Packed column supercritical fluid chromatography of sodium stearyl fumarate aqueous suspension

A method for the determination of sodium stearyl fumarate aqueous suspension is described. This straightforward method is based on homogenisation of the sample, dilution of a known aliquot with methanol to a suitable clear solution and mixing with an internal standard; (S)-naproxen. Separation and quantification is performed by packed column supercritical fluid chromatography on a commercial tartaric acid network polymeric column (tertbutylbenzoyl) with UV-detection at 214 nm. The precision of the presented method upon repeated analysis of a 20 mg/ml suspension is 0.5% (n = 8), and the yield is near 100%. Less than 5 min is required for the chromatographic separation with a resolution of about 3 to the internal standard. With some modification of the chromatographic conditions water samples can also be analysed.

Fumarate reductase: structural and mechanistic insights from the catalytic reduction of 2-methylfumarate

The soluble fumarate reductase (FR) from Shewanella frigidimarina can catalyse the reduction of 2-methylfumarate with a k(cat) of 9.0 s(-1) and a K(M) of 32 microM. This produces the chiral molecule 2-methylsuccinate. Here, we present the structure of FR to a resolution of 1.5 A with 2-methylfumarate bound at the active site. The mode of binding of 2-methylfumarate allows us to predict the stereochemistry of the product as (S)-2-methylsuccinate. To test this prediction we have analysed the product stereochemistry by circular dichroism spectroscopy and confirmed the production of (S)-2-methylsuccinate.

Microenvironmental pH and microviscosity inside pH-controlled matrix tablets: an EPR imaging study

Incorporation of pH modifiers is a commonly used strategy to enhance the dissolution rate of weakly basic drugs from sustained release solid dosage forms. Electron paramagnetic resonance imaging (EPRI) was applied to spatially monitor pH(M) and the rotational correlation time (tau(R)), a parameter which is closely related to the surrounding microviscosity inside HPMC (hydroxypropylmethylcellulose) matrix tablets. Fumaric, citric, and succinic acid were employed as pH modifiers. 4-(methylamino)-2-ethyl-5,5-dimethyl-4-pyridine-2-yl-2,5-dihydro-1H-imidazole-1-oxyl (MEP) was used as spin label. Fumaric and citric acid reduced the pH(M) to equal extents in the initial phase. With the progress of hydration, the more soluble citric acid diffused out from the tablet resulting in an increase in pH(M), originating at the outer layers. In contrast, fumaric acid maintained a constantly reduced pH(M) inside the entire tablet. Due to its lower acidic strength, succinic acid did not reduce the pH(M) as effectively as the other pH modifiers used. The more water-soluble acids stimulated the water penetration into the matrix system, thereby rapidly decreasing tau(R). Once the matrix tablets were hydrated, the included pH modifiers influenced tau(R) insignificantly. EPRI, a novel approach for monitoring pH(M) and tau(R) non-invasively and spatially resolved, was used successfully for the optimization of an pH-controlled formulation.

Synthesis and characterizations of biodegradable and crosslinkable poly(-caprolactone fumarate), poly(ethylene glycol fumarate), and their amphiphilic copolymer

A series of self-crosslinkable and biodegradable polymers, poly(caprolactone fumarate) (PCLF), poly(ethylene glycol fumarate) (PEGF), and their copolymer PEGF-co-PCLF, has been developed for tissue engineering applications using a novel synthesis method. The current method employs potassium carbonate (K2CO3), other than the previously reported triethylamine, as the proton scavenger. The new synthetic route is more convenient and less time-consuming to carry out, and the synthesized polymers have a much lighter color, which renders them more suitable for self-crosslinking via photo-initiation. This group of polymers are essentially copolymers of fumaryl chloride, which contains double bonds for in situ crosslinking, with poly(epsilon-caprolactone) (PCL) or/and poly(ethylene glycol) (PEG) that has a flexible chain to facilitate self-crosslinking. Both PCLF and PEGF, and their amphiphilic copolymer PEGF-co-PCLF could be self-crosslinked or photocrosslinked to produce scaffolds without the use of a crosslinking agent. Our results suggest that these polymers are potentially useful as injectable, self-crosslinkable, and photo-crosslinkable materials for diverse tissue engineering applications.

