bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of a galactose‐carrying gelatin sponge for hepatocytes culture and transplantation
Authors: Hong Sung Ran , Lee Young Moo , Akaike Toshihiro
Published: November 2003

This study proposes a new three‐dimensional culture of mouse hepatocytes in a porous galactose‐carrying modified gelatin sponge matrix. The modification of gelatin using galactose residues significantly increased the attachment of hepatocytes on the substrate. A modified gelatin sponge with lactobionic acid (MGLA) was prepared to increase the specific interaction between the hepatocytes and the matrix. Hepatocytes cultured in a three‐dimensional MGLA sponge released much less lactate dehydrogenase than those cultured on a collagen Type I‐coated monolayer. Moreover, the survival rate of hepatocytes cultured on an MGLA sponge was longer than the survival rate of hepatocytes cultured on a collagen Type I‐coated monolayer. Hepatic specific metabolic functions, namely, the secretion of serum albumin and the synthesis of urea, were well maintained and promoted by spheroidal hepatocytes formed in the MGLA sponge. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 733–741, 2003
Nonadhesive nanotopography: Fibroblast response to poly(n‐butyl methacrylate)‐poly(styrene) demixed surface features
Authors: Dalby M. J. , Riehle M. O. , Johnstone H. J. H. , Affrossman S. , Curtis A. S. G.
Published: November 2003

It is becoming clear that cells do not only respond to micrometric scale topography, but may also respond to topography at the nanometric scale. Nano‐fabrication methods such as electron beam lithography are, however, expensive and time consuming. Polymer demixing of poly(styrene) and poly(4‐bromostyrene) has been found to produce nano‐scale islands of reproducible height, and the islands have been previously shown to effect cell events such as adhesion, spreading, proliferation, and differentiation. This study uses demixed poly(styrene) and poly(n‐butyl methacrylate) to produce nano‐islands with closer packing and narrower widths compared with those previously studied. Observations have been made of morphological and cytoskeletal changes in human fibroblasts interacting with 10‐ and 50‐nm‐high islands. The methods used included scanning electron microscopy, fluorescent microscopy, and optical microscopy. The results indicated that the cells do not respond differently to the 10‐nm islands compared with planar samples but, in contrast, the 50‐nm islands are nonadhesive. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1025–1032, 2003
Hydroxyapatite whiskers provide improved mechanical properties in reinforced polymer composites
Authors: Roeder Ryan K. , Sproul Michael M. , Turner Charles H.
Published: November 2003

Synthetic hydroxyapatite (HA) whiskers have been utilized as a new, biocompatible reinforcement for orthopedic biomaterials. High‐density polyethylene (HDPE) was reinforced with either the synthesized HA whiskers or a commercially available spherical HA powder using a novel powder processing technique that facilitated uniform dispersion of the reinforcements in the matrix prior to compression molding. Composites were processed for up to 60 vol % HA whiskers and up to 50 vol % spherical HA. The mechanical properties of the new composite biomaterials were examined by uniaxial tensile tests. As expected, increased volume fraction of either reinforcement type over 0–50 vol % resulted in increased elastic modulus, a maximum in ultimate tensile stress, and decreased work to failure. Composites reinforced with HA whiskers had higher elastic modulus, ultimate tensile strength, and work to failure relative to composites reinforced with spherical HA. Thus, HA whisker‐reinforced HDPE composites possessed improved mechanical properties over those reinforced with spherical HA. HA whisker‐reinforced composites were anisotropic due to alignment of the whiskers in the matrix during processing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 801–812, 2003
Effect of hydrophilicity and agmatine modification on degradation of poly(propylene fumarate‐co‐ethylene glycol) hydrogels
Authors: Tanahashi Kazuhiro , Mikos Antonios G.
Published: November 2003

We synthesized positively charged biodegradable hydrogels with different poly(propylene fumarate‐co‐ethylene glycol) [P(PF‐co‐EG)] block copolymers and agmatine‐modified poly(ethylene glycol)‐tethered fumarate [Agm‐PEGF] by radical crosslinking and investigated the effect of copolymer composition and agmatine modification on their degradation. Hydrogels were incubated in phosphate‐buffered saline (PBS) at 37°C with periodic PBS changes. All hydrogels experienced a slight mass loss over 4 weeks, ranging from 10–20%. Hydrogels with a molar ratio of ethylene glycol repeating units to propylene fumarate repeating units (EG/PF) of 9.3 degraded faster than hydrogels with an EG/PF ratio of 0.6. Agmatine‐modified hydrogels degraded faster than unmodified hydrogels. The weight swelling ratio of the hydrogels at pH 7 increased over 4 weeks while increases in the EG/PF ratio and agmatine modification showed greater swelling. After 2 weeks, degraded hydrogels swollen at pH 3 demonstrated significantly lower weight swelling ratios than at pH 5, 7, and 9. Our results suggest that the hydrophilicity of the P(PF‐co‐EG) copolymer and agmatine modification have a small effect on the degradation of P(PF‐co‐EG) hydrogels. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1148–1154, 2003
Biomedical application of a superabsorbent hydrogel for body water elimination in the treatment of edemas
Authors: Sannino A. , Esposito A. , Rosa A. De , Cozzolino A. , Ambrosio L. , Nicolais L.
Published: November 2003

