Łukasz John

Imaging physicochemical reactions occurring at the pore surface in binary bioactive glass foams by micro ion beam analysis.

In this work, the physicochemical reactions occurring at the surface of bioactive sol-gel derived 3D glass scaffolds via a complete PIXE characterization were studied. 3D glass foams in the SiO(2)-CaO system were prepared by sol-gel route. Samples of glass scaffolds were soaked in biological fluids for periods up to 2 days. The surface changes were characterized using particle induced X-ray emission (PIXE) associated to Rutherford backscattering spectroscopy (RBS), which are efficient methods to perform quantitative chemical maps. Elemental maps of major and trace elements at the glass/biological fluids interface were obtained at the micrometer scale for every interaction time. Results revealed interconnected macropores and physicochemical reactions occurring at the surface of pores. The micro-PIXE-RBS characterization of the pores/biological fluids interface shows the glass dissolution and the rapid formation of a Ca rich layer with the presence of phosphorus that came from biological fluids. After 2 days, a calcium phosphate-rich layer containing magnesium is formed at the surface of the glass scaffolds. We demonstrate that quantities of phosphorus provided only by the biological medium have a significant impact on the development and the formation of the phosphocalcic layer.

Novel organic–inorganic hybrids based on T8 and T10 silsesquioxanes: synthesis, cage-rearrangement and properties

In this paper, we present a simple approach for the synthesis of well-defined macromolecules based on precisely isolated amino- and amido-functionalized octa T8 and deca T10 silsesquioxanes (SQs). Here, we show that reorganization of the siloxane cage-like core (T8 → T10) can be easily performed, including isolation of intermediates, and cage rearrangement achieved by using Bronsted superacid, trifluoromethanesulfonic acid (CF3SO3H). Moreover, T10-like SQs can be obtained in a one-step reaction by alkoxysilane condensation in trifluoromethanesulfonic acid conditions. The resulting decamers of amine-SQ and an amido-functionalized derivative containing long alkyl chains are reported for the first time in the literature. The non-fluorinated amido derivatives due to their lamellar-like nature and specific packing can serve as transparent hydrophobic coatings in various industrial applications. The obtained compounds were fully characterized using FT-IR, UV-vis, multinuclear NMR (1H, 13C, 29Si), DOSY NMR, TG-DTA, DSC, HR-MS, TEM, EDS and elemental analysis.

Lactide as the Playmaker of the ROP Game: Theoretical and Experimental Investigation of Ring-Opening Polymerization of Lactide Initiated by Aminonaphtholate Zinc Complexes

A family of homo- and heteroleptic zinc complexes bearing aminonaphtholate ligands was synthesized and fully characterized. Using NMR spectroscopy and DFT calculation, bis-alkoxy-bridged complexes [LZn(μ-OR)]2 were confirmed to have dimeric structures in solution, analogous to those obtained via X-ray crystallography. Surprisingly, a detailed experimental and theoretical study of the catalytic activity of [LZn(μ-OR)]2 in the ring-opening polymerization (ROP) of lactides showed that although well-defined alkoxy dimers possess a single-site structural motif, the most active initiator is obtained during in situ alcoholysis of the alkylzinc precursor. These results indicate that rational ancillary and alkoxy ligand design that takes into account its mutual interaction on monomer coordination may be key to the synthesis of new high-performance ROP catalysts.

Synthesis and microstructural properties of the scaffold based on a 3-(trimethoxysilyl)propyl methacrylate–POSS hybrid towards potential tissue engineering applications

The aim of this work was to develop an efficient approach to prepare a macroporous scaffold for sophisticated bone replacement, avoiding a long-lasting and complex methodology. Such a scaffold based on the 3-(trimethoxysilyl)propyl methacrylate–POSS hybrid was synthesized via the reaction of 3-(trimethoxysilyl)propyl methacrylate and the trifluoromethanesulfonate–POSS salt. The results show that the chemical composition, structural dimensions, topography, and microstructural properties of the scaffold fulfill the potential requirements for hard-tissue engineering. The microstructural properties were evaluated with the use of X-ray microcomputed tomography (micro-CT) and nanoindentation tests. The former makes it possible to estimate the geometrical measures of the microstructure (porosity, thickness distribution, etc.), whereas the latter makes it possible to estimate the mechanical properties of the constituents of the material (hardness, stiffness modulus, creep, etc.). The aforementioned laboratory testing methods are modern techniques, currently being developed for materials science, making it possible to determine the microstructural/measures of the analyzed system.

