An orthorhombic benzene-silicalite-1 single crystal was obtained from a monoclinic twin crystal, and the structure was determined by a single-crystal method for the first time.
A simple method for preparing orthorhombic single crystals of benzene-silicalite-1 was developed. A silicalite-1 crystal was pressed with a weight of 2 g along the +c and −c crystallographic axes while the temperature was increased to 473 K. The temperature was then slowly reduced to 313 K, and these heating and cooling steps were repeated three times. After the orthorhombic single crystals adsorbed benzene, the crystal structure of the resulting benzene-silicalite-1 was determined. There were two kinds of benzene molecules in the asymmetric unit. One was located at the intersection of the straight channels and the sinusoidal channels with the benzene ring parallel to the ac plane. The other benzene was located in the middle of the straight channel.
ZSM-5; MFI; silicalite-1; benzene-silicalite-1
Mesoporous silica SBA-15 was modified in a three-step process to obtain a material with poly-N-isopropylacrylamide (PNIPAAM) grafted onto the inner pore surface. Water sorption calorimetry was implemented to characterize the materials obtained after each step regarding the porosity and surface properties. The modification process was carried out by (i) increasing the number of surface silanol groups, (ii) grafting 1-(trichlorosilyl)-2-(m-/p-(chloromethylphenyl) ethane, acting as an anchor for (iii) the polymerization of N-isopropylacrylamide. Water sorption isotherms and the enthalpy of hydration are presented. Pore size distributions were calculated on the basis of the water sorption isotherms by applying the BJH model. Complementary measurements with nitrogen sorption and small-angle X-ray diffraction are presented. The increase in the number of surface silanol groups occurs mainly in the intrawall pores, the anchor is mainly located in the intrawall pores, and the intrawall pore volume is absent after the surface grafting of PNIPAAM. Hence, PNIPAAM seals off the intrawall pores. Water sorption isotherms directly detect the presence of intrawall porosity. Pore size distributions can be calculated from the isotherms. Furthermore, the technique provides information regarding the hydration capability (i.e., wettability of different chemical surfaces) and thermodynamic information.
Hypocalcemia and an increase in creatinine level are the most important serious effects associated with foscarnet (PFA) therapy. In an animal model, we have explored the potential protective role of liposome-encapsulated foscarnet (LE-PFA) on these metabolic abnormalities. PFA administered as one bolus injection (0.5 or 1.0 g/kg) caused significant rapid decreases (approximately 20%) in the levels of calcium and phosphorus in serum within a few minutes and up to 30 min after injection. LE-PFA did not induce any of these changes, while peak levels in serum and the half-life of this formulation were much higher than those of the free drug. PFA administered for 2 weeks (340 or 500 mg/kg/day) resulted in no changes in creatinine or blood urea nitrogen levels in serum at the low-dosage level, but at the higher-dosage level, the creatinine level in serum increased by day 5 posttreatment. Furthermore, there was no increase in the creatinine or blood urea nitrogen level after 2 weeks of treatment with LE-PFA at a dosage of 35 mg/kg/day. When the pharmacokinetics of both free PFA and LE-PFA were compared, the plasma half-life of the encapsulated drug was approximately four times longer than that of the free drug. In addition, the systemic clearance of LE-PFA was approximately one-fifth of that of the free drug. In conclusion, free PFA causes hypocalcemia and hypophosphatemia and increases the creatinine level in serum, whereas the LE form of this drug seems to protect against the abnormal changes in calcium and phosphorus levels caused by the free drug. By preventing hypocalcemia and increasing its half-life, LE-PFA can be used at lower doses and at longer intervals. Clinical investigations of these formulations may be worthwhile.
