Simplified kinetic calibration of solid-phase microextraction for in vivo pharmacokinetics

Solid-phase microextraction (SPME) has been demonstrated to be useful for in vivo sampling in pharmacokinetic studies. In this study, a single time-point kinetic calibration for in vivo dynamic monitoring was developed by simplification of the laborious multiple time-point kinetic calibration, based on the independent desorption kinetics of the preloaded standards from SPME fibers with the changing analyte concentrations. The theoretical foundation and practical application conditions, such as the replicate numbers, the optimal time-point for desorption, and the sampling time, were systematically investigated. Furthermore, the feasibility of using regular standards rather than deuterated ones for the kinetic calibration was justified by comparing to the data obtained using the deuterated standards. All the methods were verified by in vitro and in vivo experiments. The results from in vivo SPME were validated by the blood drawing and chemical assay. These simplified calibration methods improved the quantitative applications of SPME for dynamic monitoring and in vivo sampling, enhance the multiplexing capability and automatic potentials for high throughput analysis, and decrease expenses on reagents and instruments.     

Semi-automated in vivo solid-phase microextraction sampling and the diffusion-based interface calibration model to determine the pharmacokinetics of methoxyfenoterol and fenoterol in rats

In vivo solid-phase microextraction (SPME) can be used to sample the circulating blood of animals without the need to withdraw a representative blood sample. In this study, in vivo SPME in combination with liquid–chromatography tandem mass spectrometry (LC–MS/MS) was used to determine the pharmacokinetics of two drug analytes, R,R-fenoterol and R,R-methoxyfenoterol, administered as 5 mg kg⁻¹i.v. bolus doses to groups of 5 rats. This research illustrates, for the first time, the feasibility of the diffusion-based calibration interface model for in vivo SPME studies. To provide a constant sampling rate as required for the diffusion-based interface model, partial automation of the SPME sampling of the analytes from the circulating blood was accomplished using an automated blood sampling system. The use of the blood sampling system allowed automation of all SPME sampling steps in vivo, except for the insertion and removal of the SPME probe from the sampling interface. The results from in vivo SPME were compared to the conventional method based on blood withdrawal and sample clean up by plasma protein precipitation. Both whole blood and plasma concentrations were determined by the conventional method. The concentrations of methoxyfenoterol and fenoterol obtained by SPME generally concur with the whole blood concentrations determined by the conventional method indicating the utility of the proposed method. The proposed diffusion-based interface model has several advantages over other kinetic calibration models for in vivo SPME sampling including (i) it does not require the addition of a standard into the sample matrix during in vivo studies, (ii) it is simple and rapid and eliminates the need to pre-load appropriate standard onto the SPME extraction phase and (iii) the calibration constant for SPME can be calculated based on the diffusion coefficient, extraction time, fiber length and radius, and size of the boundary layer. In the current study, the experimental calibration constants of 338.9 ± 30 mm⁻³ and 298.5 ± 25 mm⁻³ are in excellent agreement with the theoretical calibration constants of 307.9 mm⁻³ and 316.0 mm⁻³ for fenoterol and methoxyfenoterol respectively.     

Comparison and validation of calibration methods for in vivo SPME determinations using an artificial vein system