Strontium-doped organic-inorganic hybrids towards three-dimensional scaffolds for osteogenic cells

Biomimetic organic-inorganic hybrid bioscaffolds are developed to complement or replace damaged fragments in bone tissue surgery. The aim of this work was to develop a simple and fast method to prepare composite material for bone engineering, avoiding time consuming and complex methodologies. The resulting materials (also called in this work as hybrid composites or hybrid scaffolds) have a three-dimensional macroporous polymer-like network derived from triethoxyvinylsilane (TEVS) and 2-hydroxyethylmethacrylate (HEMA) monomers, with incorporated calcium, strontium, and phosphate ions. The materials were fully characterized using FT-IR, biomineralization studies, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, scratch tests, Youngs modulus and compressive strength tests, and gas physisorption. We report a comprehensive study on the in vitro effect of novel strontium doped materials on human bone cells. In vitro investigations were conducted using a normal human osteoblast cell line that mimics the cellular events of the in vivo intramembranous bone formation process. The materials do not have a negative impact on the survival of the normal human osteoblasts; moreover, materials doped with strontium show that not only are cells able to survive, but they also attach to and grow on a bioscaffolds surface. For this reason, they may be used in future in vivo experiments.

Transformation of barium-titanium chloro-alkoxide compound to BaTiO3 nanoparticles by BaCl2 elimination.

In this Article, we present how the molecular precursor of binary oxide material having an excess of alkali earth metal can be transformed to the highly phase pure BaTiO3 perovskite. Here, we synthesized and compared two barium-titanium complexes with and without chloride ligands to determine the influences of different ligands on the phase purity of binary oxide nanoparticles. We prepared two barium-titanium complexes, i.e., [Ba4Ti2(μ6-O)(OCH2CH2OCH3)10(HOCH2CH2OCH3)2(HOOCCPh3)4] (1) and [Ba4Ti2(μ6-O)(μ3,η2-OCH2CH2OCH3)8(μ-OCH2CH2OCH3)2(μ-HOCH2CH2OCH3)4Cl4] (2). The barium-titanium precursors were characterized using elemental analysis, infrared and nuclear magnetic resonance spectroscopies, and single-crystal X-ray structural analysis, and their thermal decomposition products were compared. The complex 1 decomposed at 800 °C to give a mixture of BaTiO3 and Ba2TiO4, whereas 2 gave a BaCl2/BaTiO3 mixture. Particles of submicrometer size (30-50 nm) were obtained after leaching of BaCl2 from the raw powder using deionized water. Preliminary studies of barium titanate doped with Eu(3+) sintered at 900 °C showed that the dominant luminescence band arose from the strong electric dipole transition, (5)D0-(7)F2.

Unexpected Reactions between Ziegler–Natta Catalyst Components and Structural Characterization of Resulting Intermediates

