Formulation and In Vitro Evaluation of Bisphosphonate Loaded Microspheres for Implantation in Osteolysis

ABSTRACT

Chitosan and poly(lactide-co-glycolide) acid (PLGA) microspheres loaded with alendronate sodium (AS) were prepared for orthopedic as well as dental applications. In orthopedics the aim was to make the total joint prostheses stay in the body for a long time without causing bone tissue loss, while in dentistry it was aimed to treat the alveolar bone resorption caused by periodontitis and also to make the dental treatment using implants easier by reducing the bone loss in patients with osteoporosis. Solvent evaporation method was used to prepare AS loaded PLGA microspheres and emulsion polimerization method was used to prepare AS loaded chitosan microspheres. Particle size, loading efficacy, surface characteristics, and in vitro release characteristics were examined on prepared formulations. After the examination of the scanning electron microscopy photographs of microspheres, chitosan microspheres were observed to have spherical structure and smooth surface characteristics while PLGA microspheres were observed to have spherical porous surface structure. Loading efficacy was found to be 3.30% for chitosan microspheres and 7.70% for PLGA microspheres. It was observed that 85% of AS had been released at the end of the third day from chitosan microspheres whereas 58% was released at the end of the fifth day from PLGA microspheres. It was found that chitosan microspheres gave first order release while PLGA microspheres gave zero order release.     

Cooperative target pursuit by multiple UAVs in an adversarial environment

This paper presents the development of a cooperation strategy for multiple UAVs to pursue a target moving in an adversarial environment where threat exposure should be minimized, and obstacles and restricted areas should be avoided. A probabilistic approach is used to model the adversarial environment. A cost function is defined to quantify placement of UAVs around the target in formation in terms of threat exposure level and distance to the target. The cost function is used to develop a cooperation strategy for a team of UAVs to follow the target such that the total threat exposure of the team and the average distance to the target throughout the pursuit are minimized according to the weighting coefficients specified. The cooperation strategy has the feature of collision avoidance as well as data-fusion-based estimation of the target trajectory based on noisy measurements. Simulation results have demonstrated that the cooperation reduces the risk of losing the target during the pursuit while avoiding obstacles and restricted areas. Further, the UAVs guided by the cooperation strategy can follow the target closer without increasing the total threat exposure level as compared to cases where the UAVs pursue the target without cooperation.     

Modeling of ferrofluid magnetic actuation with dynamic magnetic fields in small channels

One of the most important and promising research areas in biomedical and micropumping applications is magnetic actuation of ferrofluids with dynamic magnetic fields. For ensuring the use of ferrofluids in various applications in engineering fields, their flows generated by magnetic fields should be extensively investigated and simulated. In this study, simulations of ferrofluid actuation with dynamic magnetic fields were performed by modeling it using the COMSOL Multiphysics software, and iron oxide nanoparticle-based ferrofluids at different angles of rotating magnets were considered to provide insight into ferrofluid flow in small channels. Ferrofluid flows were modeled at different magnetic flux densities provided by rotating magnets, and velocity profiles inside the channel were analyzed. It was shown that ferrofluid actuation can be considered as a futuristic micropumping alternative, simulation results matched well with the experimental results of previous work, and the established model could serve as a tool to analyze ferrofluid flows generated by dynamic magnetic fields. The results of the model show that flow rates up to 100 µl/s can be reached at a rotation angle of 30° by using dynamic magnetic fields. Various applications including biomedical applications might be envisaged.     

Kinetics of the F,F2/Gd(s,v) reactions

The reaction of gadolinium with fluorine was studied in a low pressure, transonic flow reactor. Atomic fluorine reactant was generated by microwave discharge dissociation of F₂ in argon. Kinetic measurements included the rate of change of the electrical resistance of isothermal gadolinium filaments due to reaction with atomic and molecular fluorine and the intensity of chemiluminescence from the vapor phase Gd/F₂ reactionvs time, temperature, and F₂ partial pressure. The surfaces of reacted Gd specimens were examined by scanning electron microscopy, polished specimen cross sections were viewed under the optical microscope, and the Gd/F₂ chemiluminescent emission spectrum was obtained. A nonpassivating, metal rich, high melting and involatile fluoride, GdF_x, forms on the metal at temperatures above 1180 K. An orthorhombic, passivating GdF₃ forms at lower temperatures. The surface Gd activity remains high at the GdF_x/fluorine interface, and F-atom reaction is first order with a reaction probability approximately 0.28. Rapid reaction atT < 1180 K is followed by an abrupt transition to passivated behavior. This change in reactivity is attributed to a phase transition from GdF_x to orthorhombic GdF₃ that occurs as the oxygen impurity concentration of the reacting metal decreases from its value near the original specimen surface to that of the bulk material.     

Synthesis,characterization, mesomorphic and electrical properties of tetrakis(alkylthio)-substituted lutetium(III) bisphthalocyanines

The synthesis of new lutetium(III) bisphthalocyanines substituted with alkylthio groups (1–5) is described. These compounds (Pc₂Lu) are soluble in most common organic solvents and have been fully characterized (elemental analysis, FT-IR, UV–Vis spectroscopy, mass spectrometry). The thermal stabilities of the Pc compounds were determined by thermogravimetric analysis (TGA). The mesogenic properties of these new materials forming columnar-hexagonal (Col_h) mesophases were studied by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. The compounds 2–5 exhibit a double clearing point. DC electrical properties of these compounds in different phases were determined by measuring I–V characteristics and dark current of their thin films on interdigital electrodes. The measurements were carried out in ambient air, in vacuum and in high purity nitrogen (N₂) flow in the temperature range between 300 and 420 K. Dark current measurements obtained in the crystal, liquid crystal (LC) and isotropic liquid phases were in agreement with the phase transitions of these compounds obtained by DSC and optical microscopy results. The relation between the phase transition and conductivity of the Pc₂Lu derivatives were investigated. Also, the influence of the nature of the substituted group (alkylthia and alkoxy) upon the DC electrical properties of the Pc₂Lu derivatives was investigated. The DC conductivities and the thermal activation energies depending on alkyl chain lengths of these compounds were found to be in the range of 10^?8 to 10^?5 S/cm and 0.12–0.38 eV in solid phase.     

An ambipolar neutral state green polymeric electrochromic

The synthesis and properties of highly stable neutral state green polymeric electrochromic, P1, which is based on 5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(1H-pyrrol-2-yl)quinoxaline were highlighted. P1 exhibits three well-defined absorption bands with a narrow band gap (1.17 eV). The n- and p-doping (ambipolar) processes suggest that P1 is one of the most promising neutral state green polymers and it can be used in supercapacitors as either cathode or anode electrode material. Apart from the stability and the robustness of the polymer film, P1 shows multi-electrochromic behavior; gray-purple in the reduced form and highly transmissive blue color in the oxidized state.     

The synthesis and characterization of Cu(II) phthalocyanine bearing peripheral monoazacrown ethers and a spectral investigation of its film forming character

The synthesis, liquid crystalline behavior and self-organizing properties of Cu(II)Pc bearing monoazacrown ether moieties that contain long alkyloxyphenyl N-pivotal groups are described. The Cu(II) phthalocyanine derivative has a hexagonal, columnar structure; optical absorption and vibrational spectroscopy revealed a predominantly co-facial interaction between the chromophores and their orientation parallel to a NaCl surface. It is proposed that such homeotropic alignment is attributable to the ability of the pendant monoazacrown ether groups to coordinate the Na⁺ ions within the NaCl surface.