The success of in vivo solid phase microextraction (SPME) depends significantly on the selection of calibration method. Three kinetic in vivo SPME calibration methods are evaluated in this paper: (1) on-fibre standardization (OFS), (2) dominant pre-equilibrium desorption (DPED), and (3) the diffusion-based interface (DBI) model. These are compared in terms of precision, accuracy, and ease of experimental use by employing a flow device simulating an animal circulatory system. In addition, the kinetic calibration methods were validated against established SPME equilibrium extraction (EE) external calibration and a conventional sample preparation method involving protein precipitation. The comparison was performed using a hydrophilic drug fenoterol as the analyte of interest. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for the determinations. All three kinetic methods compared well with both EE extraction and the conventional method in terms of accuracy (93-119%). In terms of precision, the DBI model had the best precision in whole blood and buffered phosphate saline solution with %RSD similar to the standard techniques (9-15%). DPED had the poorest precision of %RSD (20-30%) possibly due to errors associated with uncertainty in the amount of standard loaded on-fibre and remaining on the fibre after desorption. In addition, incurred errors could result due to the greater number of fibres used in comparison to the other two calibration methods. The precision of the OFS procedure was better than for DPED primarily because the use of multiple fibres is eliminated. In terms of the ease of use for calibration, the DBI model was the simplest and most convenient as it did not require standards once it had been calibrated or the uptake constant was calculated. This research suggests the potential use of DBI model as the best kinetic calibration method for future in-vein blood SPME investigations.     

In vivo solid-phase microextraction for single rodent pharmacokinetics studies of carbamazepine and carbamazepine-10,11-epoxide in mice

The use of solid-phase microextraction (SPME) for in vivo sampling of drugs and metabolites in the bloodstream of freely moving animals eliminates the need for blood withdrawal in order to generate pharmacokinetics (PK) profiles in support of pharmaceutical drug discovery studies. In this study, SPME was applied for in vivo sampling in mice for the first time and enables the use of a single animal to construct the entire PK profile. In vivo SPME sampling procedure used commercial prototype single-use in vivo SPME probes with a biocompatible extractive coating and a polyurethane sampling interface designed to facilitate repeated sampling from the same animal. Pre-equilibrium in vivo SPME sampling, kinetic on-fibre standardization calibration and liquid chromatography–tandem mass spectrometry analysis (LC–MS/MS) were used to determine unbound and total circulating concentrations of carbamazepine (CBZ) and its active metabolite carbamazepine-10,11-epoxide (CBZEP) in mice (n = 7) after 2 mg/kg intravenous dosing. The method was linear in the range of 1–2000 ng/mL CBZ in whole blood with acceptable accuracy (93–97%) and precision (<17% RSD). The single dose PK results obtained using in vivo SPME sampling compare well to results obtained by serial automated blood sampling as well as by the more conventional method of terminal blood collection from multiple animals/time point. In vivo SPME offers the advantages of serial and repeated sampling from the same animal, speed, improved sample clean-up, decreased animal use and the ability to obtain both free and total drug concentrations from the same experiment.     

Microsensor in vivo monitoring of oxidative burst in oilseed rape (Brassica napus L.) leaves infected by Sclerotinia sclerotiorum

Oxidative burst is the rapid and transient production of large amounts of reactive oxygen species, including superoxide anion, hydrogen peroxide (H₂O₂), and hydroxyl radical. A rapid and simple technique was employed for in vivo detection of oxidative burst in oilseed rape (Brassica napus L.) leaves, using a modified electrode. Platinum (Pt) micro-particles were dispersed on a Pt electrode, coated with a poly (o-phenylenediamine) film. This exhibited high sensitivity, selectivity and stability in H₂O₂ detection. Amperometry was used to obtain satisfactory linear relationships between reductive current intensities and H₂O₂ concentrations at −0.1 V potential in different electrolytes. This electrode was used in vivo to detect oxidative burst in oilseed rape following fungal infection. Oxidative bursts induced by infection of the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary exhibited notably different mechanisms between a susceptible and a resistant glucose oxidase-transgenic genotype.     