A 3D porous lanthanide–fumarate framework with water hexamer occupied cavities, exhibiting a reversible dehydration and rehydration procedure

[Sm2(fumarate)3(H2O)4] x 3 H2O, a new porous pillared layer framework with 0D cavities for the accommodation of chair-like hexameric water clusters, possesses three kinds of fumarate ligand with their two COO ends adopting different coordination modes and shows reversible de- and re-hydration behavior.

Determination of electron donors by comparing reaction rates for in situ bioremediation of nitrate-contaminated groundwater

Groundwater contaminated by nitrates occurs frequently. In this research, fumarate, acetate, formate, lactate, propionate, ethanol, and methane were evaluated as a potential electron donor and carbon source by comparing the denitrification rate for the in situ bioremediation of nitrate contaminated groundwater. The denitrification rate for each substance was the quickest in the order of: fumarate > hydrogen > formate/Lactate > ethanol > propionate > methanol > acetate. Microcosm studies were performed with fumarates and acetates. When fumarates were used as a substrate, nitrates were removed completely at a rate of 0.66 mmol/day, while the conversion rate from nitrate to nitrogen gas and other by-products was 87%. For the microcosm test, 42 mg of fumarates were needed to remove 30 mg of NO(3)--N/L. When using acetate as a sole carbon source, 31% of nitrates were removed during the initial adjustment period. Among the removed fractions, however, 83% of the nitrates were removed by the cell growth. Overall, the nitrate removal rate was 0.37 mmol/day when acetate was used as a sole carbon source. The acetate showed longer lag time before denitrification occurred, which implied that fumarate would have been a better carbon source compared to acetate as more amounts were utilized for nitrate removal than cell growth.

Chemistry of Ru(&6-1,3,5-cyclooctatriene)(η2-dimethyl fumarate)2

The chemistry of a novel zerovalent Ru complex, Ru(eta6-cot)(eta2-dmfm)2 (1) (cot=1,3,5-cyclooctatriene; dmfm=dimethyl fumarate), is reviewed with a focus on its reactivity toward phosphines, amines, and H2O, as well as arenes and p-quinones. A variety of novel zerovalent Ru complexes were synthesized from Ru(eta6-cot)(eta2-dmfm)2 (1), and it was shown that the complexes preferably bear both electron-donating and -accepting ligands simultaneously to exhibit thermodynamic stability. The first isolable zerovalent Ru aqua complexes were successfully prepared, and in these complexes, the generation of a chiral center on the O atom of the coordinated H2O was disclosed. In addition, the characteristic catalytic activity of 1 in organic synthesis was considered by reviewing recently developed novel reactions: (i) dimerization of 2,5-norbornadiene to pentacyclo[6.6.0.0(2,6).0(3,13).0(10,14)]tetradeca-4,11-diene (PCTD), (ii) intramolecular hydroamination of aminoalkynes to cyclic imines, (iii) formal [4+2] cycloaddition of alkynes with dmfm to trans-4-cyclohexene-1,2-dicarboxylates, and (iv) co-dimerization of dihydrofurans with alpha,beta-unsaturated esters to 2-alkylidenetetrahydrofurans. The products obtained here are expected to be used as novel functional organic monomers.

Synthesis and characterization of novel injectable, biodegradable and in situ crosslinkable poly(hexamethylene-carbonate-fumarate), poly(hexamethylene carbonate) diacrylate and poly(ethylene glycol fumarate-co-hexamethylene carbonate-fumarate) scaffolds for bone tissue engineering

A series of novel self-crosslinkable and biodegradable polymers; poly(hexamethylene carbonate-fumarate), poly(hexamethylene carbonate) diacrylate and their amphiphilic copolymers with polyethylene glycol, poly(ethylene glycol fumarate-co-hexamethylene carbonate-fumarate) (PEGF-co-PHMCF) were developed for tissue engineering using novel synthesis approach. These novel polymers were fully characterized using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, rheometry and shrinkage strain measurement. The cytocompatibility of macromers and their networks were evaluated by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] MTT assay. The synthetic macromers were light colored with self-crosslinking ability via both photocrosslinking and chemical crosslinking. These polymers can be used as precursors to prepare polymer networks and scaffolds with controlled hydrophilicity, biodegradability and mechanical characteristics for application in cell delivery, tissue engineering and controlled release of biologically active agents.