A novel system of body water elimination to be used for the treatment of edemas, based on superabsorbent cellulose derivatives able to absorb large amounts of water and water solutions, has been investigated. Hydrogels have been synthesized starting from water solutions of carboxymethylcellulose sodium salt and hydroxyethylcellulose, chemically crosslinked with divinylsulphone. Polyelectrolyte hydrogels displayed high sensitivity in sorption capacity to variations of the ionic strength and pH of the external solution, which is a key parameter for the application under investigation. Further, swelling properties have been modulated acting on the degree of crosslinking of the macromolecular network, and a direct method for the measurement of this parameter based on NMR solid‐state analysis has been provided. The hydrogel biocompatibility has been studied in terms of its capacity either to induce nitric oxide and lactate dehydrogenase release by macrophages or influence their viability. The eventual release of toxic substances from the hydrogel was also investigated using Swiss 3T3 fibroblasts. The results obtained from the biocompatibility studies carried out in this work are consistent with the hypothesis that this gel may represent an alternative to diuretic therapies in those pathologic conditions in which edemas occur. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1016–1024, 2003
Alternating gene expression in fibroblasts adhering to multilayers of chitosan and dextran sulfate
Authors: Serizawa Takeshi , Yamaguchi Miyuki , Kishida Akio , Akashi Mitsuru
Published: November 2003

The alternating compatibility of fibroblast cells adhering to multilayers of chitosan and dextran sulfate (Dex) on a substrate was analyzed at the gene expression level. A greater number of round‐shaped cells adhered to the films with an outermost surface composed of Dex, although the total number of adherent cells was independent of the film surface. Greater expression of heat‐shock protein 70B mRNA was demonstrated in cells adhering to films with the Dex surface. It was found that analysis of gene expression was a powerful tool for evaluating the bioactivity of multilayers. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1060–1063, 2003
Plasma‐enhanced chemical vapor deposited silicon carbide as an implantable dielectric coating
Authors: Cogan Stuart F. , Edell David J. , Guzelian Andrew A. , Ping Liu Ying , Edell Robyn
Published: November 2003

Amorphous silicon carbide (a‐SiC) films, deposited by plasma‐enhanced chemical vapor deposition (PECVD), have been evaluated as insulating coatings for implantable microelectrodes. The a‐SiC was deposited on platinum or iridium wire for measurement of electrical leakage through the coating in phosphate‐buffered saline (PBS, pH 7.4). Low leakage currents of <10−11 A were observed over a ±5‐V bias. The electronic resistivity of a‐SiC was 3 × 1013 Ω‐cm. Dissolution rates of a‐SiC in PBS at 37 and 90°C were determined from changes in infrared absorption band intensities and compared with those of silicon nitride formed by low‐pressure chemical vapor deposition (LPCVD). Dissolution rates of LPCVD silicon nitride were 2 nm/h and 0.4 nm/day at 90 and 37°C, respectively, while a‐SiC had a dissolution rate of 0.1 nm/h at 90°C and no measurable dissolution at 37°C. Biocompatibility was assessed by implanting a‐SiC‐coated quartz discs in the subcutaneous space of the New Zealand White rabbit. Histological evaluation showed no chronic inflammatory response and capsule thickness was comparable to silicone or uncoated quartz controls. Amorphous SiC‐coated microelectrodes were implanted in the parietal cortex for periods up to 150 days and the cortical response evaluated by histological evaluation of neuronal viability at the implant site. The a‐SiC was more stable in physiological saline than LPCVD Si3N4 and well tolerated in the cortex. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 856–867, 2003
Preparation and characterization of macroporous chitosan–gelatin/β‐tricalcium phosphate composite scaffolds for bone tissue engineering
Authors: Yin Yuji , Ye Fen , Cui Junfeng , Zhang Fujiang , Li Xiulan , Yao Kangde
Published: November 2003

A biodegradable composite scaffold was developed using β‐tricalcium phosphate (β‐TCP) with chitosan (CS) and gelatin (Gel) in the form of a hybrid polymer network (HPN) via co‐crosslinking with glutaraldehyde. Various types of scaffolds were prepared by freezing and lyophilizing. These scaffolds were characterized by Fourier transform infrared, X‐ray diffractometer, and scanning electron microscopy. The macroporous composite scaffolds exhibited different pore structures. Compressive properties were improved, especially compressive modulus from 3.9–10.9 MPa. Biocompatibility was evaluated subcutaneously on rabbits. A mild inflammatory response was observed over 12 weeks. The results suggest that the scaffolds can be utilized in nonloading bone regeneration. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 844–855, 2003
Platelet responses and coagulation activation on polylactide and heparin–polycaprolactone‐L‐lactide ‐coated polylactide stent struts
Authors: Hietala Eeva‐Maija , Maasilta Paula , Välimaa Tero , Harjula Ari L.J. , Törmälä Pertti , Salminen Ulla‐Stina , Lassila Riitta
Published: November 2003