The inhibitors present in dilute acid-treated lignocellulosic hydrolysates would show great effect on the growth and product formation of microorganisms. To understand their inhibitory law and mechanism on oleaginous microorganism could help improving the efficiency of lignocellulose hydrolysis, detoxification, and lipid fermentation. The effects of four representative alcohol compounds present in lignocellulosic hydrolysates, including furfuryl alcohol, vanillyl alcohol, catechol, hydroquinone on the cell growth and lipid accumulation of Trichosporon fermentans were systematically investigated in this work. The toxicity of selected alcohol compounds was well related to their log P value except furfuryl alcohol, whose log P value was the minimum but with the highest toxicity to T. fermentans. The inhibition of all the alcohol compounds on the growth of T. fermentans was more serious than on the lipid synthesis. Also, the growth of T. fermentans was more sensitive to the variation of inoculum size, temperature, and initial pH than lipid synthesis in the presence of alcohol compounds. Initial pH had more profound influence on the lipid fermentation than inoculum size and cultural temperature did. Careful control of fermentation conditions could be helpful for improving lipid yield of T. fermentans in lignocellulosic hydrolysates. Among the four alcohol compounds tested, most alcohol compounds showed inhibition on both sugar consumption and malic enzyme activity of T. fermentans. However, vanillyl alcohol had little influence on the malic enzyme activity. Similarly, all alcohol compounds except vanillyl alcohol exerted damage on the cell membrane of T. fermentans.
The malarial PfA-M1 metallo-aminopeptidase is considered a putative drug target. The natural product dipeptide mimetic, bestatin, is a potent inhibitor of PfA-M1. Herein we present a new, efficient and high-yielding protocol for the synthesis of bestatin derivatives from natural and unnatural N-Boc-D-amino acids. A diverse library of bestatin derivatives was synthesized with variants at the sidechain of either the α-hydroxy-β-amino acid (P1) or the adjacent natural α-amino acid (P1’). Surprisingly, we found that extended aromatic sidechains at the P1 position resulted in potent inhibition against PfA-M1. To understand these data, we determined the X-ray co-crystal structures of PfA-M1 with two derivatives having either a Tyr(OMe) 15 or Tyr(OBzl) 16 at the P1 position and observed substantial inhibitor-induced rearrangement of the primary loop within the PfA-M1 pocket that interacts with the P1 sidechain. Our data provide important insights for the rational design of more potent and selective inhibitors of this enzyme that may eventually lead to new therapies for malaria.
The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.
biodegradable polymers; drug delivery; controlled release; electrospun nanofibers; wound dressing
A new series of 30 miscellaneous National Toxicology Program chemicals has been evaluated prospectively for carcinogenicity and overt toxicity by COMPACT (Computer Optimised Molecular Parametric Analysis for Chemical Toxicity. CYP1A and CYP2E1). Evaluations were also made by Hazardexpert, and for metal ion redox potentials; and these, together with COMPACT, were compared with results from the Ames test for mutagenicity in Salmonella, the micronucleus test, and 90-day subchronic rodent pathology. Seven of the 30 chemicals (nitromethane, chloroprene, xylenesulphonic acid, furfuryl alcohol, anthraquinone, emodin, cinnamaldehyde) were positive for potential carcinogenicity in the COMPACT evaluation; xylenesulphonic acid and furfuryl alcohol were only equivocally positive. Four of the 30 chemicals-scopolamine, D&C Yellow No. 11, citral, cinnamaldehyde-were positive by Hazardexpert; 6 of 30-D&C Yellow No. 11, 1-chloro-2-propanol, anthraquinone, emodin, sodium nitrite, cinnamaldehyde-were positive in the Ames test; 2 of 30-phenolphthalein and emodin-were positive in the in vivo cytogenetics test; and 3 of 30-molybdenum trioxide, gallium arsenide, vanadium pentoxide-were metal compounds with redox potentials of the metal/metal ion indicative of possible carcinogenicity. The overall prediction for carcinogenicity was positive for 12 of 30 chemicals: nitromethane, chloroprene, D&C Yellow No. 11, molybdenum trioxide, 1-chloro-2-propanol, furfuryl alcohol, gallium arsenide, anthraquinone, emodin, sodium nitrite, cinnamaldehyde, vanadium pentoxide). This overall prediction has been made on the basis of the results of the computer tests and from consideration of the information from bacterial mutagenicity, together with likely lipid solubility and pathways of metabolism and elimination.