In vitro evaluation of new biocompatible coatings for solid-phase microextraction: Implications for drug analysis and in vivo sampling applications

A new line of solid-phase microextraction (SPME) coatings suitable for use with liquid chromatography applications was recently developed to address the limitations of the currently available coatings. The proposed coatings were immobilized on the metal fiber core and consisted of a mixture of proprietary biocompatible binder and various types of coated silica (octadecyl, polar embedded and cyano) particles. The aim of this research was to perform in vitro assessment of these new SPME fibers in order to evaluate their suitability for drug analysis and in vivo SPME applications. The main parameters examined were extraction efficiency, solvent resistance, preconditioning, dependence of extraction kinetics on coating thickness, carryover, linear range and inter-fiber reproducibility. The performance of the proposed coatings was compared against commercial Carbowax-TPR (CW-TPR) coating, when applicable. The fibers were evaluated for the extraction of drugs of different classes (carbamazepine, propranolol, pseudoephedrine, ranitidine and diazepam) from plasma and urine. The analyses were performed using liquid chromatography-tandem mass spectrometry. The results show that the fibers perform very well for the extraction of biological fluids with no sample pre-treatment required and can also be used for in vivo sampling applications of flowing blood. A coating thickness of 45 μm was found to be a good compromise between extraction capacity and extraction kinetics. Due to the high extraction efficiency of these coatings, pre-equilibrium SPME with very short extraction times (2 min) can be employed to increase sample throughput. Inter-fiber reproducibility was ≤11% R.S.D. (n = 10) for model drugs examined in plasma, which is a significant improvement over polypyrrole coatings reported in literature, and permits single fiber use for in vivo applications.     

Evaluation of in vivo solid phase microextraction for minimally invasive analysis of nonvolatile phytochemicals in Amazonian plants

Introduction

Although solid phase microextraction (SPME) has been used extensively for fingerprinting volatile compounds emitted by plants, there are very few such reports for direct insertion SPME. In this research, direct contact of SPME probes with the interstitial fluid of plants was investigated as a method for phytochemical analysis.

Objective

Medicinal plants from the Amazon have been the source of numerous drugs used in western medicine. However, a large number of species used in traditional medicine have not been characterized chemically, partly due to the difficulty of field work. In this project, the phytochemical composition of plants from several genera was fingerprinted by combining convenient field sampling by solid phase microextraction (SPME) with laboratory analysis by LC-MS. The new method was compared with classical sampling followed by liquid extraction (LE).

Methodology

SPME probes were prepared by coating stainless steel wires with a mixture of polyacrylonitrile and either RP-amide or HS-F5 silica particles. Sampling was performed by inserting the microextraction probes into various tissues of living plants in their natural environment. After in vivo extraction, the probes were sealed under vacuum and refrigerated until analyzed. The probes were desorbed in mobile phase and analyzed on a Waters Acquity UPLC with triple quadrupole mass spectrometer in positive ion mode.

Results

Twenty Amazonian plant species were sampled and unique metabolomic fingerprints were obtained. In addition, quantitative analysis was performed for previously identified compounds in three species. Comparison of the fingerprints obtained by in vivo SPME with those obtained by LE showed that 27% of the chromatographic features were unique to SPME, 57% were unique to LE, and 16% were common to both methods.

Conclusion

In vivo SPME caused minimal damage to the plants, was much faster than traditional liquid extraction, and provided unique fingerprints for all investigated plants. SPME revealed unique chromatographic features, undetected by traditional extraction, although it produced only half as many peaks as ethanol extraction.     

In vitro and in vivo antitumor activity of novel 3D-organotin supramolecular coordination polymers based on CuCN and pyridine bases

Two novel organotin supramolecular coordination polymers (SCP), namely, ³_∞[Me₃SnCu(CN)₂·(EN)₂], 1 and ³_∞[Ph₃SnCu(CN)₂·(3-mpy)₂], 2 are obtained by the reactions of K₃[Cu(CN)₄], ethyl nicotinate (EN) or 3-methylpyridine (3-mpy) and Me₃SnCl or Ph₃SnCl in H₂O/acetonitrile solution at room temperature. 2D-layers are constructed via H-bonds between the parallel 1D-puckered chains which contain nanometer-sized [-CN(R₃Sn)NC-] spacers connecting the tetrahedral (T-4) copper sites. The network structures of 1 and 2 consist of infinite layers connected by interlayer H-bonds forming 3D-framworks. 2 is the first compound in this family containing the Ph₃Sn cation. The electronic absorption spectra of 1 and 2 reveal a broad band at 320 nm due to CT transition while the emission spectra exhibit high energy bands at 400-460 nm due to metal-centered (MC) transitions and low energy bands at 485-530 nm corresponding to MLCT. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the in vitro antitumor effects of the SCP 1 and 2 on human breast cancer cell line, ZR-75-1. Cell cycle analysis revealed that the SCP 1 and 2 induced apoptosis in ZR-75-1 breast cancer cell line through activating caspase-3. Moreover, in vivo model, the compound SCP 2 suppressed tumor growth developed mammary carcinoma by 52.3%. Taken together, our novel compounds selectivity exhibit specific in vivo and in vitro antitumor effects.     