In this work, we investigated precursors and procatalysts with well-defined crystal structures and morphologies in Ziegler-Natta systems to improve our understanding of the nature of the active metal sites. Molecular cluster precursors such as [Mg4Ti3(μ6-O)(μ3-OH)3(μ-OEt)9(OEt)3(EtOH)3Cl3], [Mg4Ti3(μ6-O)(μ3-OH)(μ3-OEt)2(μ-OEt)9(OEt)3(EtOH)3Cl3], and [Mg6Ti4(μ6-O)2(μ3-OH)4(μ-OEt)14(OEt)4(EtOH)2Cl2] were prepared via simple elimination of the cyclopentadienyl ring from Cp2TiCl2 as CpH in the presence of magnesium metal and ethanol. Titanocene dichloride acts as both a source of titanium and a magnesium-chlorinating agent. The resulting novel complexes were characterized using single-crystal X-ray diffraction. In these compounds, Ti(OEt)4 molecules are grafted onto Mg4 and Mg6 ethoxide cubane-like surfaces; this strongly affects the procatalyst morphology, which is transferred to the polymer. Mg4(OR)8 units act as carriers for the AlR3 co-catalyst, resulting in return of alkyl functions to the Ti center.

First step towards a model system of the drug delivery network based on amide-POSS nanocarriers

Among the varied and diverse family of drug delivery systems (DDSs), such as polymer–drug conjugates, polymeric micelles, dendrimers and molecular containers, polyhedral oligomeric silsesquioxanes (POSS) occupy a special position within the group of biocompatible drug carriers. The extraordinary recommendation of POSS for such systems derives from their three-dimensional structure, nanoscale size, low toxicity, and efficient cellular uptake. These conjugates can be strictly designed compared for instance to micelles, dendrimeric-drug or polymer/inorganic hybrid composites, in which the amount of therapeutics attached to the carrier is rather random, and there is a high probability that some of the drug molecules can be completely trapped inside the ramified structures. The combination of fully functionalized amide-POSS and pharmaceuticals might create a so-called sophisticated DDS. In such a system, the adsorbed drug molecules can be released under physiological conditions and then the POSS-based carrier will be hydrolyzed (at pH = 7.40) to a non-toxic carboxylic acid salt and a water soluble polyhedral oligomeric silsesquioxane containing an aminopropyl group that can be safely removed from the organism.

Designing of macroporous magnetic bioscaffold based on functionalized methacrylate network covered by hydroxyapatites and doped with nano-MgFe2O4 for potential cancer hyperthermia therapy

In this paper, we report on synthesis and characterization of three-dimensional biocomposite based on a polymerized 3-(trimethoxysilyl)propyl methacrylate/ethylene glycol dimethacrylate (pTMSPMA/pEGDMA) framework. The resulting composite was doped with Ca2+ and PO43- or decorated by hydroxyapatite (HA) and carbonate hydroxyapatite (CHA) to aid potential bone fixation and the in vitro bioactivity was evaluated. During the construction of the macroporous scaffold, the size and shape of pores were modified depending on the type of porogens which was applied (commercially available sugar, NaCl, or NH4Cl). Delivered 3D biomaterial was next used in preparation of a magnetic scaffold containing the core/shell magnetic nanoparticles covered with silicon-rich layer creating the amorphous magnetic dead layer. Preliminary magnetic studies showed that nanocrystalline MgFe2O4@SiO2 possesses a superparamagnetic properties, narrow hysteresis loop and virgin curve. The developed magnetic scaffold fulfills the requirements of a promising biomaterial for potential cancer hyperthermia therapy.

Synthesis of cubic spherosilicates for self–assembled organic–inorganic biohybrids based on functionalized methacrylates

The aim of this work is to develop an efficient synthetic approach to hexahedral cage-like organic–inorganic siloxane core biohybrids containing side chains fully functionalized by methacrylate groups derived from monomers such as 2-hydroxyethyl methacrylate (HEMA) or ethylene glycol dimethacrylate (EGDMA). The resulting hybrids were characterized using spectroscopic methods (FTIR, 1H, 13C, 29Si NMR), thermogravimetric and DSC analyses, and high resolution mass spectrometry (HR-MS). The obtained compounds, after polycondensation/polymerization reactions, were utilized in constructing 3D macroporous scaffolds which were examined using a scanning electron microscope (SEM). Covalent networks created by fully functionalized cubic spherosilicates can mimic certain biomaterials and constitute sophisticated, highly organized building blocks of complex systems.