Methanococcus deltae (Delta)LH was grown on H(inf2)-CO(inf2) in the presence of various concentrations of furfural. Furfural at higher concentrations, namely, 20 and 25 mM, inhibited growth of this organism. At concentration of 5 and 10 mM, no inhibition of growth was observed. The other methanogens in this study were not inhibited by 10 mM furfural. Among the methanogens tested, M. deltae was capable of transforming furfural, whereas Methanobacterium thermoautotrophicum Marburg, Methanosarcina barkeri 227, Methanococcus thermolithotrophicus, and Methanobrevibacter ruminantium lacked this capability. One hundred percent removal of furfural was observed within 48 h of incubation in M. deltae cultures. The end product observed during furfural metabolism was furfuryl alcohol. An almost stoichiometric amount of furfuryl alcohol was produced by M. deltae. This transformation is likely to be of value in the detoxification of furfural and in its ultimate conversion to methane and CO(inf2) by anaerobic digestion.
Magnetic nanofibers of ZnFe2O4 / γ-Fe2O3 composite were synthesized by electrospinning from a sol-gel solution containing a molar ratio Fe/Zn of 3. The effects of the calcination temperature on the phase composition, particle size and magnetic properties have been investigated. Zinc ferrite fibers were obtained by calcinating the electrospun fibers in air from 300 °C to 800 °C and characterized by thermogravimetric analyses, Fourier transformed infrared spectroscopy, x-ray photoemission spectroscopy, x-ray diffraction, vibration sample magnetometry and magnetic force microscopy. The resulting fibers, with diameters ranging from 90 to 150 nm, were ferrimagnetic with high saturation magnetization as compared to bulk. Increasing the calcination temperature resulted in an increase in particle size and saturation magnetization. The observed increase in saturation magnetization was most likely due to the formation and growth of ZnFe2O4 /γ-Fe2O3 diphase crystals. The highest saturation magnetization (45 emu/g) was obtained for fibers calcined at 800 °C.
Zinc Ferrite; Magnetic Fibers; Electrospinning; Poly(vinyl) alcohol; Calcination
Acrylamide (AM) and methacrylic acid (MAA) copolymer microgels were prepared by a reverse suspension polymerization technique. The microgels were used as templates for the preparation of silver-poly(acrylamide-co-methacrylic acid) [Ag-P(AM-co-MAA)] composite microspheres. The surface structures of the microspheres prepared in this way are characterized by zigzag-like structures. It was found that the composition of the microgels, the nature and dosage of surfactants, the quantity of the metal, and even the reduction methods employed have a significant effect upon the surface structures of the microspheres. X-ray diffraction analysis confirmed that Ag formed during the process is in a crystal state of a face-centered cubic structure.
Microgel; Ag nanoparticles; Composite materials; Template method
The prevalence and characteristics of fetal alcohol syndrome (FAS) and partial fetal alcohol syndrome (PFAS) were determined in a third primary school cohort in a community in South Africa (S.A.).
An active case ascertainment, two-tier screening methodology, and the revised Institute of Medicine diagnostic criteria were employed among 818 first grade pupils. Characteristics of children with FAS and PFAS are contrasted with a randomly-selected control group. Data were collected and analyzed for children in the study regarding: 1.) physical growth and development, including dysmorphology, 2.) intelligence and behavioral characteristics, and 3.) their mother’s social, behavioral, and physical characteristics.
The rate of FAS and PFAS in this area continues as the highest reported in any overall community and is much higher than rates elsewhere. In this cohort it is 68.0 to 89.2 per 1,000. Severe episodic drinking on weekends among mothers of children with FAS and PFAS accounts for 96% of all alcohol consumed. Various measures of maternal drinking are significantly correlated with negative outcomes of children in the areas of non-verbal intelligence (-0.26), verbal intelligence (-0.28), problem behavior (0.31), and overall dysmorphology score (0.59). Significantly more FAS and PFAS exists among children of rural residents (OR = 3.79).
