bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi‐residue method for the analysis of pharmaceutical compounds in sewage sludge, compost and sediments by sonication‐assisted extraction and LC determination
Authors: Martín Julia , Santos Juan Luis , Aparicio Irene , Alonso Esteban
Published: May 2010

A method for the simultaneous determination of 16 pharmaceutical compounds in three types of sewage sludge (primary, secondary and anaerobically digested dehydrated sludge), compost and sediment samples is described. Pharmaceutical compounds evaluated were nonsteroidal anti‐inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen, naproxen and salicylic acid), antibiotics (sulfamethoxazole and trimethoprim), an anti‐epileptic drug (carbamazepine), a β‐blocker (propranolol), a nervous stimulant (caffeine), estrogens (17α‐ethinylestradiol, 17β‐estradiol, estriol and estrone) and lipid regulators (clofibric acid, metabolite of clofibrate and gemfibrozil). The method is based on the ultrasonic‐assisted extraction, clean‐up by SPE and analytical determination by HPLC with diode array and fluorescence detectors. The best extraction recoveries were achieved in a three‐step extraction procedure with methanol and acetone as extraction solvents. Extraction recoveries of several pharmaceutical compounds as caffeine were highly dependent on the type of sample evaluated. The applicability of the method was tested by analyzing primary, secondary and anaerobically digested dehydrated sludge, compost and sediment samples from Seville (Southern Spain). Ten of the sixteen pharmaceutical compounds were detected in sludge samples and five in compost and sediment samples. The highest concentration levels were recorded for ibuprofen in sewage samples, whereas salicylic acid and 17α‐ethinylestradiol were detected in all of the samples analyzed.
Micellar and aqueous‐organic liquid chromatography using sub‐2 μm packings for fast separation of natural phenolic compounds
Authors: Cao Jun , Qu Haibin , Cheng Yiyu
Published: May 2010

The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous‐organic LC using a short column packed with 1.8 μm particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0–30% ACN/5% 1‐butanol/1–6 mM SDS) and micellar (0–30% ACN/5% 1‐butanol/40–60 mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4 mM SDS/5% 1‐butanol or 50 mM SDS/5% 1‐butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous‐organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5 mL/min, with analysis time below 9 min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous‐organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples.
Simultaneous analysis of parabens in cosmetic products by stir bar sorptive extraction and liquid chromatography
Authors: Melo Lidervan P. , Queiroz Maria Eugênia C.
Published: May 2010

A sensitive and precise stir bar sorptive extraction (SBSE) combined with LC (SBSE/LC) analysis is described for simultaneous determination of methyl, ethyl, propyl, and butyl parabens in commercial cosmetic products in agreement with the European Union Cosmetics Directive 76/768/EEC. Important factors in the optimization of SBSE efficiency are discussed, such as time and temperature of extraction, pH, and ionic strength of the sample, matrix effects, and liquid desorption conditions by different modes (magnetic stirring, ultrasonic). The LOQs of the SBSE/LC method ranged from 30 to 200 ng/mg, with linear response over a dynamic range, from the LOQ to 2.5 μg/mg, with a coefficient of determination higher than 0.993. The interday precision of the SBSE/LC method presented a coefficient of variation lower than 5%. The effectiveness of the proposed method was proven for analysis of commercial cosmetic products such as body creams, antiperspirant creams, and sunscreens.
Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction for the sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS
Authors: Zhao Ru‐Song , Wang Xia , Sun Jing , Yuan Jin‐Peng , Wang Shan‐Shan , Wang Xi‐Kui
Published: May 2010

A novel dispersive liquid‐phase microextraction method without dispersive solvents has been developed for the enrichment and sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS. This method used only green solvent 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as extraction solvent and overcame the demerits of the use of toxic solvents and the instability of the suspending drop in single drop liquid‐phase microextraction. Important factors that may influence the enrichment efficiencies, such as volume of ionic liquid, pH of solutions, extraction time, centrifuging time and temperature, were systematically investigated and optimized. Under optimum conditions, linearity of the method was observed in the range of 0.1–20 μg/L for triclocarban and 0.5–100 μg/L for triclosan, respectively, with adequate correlation coefficients (R>0.9990). The proposed method has been found to have excellent detection sensitivity with LODs of 0.04 and 0.3 μg/L, and precisions of 4.7 and 6.0% (RSDs, n=5) for triclocarban and triclosan, respectively. This method has been successfully applied to analyze real water samples and satisfactory results were achieved.
Beneficial effects of vaccenic acid on postprandial lipid metabolism and dyslipidemia: Impact of natural trans‐fats to improve CVD risk
Authors: Wang Ye , Jacome‐Sosa M. Miriam , Vine Donna F. , Proctor Spencer D.
Published: May 2010

