New approach to bone tissue engineering: simultaneous application of hydroxyapatite and bioactive glass coated on a poly(L-lactic acid) scaffold

A combination of bioceramics and polymeric nanofibers holds promising potential for bone tissue engineering applications. In the present study, hydroxyapatite (HA), bioactive glass (BG), and tricalcium phosphate (TCP) particles were coated on the surface of electrospun poly(L-lactic acid) (PLLA) nanofibers, and the capacity of the PLLA, BG-PLLA, HA-PLLA, HA-BG-PLLA, and TCP-PLLA scaffolds for bone regeneration was investigated in rat critical-size defects using digital mammography, multislice spiral-computed tomography (MSCT) imaging, and histological analysis. Electrospun scaffolds exhibited a nanofibrous structure with a homogeneous distribution of bioceramics along the surface of PLLA nanofibers. A total of 8 weeks after implantation, no sign of complication or inflammation was observed at the site of the calvarial bone defect. On the basis of imaging analysis, a higher level of bone reconstruction was observed in the animals receiving HA-, BG-, and TCP-coated scaffolds compared to an untreated control group. In addition, simultaneous coating of HA and BG induced the highest regeneration among all groups. Histological staining confirmed these findings and also showed an efficient osseointegration in HA-BG-coated nanofibers. On the whole, it was demonstrated that nanofibrous structures could serve as an appropriate support to guide the healing process, and coating their surface with bioceramics enhanced bone reconstruction. These bioceramic-coated scaffolds can be used as new bone-graft substitutes capable of efficiently inducing osteoconduction and osseointegration in orthopedic fractures and defects.     

Liposomal diltiazem HCl as ocular drug delivery system for glaucoma

In this study, unilamellar liposomal vesicles of diltiazem HCl (DH) were prepared using either reversed phase evaporation (REV) or proliposome methods. Soya phosphatidylcholine (SPC) was used for preparing the liposomes, and the vesicles were rigidified using cholesterol (Chol) or cetyl alcohol (CA) in different molarities. The major differences in both the entrapment efficiency percent (EE%) and drug release were evaluated as a function of the method of preparation, Chol or CA contents, and charging lipids. Moreover, the morphology of the vesicles was confirmed by transmission electron microscopy. The effects of Chol or CA incorporation into the liposomes were discussed based on thermal analysis. The in vivo evaluation of liposomal DH was assessed using intra-ocular pressure (IOP), reducing effects in rabbit eyes. Liposomes prepared via REV exhibited higher EE% and lower release rates when compared with those prepared from proliposomes. The incorporation of either Chol or CA in the liposomes enhanced the EE% and decreased the release rates; however, Chol yielded higher results than CA. In addition, both dicetyl phosphate (DCP; negative charge inducer) and stearyl amine (SA, positive charge inducer) decreased the EE% and increased the DH release rate. The in vivo antiglaucoma effects of the liposomes were calculated according to the area above the IOP/Time curve, the maximum response and the time for the maximum response and were compared with effects of the DH solution. The results were in the following order: DH solution?相似文献   

Evaluation of the physical and antimicrobial properties of silver doped hydroxyapatite depending on the preparation method

In the present study, the effect of the preparation method on the physical and antibacterial properties of silver doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag with 0.1–5 % of silver was prepared using two different modified wet chemical precipitation methods. A comparison of thermal stability and thermodynamical properties indicated that the thermal stability and sintering temperature of HAp/Ag were higher than those of pure hydroxyapatite if Ca(NO₃)₂·4H₂O, AgNO₃, NH₄OH and (NH₄)₂HPO₄ were used as raw materials. Phase composition and silver release were determined by XRD and ICP-MS. The study showed that, after 50 h in simulated body fluid 0.8–1.8 % of silver of the total silver amount was released from compact HAp/Ag scaffolds, and release kinetics strongly depended on the HAp/Ag preparation method. In vitro antibacterial activity of samples from each method against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa was approved. Results showed that, in the case of using Ca(OH)₂, H₃PO₄ and AgNO₃ as raw materials for HAp/Ag synthesis, higher antibacterial activity towards both bacterial strains could be obtained.     

Pro-labour myometrial gene expression: are preterm labour and term labour the same?