Degradation and thermal properties of in situ compatibilized PS/POE blends

This paper reported the degradation behaviors and thermal properties of polystyrene (PS)/polyolefin elastomer (POE) blends with AlCl₃ as the catalyst of Friedel-Crafts alkylation reaction. Gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) were adopted to reveal the effects of in situ grafting reaction and degradation of blending compounds on the thermal properties of PS/POE blends. It was found that the changes in both catalyst content and blend composition influenced the competition between in situ grafting reaction and degradation, resulting in the complexity of the thermal properties of PS/POE/AlCl₃ blends.     

Synthesis and in vitro antitumor activity of phthalimide polymers containing podophyllotoxin

Polymer-linked PT (podophyllotoxin) conjugates have been designed to improve the therapeutic efficacy of PT. A new PT-conjugate, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimido-acetamidoglycinylglycine podophyllotoxin ester (ETPA-gly-gly-PT), was synthesized by covalently coupling its hydroxyl group onto the phthalimido monomer through a glycine-glycine-glycine spacer. Its homo- and copolymer with acrylic acid (AA) were prepared by photopolymerization using 2,2-dimethoxy-2-phenylacetophenone (DMP) as a photoinitiator. ETPA-gly-gly-PT and its polymers were characterized by IR and proton NMR spectra. The ETPA-gly-gly-PT content in the copolymer obtained by elemental analysis was 44 wt%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n = 13,500 for poly(ETPA-gly-gly-PT), M_n = 17,000 for poly(ETPA-gly-gly-PT-co-AA). The in vitro antitumor activity of these conjugates and polymers were determined and used to evaluate the potential applications in antitumor drugs. The IC₅₀ values indicated that the synthesized ETPA-gly-gly-PT and its polymers against cancer cells were much better inhibitors than PT.     

Quality control of Schizonepeta tenuifolia Briq by solid-phase microextraction gas chromatography/mass spectrometry and principal component analysis

The chemical composition of Schizonepeta tenuifolia Briq. (Sch.t.Briq.) is mainly composed of several volatile substances that affect multiple pharmacological targets and provide clinical efficacy. In this work, a headspace/solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS) method was developed to evaluate the profiles of volatile compounds in Sch.t.Briq. The optimization of SPME conditions was carried out using four kinds of fiber, extraction time and temperature, desorption temperature and time, and sample amount. The GC/MS analysis allowed the tentative identification of 21 compounds, with similarities higher than 85%, in accordance with the NIST/Wiley mass spectral library. Major components such as (+)-menthone (14.32%), (−)-pulegone (47.73%), 2-hydroxy-2-isopropenyl-5-methylcyclohexane (5.97%), cis-pulegone oxide (4.12%), and schizonal (5.36%) were identified by comparison of retention time and mass spectral data of standards isolated from Sch.t.Briq. The contents of these compounds were about above 78% against total amounts of volatile compounds extracted from Sch.t.Briq. Based on optimized SPME method, 19 different Sch.t.Briq. samples collected from markets in Korea and China were analyzed to obtain the profiling data of volatile compounds. In addition, principal component analysis (PCA) was performed on the profiling data in order to classify the samples collected from the different regions. PCA could possibly visualize the grouping tendencies of the studied varieties of herbal samples, as well as the identification of the volatiles responsible for discriminating the groups.     