Abnormal non‐fasting (postprandial) lipid metabolism has been recognized as a significant contributor to dyslipidemia and cardiovascular disease (CVD) risk. Clinically, impaired metabolism of lipoproteins following a meal (e.g. chylomicrons) has been demonstrated in a number of chronic diseases, including obesity, insulin resistance, as well as type 1 and 2 diabetes. Given the proposed effects of dietary trans fat to contribute to a lipid profile that increases CVD risk, there has been a public health campaign in many countries to eliminate these fatty acids from the food supply. In contrast, our group has recently reported novel lipid‐lowering benefits of a major naturally‐occurring trans fatty acid vaccenic acid (VA, shorthand lipid name 18:1 trans‐11), in an animal model of dyslipidemia and the metabolic syndrome. Studies to date have shown that dietary supplementation of VA effectively reduces not only fasting lipids, but also postprandial triacylglycerol and chylomicron concentrations in obese JCR:LA‐cp rats. Evidence from animal studies to date suggest that VA may down‐regulate hepatic fatty acid synthesis and directly influence lipogenesis in the intestine. The discovery of new bioactive properties of VA is supported by clinical studies which have provided increased momentum for industry applications. In this review we summarize the emerging beneficial view of natural trans fats that have distinct and differential properties compared to those synthetically produced in partially hydrogenated vegetable oils (PHVO), with a particular focus on fasting and postprandial lipid metabolism in CVD risk.
Stability of fat‐soluble vitamins and PUFA in simulated shallow‐frying
Authors: Hrncirik Karel
Published: May 2010

Fat‐soluble vitamins and essential polyunsaturated fatty acids (PUFA) are nutrients that are sensitive to heat treatment and oxidation and therefore can be partly lost during cooking. It is well‐documented that a long‐term deep‐frying process leads to a substantial degradation of PUFA and vitamins in a frying medium. In this study, the stability of vitamins and fatty acids was investigated in a series of liquid margarines (82% fat) varying in fat blend and the content of minor components. The tested samples were subjected to the standardised treatment that has been developed to mimic shallow‐frying of food at 180°C and the recovery of individual nutrients is reported. The results show that fat‐soluble vitamins possessed reasonable stability under the condition of the shallow‐frying test. Essential PUFA of the frying medium were hardly affected by the treatment. Overall evaluation of the results suggests that oil‐based cooking media rich in vitamins and PUFA have a positive impact on nutritional value of food prepared by appropriate means of cooking.
Dietary cholesterol, blood cholesterol and cardiovascular disease
Authors: Stanley John
Published: May 2010

Cholesterol is an essential cellular nutrient and homeostatic mechanisms exist to balance rates of cholesterol production and utilisation and minimise effects of dietary cholesterol on blood cholesterol and hence cardiovascular disease risk. In non‐diabetic populations, there is little evidence from epidemiological studies for associations between dietary cholesterol or the consumption of cholesterol rich foods and cardiovascular disease risk, or from intervention trials for major effects of dietary cholesterol on blood cholesterol levels. By contrast, evidence is emerging from epidemiological studies that consumption of eggs is associated with cardiovascular disease in diabetics, and from intervention trials that dietary cholesterol has greater effects on blood cholesterol levels in insulin resistant people. Since insulin plays a role in cholesterol homeostasis, these are not surprising findings.
Racial and ethnic disparities in access to liver transplantation
Authors: Mathur Amit K. , Schaubel Douglas E. , Gong Qi , Guidinger Mary K. , Merion Robert M.
Published: May 2010