Despite modern stent technology and effective antiplatelet therapy, metallic stents carry the risk of (sub)acute thrombosis. Our aim was to examine short‐term differences in platelet deposition and coagulation activation between biodegradable polylactide (PLA), heparin–polycaprolactone‐L‐lactide‐coated polylactide (hepa‐P(CL95/L‐LA5)‐PLA), and stainless steel (SS) stent struts. Gel‐filtered platelets (GFP) and platelet‐rich plasma (PRP) were labeled with 10 nM 3H‐serotonin. Platelet deposition was measured after incubation of the stent struts in human serum albumin‐coated wells at 37°C in either GFP or PRP. Platelet morphology was studied by scanning electron microscopy (SEM). For coagulation activation, the stent struts were incubated in either PRP or platelet‐poor plasma (PPP), anticoagulated with D‐phenylalanyl‐L‐prolyl‐L‐arginine chloromethyl ketone (PPACK), followed by measurement of fibrinogen, thrombin time (TT), prothrombin fragment 1+2 (F1+2), and thrombin‐antithrombin complex (TAT). SS showed adherence of larger amounts of GFPs than did PLA at a platelet density of 300 × 106/mL (p < 0.05). Furthermore, representative SEM studies showed more platelet spreading on SS than on PLA stent struts. Between PLA and SS, coagulation activity did not differ at any assessment. Based on prolonged TT values in plasma, the heparin coating strongly inhibited coagulation (p < 0.05). The values of soluble TAT and F1+2 for PLA were similar to those of controls, i.e., to incubated suspensions without a stent strut. In conclusion, when compared with stainless steel, both PLA and hepa‐P(CL95/L‐LA5)‐PLA appear hemocompatible as intravascular stent materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 785–791, 2003
Fracture of ceramic/ceramic/polymer trilayers for biomechanical applications
Authors: Deng Yan , Miranda Pedro , Pajares Antonia , Guiberteau Fernando , Lawn Brian R.
Published: November 2003

Fracture damage in trilayers consisting of outer and inner brittle layers bonded to a compliant (polycarbonate) substrate and subjected to concentrated surface loading is analyzed. The principal mode of fracture is radial cracking at the undersurface of the inner (core) layer, even in the strongest of core ceramics—other damage modes, including radial cracking in the outer (veneer) layer, are less invasive in these all‐brittle coating systems. Tests on simple trilayer structures fabricated from glasses, sapphire, and dental ceramics are used to examine the dependence of the critical load for radial fracture in terms of relative outer/inner layer thickness and modulus, and inner layer strength. An explicit relation for the critical load, based on a flexing plate model in which the outer/inner bilayer is reduced to an “equivalent” monolithic coating with “effective” composite modulus, is used to examine these dependencies. The theoretical relation describes all the major trends in the critical load data over a broad range of variables, thus providing a sound basis for trilayer design. Relevance of the analysis to dental crowns and other biomechanical applications is a central theme of the study. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 828–833, 2003
Interactions of corneal cells with transforming growth factor β2‐modified poly dimethyl siloxane surfaces
Authors: Merrett K. , Griffith C.M. , Deslandes Y. , Pleizier G. , Dubé M.A. , Sheardown H.
Published: November 2003

The downgrowth of corneal epithelial cells at the interface of an artificial cornea and the host eye tissue poses a significant problem to be overcome in developing a successful implant. As a means of inhibiting the proliferation of corneal epithelial cells on the stromal surface of the implant, we examined the immobilization of transforming growth factor beta‐2 (TGF‐β2) via a bifunctional poly ethylene glycol (PEG) spacer to poly dimethyl siloxane (PDMS) surfaces. Growth factor immobilization was confirmed by modification with 125I‐labeled TGF‐β2. The modified surfaces were also characterized by advancing water contact angles, X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the amount of growth factor covalently bound to the surface was difficult to quantify apparently due to strong interactions between the growth factor and the PEG layer and high levels of adsorption, differences in the modified surfaces, suggestive of the presence of a significant amount of TGF‐β2, were found. In vitro interactions of the modified surfaces with human corneal epithelial and stromal cells were examined. Growth factor surface concentrations as well as culture in the absence and presence of serum and other adhesive proteins were examined. Corneal stromal and epithelial cells cultured on the TGF‐β2—modified surfaces consistently gave results opposite to those expected. Likely, the most notable and surprising result was the almost complete lack of adhesion of the stromal cells, with coverages averaging between 3 and 5%. In comparison, corneal epithelial cell growth appeared to be promoted by the presence of the immobilized growth factor, with cell coverages averaging 50–60% at 7 days of culture. A TGF‐β2 concentration effect was noted with both cell types in the absence of serum, with increases in the coverage at higher TGF‐β2 concentrations. The observed cell growth appeared to be the result of interactions between the cells and active growth factor, because the addition of anti‐TGF‐β2 to the culture medium reduced cell coverage to levels similar to those noted on control surfaces. Therefore, although TGF‐β2–modified surfaces may not be suitable as corneal epithelial cell inhibiting surfaces, interactions of surface immobilized growth factor and corneal cells are complex and should be further examined. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 981–993, 2003
Determination of specific interactions between glucose ligand carrying polymer and glucose transporter type‐1 (GLUT‐1) using different cell types
Authors: Chung Jong‐Hoon , Park Keun‐Hong , Seo Byong‐Moo , Kim Eun‐Seok , Hong Jong‐Rak , Chung Il‐Hyuk , Kang Nara , Baek Jeong‐Hwa , Min Byung‐Moo , Choung Yun‐Hoon , Akaike Toshihiro , Choung Pill‐Houng
Published: November 2003

