Tantalum nanoparticles enhance the osteoinductivity of multiscale composites based on poly(lactide-co-glycolide) electrospun fibers embedded in a gelatin hydrogel

Bioresorbable polymeric materials have risen great interest as implants for bone tissue regeneration, since they show substantial advantages with respect to conventional metal devices, including biodegradability, flexibility, and the possibility to be easily modified to introduce specific functionalities. In the present work, an innovative nanocomposite scaffold, properly designed to show biomimetic and osteoinductive properties for potential application in bone tissue engineering, was developed. The scaffold is characterized by a multi-layer structure, completely different with respect to the so far employed polymeric implants, consisting in a poly(d,l-lactide-co-glycolide)/polyethylene glycol electrospun nanofibrous mat sandwiched between two hydrogel gelatin layers enriched with tantalum nanoparticles (NPs). The composition of the electrospun fibers, containing 10 wt% of polyethylene glycol, was selected to ensure a proper integration of the fibers in the gel phase, essential to endow the composite with flexibility and to prevent delamination between the layers. The scaffold maintained its structural integrity after six weeks of soaking in physiological solutions, albeit the gelatin phase was partially released. The combined use of gelatin, bioresorbable electrospun fibers and tantalum NPs endows the final device with biomimetic and osteoinductive properties. Indeed, results of the in vitro tests demonstrate that the obtained scaffolds clearly represent a favorable milieu for normal human bone-marrow derived mesenchymal stem cells viability and osteoblastic differentiation; moreover, inclusion of tantalum NPs in the scaffold improves cell performance with particular regard to early and late markers of osteoblastic differentiation.     

Enhancement of harmonic generation by Fresnel-lensing effects

We present experimental results of enhanced second- and third-harmonic generation efficiency from Fresnel-lensing effects. We obtained enhancement by a factor of 6 in the third-harmonic yield by simply limiting the laser beam with an iris. Higher enhancement factors (up to 16) were obtained with a Fresnel zone plate. The experimental findings are in good agreement with the results of a simple theoretical analysis.     

Alpha-cyclodextrin functionalized CdS nanocrystals for fabrication of 2/3 D assemblies

Different types of cyclodextrins (CDs) have been tested as mediators for the water phase transfer of organic-capped CdS nanocrystals (NCs), and alphaCD has been demonstrated to be the most effective system. The formation of a complex based on alphaCDs and colloidal NCs has been considered to be responsible for the phase transfer process and extensively investigated by optical, structural, and calorimetric measurements, as a function of the experimental parameters (pH and NC and CD concentration). A mechanism for the complexation phenomena has been suggested. The fabrication of 2/3 D supramolecular architectures has been proposed according to two different strategies. First, a layer-by-layer procedure has been used to obtain multilayered structures where polyelectrolyte layers have been intercalated with negatively charged alphaCD-CdS NC complexes by exploiting electrostatic interaction between polyelectrolyte and cyclodextrin OH groups. Second, a monolayer of CdS NCs has been deposited onto a self-assembled monolayer of sulfated CDs, thus combining the use of an electrostatic-force-based approach and host-guest chemistry. The important role played by host-guest interactions has then been revealed.     

Gleichzeitige Jod- und Schwefelbestimmung in organischen Verbindungen

Zusammenfassung Bei der Schwefelbestimmung nach Schöniger wird aus jodhaltigen Verbindungen elementares Jod freigesetzt. Die dadurch verursachte Störung der Sulfattitration nach Fritz und Yamamura wurde ausgeschaltet. Außerdem wurde ein einfaches und schnelles Verfahren zur gleichzeitigen Jod- und Schwefelbestimmung beschrieben.

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Simultaneous iodine and sulphur determination in organic compounds

Summary In the sulphur determination according to Schöniger, elemental iodine is released from iodine-containing compounds. The disturbance of the sulphate titration according to Fritz and Yamamura caused by this was eliminated. In addition, a simple and rapid technique for simultaneous determination of iodine and sulphur was described.