Access to liver transplantation is reportedly inequitable for racial/ethnic minorities, but inadequate adjustments for geography and disease progression preclude any meaningful conclusions. We aimed to evaluate the association between candidate race/ethnicity and liver transplant rates after thorough adjustments for these factors and to determine how uniform racial/ethnic disparities were across Model for End-Stage Liver Disease (MELD) scores. Chronic end-stage liver disease candidates initially wait-listed between February 28, 2002 and February 27, 2007 were identified from Scientific Registry for Transplant Recipients data. The primary outcome was deceased donor liver transplantation (DDLT); the primary exposure covariate was race/ethnicity (white, African American, Hispanic, Asian, and other). Cox regression was used to estimate the covariate-adjusted DDLT rates by race/ethnicity, which were stratified by the donation service area and MELD score. With averaging across all MELD scores, African Americans, Asians, and others had similar adjusted DDLT rates in comparison with whites. However, Hispanics had an 8% lower DDLT rate versus whites [hazard ratio (HR) = 0.92, P = 0.011]. The disparity among Hispanics was concentrated among patients with MELD scores < 20, with HR = 0.84 (P = 0.021) for MELD scores of 6 to 14 and HR = 0.85 (P = 0.009) for MELD scores of 15 to 19. Asians with MELD scores < 15 had a 24% higher DDLT rate with respect to whites (HR = 1.24, P = 0.024). However, Asians with MELD scores of 30 to 40 had a 46% lower DDLT rate (HR = 0.54, P = 0.004). In conclusion, although African Americans did not have significantly different DDLT rates in comparison with similar white candidates, race/ethnicity-based disparities were prominent among subgroups of Hispanic and Asian candidates. By precluding the survival benefit of liver transplantation, this inequity may lead to excess mortality for minority candidates. Liver Transpl 16:1033-1040, 2010. © 2010 AASLD.
Interaction of Hsp27 with Native Phosphorylase Kinase under Crowding Conditions
Authors: Chebotareva Natalia A. , Makeeva Valentina F. , Bazhina Svetlana G. , Eronina Tatyana B. , Gusev Nikolai B. , Kurganov Boris I.
Published: May 2010

Interaction of the wild type (wt) heat shock protein Hsp27 and its three‐dimensional (3D) mutant (mimicking phosphorylation at Ser15, 78, and 82) with rabbit skeletal muscle phosphorylase kinase (PhK) has been studied under crowding conditions modeled by addition of 1 M trimethylamine N‐oxide (TMAO). According to the data of sedimentation velocity and dynamic light scattering, crowding provokes the formation of large‐sized associates of both PhK and Hsp27. Under crowding conditions, small associates of PhK and Hsp27 interact with each other thus leading to dissociation of large homooligomers of each protein. Taking into account high concentrations of PhK in the cell, we speculate that native PhK might modulate the oligomeric state and chaperone‐like activity of Hsp27.

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Preparation of Collagen‐Glycosaminoglycan Sponges with Open Surface Porous Structures Using Ice Particulate Template Method
Authors: Ko Young‐Gwang , Grice Sarah , Kawazoe Naoki , Tateishi Tetsuya , Chen Guoping
Published: May 2010

Funnel‐like sponges of collagen incorporated with glycosaminoglycan (GAG) were prepared by freeze‐drying using ice particulates as templates. The funnel‐like collagen‐GAG sponges showed similar porous structures to those of funnel‐like collagen sponges. The funnel‐like collagen‐GAG and collagen sponges have one top surface layer and one bulk porous layer. The large, top surface pores were determined by ice particulates that were used as templates, and the inner bulk pores were determined by freezing temperature. The funnel‐like pore structures facilitated homogenous cell distribution, improved cell viability, and resulted in homogenous tissue formation. Incorporation of GAG increased the mechanical property and cell viability of collagen sponges.

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Conformational Parameters of Poly(N‐methyl‐N‐vinylacetamide) Molecules Through the Hydrodynamic Characteristics Studies
Authors: Pavlov George M. , Okatova Olga V. , Mikhailova Anastasia V. , Ulyanova Natalia N. , Gavrilova Irina I. , Panarin Evgenii F.
Published: May 2010

Water‐soluble PMVA was synthesized by radical polymerization methods. A number of polymer samples were fractionated in the chloroform‐diethyl ether system. Fractions were studied by molecular hydrodynamics methods (sedimentation velocity, translational isothermal diffusion and viscosity) in H2O and DMF. The molecular masses of fractions were determined and the Kuhn‐Mark‐Houwink‐Sakurada relationships were obtained in the molecular mass range of 3.5 < M × 10−3 g · mol−1 <540. A negative temperature coefficient of the characteristic viscosity was obtained in both solvents. The Kuhn statistic segment length and the hydrodynamic diameter of the molecule were estimated for PMVA. The hydrodynamic volumes, occupied by the molecules of PMVA, poly(1‐vinyl‐2‐pyrrolidone), poly(vinylformamide), and pullulan were compared.