Three new Lycopodium alkaloids from Huperzia carinata and Huperzia squarrosa

Eleven Lycopodium alkaloids with lycodine-type, lycopodine-type, and fawcettimine-related skeletons were isolated from the whole plants of Huperzia carinata (Desv. Ex. Poir.) Trevis and Huperzia squarrosa (G. Forst) Trevis (Huperziaceae). Among them, 8,15-dihydrohuperzine A (2), lycocarinatine A (3), and lycoposerramine U N-oxide (11) are new compounds. The structures of these new alkaloids were elucidated on the basis of 2D NMR correlations. Some of these isolated alkaloids were assayed for acetylcholinesterase (AChE) inhibitory activity.     

Study of kinetic desorption rate constant in fish muscle and agarose gel model using solid phase microextraction coupled with liquid chromatography with tandem mass spectrometry

This study aims to use solid phase microextraction (SPME), a simple tool to investigate diffusion rate (time) constant of selected pharmaceuticals in gel and fish muscle by comparing desorption rate of diffusion of the drugs in both agarose gel prepared with phosphate-buffered saline (PBS; pH 7.4) and fish muscle. The gel concentration (agarose gel model) that could be used to simulate tissue matrix (fish muscle) for free diffusion of drugs under in vitro and in vivo conditions was determined to model mass transfer phenomena between fibre polymer coating and environmental matrix such that partition coefficients and desorption time constant (diffusion coefficient) can be determined. SPME procedure involves preloading the extraction phase (fibre) with the standards from spiked PBS for 1 h via direct extraction. Subsequently, the preloaded fibre is introduced to the sample such fish or agarose gel for specified time ranging from 0.5 to 60 h. Then, fibre is removed at specified time and desorbed in 100 μL of desorption solution (acetonitrile: water 1:1) for 90 min under agitation speed of 1000 rpm. The samples extract were immediately injected to the instrument and analysed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The limit of detection of the method in gel and fish muscle was 0.01–0.07 ng mL⁻¹ and 0.07–0.34 ng g⁻¹, respectively, while the limit quantification was 0.10–0.20 ng mL⁻¹ in gel samples and 0.40–0.97 ng g⁻¹ in fish sample. The reproducibility of the method was good (5–15% RSD). The results suggest that kinetics of desorption of the compounds in fish tissue and different viscosity of gel can be determined using desorption time constant. In this study, desorption time constant which is directly related to desorption rate (diffusion kinetics) of selected drugs from the fibre to the gel matrix is faster as the viscosity of the gel matrix reduces from 2% (w/v) to 0.8% (w/v). As the concentration of gel reduces, viscosity of the gel will be reduced therefore allowing faster diffusion which invariably affect desorption time constant. Also, desorption time constant of model drugs in the fish muscle and 0.8–0.9% (w/v) gel model are similar based on free diffusion of studied compounds. In addition, in vitro and in vivo desorption time constant comparison shows that desorption time constant in an in vivo system (live fish muscle) is generally higher than an in vitro system (dead fish muscle) except for sertraline and nordiazepam. This study demonstrates SPME as a simple investigative tool to understand kinetics of desorption in an in vivo system with a goal to measure desorption rate of pharmaceuticals in fish.     

Synthesis and structural characterization of three copper coordination polymers with pyridine derivatives from hydro(solvo)thermal in situ decarboxylation reactions of 2,5-dicarboxylpyridine