Preterm labour (PTL) is the most important cause of neonatal morbidity and mortality. While some causes have been identified, the mechanisms involved remain elusive. This study investigates whether term labour (TL) is an appropriate model for PTL by examining pro-labour gene expression, using quantitative rtPCR, and protein synthesis, using Western analysis, in preterm and term myometrial samples obtained from the upper and lower uterine segments before and after the onset of labour. In the lower segment, the levels of prostaglandin H synthase type-2 (PGHS-2), interleukin-1beta (IL-1beta), IL-6 and IL-8 mRNA expression were significantly higher in TL compared with PTL samples. Compared with non-labour controls, the expression of IL-1beta and IL-8 mRNA was increased in both PTL and TL samples and the expression of PGHS-2 and IL-6 mRNA was increased in TL samples only. In the upper segment, there were no differences between PTL and TL samples and the mRNA expression of PGHS-2 and IL-1beta was increased in TL compared with term no labour samples. No effect of PTL or TL was seen on either oxytocin receptor or connexin-43 mRNA expression or protein levels. The multiple regression analysis and studies in primary cultures of uterine myocytes suggest that the inflammatory cytokines, IL-1beta and tumour necrosis factor-alpha, are the most important regulators of PGHS-2 and IL-8. Our data show that preterm and term labouring myometrium are significantly different and that the most marked labour-induced changes in gene expression are in the lower segment. These changes may occur in response to the release of inflammatory cytokines by the labour-associated inflammatory infiltration.     

Novel derivatives of 3D woven T-shaped composites with improved performance

Conventional 3D woven T-shaped preforms were modified for improving joint/ peel off strength of associated T-shaped polymeric composites. Preforms were modified at weaving level by preferred yarns orientations for better performance in associated composites. Major modifications studied are; the addition of supporting layer, single or double-crossing in joint layers and crossing along with supporting layer (in a single sample). Novel derivatives were compared with conventionally used (on-loom and off-loom) T-shaped 3D woven composites. Microscopic analysis was also carried out to analyze the orientation of yarns and analysis of samples from failure point after testing. By combined variation of crossing and supporting layers improvement of 47.37% in peel off strength and 70.37% in impact strength was observed. Modified T shapes can serve to be a good replacement for conventional T-shaped stiffener (used to avoid folding under loads) and in joints.     

A novel fault ride-through technique for grid-connected Photo Voltaic energy systems

In this article, a novel fault ride-through technique has been implanted with a double control loop method. This method is implemented with voltage-source converters, where the active and reactive power could be easily done with the voltage control loop and inherent current control loop. The proposed system has been implemented to grid-connected photovoltaic systems, and the results have been explored and compared with the existing techniques. An additional control strategy is implemented successfully for satisfactory performance of the system during low irradiance periods, and the system is made capable to provide Q-support to the grid according to the system operators request with the help of Q-set point.     

Electrochemical copolymerization of m-toluidine and o-phenylenediamine

Electroactive copolymers of m-toluidine (MT) and o-phenylenediamine (OPD) were prepared electrochemically in aqueous sulfuric acid by potential cycling and characterized with cyclic voltametry, in situ conductivity measurements and FT-IR spectroscopy. The voltammograms of the copolymers exhibit different behavior for different concentrations of OPD in the comonomer feed. At optimum conditions the resulting poly(OPD-co-MT) shows an extended useful potential range of the redox activity as compared to the corresponding homopolymers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymer was electrochemically active even at pH 8.0. The stability of the copolymer film was also tested. The copolymer has a potential region of maximum conductivity different from that of PMT and POPD. The conductivity of the copolymer is between the conductivity of the homopolymers. The vibrational bands at 3122/3450 and 2922/875 cm⁻¹ in the FT-IR spectra of the copolymer indicate the presence of both OPD and MT units, respectively, in the copolymer backbone.     

Electrosynthesis and structural characterization of a novel aryl ether trimer

The structure of a novel trimer formed by three p-tert-butyl anisole moieties via the controlled potential electrolysis of p-tert-butyl anisole was determined by X-ray diffraction method. By cyclic voltammetry, we report a multistep electron transfer, each followed by a chemical reaction, resulting in an ECECEC mechanism. Preparative scale oxidation of p-tert-butyl anisole in dry acetonitrile leads to its two first oligomers. The symmetrical dimer, 2,2′-dimethoxy-5,5′-di-tert-butylbiphenyl, shows that the favored coupling sites are those in the ortho position of the methoxy group. The title compound, namely the 1-methoxy-bis-2,3-(2′-methoxy-5′-tert-butylphenyl)-4-tert-butylbenzene crystallizes in triclinic space group P-1 with a = 10.571(3) Å, b = 11.739(1) Å, c = 12.733(2) Å, α = 74.64(1)°, β = 88.71(2)°, γ = 76.58(2)°, V = 1480.8(5) Å³, and Z = 2. The structural analysis reveals that two p-tert-butyl anisole moieties are linked in ortho position on a third p-tert-butyl anisole fragment.