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Self‐Association of Unfolded Outer Membrane Proteins
Authors: Tan Alexandra Ebie , Burgess Nancy K. , DeAndrade Diana S. , Marold Jacob D. , Fleming Karen G.
Published: May 2010

We have investigated self‐association propensities of aqueous unfolded (UAQ) forms of eight outer membrane proteins (OMPs), OmpA, OmpW, OmpX, PagP, OmpT, OmpLa, FadL, and Omp85. We found that high urea concentrations maintain all of these OMPs as monomers and that OmpA and OmpX remain monomeric upon dilution to 1 M urea. A pH screen showed that basic pH supports the least amount of UAQ OMP self‐association, consistent with earlier studies showing that basic pH was optimal for better folding efficiencies. The addition of KCl increased UAQ OMP self‐association, although the magnitudes of the responses were varied. These studies showed that urea can be used to tune the amount of UAQ OMP self‐association and indicate that the presence of some urea may be useful in optimizing folding conditions because it diminishes aggregation.

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Complex Assembly Behavior During the Encapsulation of Green Fluorescent Protein Analogs in Virus Derived Protein Capsules
Authors: Minten Inge J. , Nolte Roeland J. M. , Cornelissen Jeroen J. L. M.
Published: May 2010

Enzymes encapsulated in nanocontainers are a better model of the conditions inside a living cell than free enzymes in solution. In a first step toward the encapsulation of multiple enzymes inside the cowpea chlorotic mottle virus (CCMV) capsid, enhanced green fluorescent protein (EGFP) was attached to CCMV capsid proteins. The capsid protein–EGFP complex was then co‐assembled with wild‐type capsid protein (wt CP) in various ratios. At higher complex to wt CP ratios, the number of EGFP per capsid decreased instead of leveling off. We propose that this unexpected behavior is caused by pH‐induced disassembly of the capsid protein–EGFP complex as well as by concentration and ratio dependent dimerization of the complex, making it partially unavailable for incorporation into the capsid.

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Polyoxazoline Thermoresponsive Micelles as Radionuclide Delivery Systems
Authors: Hruby Martin , Filippov Sergey K. , Panek Jiri , Novakova Michaela , Mackova Hana , Kucka Jan , Vetvicka David , Ulbrich Karel
Published: May 2010

Thermoresponsive polymer micelles are promising drug and radionuclide carriers with a strong passive targeting effect into solid tumors. We have synthesized ABA triblock copolymers poly[2‐methyl‐2‐oxazoline‐block‐(2‐isopropyl‐2‐oxazoline‐co‐2‐butyl‐2‐oxazoline)‐block‐2‐methyl‐2‐oxazoline]. These polymers are molecularly dissolved in aqueous millieu below the cloud point temperature (CPT) of the thermoresponsive central block and above CPT form polymer micelles at CMC 5–10 × 10−5 g · mL−1 with diameter ≈200 nm. The phenolic moiety introduced into the copolymer allowed radionuclide labeling with iodine‐125 ongoing in good yield with sufficient in vitro stability under model conditions.

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Ultrasonically Induced Release from Nanosized Polymer Vesicles
Authors: Pangu Gautam D. , Davis Kevin P. , Bates Frank S. , Hammer Daniel A.
Published: May 2010

Vesicles made from synthetic diblock copolymers, polymersomes, have great potential for targeted imaging and drug delivery. Ultrasound is gaining attention as a therapeutic tool in addition to its use in diagnostics. We report on the response of nanoscale vesicles made from PEO‐b‐PBD copolymers to ultrasound at 20 kHz. Leakage of a fluorescent dye from vesicle core was measured to study the permeation. Ultrasound causes significant leakage from the core above threshold intensity, suggesting that leakage is governed by acoustic cavitation. Size measurements and direct visualization of vesicles show that ultrasound does not completely rupture them into fragments but causes transient poration. The extent of leakage inversely depends on membrane thickness and directly depends on sonication time and intensity.

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Efficient Encapsulation of Plasmid DNA in pH‐Sensitive PMPC–PDPA Polymersomes: Study of the Effect of PDPA Block Length on Copolymer–DNA Binding Affinity
Authors: Lomas Hannah , Du Jianzhong , Canton Irene , Madsen Jeppe , Warren Nicholas , Armes Steven P. , Lewis Andrew L. , Battaglia Giuseppe
Published: May 2010

We report the self‐assembly of a series of amphiphilic diblock copolymers comprising a biocompatible, hydrophilic block, poly(2‐methacryloyloxyethyl phosphorylcholine) (PMPC) and a pH‐sensitive block, poly(2‐(diisopropylamino)ethyl methacrylate) (PDPA), into a dispersion of colloidally stable, nanometer‐sized polymersomes at physiological pH and salt concentration. The pH‐sensitivity of the PDPA block affords the electrostatic interaction of these block copolymers with nucleic acids at endocytic pH, as a result of the protonation of its tertiary amine groups at pH values below its pKa. Herein we investigate the effect of PDPA block length on the binding affinity of the block copolymer to plasmid DNA.