     

Water soluble progesterone–hydroxypropyl-β-cyclodextrin complex for injectable formulations

The use of cyclodextrin to increase the water solubility of progesterone (P) was described by Pitha as a complex with β-cyclodextrin and derivates to obtain a water soluble formulation (Pitha, J.: US patent n. 4,727,064). Hydroxypropyl-β-cyclodextrin (HPBCD) has a high water solubility which allows the solubilization of high quantity of P. Considering a 1:2 guess/host complex stoichiometry it is possible to obtain up to 50 mg/ml of P concentration, which is a considerable dosage for drug development in the progesterone therapy. In our drug development the P/HPBCD complex in water showed the formation of a light precipitate during stability ICH conditions. A precipitate formation was described already by Choi (J. Korean Pharm. Sci. 31(3), 151, 2001) and also by Pitha (US patent n. 4,727,064) but the chemical structure was not elucidated. In our case the precipitate was purified and it turned out to contain progesterone and residual unmodified β-cyclodextrin. We have developed a production process in which the residual unreacted β-cyclodextrin is separated from the HPBCD by the formation of the insoluble inclusion complex (Zoppetti et al.: European Patent deposit n. 05108494.5). The resulting P/HPBCD contains up to 0.1% of residual β-cyclodextrin and does not produce precipitate during the stability study. The complex stoichiometry and the complex constant were calculated by the phase solubility study according to Higuchi and Connors (Adv. Anal. Chem. Instrum. 4, 117, 1965) and the presence of the inclusion complex was demonstrated by DSC, NMR, X-ray, FTIR. The formulation prepared at pilot scale as injectable form compared with the commercial oil formulation demonstrated a favourable kinetic in humans.     

Random terpolymers for electroluminescent devices: Synthesis and characterization of new cyano‐containing poly(fluorenylene‐vinylene)s

The synthesis of new random poly(2,7‐fluorenylene‐vinylene)s was achieved by a Suzuki–Heck cascade polymerization reaction. The poly(fluorenylene‐vinylene) base structure was modified by the regio‐random incorporation of 1‐cyano‐2,5‐phenylene as electron withdrawing unit ( CN‐PFV1 ) and its properties were compared with terpolymers also embodying 1,4‐dioctyloxy‐2,5‐phenylene ( CN‐PFV2 ) or 3,6‐N‐octylcarbazole ( CN‐PFV3 ) as electron‐donating moieties. Thermal analysis revealed a high thermal stability (T_d > 389 °C) and the absence of glass transitions for all polymers. Cyclic voltammetry indicated a high electron affinity of the materials (2.96–3.21 eV) attributed to the presence of the cyano‐containing comonomer. In dilute solutions, the copolymers showed a broad green fluorescence with quantum yields ranging from 0.42 to 0.79, while in the solid state, a relatively narrow emission centered at ～ 560 nm, governed by the low‐energy segments within the π‐conjugated backbone, was observed. The electroluminescence properties of the materials were tested in OLED devices of ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Ca/Al or ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Alq₃/Ca/Al configurations, showing a bright green‐yellow emission that, in the case of CN‐PFV2 , reached 1403 cd/m² with efficiencies as high as 0.13 cd/A. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6051–6063, 2008     

Biological fixation of endosseous implants

Primary implant stability is ensured by a mechanical fixation of implants. However, during implant healing a biological anchorage is necessary to achieve final osseointegration.

Aim of this study was to investigate the histological aspects of biological fixation around titanium screws.

Forty-eight titanium screws with different surfaces (smooth, plasma sprayed, sand blasted) were inserted in tibiae and femura of sheep and analyzed by light microscope and SEM 1 hour, 14 and 90 days after implantation.

One hour after implantation the implant-bone gap was filled with a blood clot and host bone chips arising from burr surgical preparation or friction during implant insertion. Fourteen days after implantation new trabecular bone and enveloped bone chips were observed in the gap: no osteogenesis developed where implant threads were in contact with host bone. Ninety days after surgery all trabecular bone and most of the bone chips were substituted by a mature lamellar bone with few marrow spaces.

Our results suggest that the trabecular bone and bone chips represent a three-dimensional network ensuring a biological implant fixation in all different implant surfaces 2 weeks after surgery. Host bone chips could favour the peri-implant osteogenesis. Inter-trabecular and implant-trabecular marrow spaces of both trabecular and lamellar bone may favour the peri-implant bone turnover.     

The decomposition of nitramide in 80% dimethyl sulfoxide-20% water solvent system

The base-catalyzed decomposition of nitramide in 80% dimethyl sulfoxide (DMSO)-20% water (by weight) has been investigated. The Brønsted catalysis law for a series of seven carboxylate ions in this mixed solvent is compared with the Brønsted relationship previously obtained in water. There is no real change in mechanism upon changing the solvent from pure water to this aqueous mixture, which is approximately equimolar in the two-solvent components.