Creating carbon–carbon bonds with samarium diiodide for the synthesis of modified amino acids and peptides

In this perspective, an overview of our experiences on the application of samarium diiodide in organic synthesis for the preparation of amino acid and peptide analogues is presented. Three different carbon-carbon bond forming reactions are discussed, including side chain introductions, gamma-amino acid synthesis and acyl-like radical additions for the construction of C-C mimics of the peptidic bonds.

Functional bone engineering using ex vivo gene therapy and topology-optimized, biodegradable polymer composite scaffolds

Bone tissue engineering could provide an alternative to conventional treatments for fracture nonunion, spinal fusion, joint replacement, and pathological loss of bone. However, this approach will require a biocompatible matrix to allow progenitor cell delivery and support tissue invasion. The construct must also support physiological loads as it degrades to allow the regenerated tissue to bear an increasing load. To meet these complex requirements, we have employed topology-optimized design and solid free-form fabrication to manufacture biodegradable poly(propylene fumarate)/beta-tricalcium phosphate composites. These scaffolds were seeded with primary human fibroblasts transduced with an adenovirus expressing bone morphogenetic protein-7 and implanted subcutaneously in mice. Specimens were evaluated by microcomputed tomography, compressive testing, and histological staining. New bone was localized on the scaffold surface and closely followed its designed contours. Furthermore, the total stiffness of the constructs was retained for up to 12 weeks after implantation, as scaffold degradation and tissue invasion took place.

Heteronuclear decoupling interference during symmetry-based homonuclear recoupling in solid-state NMR

We examine the influence of continuous-wave heteronuclear decoupling on symmetry-based double-quantum homonuclear dipolar recoupling, using experimental measurements, numerical simulations, and average Hamiltonian theory. There are two distinct regimes in which the heteronuclear interference effects are minimized. The first regime utilizes a moderate homonuclear recoupling field and a strong heteronuclear decoupling field; the second regime utilizes a strong homonuclear recoupling field and a weak or absent heteronuclear decoupling field. The second regime is experimentally accessible at moderate or high magic-angle-spinning frequencies and is particularly relevant for many realistic applications of solid-state NMR recoupling experiments to organic or biological materials.

In-situ preparation of poly(propylene fumarate)—hydroxyapatite composite

In-situ precipitation of hydroxyapatite (HAp) in the presence of poly(propylene fumarate) (PPF) is investigated. Amorphous calcium phosphate (ACP) precipitates in the presence of the polymer and remains in the amorphous form for a relatively long time, e.g. even after 24 h of coexistence with the mother solution. Our observations suggest that PPF interacts with the surface of the ACP particles and prevents them from transformation to crystalline hydroxyapatite. The PPF polymer seems to be more efficient in hindering the ACP to HAp transformation at higher pH conditions. From spectroscopic observations we hypothesize that the C=O bond of the PPF molecules interact with the calcium ion of the ACP particles. In case of low molecular weight PPF this interaction may lead to the incorporation of the polymer within the growing ACP particles.

Functional roles of ATP-binding residues in the catalytic site of human mitochondrial NAD(P)+-dependent malic enzyme

Human mitochondrial NAD(P)+-dependent malic enzyme is inhibited by ATP. The X-ray crystal structures have revealed that two ATP molecules occupy both the active and exo site of the enzyme, suggesting that ATP might act as an allosteric inhibitor of the enzyme. However, mutagenesis studies and kinetic evidences indicated that the catalytic activity of the enzyme is inhibited by ATP through a competitive inhibition mechanism in the active site and not in the exo site. Three amino acid residues, Arg165, Asn259, and Glu314, which are hydrogen-bonded with NAD+ or ATP, are chosen to characterize their possible roles on the inhibitory effect of ATP for the enzyme. Our kinetic data clearly demonstrate that Arg165 is essential for catalysis. The R165A enzyme had very low enzyme activity, and it was only slightly inhibited by ATP and not activated by fumarate. The values of K(m,NAD) and K(i,ATP) to both NAD+ and malate were elevated. Elimination of the guanidino side chain of R165 made the enzyme defective on the binding of NAD+ and ATP, and it caused the charge imbalance in the active site. These effects possibly caused the enzyme to malfunction on its catalytic power. The N259A enzyme was less inhibited by ATP but could be fully activated by fumarate at a similar extent compared with the wild-type enzyme. For the N259A enzyme, the value of K(i,ATP) to NAD+ but not to malate was elevated, indicating that the hydrogen bonding between ATP and the amide side chain of this residue is important for the binding stability of ATP. Removal of this side chain did not cause any harmful effect on the fumarate-induced activation of the enzyme. The E314A enzyme, however, was severely inhibited by ATP and only slightly activated by fumarate. The values of K(m,malate), K(m,NAD), and K(i,ATP) to both NAD+ and malate for E314A were reduced to about 2-7-folds compared with those of the wild-type enzyme. It can be concluded that mutation of Glu314 to Ala eliminated the repulsive effects between Glu314 and malate, NAD+, or ATP, and thus the binding affinities of malate, NAD+, and ATP in the active site of the enzyme were enhanced.