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Fabrication of Photonic/Microfluidic Integrated Devices Using an Epoxy Photoresist
Authors: Kowpak Thomas , Watts Benjamin R. , Zhang Zhiyi , Zhu Shiping , Xu Changqing
Published: May 2010

Using a single layer of SU‐8 photoresist to fabricate optical waveguide cores and microfluidic channels on Pyrex glass is an ideal way to achieve photonic/microfluidic integration on a single chip. To address the problem of poor bonding, a thin nanoscale intermediate polymer layer was applied to reduce the stress generated from the material processing while maintaining strong adhesion between the patterning polymer layer and Pyrex. It was found that a 186–600 nm thick intermediate layer of a specialty epoxy photoresist effectively served the purpose without deteriorating the optical performance of the involved waveguides. Quality photonic/microfluidic integrated devices with satisfied optical performance were fabricated.

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Performance of MWCNT/HDPE Nanocomposites at High Strain Rates
Authors: Al‐Lafi Waleed , Jin Jie , Xu Sunxi , Song Mo
Published: May 2010

Performance of HDPE/MWCNT composite at high strain rate up to 104 s−1 was investigated in a split Hopkinson pressure bar. The results revealed that the incorporation of MWCNTs into HDPE can enhance the impact strength of HDPE. High strain rate impact has a significant influence on morphology, density, crystallinity and melting temperature of the composite. With increase in strain rate, the densities of both HDPE and HDPE/MWCNT composite decreased. The drop of the density of HDPE/MWCNT composite was quicker than that of HDPE density. This could be the reason that much more cracks were formed in the HDPE/MWCNT composite, which could result in high energy dissipation, during SHPB test. The corporation of MWCNTs did lead to the decrease in yield stress.

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Efficient Liposomal Nanocarrier‐mediated Oligodeoxynucleotide Delivery Involving Dual Use of a Cell‐Penetrating Peptide as a Packaging and Intracellular Delivery Agent
Authors: Saw Phei Er , Ko Young Tag , Jon Sangyong
Published: May 2010

The effective use of oligonucleotide therapeutics, such as antisense oligodeoxynucleotides (ODNs) and small interfering RNAs (siRNAs), requires efficient delivery systems capable of intracellular penetration. Cell‐penetrating peptides (CPPs), including arginine‐rich peptides, have been extensively studied as tools for enhancing intracellular uptake efficiency of various bioactive molecules, including nanoparticles and liposomes. CPPs also have an ability to form tight complexes with nucleic acids, such as ODNs and siRNAs, making CPPs effective as packaging agents. Here, we constructed a CPP‐modified liposome loaded with complexes of nona‐arginine (9R) and NF‐κB decoy ODNs, and evaluated intracellular uptake and anticancer activity in vitro. We found that 9R/ODN complexes were efficiently loaded into liposomes that were effectively internalized into U87MG glioblastoma cells and sensitized cells to the effects of paclitaxel. To the best of our knowledge, this is the first report describing the dual use of 9R CPP as a cell penetrating and a complexing agent within a single nanoparticle.

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Novel Triblock Oligopeptides as Efficient Nonviral Vectors: Characterisation and Further Insights
Authors: Seow Wei Yang , Yang Yi‐Yan , George Andrew J. T.
Published: May 2010

The delivery of immunomodulatory genes into the cornea prior to transplantation is one promising strategy to improve graft survival rates. We recently reported a class of novel triblock oligopeptides that could mediate efficient gene transfer into corneal endothelial cells. Now these peptides are characterised further and it is show that they lack distinct secondary structures. Peptide complexes are also demonstrated to be weakly haemolytic and transfection efficiency is shown to be sensitive to several experimental conditions. SEM and FRET confocal images are used to study the particle morphology and to show that they condense their DNA cargo well.

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Water‐Soluble Conjugated Polymers for Fluorescent‐Enzyme Assays
Authors: Feng Fude , Liu Libing , Yang Qiong , Wang Shu
Published: May 2010

Enzyme assays are receiving more and more research and application interest because of the rapidly increasing demands of clinical diagnosis, environmental analysis, drug discovery, and molecular biology. Water‐soluble light‐harvesting conjugated polymers (CPs) coordinate the action of a large number of absorbing units to afford an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. This Feature Article highlights recent developments of water‐soluble CPs for fluorescent assays of enzymes. Different signal transduction mechanisms, such as electron transfer, fluorescence resonance energy transfer (FRET), and aggregation or conformation changes of CPs, are employed in these assays according to the dissimilar nature of enzymes. Potential challenges and future research directions in these approaches based on CPs are also discussed.