A high rate of FAS and PFAS was again documented in this community, and it has increased. Given population similarities, we suspect that other communities in the Western Cape Province of South Africa also have high rates. Programs for prevention are needed.
fetal alcohol syndrome; epidemiology; South Africa; alcohol abuse
The random clustering of amorphous calcium phosphate (ACP) particles within resin matrices is thought to diminish the strength of their polymerized composites. The objective of this study was to elucidate the effect of ball-milling on the particle size distribution (PSD) of ACP fillers and assess if improved dispersion of milled ACP in methacrylate resin sufficiently enhanced filler/matrix interactions to result in improved biaxial flexure strength (BFS) without compromising the remineralizing potential of the composites. Un-milled and wet milled zirconia-hybridized ACP (Zr-ACP) fillers were characterized by PSD analysis, X-ray diffraction, thermogravimetric and chemical analysis, infrared spectroscopy and scanning electron microscopy. Composite specimens made from a photoactivated, ternary methacrylate resin admixed with a mass fraction of 40 % of un-milled or milled Zr-ACP were evaluated for the BFS (dry and wet) and for the release of calcium and phosphate ions into saline solutions. While having no apparent effect on the structure, composition and/or morphology/topology of the fillers, milling significantly reduced the average size of Zr-ACP particulates (median diameter, dm = 0.9 μm ± 0.2 μm) and the spread of their PSD. Better dispersion of milled Zr-ACP in the resins resulted in the improved BFS of the composites, even after aqueous soaking, and also gave a satisfactory ion release profile. The demonstrated improvement in the mechanical stability of anti-demineralizing/remineralizing ACP composites based on milled Zr-ACP filler may be beneficial in potentially extending their dental utility.
bioactive material; calcium phosphate(s); composite/hard tissue; ion release; particle size distribution
Polyimide/SiO2 composite films were prepared from tetraethoxysilane (TEOS) and poly(amic acid) (PAA) based on aromatic diamine (4-aminophenyl sulfone) (4-APS) and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride) (BTDA) via a sol-gel process in N-methyl-2-pyrrolidinone (NMP). The prepared polyimide/SiO2 composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA) and the formation of SiO2 particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO2 particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO2 composite films were investigated using TGA in N2 atmosphere. The activation energy of the solid-state process was calculated using Flynn–Wall–Ozawa’s method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions.
polyimide; silica; activation energy; thermogravimetric analysis
The yeast chitin synthase Chs3 provides a well-studied paradigm for polytopic membrane protein trafficking. In this study, high-throughput analysis of the yeast deletion collection identifies a requirement for Pfa4, which is an uncharacterized protein with protein acyl transferase (PAT) homology, in Chs3 transport. PATs, which are the enzymatic mediators of protein palmitoylation, have only recently been discovered, and few substrates have been identified. We find that Chs3 is palmitoylated and that this modification is Pfa4-dependent, indicating that Pfa4 is indeed a PAT. Chs3 palmitoylation is required for ER export, but not for interaction with its dedicated ER chaperone, Chs7. Nonetheless, both palmitoylation and chaperone association are required to prevent the accumulation of Chs3 in high–molecular mass aggregates at the ER. Our data indicate that palmitoylation is necessary for Chs3 to attain an export-competent conformation, and suggest the possibility of a more general role for palmitoylation in the ER quality control of polytopic membrane proteins.
A homologous series of pore-forming amphiphiles (PFAs), derived from cholic acid, lysine and spermine, have been used as “thermal-gates” for releasing sucrose from liposomes made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-e-[phospho-rac(1-glycerol)] (sodium salt) [DPPG]. Binding measurements have established that these PFAs are fully bound to these liposomes in their gel state, and that their transfer to fluid phase membranes is negligible. Release experiments have shown that thermal-gating is sensitive to both the size and the concentration of the PFA that is used. Increases in the extent of release of sucrose with increasing temperature that have been found in the gel/fluid coexistence region indicate the existence of heterogeneity among the liposomes.
