Drug Release from Lipogels According to Gelling Conditions and Mechanical Treatment

The release rate of a drug dissolved in the liquid phase of lipogels may be greatly affected by the type and concentration of gelling agent and by processing conditions and mechanical treatment of the ointment. These differences in release rate are reduced after application of mechanical stress comparable with the strain exerted on the ointment during application to the skin. Therefore, changes in the concentration of gelling agents used to achieve suitable consistency and manufacturing and packing processes that meet industrial and marketing requirements do not appear to exert a practical influence on drug availability after application to the skin.     

Polymer biomaterials (polyphosphazenes) in the repair of peripheral nervous system

Biodegradable polymers gives interesting perspectives of use in making artificial conduits for peripheral nerve reconstruction. Poliphosphazenes are materials highly biocompatible and have a controllable reabsorption rate. According to the substitutes that are introduced in the molecule, they can also be used as a framework for drug release. Conduits obtained with poli [bis(etilalanate) phosphazene] were evaluated as guides for nerve regeneration in an experimental animal model. In six Wistar rats, under general anesthesia and with microsurgical technique, the ischiatic nerve was isolated. On the right side a segment of the nerve was removed in order to create a 10 mm gap. The defect was then repaired using the conduit. On the controlateral limb the nerve continuity was restored using as an autograft the segment removed from the right. Control were performed at 30, 90, 180 days and consisted in histological and electron microscopy investigations. They showed the gradual degradation of the conduit without signs of local and general toxicity. The regeneration of the nerve fibers in the lumen of the conduit was not significantly different from the one obtained with the autologous grafts. So poliphosphazene conduits may be considered effective as a guide for nerve regeneration, above all for the possibility of use the polymer as a carrier for neurite-promoting factors.     

Accumulation of polarization-mode dispersion in cascades ofcompensated optical fibers

First-order compensation of polarization-mode dispersion (PMD) leaves residual, higher order PMD. We analyze the accumulation of residual distortion in cascades of compensated fibers. Total distortion is calculated and limitations on the total propagation length are given. While compensation can greatly extend the total propagation distance, its effectiveness diminishes rapidly as the bandwidth is increased     

Hydroxy- and fluorapatite films on Ti alloy substrates: Sol-gel preparation and characterization

In this paper we describe the preparation of hydroxyfluorapatite (HFA) and fluorapatite (FA) films deposited on titanium alloys by means of the dip-coating method starting from a sol-gel prepared colloidal solution. These materials are compared with hydroxyapatite (HA) films prepared via sol gel and commercial films prepared by means of plasma spray. The film characterization from the point of view of the composition and crystallinity, performed by means of XRD, FTIR and Raman Spectroscopies, has shown a good purity degree, and compositional homogeneity for the sol-gel materials, though traces of carboxy-hydroxy apatite were found. Also, the samples exhibit a good crystallinity. SEM pictures, taken on HA coating deposited via sol-gel, revealed a homogeneous surface structure and optimum features to set up a good prosthesis-tissue interface.     

Influence of membrane oxygenators on the pulsatile flow in extracorporeal circuits: an experimental analysis

An experimental analysis was carried out to evaluate the effects induced by two typical extracorporeal circuits on the pressure and flow generated by a roller pump with a pulsatile module. The hydraulic behaviour of the patient was simulated by means of a mechanical mock-up system consisting of a few lumped parameters reproducing the physiologic vascular impedance. Pressure and flow tracings were acquired at different locations along the circuit using an automatic data acquisition system. Nine lest conditions with different pulse frequency and systolic time values were examined using a mean volumetric flow rate of approximately 4 l/min. A complete analysis of the results obtained in terms of pressure drops and inflow-outflow differences across the components of the arterial line, as well as the calculation of the hydraulic pulsatile power along the circuit, allowed us to assess the influence of the various components upon the pulsatility. The results indicated that the membrane oxygenators tested slightly affect the pulsatility of the flow and the pressure; on the contrary the arterial pipe line is responsible for large damping and head losses. To optimize the use of pulsatile flow for cardiopulmonary bypass it is necessary to reduce the length of the arterial pipe lines thus integrating the circuit as much as possible.     

Osteopenic bone cell response to strontium-substituted hydroxyapatite

Ionic substitution is a powerful tool to improve the biological performance of calcium phosphate based materials. In this work, we investigated the response of primary cultures of rat osteoblasts derived from osteopenic (O-OB) bone to strontium substituted hydroxyapatite (SrHA), and to hydroxyapatite (HA) as reference material, compared to normal (N-OB) bone cells. Strontium (Sr) and calcium (Ca) cumulative releases in physiological solution are in agreement with the greater solubility of SrHA than HA, whereas the differences between the two materials are levelled off in DMEM, which significantly reduced ion release. O-OB cells grown on SrHA exhibited higher proliferation and increased values of the differentiation parameters. In particular, Sr substitution increased the levels of proliferation, alkaline phosphatase, and collagen type I, and down-regulated the production of interleukin-6 of O-OB cells, demonstrating a promising future of SrHA in the treatment of bone lesions and defects in the presence of osteoporotic bone.     

Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry

Spatially resolved spectral interferometry is used to measure the mode content of a Yb-doped photonic-crystal fiber rod amplifier with a 2300 μm(2) mode area. The technique, known as S(2) imaging, was adapted for the short fiber amplifier at full power and revealed a small amount of a copolarized LP(11) mode. Simulations illustrate the potential for weak mode suppression in this fiber and agree qualitatively with the measurements of S(2) and M(2). Higher-order-mode content depends on the alignment of the input signal at injection and ranged from -18 dB for optimized alignment to -13 dB when the injection alignment was offset along the LP(11) axis by 30% of the 55 μm mode-field diameter.     

Effects of synthetic salmon calcitonin and alendronate on bone quality in ovariectomized rats

BACKGROUND: The aim of this study was to assess the effect of calcitonin (CCT) and alendronate (ALN) on bone quality through histomorphometric, histological, densitometric and crystallographic evaluations in an experimental model of osteoporosis obtained in ovariectomized rats. METHODS: The animals were randomly assigned to the treatment with CCT (2 IU/kg/day, N-12) or with ALN (6 micrograms/kg/day, N-12) given subcutaneously, starting three months after ovariectomy: treatment lasted 60 days. Six rats untreated after ovariectomy and other 6 non ovariectomized (intact) were taken as controls. At the end of treatment the animals were sacrificed and femurs explanted for laboratory examinations. Results were evaluated by an ANOVA followed by the Tukey's test when appropriate. RESULTS: The histomorphometric analysis showed a significant increase of the trabecular bone volume and of the cortical bone thickness either with CCT and ALN in comparison with the ovariectomized untreated controls. Optic and electronic microscopy examinations suggest a higher bone remodeling after ALN than after CCT, but accompanied by areas of imperfect mineralization, and more irregular osteon and collagen fibres disposition. The densitometry carried out at the femoral head and diaphysis showed a similar bone mass increase following either CCT and ALN, but significantly higher in comparison to the untreated controls. At the diaphysis level ALN was superior in increasing the bone mass also when compared to the intact rats. The mineralogic exams showed that CCT acted on the re-elaboration of the mineral phase approaching the molar ratio Ca/PO4 to the physiological values typical of senescence, and crystallography revealed that the formation of hydroxyapatite crystals follows a physiological mineral redeposition: those phenomena were not observed for ALN. CONCLUSIONS: In conclusion both CCT and ALN could reduce the bone loss due to osteoporosis, by increasing the bone mass and thickness. Nevertheless the submicroscopic and chemical bone structure are less similar to the physiologic ones after treatment with ALN.