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pDNA/poly(L‐lysine) Polyplexes Functionalized with a pH‐Sensitive Charge‐Conversional Poly(aspartamide) Derivative for Controlled Gene Delivery to Human Umbilical Vein Endothelial Cells
Authors: Sanjoh Mai , Hiki Shigehiro , Lee Yan , Oba Makoto , Miyata Kanjiro , Ishii Takehiko , Kataoka Kazunori
Published: May 2010

An efficient endosome‐escaping function was integrated into the polyplex of plasmid DNA (pDNA) with poly(L‐lysine) (PLys) to improve its gene transfection efficiency through electrostatic coating with charge‐conversional polymer (CCP). CCP showed charge‐conversional function responding to endosomal pH, leading to the release of pDNA/PLys polyplex into the cytoplasm. The cells took up the intact CCP‐integrated ternary polyplex, which exerted appreciably higher transfection efficiency with lower cytotoxicity than pDNA/PLys polyplex against human umbilical vein endothelial cells (HUVECs). This is consistent with the facilitated endosomal escape of the CCP‐integrated ternary polyplex compared to the pDNA/PLys polyplex as directly observed with confocal laser‐scanning microscopy.

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Sensing Diffraction Gratings of Antigen‐Responsive Hydrogel for Human Immunoglobulin‐G Detection
Authors: Ye Gang , Yang Canqiang , Wang Xiaogong
Published: May 2010

Sensing diffraction gratings of antigen‐responsive hydrogel were developed for human immunoglobulin‐G (H‐IgG) detection. The IgG‐sensing gratings were fabricated by soft lithographic duplication of photoinduced surface relief gratings on azo polymer films to the hydrogel surfaces. The quantitative detection of H‐IgG was achieved by detecting modulation of the diffraction efficiency when the gratings were exposed to antigen solutions. The gratings showed high sensitivity and specificity for the H‐IgG detection. The detection could be performed at a reasonably fast rate with good reusability. In the process, no fluorophore labeling or additional signal enhancement was required.

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Light‐Responsive Block Copolymers
Authors: Schumers Jean‐Marc , Fustin Charles‐André , Gohy Jean‐François
Published: May 2010

Stimuli‐responsive polymers are the subject of intense research because they are able to show responses to various environmental changes. Among those stimuli, light has attracted much attention since it can be localized in time and space and it can also be triggered from outside of the system. In this paper, we review light‐responsive block copolymers (LRBCs) that combine characteristic features of block copolymers, e.g., self‐assembly behavior, and light‐responsive systems. The different photo‐responsive moieties that have been incorporated so far in block copolymers as well as the proposed applications are discussed.

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Functionalization of Fullerenes with Cyclopentadienyl and Anthracenyl Capped Polymeric Building Blocks via Diels–Alder Chemistry
Authors: Nebhani Leena , Barner‐Kowollik Christopher
Published: May 2010

Cyclopentadienyl (Cp) capped polymers [polyethylene glycols (PEGs), $\overline M _{\rm n}$ = 2 000 g · mol−1], react readily with fullerenes in a 1:1 molar ratio (relative to the amount of fullerenes and Cp‐end groups) at ambient temperature within 5 min in the absence of any catalyst in a Diels–Alder (DA) reaction to provide fullerene‐PEG hybrids. Similarly, anthracenyl capped PEGs react with fullerenes (in a 1:3 molar ratio) in DA reactions to yield the corresponding hybrids, albeit over a period of 1.5 h at 80 °C and a lesser conversion. The efficiency of the transformation is monitored via electrospray ionization mass spectrometry (ESI‐MS), demonstrating that the fullerenes can be transformed into polymer hybrids; most efficiently when Cp‐functional polymer is used as the diene. In addition, the obtained hybrids were subjected to UV/Vis as well as thermogravimetric analysis further underpinning the formation of mono‐substituted C60‐PEG hybrids [wt.‐%exp 70 ± 5 (PEG), 30 ± 5 (C60), wt.‐%theo 68 (PEG), 32 (C60)].

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Analysis of the Adequacy of the Representation of Entanglement Effects by Chain Loops
Authors: Martins José A.
Published: May 2010

It is generally considered that polymer chains are intertwined or “entangled” – because they cannot penetrate each other – and that these entanglements are responsible for melt elastic properties. There is no physical definition of entanglement. They are considered to be binary interactions between polymer chains and represented with the looping picture or by slip‐links. The interaction energy of chain loops and of two Kuhn monomers is evaluated for several polymers. It is lower than the melt thermal energy, implying that chain loops or any other binary interactions between chain segments cannot account for the properties assigned to entanglements.