In order to develop a biomimetic polymer for cell recognition, poly [3‐O‐(4′‐vinylbenzyl)‐D‐glucose] (PVG) and different types of glucose transport (GLUT)‐carrying cells, namely, HepG2 cells (GLUT‐1), 3T3‐L1 fibroblast cells (GLUT‐1 and GLUT‐4), and MIN6 cells (GLUT‐2), were tested for specific interaction. To clarify the nature of interaction between PVG and the different cell types, rhodamine‐B isothiocyanate (RITC)‐labeled polymers were used to prove and visualize the interactions. In this study, we found that labeled polymer strongly binds to HepG2 cells. The fluorescence intensity of PVG with in the presence of HepG2 cells was found to be stronger than that of 3T3‐L1 fibroblast cells (0.11 ± 0.05) and MIN6 cells, which carry GLUT‐2 (0.028 ± 0.01); a confocal laser microscopic study confirmed this interaction. To confirm the specificity of the interaction mediated by GLUT, the cells were pretreated with phloretin, an inhibitor of GLUT‐1, before adding RITC‐labeled PVG polymer to the cell culture medium. This treatment suppressed the interaction of PVG with HepG2 cells and partially suppressed its interaction with 3T3‐L1 fibroblast cells. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1055–1059, 2003
Pore size in implanted polypropylene filters is critical for tissue organization
Authors: Rosengren Agneta , Bjursten Lars Magnus
Published: November 2003

Widely different implant materials induce surprisingly similar tissue reactions invivoin contrast to theirin vitroresponses. Increasing attention has recently been given to the surface texture of the material. When both the material composition and the surface topography are varied, the surface topography seems to be the predominant factor for the induced tissue response. The present study addresses differences in the tissue response to commercially available Millipore mesh filters of polypropylene with pore sizes of 0.6, 10.0 or 30.0 μm. The Millipore filters with adjacent tissue were directly sectioned in a cryostat and evaluated via an immunofluorescence technique with double and triple staining, allowing simultaneous analysis of different antigens in tissue sections. These results show that macrophages, total cells, necrotic cells, nitric oxygen distribution, early angiogenesis, and capsule thickness were influenced by the surface structure. Implants with pore sizes of 0.6 μm, where entrance of inflammatory cells was inhibited, induce the most pronounced foreign body capsule formation. The 10‐ and 30‐μm filters, in contrast, had large amounts of macrophages inside the filter structure, although very few inflammatory cells were found outside the filters. The inflammatory cells within the filters appeared not to influence the foreign body capsule induction. The critical factor for the formation of a foreign body capsule seems to be the localization of implant‐close macrophages. Whether this is due to differences in cell activation or in signal transduction to collagen‐synthesizing fibroblasts remains an open question. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 918–926, 2003
Cellular response to calcium phosphate glasses with controlled solubility
Authors: Navarro Melba , Ginebra Maria‐Pau , Planell Josep A.
Published: November 2003

In the last decades, the research on materials for bone regeneration has focused on materials that are degradable and capable of stimulating tissue regeneration. In this context, phosphate glasses offer an interesting alternative, given the wide range of solubility they present and their similarity with respect to the chemical composition of the bone mineral phase. In the current work, two different formulations of phosphate glasses in the system P2O5CaONa2OTiO2 are developed. The incorporation of TiO2 into the glass network allows for better control of the glass dissolution rate. Although these glasses have been studied extensively from the physicochemical point of view, little is known about their biocompatibility. To evaluate the biological response to these materials, we have used a human skin fibroblast model. The cells were incubated in vitro following two different methods. The first was incubated in direct contact with the glasses and the second one, in the presence of their extracts. The effects of the materials on cell growth were determined by means of toxicity (WST assay), adhesion, and proliferation tests. The results showed that the in vitro behavior of soluble phosphate glasses is strongly affected by their solubility. On the other hand, the results showed that the cellular response is highly affected by the testing procedure. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1009–1015, 2003
Inclusion–exclusion in public policies and policy analyses: the case of Philippine land reform, 1972–2002
Authors: Borras Saturnino M.
Published: November 2003

Most policy analyses, especially those on land reform, focus on issues and data that are within the official policy scope. This ‘policy scope‐centered’ approach has led to only partial understanding of policy choices, implementation and outcomes. A more complete, and so more powerful, analysis requires the inclusion of issues and data that are excluded from the policy scope. This paper is a preliminary inquiry into the inclusion–exclusion question in the official scope of Philippine land reform policy. It is an initial attempt to raise new questions for further research, and suggests a different strategy for approaching land reform data. Copyright © 2003 John Wiley & Sons, Ltd.
The private sector and water and sanitation services—policy and poverty issues
Authors: Carter Richard C. , Danert Kerstin
Published: November 2003

