillonite nanocomposites: (i) two-step process: first intercalation of anilinium into Ca–montmorillonite structure followed with oxidisation; (ii) two-step process: first oxidisation with subsequent addition of Ca–montmorillonite aqueous suspension; (iii) one-step process: oxidisation and polymerisation in the presence of Ca–montmorillonite aqueous suspension. Structure and properties of samples have been investigated using combination of X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, elemental analysis and conductivity measurements in order to find the relationship between technology, structure and electrical properties. Results confirmed the crucial effect of the preparative procedure on polyaniline/montmorillonite composites.

Influence of Microwave Treatment on Ghassoul Stability

Moroccan clay with a significant portion of stevensite, locally known as Ghassoul, is a very good sorbent. For the facilitation of the sorbent separation, it is convenient to use its magnetically modified form. Recently, the composites of FexOy/Ghassoul have been prepared using simple microwave assisted synthesis and the effect of method preparation on composite composition has been proven. The aim of the presented work was to evaluate the effect of the microwave radiation on the structure and stability of native Ghassoul. Water extracts were prepared by batch method using deionized water. The leachate was prepared for 1, 6 and 24 hours in 1:1000 ratio of solid and liquid phase from the original material and the material after interaction with microwave radiation. In the filtrate, pH was determined as well as concentrations of Al, Ca, K, Mg, Na and Si using Atomic emission spectrometry with inductively coupled plasma. The results imply that microwave treatment of the material changes the pH of the leachates to more acidic compared to the original material in which the pH increases. Even the microwave treatment of Ghassoul did not cause changes in Al, in contrast with Si which was leached considerably more in the case of the microwave-treated sample. Opposite result was observed in the case of Na and Mg. Leached amounts of Ca were comparable in both the treatments, leached amounts K were not affected by the treatment and leaching time.

Interaction of antitumoral drug erlotinib with biodegradable triblock copolymers: a molecular modeling study

Combination of molecular dynamics simulations and miscibility calculations was used to investigate erlotinib drug delivery systems based on poly-ε-caprolactone–polyethylene glycol–poly-ε-caprolactone (PCL–PEG–PCL) and poly-ε-caprolactone–polyglycolic acid–poly-ε-caprolactone (PCL–PGA–PCL) biodegradable copolymers. The molecular modeling strategy involving visual observation of models, concentration profile analysis, Flory–Huggins χ parameter, cohesive energy density, and mean square displacement calculations reproduced experimental evidence of erlotinib release from PCL–PEG–PCL matrix successfully. Increasing portion of PCL in PCL–PEG–PCL copolymer led to dissolution of erlotinib aggregates recorded in visual and concentration profile analyses. Higher portion of PCL led to higher cohesive energy density and lower mean square displacement values. Success of this strategy in reproduction of experimental data made an opportunity to utilize the same modeling design in prediction of erlotinib release from similar but not yet experimentally tested PCL–PGA–PCL matrix. In this case, agglomeration of erlotinib molecules and stronger cohesive energy density values were observed.