The present investigation was undertaken with the objective of developing a solid formulation containing nitrendipine nanocrystals for oral delivery. Nitrendipine nanocrystals were prepared using a tandem precipitation–homogenization process. Then, spray drying, a cost-effective method very popular in industrial situations, was employed to convert the nanocrystals into a solid form. The parameters of the preparation process were investigated and optimized. The optimal process was as follows: firstly, nitrendipine/acetone solution (100 mg/ml) was added to a polyvinyl alcohol solution (1 mg/ml) at 10°C, then the pre-suspension was homogenized for 20 cycles at 1,000 bar. Both differential scanning calorimetry and X-ray diffraction analysis indicated that nitrendipine was present in crystalline form. The in vitro dissolution rate of the nanocrystals was significantly increased compared with the physical mixture and commercial tablet. The in vivo testing demonstrated that the Cmax of the nanocrystals was approximately 15-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively. In addition, the AUC0→24 of the nanocrystals was approximately 41-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively.
bioavailability; dissolution; nanocrystals; nanotechnology; nitrendipine
Bacterial cellulose has been used in the food industry for applications such as low-calorie desserts, salads, and fabricated foods. It has also been used in the paper manufacturing industry to enhance paper strength, the electronics industry in acoustic diaphragms for audio speakers, the pharmaceutical industry as filtration membranes, and in the medical field as wound dressing and artificial skin material. In this study, different types of plastic composite support (PCS) were implemented separately within a fermentation medium in order to enhance bacterial cellulose (BC) production by Acetobacter xylinum. The optimal composition of nutritious compounds in PCS was chosen based on the amount of BC produced. The selected PCS was implemented within a bioreactor to examine the effects on BC production in a batch fermentation. The produced BC was analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among thirteen types of PCS, the type SFYR+ was selected as solid support for BC production by A. xylinum in a batch biofilm reactor due to its high nitrogen content, moderate nitrogen leaching rate, and sufficient biomass attached on PCS. The PCS biofilm reactor yielded BC production (7.05 g/L) that was 2.5-fold greater than the control (2.82 g/L). The XRD results indicated that the PCS-grown BC exhibited higher crystallinity (93%) and similar crystal size (5.2 nm) to the control. FESEM results showed the attachment of A. xylinum on PCS, producing an interweaving BC product. TGA results demonstrated that PCS-grown BC had about 95% water retention ability, which was lower than BC produced within suspended-cell reactor. PCS-grown BC also exhibited higher Tmax compared to the control. Finally, DMA results showed that BC from the PCS biofilm reactor increased its mechanical property values, i.e., stress at break and Young's modulus when compared to the control BC. The results clearly demonstrated that implementation of PCS within agitated fermentation enhanced BC production and improved its mechanical properties and thermal stability.
The work presented here aims at utilizing poly-N-isopropyl-acrylamide/acrylic acid copolymers to create nanostructured layers on mica surfaces by a simple spin-casting procedure. The average composition of the copolymers determined by elemental analysis correlates excellently with the feed composition indicating that the radical polymerization process is statistical. The resulting surfaces were characterized by Atomic Force Microscopy (magnetic AC-mode) at the copolymer/air interface. Postpolymerization modification of the acrylic acid functions with perfluoro-octyl-iodide decreased the tendency towards spontaneous formation of nanopores. Crosslinking of individual polymer chains permitted the generation of ultraflat layers, which hosted the mycobacterial channel protein MspA, without compromising its channel function. The comparison of copolymers of very similar chemical composition that have been prepared by living radical polymerization and classic radical polymerization indicated that differences in polydispersity played only a minor role when poly-N-isopropyl-acrylamide/acrylic acid copolymers were spincast, but a major role when copolymers featuring the strongly hydrophobic perfluoro-octyl-labels were used. The mean pore diameters were 23.8±4.4 nm for P[(NIPAM)95.5-co-(AA)4.5] (PDI (polydispersity index)=1.55) and 21.8±4.2 nm for P[(NIPAM)95.3-co-(AA)4.7] (PDI=1.25). The depth of the nanopores was approx. 4 nm. When depositing P[(NIPAM)95-co-(AA)2.8-AAC8F17 2.2] (PDI=1.29) on Mica, the resulting mean pore diameter was 35.8±7.1 nm, with a depth of only 2 nm.