Probing the Low-Barrier Hydrogen Bond in Hydrogen Maleate in the Gas Phase: A Photoelectron Spectroscopy and ab Initio Study

The strength of the low-barrier hydrogen bond in hydrogen maleate in the gas phase was investigated by low-temperature photoelectron spectroscopy and ab initio calculations. Photoelectron spectra of maleic and fumaric acid monoanions (cis-/trans-HO(2)CCH=CHCO(2)(-)) were obtained at low temperatures and at 193 nm photon energy. Vibrational structure was observed for trans-HO(2)CCH=CHCO(2)(-) due to the OCO bending modes; however, cis-HO(2)CCH=CHCO(2)(-) yielded a broad and featureless spectrum. The electron binding energy of cis-HO(2)CCH=CHCO(2)(-) is about 1 eV blue-shifted relative to trans-HO(2)CCH=CHCO(2)(-) due to the formation of intramolecular hydrogen bond in the cis-isomer. Theoretical calculations (CCSD(T)/ aug-cc-pVTZ and B3LYP/aug-cc-pVTZ) were carried out to estimate the strength of the intramolecular hydrogen bond in cis-HO(2)CCH=CHCO(2)(-). Combining experimental and theoretical calculations yields an estimate of 21.5 +/- 2.0 kcal/mol for the intramolecular hydrogen bond strength in hydrogen maleate.

Conformational analysis and crystal structure of {[1-(3-chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt

{[1-(3-Chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt (C(20)H(22)ClF(2)N(3)O, C(4)H(4)O(4)) (1) was synthesized and characterized by the complete (1)H, (13)C and (19)F NMR analyses. The conformation of the piperidin ring, in the solution state, was particularly studied from the coupling constants determined by recording a double-quantum filtered COSY experiment in phase-sensitive mode. (1)H NMR line-shape analysis was used, at temperatures varying between -5 and +60 degrees C, to determine the enthalpy of activation of the rotational barrier around the CN bond. Compound 1 crystallizes in the triclinic space group P1 with a=8.517(3) Angstrom, b=12.384(2) Angstrom, c=12.472(3) Angstrom, alpha=70.88(2) degrees, beta=82.04(2) degrees, gamma=83.58(2) degrees. The results strongly indicate that the solid and solution conformations are similar. Thermal stability and phases transitions were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore polymorphism screening was studied from recrystallization of 1 performed in seven solvents and by slurry conversion in water. The X-ray powder diffraction (XRPD) and differential scanning calorimetry results suggested that 1 crystallizes into one crystalline form which melts at 157 degrees C (DeltaH=132 J g(-1)).

Evidence of covalent interaction of fumaric acid esters with sulfhydryl groups in peptides

Fumaric acid esters, namely dimethylfumarate, have been used for the treatment of psoriasis for many years. Still, their mode of action is not fully clear. Because addition of nucleophiles to the double bonds of fumarates can occur (Michael analogous addition), a study of the interaction of fumarates with cysteine and cysteine-containing peptides possessing nucleophilic sulfhydryl group was carried out. Experiments were performed in aqueous medium at pH 7.4 and at 37 degrees C to simulate physiological conditions. It was proven by mass spectrometric measurements using an ion-trap and time-of-flight instrument that a covalent bond can form between fumarates and the sulfhydryl group of cysteine or cysteinyl residues in peptides. Structures of the interaction products were elucidated by multistage mass spectrometry applying collision-induced dissociation. Higher reactivity of dimethylfumarate in comparison to monomethylfumarate and fumaric acid was observed.