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Nonbalanced SSFP‐based quantitative magnetization transfer imaging
Authors: Gloor Monika , Scheffler Klaus , Bieri Oliver
Published: May 2010

The previously reported concept for quantitative magnetization transfer (MT) imaging using balanced steady‐state free precession (SSFP) is applied to nonbalanced SSFP sequences. This offers the possibility to derive quantitative MT parameters of targets with high‐susceptibility variations such as the musculoskeletal system, where balanced SSFP suffers from off‐resonance‐related signal loss. In the first part of this work, an extended SSFP free induction decay (SSFP‐FID) signal equation is derived based on a binary spin‐bath model. Based on this new description, quantitative MT parameters such as the fractional pool size, magnetization exchange rate, and relaxation times can be assessed. In the second part of this work, MT model parameters are derived from an ex vivo muscle sample, in vivo human femoral muscle, and in vivo human patellar cartilage. Motion sensitivity issues are discussed and results from two‐pool SSFP‐FID are compared to results from two‐pool balanced SSFP and common quantitative MT models. In summary, this work demonstrates that SSFP‐FID allows for quantitative MT imaging of targets with high‐susceptibility variations within short acquisition times. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
In vivo MRI measurement of fetal blood oxygen saturation in cardiac ventricles of fetal sheep: A feasibility study
Authors: Wedegärtner Ulrike , Kooijman Hendrik , Yamamura Jin , Frisch Michael , Weber Christoph , Buchert Ralph , Huff Anna , Hecher Kurt , Adam Gerhard
Published: May 2010

The purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO2) with T2‐weighted MR sequences using a fetal sheep model. T2 measurements were performed on a 1.5‐T scanner using a T2 preparation pulse in combination with a three‐dimensional balanced steady‐state free precession sequence repeated at different echo times. Eight sheep fetuses were examined during a control, hypoxic, and recovery phase to perform T2‐weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO2. During each phase, fetal carotid artery sO2 was directly measured and correlated with MR sO2. A Bland‐Altman plot was performed. Fetal carotid artery sO2 was 69% sO2 during control, 16% sO2 during hypoxemia, and 67% sO2 during recovery. Mean values of the MR sO2 were 49% sO2 and 40% sO2 for control, 6% sO2 and 3% sO2 for hypoxemia, and 51% sO2 and 43% sO2 for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO2 and MR sO2 were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland‐Altman plot, MR sO2 was lower compared to fetal carotid artery sO2 (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO2 with MR oximetry. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI
Authors: Helms Gunther , Dathe Henning , Dechent Peter
Published: May 2010

Attempts to optimize the magnetization transfer ratio (MTR) obtained from spoiled gradient echo MRI have focused on the properties of the magnetization transfer pulse. In particular, continuous‐wave models do not explicitly account for the effects of excitation and relaxation on the MTR. In this work, these were modeled by an approximation of free relaxation between the radiofrequency pulses and of an instantaneous saturation event describing the magnetization transfer pulse. An algebraic approximation of the signal equation can be obtained for short pulse repetition time and small flip angles. This greatly facilitated the mathematical treatment and understanding of the MTR. The influence of inhomogeneous radiofrequency fields could be readily incorporated. The model was verified on the human brain in vivo at 3 T by variation of flip angle and pulse repetition time. The corresponding range in MTR was similar to that observed by a 4‐fold increase of magnetization transfer pulse power. Choice of short pulse repetition time and larger flip angles improved the MTR contrast and reduced the influence of radiofrequency inhomogeneity. Optimal contrast is obtained around an MTR of 50%, and noise progression is reduced when a high reference signal is obtained. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
2D and 3D radial multi‐gradient‐echo DCE MRI in murine tumor models with dynamic R*2‐corrected R1 mapping
Authors: Vautier Julien , Heilmann Melanie , Walczak Christine , Mispelter Joël , Volk Andreas
Published: May 2010