Poor access to water and sanitation is a major poverty issue affecting a large part of the developing world. In their urgency to meet internationally agreed water and sanitation targets, Governments and International Agencies seek new ways and means, including increased use of the private sector. Commercial participation in the water sector is not without vociferous critics, as well as strong proponents. Even accepting the international water and sanitation targets for service coverage—and these authors question their feasibility—it seems clear that no single player in the partnership between public sector, private sector and communities can be responsible for achieving them. Each player has individual roles and requirements, and the strengths of each are needed. Dogmatic promotion or rejection of ‘privatization’ is unhelpful. We appeal to the politically naïve to try to understand privatization's opponents, and for those who protest against the ‘commodification’ of water to shelve their dogmas as they join the common pursuit of permanently improved services for the poor. Copyright © 2003 John Wiley & Sons, Ltd.
The private sector in rural water and sanitation services in Uganda: understanding the context and developing support strategies
Authors: Danert Kerstin , Carter Richard C. , Rwamwanja Ronnie , Ssebalu Jamil , Carr Graham , Kane David
Published: November 2003

This article analyses private sector delivery of water and sanitation services in Uganda. Uganda's policies of decentralization and privatization, combined with enhanced sector funding through debt relief, provide the context for the work described. After a brief description of the attributes of small water sector enterprises, the findings of extensive interviews with all the major stakeholders in eight of Uganda's 56 districts are set out under eight thematic headings (corruption; community participation; role of NGOs; private sector support services; networks and associations; local Government procurement procedures; construction quality; business viability) and two sets of root causes. The paper concludes that a sector strategy requires a limited number of focus areas in order to avoid overwhelming the institutions and local ownership. The strategy should lie between the extremes of prescriptive and process oriented approaches. Monitoring mechanisms should balance quantitative with qualitative data. Finally, a balance is needed between the drive for short‐term impact through physical outputs and the long‐term sustainability of water and sanitation services so delivered. Copyright © 2003 John Wiley & Sons, Ltd.
Public–private partnerships in water: a South African perspective on the global debate
Authors: Muller Mike
Published: November 2003

Despite widespread consensus on the importance of meeting the basic human rights of all people for safe water and adequate sanitation, the debate on the role of the private sector is loud, and at times destructive. In South Africa the gross inequalities inherited with the end of apartheid in 1994 drive the strategies of the Department of Water Affairs and Forestry (DWAF). Government policy has deliberately avoided adopting a particular stance on privatization, preferring to focus on the goal rather than the instrument. Nevertheless it has been recognized that a strong public sector is needed. Experience is showing that there are roles for a wide variety of public, private and civil society partners. South Africa could not have achieved what it has since 1994, were it not for a well developed private sector capacity. However, criticism of private sector operation has been noisy. Protest against ‘commoditization’ and pricing of water has been particularly vociferous. In the attempt to enter into dialogue with the critics, the importance of consensus in society has been highlighted. South Africa's inequalities are mirrored on a global scale and its experience is thus relevant to the global water policy debate. The involvement of the private sector should not be forced through global agreements such as GATS or loan conditionality, and international finance should put the poor first. Copyright © 2003 John Wiley & Sons, Ltd.
Flow of funds: implications for research on financial sector development and the real economy
Authors: Green Christopher J. , Murinde Victor
Published: November 2003

This paper provides a selective survey of the leading theoretical and empirical issues surrounding the flow of funds: its meaning and origin, problems of construction, its use in financial modelling and its role as a tool of analysis of intersectoral financial flows. It is argued that there is an intimate connection between the flow of funds, interest rates and asset prices, and hence incomes and expenditures in an economy. The paper discusses flow of funds analysis in the context of developing countries, concentrating on possible applications and methodologies, and the issue of data collection and organization. We explore the reasons for lack of success at empirical flow of funds modelling and propose ‘promising research ideas’ (PRIs) to apply flow of funds analysis to study the relationship between financial sector development and the real economy, particularly to identify effective financial sector policies in developing countries. Copyright © 2003 John Wiley & Sons, Ltd.
Retention modeling and simultaneous optimization of pH value and gradient steepness in RP‐HPLC using feed‐forward neural networks
Authors: Shan Yichu , Zhao Ruihuan , Zhang Yukui , Zhang Weibing , Tian Yan
Published: November 2003

A novel approach is proposed for the simultaneous optimization of mobile phase pH and gradient steepness in RP‐HPLC using artificial neural networks. By presetting the initial and final concentration of the organic solvent, a limited number of experiments with different gradient time and pH value of mobile phase are arranged in the two‐dimensional space of mobile phase parameters. The retention behavior of each solute is modeled using an individual artificial neural network. An “early stopping” strategy is adopted to ensure the predicting capability of neural networks. The trained neural networks can be used to predict the retention time of solutes under arbitrary mobile phase conditions in the optimization region. Finally, the optimal separation conditions can be found according to a global resolution function. The effectiveness of this method is validated by optimization of separation conditions for amino acids derivatised by a new fluorescent reagent.
Comparison of silylation and esterification/acylation procedures in GC‐MS analysis of amino acids
Authors: Sobolevsky Tim G. , Revelsky Alexander I. , Miller Barbara , Oriedo Vincent , Chernetsova Elena S. , Revelsky Igor A.
Published: November 2003