Synthesis, material properties, and biocompatibility of a novel self-cross-linkable poly(caprolactone fumarate) as an injectable tissue engineering scaffold

A novel self-cross-linkable and biodegradable macromer, poly(caprolactone fumarate) (PCLF), has been developed for guided bone regeneration. This macromer is a copolymer of fumaryl chloride, which contains double bonds for in-situ cross-linking, and poly(epsilon-caprolactone), which has a flexible chain to facilitate self-cross-linkability. PCLF was characterized with Fourier transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Porous scaffolds were fabricated with sodium chloride particles as the porogen and a chemical initiation system. The PCLF scaffolds were characterized with scanning electron microscopy and micro-computed-tomography. The cytotoxicity and in vivo biocompatibility of PCLF were also assessed. Our results suggest that this novel copolymer, PCLF, is an injectable, self-cross-linkable, and biocompatible macromer that may be potentially used as a scaffold for tissue engineering applications.

Methods: A Comparative Analysis of Radiography, Microcomputed Tomography, and Histology for Bone Tissue Engineering

This study focused on the assessment of radiography, microcomputed tomography, and histology for the evaluation of bone formation in a 15.0-mm defect in the rabbit radius after the implantation of a tissue-engineered construct. Radiography was found to be useful as a noninvasive method for obtaining images of calcified tissue throughout the time course of the experiment. With this method, however, image quality was low, making it difficult to obtain precise information about the location and quantity of the bone formed. Microcomputed tomography was used to create three-dimensional reconstructions of the bone (25-microm resolution). These reconstructions allowed for greater spatial resolution than the radiography, but did not allow for imaging of the implanted scaffold material or the surrounding, nonmineralized tissue. To visualize all materials within the defect area at the cellular level, histology was used. Histological analysis, however, is a destructive technique that did not allow for any further analysis of the samples. Each technique examined here has its own advantages and limitations, but each yields unique information regarding bone regeneration. It is only through the use of all three techniques that complete characterization of the bone growth and tissue/construct responses after implantation in vivo.

Development of a multi particulate extended release formulation for ZK 811 752, a weakly basic drug

ZK 811 752, a potent candidate for the treatment of autoimmune diseases, demonstrated pH-dependent solubility. The resulting release from conventional mini matrix tablets decreased with increasing pH-values of the dissolution medium. The aim of this study was to overcome this problem and to achieve pH-independent drug release. Mini matrix tablets were prepared by direct compression of drug, matrix former (polyvinylacetate/polyvinylpyrrolidone; Kollidon SR) and excipients (lactose, calcium phosphate or maize starch). To solve the problem of pH-dependent solubility fumaric acid was added to the drug-polymer excipient system. The addition of fumaric acid was found to maintain low pH-values within the mini tablets during release of ZK 811 752 in phosphate buffer pH 6.8. Thus, micro environmental conditions for the dissolution of the weakly basic drug were kept constant and drug release was demonstrated to be pH-independent. Incorporation of water-soluble (lactose) or highly swellable (maize starch) excipients accelerated drug release in a more pronounced manner compared to the water-insoluble excipient calcium phosphate. Stability studies demonstrated no degradation of the drug substance and reproducible drug release patterns for mini matrix tablets stored at 25 degrees C/60% RH and 30 degrees C/70% RH for up to 6 months.

In vitro degradation of porous poly(propylene fumarate)/poly(dl-lactic-co-glycolic acid) composite scaffolds

This study investigated the in vitro degradation of porous poly(propylene fumarate) (PPF-based) composites incorporating microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) during a 26-week period in pH 7.4 phosphate-buffered saline at 37 degrees C. Using a fractional factorial design, four formulations of composite scaffolds were fabricated with varying PEG content of the microparticles, microparticle mass fraction of the composite material, and initial leachable porogen content of the scaffold formulations. PPF scaffolds without microparticles were fabricated with varying leachable porogen content for use as controls. The effects of including PLGA/PEG microparticles in PPF scaffolds and the influence of alterations in the composite formulation on scaffold mass, geometry, water absorption, mechanical properties and porosity were examined for cylindrical specimens with lengths of 13 mm and diameters of 6.5 mm. The composite scaffold composition affected the extent of loss of polymer mass, scaffold length, and diameter, with the greatest loss of polymer mass equal to 15+/-5% over 26 weeks. No formulation, however, exhibited any variation in compressive modulus or peak compressive strength over time. Additionally, sample porosity, as determined by both mercury porosimetry and micro-computed tomography did not change during the period of this study. These results demonstrate that microparticle carriers can be incorporated into PPF scaffolds for localized delivery of bioactive molecules without altering scaffold mechanical or structural properties up to 26 weeks in vitro.