The hydro(solvo)thermal self-assembles of CuI, KI and 2,5-dicarboxylpyridine [2,5-(COOH)₂py] in different molar ratios in H₂O/alcohol solutions produced three Cu coordination polymers as 2-D [N-C₂H₅py][Cu₃I₄] 1, 1-D [N-CH₃py][Cu₂I₃] 2 as well as 1-D [Cu(2-COOpy)₂]H₂O 3 (N-C₂H₅py=N-ethylpyridine, N-CH₃py=N-methylpyridine, 2-COOpy=2-carboxylpyridine). N-C₂H₅py in 1 and N-CH₃py in 2 derived from the solvothermal in situ simultaneous decarboxylation and N-alkylation reactions of 2,5-(COOH)₂py. The semi-decarboxylation reaction of 2,5-(COOH)₂py into 2-COOpy occurred in the preparation of 3. X-ray single-crystal analysis revealed that CuI is transformed into a 2-D [Cu₃I₄]⁻ layer in compound 1 and a 1-D chain in compound 2, templated by [N-C₂H₅py]⁺ and [N-CH₃py]⁺, respectively. Compound 3 is a divalent Cu compound. The Cu(II) centers with a 4+2 geometry are coordinated by μ₃-mode 2-COOpy ligands. All of the title compounds were characterized by CHN analysis, IR spectrum analysis and TG analysis. Compounds 1 and 2 exhibit fluorescence properties with the maximum emissions at 581 nm for 1 and 537 nm for 2.     

Direct monitoring of ochratoxin A in cheese with solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry

An in situ application of solid-phase microextraction (SPME) as a sampling and sample preparation method coupled to HPLC-MS/MS for direct monitoring of ochratoxin A (OTA) distribution at different locations in a single cheese piece is proposed. To be suited to the acidic analyte, the extraction phase (carbon-tape SPME fiber) was acidified with aqueous solution of HCl at pH 2, instead of the traditional sample pre-treatment with acids before SPME sampling. For calibration, kinetic on-fiber-standardization was used, which allowed the use of short sampling time (20 min) and accurate quantification of the OTA in the semi-solid cheese sample. In addition, the traditional kinetic calibration that used deuterated compounds as standards was extended to use a non-deuterated analogue ochratoxin B (OTB) as the standard of the analyte OTA, which was supported by both theoretical discussion and experimental verification. Finally, the miniaturized SPME fiber was adopted so that the concentration distribution of OTA in a small-sized cheese piece could be directly probed. The detection limit of the resulting SPME method in semi-solid gel was 1.5 ng/mL and the linear range was 3.5–500 ng/mL. The SPME–LC-MS/MS method showed good precision (RSD: ∼10%) and accuracy (relative recovery: 93%) in the gel model. The direct cheese analysis showed comparable accuracy and precision to the established liquid extraction. As a result, the developed in situ SPME–LC-MS/MS method was sensitive, simple, accurate and applicable for the analysis of complicated lipid-rich samples such as cheese.     

Thermal and mechanical properties of in situ polymerized PS/EPDM blends

In situ polymerized PS/EPDM blends were prepared by dissolving poly(ethylene-co-propylene-co-2-ethylidene-5-norbornene) (EPDM) in styrene monomer, followed by bulk polymerization at 60 °C and 80 °C . EPDM has excellent resistance to such factors as weather, ozone and oxidation, attributed to its non-conjugated diene component, and it could be a good alternative for substituting polybutadiene-based rubbers in PS toughening. The in situ polymerized blends were characterized by dynamic mechanical analysis, thermogravimetric analysis, gel permeation chromatography, and tensile and Izod impact resistance tests. The PS/EPDM blends are immiscible and present two phases, a dispersed elastomeric phase (EPDM) in a rigid PS matrix whose phase behavior is strongly affected by the polymerization temperature. Mechanical properties of the blends are influenced by the increase in the average size of EPDM domains with the increase in the polymerization temperature and EPDM content. The blends polymerized at 60 °C containing 5 wt% of EPDM presents an increase in the impact resistance of 80% and containing 17 wt% of EPDM presents an increase in the strain at break of 170% in comparison with the value of PS. The blend polymerized at 80 °C containing 17 wt% of EPDM presents an increase in the strain at break of 480% and in impact resistance of 140% in comparison with the value of PS.     