Three derivatization agents used in GC analysis of amino acids were compared: N,O‐bis(trimethylsilyl)trifluoroacetamide, (BSTFA), N‐methyl‐N‐(tert‐butyldimethylsilyl)trifluoroacetamide (MTBSTFA), and isobutyl chloroformate (iBuCF). It was shown that the analytical characteristics achieved in the case of silylation with MTBSTFA are comparable to those obtained for esterification/acylation. However, since the former approach requires laborious sample preparation to isolate the compounds in question prior to derivatization, determination of amino acids as N(O,S)‐alkoxycarbonyl alkyl esters seems to be preferable in many cases. Application of the esterification/acylation procedure to analysis of lyophilized E. coli microbial culture was demonstrated.
Simultaneous determination of theophylline, tolbutamide, mephenytoin, debrisoquin, and dapsone in human plasma using high‐speed gradient liquid chromatography/tandem mass spectrometry on a silica‐based monolithic column
Authors: Chen Yu‐Luan , Junga Heiko , Jiang Xiangyu , Naidong Weng
Published: November 2003

Theophylline, tolbutamide, mephenytoin, debrisoquin, and dapsone are marker substrates for CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, respectively. A silica‐based monolithic column (Chromolith SpeedROD RP‐18e, 50×4.6 mm) was used to separate these five marker substrates of cytochrome P450 within only 84 s. Linear gradient elution was from acetonitrile‐water‐formic acid (10 : 90 : 1, v/v/v) to acetonitrile‐water‐formic acid (90 : 10 : 1, v/v/v) in 1.4 min. The flow rate was 2.5 mL/min. The retention time was 0.52 min for theophylline, 0.67 min for debrisoquin, 0.78 min for dapsone, 0.96 min for mephenytoin, and 1.13 min for tolbutamide. Detection was by tandem mass spectrometry using a PE Sciex API 3000 mass spectrometer with a Turbo‐Ionspray source in positive mode. A simple protein precipitation method was used. This method was validated over the concentration range of 5–2000 ng/mL based on the sample volume of 0.1 mL.
Concurrent solvent recondensation large sample volume splitless injection
Authors: Magni Paolo , Porzano Thomas
Published: November 2003

Concurrent Solvent Recondensation Large Sample Volume (CRS‐LV) splitless injection overcomes the limitation of the maximum sample volume to 1–2 μL valid for classical splitless injection. It is based on control of the evaporation rate in the vaporizing chamber, utilization of a strong pressure increase in the injector resulting from solvent evaporation, and greatly accelerated transfer of the sample vapors from the injector into the inlet of an uncoated precolumn by recondensation of the solvent. The sample vapors are transferred into the column as rapidly as they are formed in the injector (concurrent transfer). 20–50 μL of liquid sample is injected with liquid band formation. The sample liquid is received by a small packing of deactivated glass wool positioned slightly above the column entrance at the bottom of the vaporizing chamber. Solvent evaporation strongly increases the pressure in the injector (auto pressure surge), provided the septum purge outlet is closed and the accessible volumes around the vaporizing chamber are small, driving the first vapors into the precolumn. Transfer continues to be fast because of recondensation of the solvent, obtained by keeping the oven temperature below the pressure‐corrected solvent boiling point. The uncoated precolumn must have sufficient capacity to retain most of the sample as a liquid. The experimental data show virtually complete absence of discrimination of volatile or high boiling components as well as high reproducibility.
Liquid‐phase microextraction combined with liquid chromatography‐mass spectrometry. Extraction from small volumes of biological samples
Authors: Halvorsen Trine Grønhaug , Pedersen‐Bjergaard Stig , Reubsaet J. Léon E. , Rasmussen Knut E.
Published: November 2003

Liquid‐phase microextraction (LPME) is a sample preparation technique based on disposable polypropylene hollow fibres, which results in efficient sample clean‐up and high preconcentration. The present paper describes the combination of LPME with LC‐MS utilising electrospray ionisation for high sensitivity. Nine antidepressant drugs were extracted from 50 or 500 μL of plasma or whole blood samples, through a thin layer of dodecyl acetate immobilised in the pores of the hollow fibre, and into 15 μL of 200 mM formic acid as acceptor solution inside the hollow fibre. Analyte recoveries in the range 12–68% and 9–52% were obtained from 50 μL of plasma and whole blood respectively. The acceptor solution (15 μL) was diluted with 60 μL of 5 mM ammonium formate pH = 2.7 prior to injection into the LC‐MS system. The system was qualitatively investigated for matrix effects utilising a post‐column infusion system. Whole blood from 5 different persons was cleaned‐up by LPME and injected onto the analytical column while a solution of the 9 model compounds was continuously infused post‐column. No signs of ion suppression were seen for any of the model compounds. Limits of quantification (S/N = 10) were in the low ng/mL range for 6 of the 9 model compounds utilising a whole blood sample volume of only 50 μL. The repeatability of the extractions was investigated utilising paroxetine as internal standard. Acceptable RSDs (%) were obtained (< 20%) for 5 of the antidepressants. By increasing the sample volume from 50 to 500 μL of whole blood RSDs below 20% (3–16%) were observed for all 8 antidepressants.
Adsorption of polyethylene from thermodynamically good solvents on a zeolite stationary phase
Authors: Macko Tibor , Denayer Joeri F. , Pasch Harald , Baron Gino V.
Published: November 2003