Preparation of biodegradable networks by photo-crosslinking lactide, ε-caprolactone and trimethylene carbonate-based oligomers functionalized with fumaric acid monoethyl ester

Biodegradable polymer networks were prepared from fumaric acid derivatives of oligomeric esters. Photo-crosslinkable macromers were prepared by reacting star-shaped hydroxyl-group terminated lactide, epsilon-caprolactone and trimethylene carbonate based oligomers and fumaric acid monoethyl ester in the presence of N,N-dicyclohexylcarbodiimide and 4-dimethylamino pyridine at room temperature. The functionalization method is facile and suited for many hydroxyl-terminated oligomers. The reactivity of the fumarate end groups is such that, upon crosslinking by UV radical polymerization, networks with high gel contents (up to 96%) can be obtained without the addition of reactive diluents. The physical properties of the networks can be tuned by adjusting the composition, architecture and molecular weight of the oligomeric precursors. Such networks, built up of non-toxic compounds and designed to release benign degradation products, may find wide application in tissue engineering and other areas of biomedical research.

Mechanism of Benzylsuccinate Synthase: Stereochemistry of Toluene Addition to Fumarate and Maleate

Benzylsuccinate synthase catalyzes a highly unusual reaction: the addition of toluene to fumarate to form (R)-benzylsuccinic acid. The stereochemistry of this reaction has been examined using [d3-methyl]toluene and either fumarate or its cis stereoisomer, maleate, as the substrates. We demonstrate that when fumarate is the cosubstrate, deuterium is transferred from toluene to the C-3 pro-(R) position of benzylsuccinate, implying a syn addition of toluene to the double bond of fumarate. However, when maleate is the cosubstrate, the addition of toluene occurs in an anti fashion, so that deuterium transfer to the C-3 pro-(R) position of benzylsuccinate is also observed. This is consistent with the formation of the C-3 radical of benzylsuccinate as an intermediate, in which rotation about the C-2-C-3 bond can occur to relieve the sterically unfavorable cis conformation of the carboxylate groups when maleate is the cosubstrate.

Crystal engineering approach to forming cocrystals of amine hydrochlorides with organic acids. Molecular complexes of fluoxetine hydrochloride with benzoic, succinic, and fumaric acids

A crystal engineering strategy for designing cocrystals of pharmaceuticals is presented. The strategy increases the probability of discovering useful cocrystals and decreases the number of experiments that are needed by selecting API:guest combinations that have the greatest potential of forming energetically and structurally robust interactions. Our approach involves multicomponent cocrystallization of hydrochloride salts, wherein strong hydrogen bond donors are introduced to interact with chloride ions that are underutilized as hydrogen bond acceptors. The strategy is particularly effective in producing cocrystals of amine hydrochlorides with neutral organic acid guests. As an example of the approach, we report the discovery of three cocrystals containing fluoxetine hydrochloride (1), which is the active ingredient in the popular antidepressant Prozac. A 1:1 cocrystal was prepared with 1 and benzoic acid (2), while succinic acid and fumaric acid were each cocrystallized with 1 to provide 2:1 cocrystals of fluoxetine hydrochloride:succinic acid (3) and fluoxetine hydrochloride:fumaric acid (4). The presence of a guest molecule along with fluoxetine hydrochloride in the same crystal structure results in a solid phase with altered physical properties when compared to the known crystalline form of fluoxetine hydrochloride. On the basis of intrinsic dissolution rate experiments, cocrystals 2 and 4 dissolve more slowly than 1, and 3 dissolves more quickly than 1. Powder dissolution experiments demonstrated that the solid present at equilibrium corresponds to the cocrystal for 2 and 4, while 3 completely converted to 1 upon prolonged slurry in water.

[Progress in researches on the synthesis of poly (propylene fumarate) and its crosslinking characteristics]

Poly (propylene fumarate) is an unsaturated linear polyester, which degrades, in the presence of water, into propylene glycol and fumaric acid, and the degradation products can be cleared from the human body by normal metabolic processes. In this paper, different methods of the synthesis of PPF are listed, the crosslinking characteristics of polymerizing composite as well as the mechanical properties of cross-linked composite are discussed, and the potentialities of PPF composite used as particularly degradable polymeric cement for orthopedic application are reviewed.