Ag and Cu nanocrystals (NCs) were assembled into ordered porous anodic alumina (OPAA) by a single-potential-step chronoamperometry technique. The composition, morphology, microstructure, and optical property were analyzed by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and optical absorption spectroscopy. The results indicate that metallic NCs/OPAA composite possesses a significant surface plasmon resonance absorption. For continuous electrodeposition, metallic nanowires are smooth and uniform with face-centered cubic (fcc) single-crystalline structure; however, for interval electrodeposition, the nanowires are bamboo-like or pearl-chain-like with fcc polycrystalline structure. The length of the nanoparticle nanowires or the single-crystalline nanowires can be controlled well by adjusting the experimental cycle times or the continuous depositing time. The transverse dipole resonance of metallic NCs enhances and displays a blue shift with increasing electrodeposition time or experimental cycle times, which is consistent with Zong's results but contradictory to Duan's results. The formation mechanisms of the nanoparticle nanowires and the single-crystalline nanowires were discussed in detail.
Nanostructures; Chemical synthesis; Electron microscopy; Optical properties
Poly(propylene adipate)-block-poly(ɛ-caprolactone) copolymers were synthesized using a combination of polycondensation and ring-opening polymerization of ɛ-caprolactone in the presence of poly(propylene adipate). Gel permeation chromatography was used for molecular weight determination, whereas hydrogen-1 nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectroscopy were employed for copolymer characterization and composition evaluation. The copolymers were found to be block while their composition was similar to the feeding ratio. They formed semicrystalline structures, while only poly(ɛ-caprolactone) formed crystals, as shown by wide angle X-ray diffraction. Differential scanning calorimetry data suggest that the melting point and heat of fusion of copolymers decreased by increasing the poly(propylene adipate) amount. The synthesized polymers exhibited low cytotoxicity and were used to encapsulate desferrioxamine, an iron-chelating drug. The desferrioxamine nanoparticles were self-assembled into core shell structures, had mean particle size <250 nm, and the drug remained in crystalline form. Further studies revealed that the dissolution rate was mainly related to the melting temperature, as well as to the degree of crystallinity of copolymers.
biocompatible polyesters; poly(ɛ-caprolactone); poly(propylene adipate); drug encapsulation; desferrioxamine
Hexagonal molybdenum oxide (h-MoO3) was synthesized by a solution based chemical precipitation technique. Analysis by X-ray diffraction (XRD) confirmed that the as-synthesized powder had a metastable hexagonal structure. The characteristic vibrational band of Mo–O was identified from Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly depicted the morphology and size of h-MoO3. The morphology study showed that the product comprises one-dimensional (1D) hexagonal rods. From the electron energy loss spectroscopy (EELS) measurement, the elemental composition was investigated and confirmed from the characteristic peaks of molybdenum and oxygen. Thermogravimetric (TG) analysis on metastable MoO3 revealed that the hexagonal phase was stable up to 430 °C and above this temperature complete transformation into a highly stable orthorhombic phase was achieved. The optical band gap energy was estimated from the Kubelka–Munk (K–M) function and was found to be 2.99 eV. Finally, the ethanol vapor-sensing behavior was investigated and the sensing response was found to vary linearly as a function of ethanol concentration in the parts per million (ppm) range.
fiber optic sensor; hexagonal phase; molybdenum oxide; one dimensional rod; phase transition
We have developed a combinatorial method for determining optimum tissue scaffold composition for several X-ray imaging techniques. X-ray radiography and X-ray microcomputed tomography enable non-invasive imaging of implants in vivo and in vitro. However, highly porous polymeric scaffolds do not always possess sufficient X-ray contrast and are therefore difficult to image with X-ray-based techniques. Incorporation of high radiocontrast atoms, such as iodine, into the polymer structure improves X-ray radiopacity but also affects physicochemical properties and material performance. Thus, we have developed a combinatorial library approach to efficiently determine the minimum amount of contrast agent necessary for X-ray-based imaging. The combinatorial approach is demonstrated in a polymer blend scaffold system where X-ray imaging of poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) scaffolds is improved through a controlled composition variation with an iodinated-pDTEc analog (pI2DTEc). The results show that pDTEc scaffolds must include at least 9%, 16%, 38% or 46% pI2DTEc (by mass) to enable effective imaging by microradiography, dental radiography, dental radiography through 0.75 cm of muscle tissue or micro-computed tomography, respectively. Only two scaffold libraries were required to determine these minimum pI2DTEc percentages required for X-ray imaging, which demonstrates the efficiency of this new combinatorial approach for optimizing scaffold formulations.