Adsorption of linear polyethylene and isotactic polypropylene on columns packed with zeolites ZSM‐5, Y, and silicalite was studied using high‐temperature liquid phase chromatography. Linear polyethylene was fully retained on a column packed with ZSM‐5 zeolite from non‐polar solvents, such as 1,1,2,2‐tetrachloroethane and 1,3,5‐trimethylbenzene at a temperature of 140°C. Partial adsorption on ZSM‐5 zeolite was found for polyethylene in 1,2,4‐trichlorobenzene and on silicalite from 1,2,4‐trichlorobenzene and 1,3,5‐trimethylbenzene. On the other hand, adsorption of polyethylene was not found from polar liquids, such as 2‐ethylhexyl acetate, cyclohexyl acetate, and cyclohexanone. Isotactic polypropylene was not adsorbed on any tested sorbent.
Evaluation of surfactant‐assisted pressurized hot water extraction for marker compounds in Radix Codonopsis pilosula using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry
Authors: Ong Eng Shi , Len Shea Mei
Published: November 2003

In the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants.
Physical Properties of PBMA‐b‐PBA‐b‐PBMA Triblock Copolymers Synthesized by Atom Transfer Radical Polymerization
Authors: Martín‐Gomis Luis , Fernández‐García Marta , de la Fuente José Luis , Madruga Enrique López , Cerrada María L.
Published: November 2003

The physical properties of well‐defined poly(butyl methacrylate)‐block‐poly(butyl acrylate)‐block‐poly(butyl methacrylate) (PBMA‐b‐PBA‐b‐PBMA) triblock copolymers synthesized by atom transfer radical polymerization (ATRP) are reported. The glass transition and the degradation temperature of copolymers were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measurements showed phase separation for all of the copolymers with the exception of the one with the shortest length of either inner or outer blocks. TGA demonstrated that the thermal stability of triblock copolymers increased with decreasing BMA content. Dynamic mechanical analysis was used for a preceding evaluation of adhesive properties. In these block copolymers, the deformation process under tension can take place either homogeneously or by a neck formation depending on the molecular weight of the outer BMA blocks and on the length of the inner soft BA segments. Microindentation measurements were also performed for determining the superficial mechanical response and its correlation with the bulk behavior.

Stress‐strain curves for the different PBMA‐b‐PBA‐b‐PBMA specimens at room temperature and at 10 mm/min.

magnified image

Stress‐strain curves for the different PBMA‐b‐PBA‐b‐PBMA specimens at room temperature and at 10 mm/min.
Additive Effect of Triphenylphosphine on the Living Polymerization of 1,3‐Butadiene with a Cobalt Dichloride‐Methylaluminoxane Catalytic System
Authors: Nath Dilip Chandra Deb , Shiono Takeshi , Ikeda Tomiki
Published: November 2003

The additive effect of triphenylphosphine (Ph3P) was investigated in 1,3‐butadiene polymerization with cobalt dichloride (CoCl2) activated by methylaluminoxane (MAO); the catalytic system resulted in slowly‐initiated living polymerization with a high cis‐1,4 content (about 99%) at 0 °C. The polymerization behavior, such as the relationship of polymer yield and number‐average molecular weight ($\overline M _{\rm n}$) with polymerization time, was dependent on the amount of Ph3P added. In the presence of a small amount of Ph3P (Ph3P/Co = 0.025), the kinetic behavior qualitatively resembled that observed in the absence of Ph3P, which indicated that the catalytic system conducted slowly‐initiated living polymerization. An increase in the amount of Ph3P (Ph3P/Co > 0.025), however, caused chain transfer reaction. The 1H NMR analysis of the produced polymers showed that Ph3P changed the microtacticity from 99% of cis‐1,4 to 88% of 1,2‐unit, depending on the amount of Ph3P added. At the maximum amount of Ph3P (Ph3P/Co = 0.025) necessary for maintaining the livingness of the propagating species, 14% of the 1,2‐inserted unit was incorporated at the expense of the cis‐1,4‐inserted unit. The addition of Ph3P (Ph3P/Co = 0.025) during the polymerization did not affect the livingness and gave a regio‐block copolymer of 1,3‐butadiene.

Number‐average molecular weight as a function of polymerization time.

magnified image

Number‐average molecular weight as a function of polymerization time.
Chemically Amplified Photolithography of a Copolymer Containing Phenolphthalein
Authors: Lee Chan‐Woo , Yuan Zhongzhe , Kim Young‐Bum , Lee Suck‐Hyun
Published: November 2003

A convenient, low cost micro‐patterning method using a new side group polymer containing phenolphthalein is reported. A random copolymer of t‐BOC‐protected phenolphthalein methacrylate (t‐BMPP) with methyl methacrylate (MMA) was prepared by radical copolymerization in dioxane. The negative‐tone patterns of this polymer could be obtained by photo‐deprotection of the t‐BOC groups due to the effect of dissolution inhibition by the phenolic group of the phenolphthalein. The chemical and optical properties of the polymer were, as anticipated, very close to those of the corresponding phenolphthalein and the pH controlled colorimetric transition was reproducibly observed. The contrast in solubility and chromism upon alkaline treatment makes this polymer a promising candidate for investigating spatially‐directed chromism and selective deposition of pH sensitive polymers.