Solid-phase microextraction in bioanalysis: New devices and directions

The primary objective of this review is to discuss recent technological developments in the field of solid-phase microextraction that have enhanced the utility of this sample preparation technique in the field of bioanalysis. These developments include introduction of various new biocompatible coating phases suitable for bioanalysis, such as commercial prototype in vivo SPME devices, as well as the development of sampling interfaces that extend the use of this methodology to small animals such as mice. These new devices permit application of in vivo SPME to a variety of analyses, including pharmacokinetics, bioaccumulation and metabolomics studies, with good temporal and spatial resolution. New calibration approaches have also been introduced to facilitate in vivo studies and provide fast and quantitative results without the need to achieve equilibrium. In combination with the drastic improvement in the analytical sensitivity of modern liquid chromatography–tandem mass spectrometry instrumentation, full potential of in vivo SPME as a sample preparation tool in life sciences can finally be explored. From the instrumentation perspective, SPME was successfully automated in 96-well format for the first time. This opens up new opportunities for high-throughput applications (>1000 samples/day) such as for the determination of unbound and total drug concentrations in complex matrices such as whole blood with no need for sample pretreatment, studies of distribution of drugs in various compartments and/or determination of plasma protein binding and other ligand–receptor binding studies, and this review will summarize the progress in this research area to date.     

Synthesis, crystal structures and properties of three new mixed-ligand d metal complexes constructed from pyridinecarboxylate and in situ generated amino-tetrazole ligand

Three new metal-organic frameworks, [Zn(atz)(nic)]_n(1), [Zn(atz)(isonic)]_n·nHisonic(2) and [Cd(atz)(isonic)]_n(3) (Hnic=nicotinic acid, Hisonic=isonicotinic acid), have been firstly synthesized by employing mixed-ligand of pyridinecarboxylate with the in situ generated ligand of 5-amino-tetrazolate(atz⁻), and characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction. The results revealed that 1 presents a two-dimensional (2D) “sql” topological network constructed from the linear chain subunit of Zn(nic)₂ and atz⁻ ligand. A remarkable feature of 2 is a 2-fold interpenetrated diamondoid network with free Hisonic molecules locating in the channels formed by the zigzag chain subunits of Zn(isonic)₂. Complex 3 is a 3D non-interpenetrated pillared framework constructed from the double chain subunits of Cd-COO⁻-Cd. It possesses a rarely observed (4,6)-connected “fsc” topology. The thermal stabilities and fluorescent properties of the complexes were investigated. All of these complexes exhibited intense fluorescent emissions in the solid state at room temperature.     

Evaluation of an in vitro method to estimate trace elements bioavailability in edible seaweeds

Raw edible seaweed harvested in the Galician coast (Northwestern Spain), including two red seaweed types (Dulse and Nori), three brown seaweed (Kombu, Wakame and Sea Spaghetti), one green seaweed (Sea Lettuce) and one microalgae (Spirulina platensis) were studied to assess trace elements bioavailability using an in vitro method (simulated gastric and intestinal digestion/dialysis). Similarly, a cooked seaweed sample (canned in brine) consisting of a mixture of two brown seaweed (Sea Spaghetti and Furbelows) and a derived product (Agar-Agar) from the red seaweed Gelidiumm sesquipedale, were also included in the study. The total trace element content as well as the non-dialyzable fractions was carried out after a microwave acid digestion of the seaweed samples by inductively coupled plasma-mass spectrometry (ICP-MS). The dialyzable fraction was determined without any pre-treatment by ICP-MS.PIPES buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut off (MWCO) were used for intestinal digestion. Accuracy of the method was assessed by analyzing a NIES-09 certified reference material (Sargasso seaweed). The accuracy of the in vitro procedure was established by a mass balance study which led to good accuracy of the whole in vitro process, after statistical evaluation (95% confidence interval). The highest dialyzability percentages (100 ± 0.2%) were obtained for Dulse in Mn and V.