Combinatorial library; Polycarbonate; Scaffolds; Radiopacity; X-ray microcomputed tomography; X-ray radiography
The composition and morphology of nanocrystals in urines of healthy persons and lithogenic patients were comparatively investigated by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was shown that the main composition of urinary nanocrystals in healthy persons were calcium oxalate dihydrate (COD), uric acid, and ammonium magnesium phosphate (struvite). However, the main compositions of urinary nanocrystals in lithogenic patients were struvite, β-tricalcium phosphate, uric acid, COD, and calcium oxalate monohydrate (COM). According to the XRD data, the size of nanocrystals was calculated to be 23∼72 nm in healthy urine and 12∼118 nm in lithogenic urine by Scherer formula. TEM results showed that the nanocrystals in healthy urine were dispersive and uniform with a mean size of about 38 nm. In contrast, the nanocrystals in lithogenic urine were much aggregated with a mean size of about 55 nm. The results in this work indicated that the urinary stone formation may be prevented by diminishing the aggregation and the size differentiation of urinary nanocrystals by physical or chemical methods.
The purpose of this research was to design and develop hydrogels by esterification of polyvinyl alcohol (PVA) with gelatin. The membranes were characterized by Fourier Transform Infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and differential scanning calorimetry. The viscosity of the esterified product (as solution) was compared with the mixture of PVA and gelatin of the same composition. The mechanical properties of the hydrogels were characterized by tensile tests. Swelling behavior and hemocompatibility of the membrane were also evaluated. The diffusion coefficient of salicylic acid (SA), when the receptor compartment contained Ringer's solution, through the membrane was determined. SA was used as a model drug. FTIR spectra of the membranes indicated complete esterification of the free carboxylic groups of gelatin. XRD studies indicated that the crystallinity of the membranes was mainly due to gelatin. The comparison of viscosity indicated an increase in segment density within the molecular coil. The membrane had sufficient strength and water-holding capacity. Hemocompatibility suggested that the hydrogel could be tried as wound dressing and as an implantable drug delivery system. The diffusion coefficient of SA through the membrane was found to be 1.32×10−5 cm2/s. The experimental results indicated that the hydrogel could be tried for various biomedical applications.
Hydrogels; diffusion coefficient; hemocompatibility
Nanofibers containing ferrocene (Fc) have been prepared for the first time by electrospinning. In this paper, Fc was dispersed uniformly throughout the poly(vinypyrrolidone) (PVP) matrix for the purpose of combining the properties of PVP and Fc. The effects of solvents and Fc concentration on the morphologies and diameters of nanofibers were investigated. In the DMF/ethanol solvent, the morphologies of the obtained nanofibers significantly changed with the increase of Fc concentration. The results demonstrated that the morphologies of the nanofibers could be controlled through adjusting solvents and Fc concentration. Scanning electron microscopy (SEM) showed that the diameters of the obtained composite fibers were about 30–200 nm at different Fc concentrations. Thermogravimetric analysis (TGA) results confirmed the presence of ferrocene within the PVP nanofibers. X-ray diffraction (XRD) results showed that the crystalline structure of Fc in the fibers was amorphous after the electrospinning process. A biological evaluation of the antimicrobial activity of Fc/PVP nanofibers was carried out by using Gram-negative Escherichia coli (E. coli) as model organisms. The nanofibers fabricated by this method showed obvious antibacterial activity. Electrochemical properties were characterized based on cyclic voltammetry measurements. The CV results showed redox peaks corresponding to the Fc+/Fc couple, which suggested that Fc molecules encapsulated inside PVP nanofibers retian their electrochemical activity. The properties and facile preparation method make the Fc/PVP nanofibers promising for antibacterial and sensing applications.
composites; electrochemistry; electrospinning; membranes; porous materials