SEM image of parallel lines of P(MMA/PPT) generated by contact UV exposure.

magnified image

SEM image of parallel lines of P(MMA/PPT) generated by contact UV exposure.
Novel Light Emitting Diode Using Organic Electroluminescence Microcapsules
Authors: Heo Jae‐Seok , Park No‐Hyung , Ryu Jee‐Hyun , Choi Gyung‐Hyun , Suh Kyung‐Do
Published: November 2003

Novel light emitting diodes (LEDs) were prepared using electroluminescence (EL) material/polymer microcapsules (ELC). N‐vinylcarbazole as a hole‐transporting component and methyl methacrylate (MMA) were copolymerized for producing the seed particles using dispersion polymerization. An oxadiazole derivative, synthesized as a electron‐transporting component, and tris(8‐hydroxyquinolinato) aluminium(III) (Alq3) were incorporated into the polymer particles by using the solute co‐diffusion method (SCM). The LEDs for the EL characterization were fabricated in a thin sandwich configuration: Al anode/ELC/ITO cathode. The surface imaging of the LED prepared using ELC was performed by atomic force microscopy (AFM). The EL characteristics of the ELC were investigated by UV, photoelectron and luminescence spectroscopy, and the current‐voltage and the light‐voltage characteristics for the LED were determined.

Encapsulation procedure using solute co‐diffusion method (SCM).

magnified image

Encapsulation procedure using solute co‐diffusion method (SCM).
Synthesis and Characterization of Segmented Poly(ether ester)s Containing H‐Bonding Units
Authors: Signori Francesca , Solaro Roberto , Chiellini Emo , Lips Priscilla A. M. , Dijkstra Pieter J. , Feijen Jan
Published: November 2003

A series of poly(ether ester)s containing different H‐bonding units (amide, carbamate, urea) was prepared by polycondensation in bulk, using Ti(OBu)4 as a catalyst. The copolymers were obtained starting from PEG1000, 1,4‐butanediol, and a symmetrical, bis‐ester terminated monomer carrying H‐bonding units. These materials were designed for biomedical applications, in which ultimate biodegradability of the materials is required. The influence of the nature of the H‐bonding unit and of the length of the methylene spacer between H‐bonding groups on the thermal and solubility properties of copolymers was investigated. Amide containing copolymers were more thermally stable than ones containing carbamate, consistent with the observed behavior of the corresponding monomers. In most cases, differential scanning calorimetry (DSC) traces were quite complex because of phase separation and dependent on the applied cooling rate. Copolymers containing urea bonds were less soluble in most organic solvents, but their thermal properties were not significantly different than their amide containing counterparts.

Synthesis of amide‐based diester monomers.

magnified image

Synthesis of amide‐based diester monomers.
Preparation and Characterization of Acetoacetoxyethyl Methacrylate‐Based Gels
Authors: Boyko Volodymyr , Lu Yan , Richter Andreas , Pich Andrij
Published: November 2003

Novel polymeric gels have been prepared by radical copolymerization of acetoacetoxyethyl methacrylate (AAEM) and hydroxyethyl methacrylate (HEMA) in water‐ethanol medium. The influence of the HEMA:AAEM ratio and crosslinker concentration on properties of gels was studied. Independently on gel composition the maximum swelling was detected in chloroform. It was found that PAAEM gels possess phase transition temperature or upper critical solution temperature (UCST) in alcohol‐water solutions. UCST decreases in linear order from 75 to 10 °C when HEMA content in gel structure increases. The minimal UCST of AAEM/HEMA gels in binary alcohol‐water mixtures is shifted toward lower temperatures and lower alcohol concentrations when the alkyl chain of alcohol increases.

AAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).

magnified image

AAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).
Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of their Solutions, 3
Authors: Stryuk Sergej , Wolf Bernhard A.
Published: November 2003

A simple expression for the composition dependence of the Flory‐Huggins interaction parameter of polymer/solvent systems reported earlier is used to model the demixing of polymer solutions into two liquid phases. To this end, the system specific parameters ζ and ν of that approach are calculated as a function of temperature using the thermodynamic expressions resulting for the critical conditions on one side and from experimentally determined critical data for polymers of different molar mass on the other side. By means of data reported for the system cyclohexane/polystyrene it is demonstrated that binodal and spinodal lines are very accurately modeled at low temperatures (UCSTs) and at high temperatures (LCSTs). The parameters obtained from the demixing behavior match well with that calculated from the composition dependence of the vapor pressure at temperatures where the components are completely miscible. Information on the phase separation of the system trans‐decalin/polystyrene for different molecular weights and at different elevated pressures is used to show that the approach is also apt to model pressure influences. The thus obtained ζ(T;p) and ν(T;p) enable the prediction of the (endothermal) theta temperature of the system as a function of pressure in quantitative agreement with the data directly obtained from light scattering measurements with dilute solutions.

Phase diagram for trans‐decalin/polystyrene.

magnified image

Phase diagram for trans‐decalin/polystyrene.