Dynamic contrast‐enhanced MRI is extensively studied to define and evaluate biomarkers for early assessment of vasculature‐targeting therapies. In this study, two‐dimensional and three‐dimensional radial multi‐gradient‐echo techniques for dynamic R*2‐corrected R1 mapping based on the spoiled gradient recalled signal equation were implemented and validated at 4.7 T. The techniques were evaluated on phantoms and on a respiratory motion animated tumor model. R1 measurements were validated with respect to a standard inversion‐recovery spin‐echo sequence in a four‐compartment phantom covering a range of relaxation rates typically found in tumor tissue. In the range of [0.4, 3] sec−1, R1 differences were less than 10% for both two‐dimensional and three‐dimensional experiments. A dynamic contrast‐enhanced MRI pilot study was performed on a colorectal tumor model subcutaneously implanted in mice at the abdominal level. Low motion sensitivity of radial acquisition allowed image recording without respiratory triggering. Three‐dimensional Ktrans maps and significantly different mean Ktrans values were obtained for two contrast agents with different molecular weights. The radial multi‐gradient‐echo approach should be most useful for preclinical experimental conditions where the tissue of interest experiences physiologic motion, like spontaneous extracerebral tumors developed by transgenic mice, and where dynamic contrast‐enhanced MRI is performed with high‐relaxivity contrast agents. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
S‐Gal®, A novel 1H MRI reporter for β‐galactosidase
Authors: Cui Weina , Liu Li , Kodibagkar Vikram D. , Mason Ralph P.
Published: May 2010

Reporter genes and associated enzyme activity are becoming increasingly significant for research in vivo. The lacZ gene and β‐galactosidase (β‐gal) expression have long been exploited as reporters of biologic manipulation at the molecular level, and a noninvasive detection strategy based on proton MRI is particularly attractive. 3,4‐Cyclohexenoesculetin β‐D‐galactopyranoside (S‐Gal®) is a commercial histologic stain, which forms a black precipitate in the presence of β‐gal and ferric ions, suggesting potential detectability by MRI. Generation of the precipitate is now shown to cause strong T2* relaxation, revealing β‐gal activity. A series of tests with the enzyme in vitro and with tumor cells shows that this approach can be used as an assay for β‐gal activity. Proof of principle is shown in human breast tumor xenografts in mice. Upon direct injection of a mixture of 3,4‐cyclohexenoesculetin β‐D‐galactopyranoside and ferric ammonium citrate, intense contrast was observed immediately in MCF7‐lacZ tumors, but not in wild‐type tumors. 3,4‐Cyclohexenoesculetin β‐D‐galactopyranoside activation in combination with ferric ions introduces a novel approach for assaying enzyme activity by MRI in vivo. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Optimization and validation of methods for mapping of the radiofrequency transmit field at 3T
Authors: Lutti Antoine , Hutton Chloe , Finsterbusch Jürgen , Helms Gunther , Weiskopf Nikolaus
Published: May 2010

MRI techniques such as quantitative imaging and parallel transmit require precise knowledge of the radio‐frequency transmit field (B). Three published methods were optimized for robust B mapping at 3T in the human brain: three‐dimensional (3D) actual flip angle imaging (AFI), 3D echo‐planar imaging (EPI), and two‐dimensional (2D) stimulated echo acquisition mode (STEAM). We performed a comprehensive comparison of the methods, focusing on artifacts, reproducibility, and accuracy compared to a reference 2D double angle method. For the 3D AFI method, the addition of flow‐compensated gradients for diffusion damping reduced the level of physiological artifacts and improved spoiling of transverse coherences. Correction of susceptibility‐induced artifacts alleviated image distortions and improved the accuracy of the 3D EPI imaging method. For the 2D STEAM method, averaging over multiple acquisitions reduced the impact of physiological noise and a new calibration method enhanced the accuracy of the B maps. After optimization, all methods yielded low noise B maps (below 2 percentage units), of the nominal flip angle value (p.u.) with a systematic bias less than 5 p.u. units. Full brain coverage was obtained in less than 5 min. The 3D AFI method required minimal postprocessing and showed little sensitivity to off‐resonance and physiological effects. The 3D EPI method showed the highest level of reproducibility. The 2D STEAM method was the most time‐efficient technique. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Automated segmentation of myocardial scar in late enhancement MRI using combined intensity and spatial information
Authors: Tao Qian , Milles Julien , Zeppenfeld Katja , Lamb Hildo J. , Bax Jeroen J. , Reiber Johan H.C. , van der Geest Rob J.
Published: May 2010

Accurate assessment of the size and distribution of a myocardial infarction (MI) from late gadolinium enhancement (LGE) MRI is of significant prognostic value for postinfarction patients. In this paper, an automatic MI identification method combining both intensity and spatial information is presented in a clear framework of (i) initialization, (ii) false acceptance removal, and (iii) false rejection removal. The method was validated on LGE MR images of 20 chronic postinfarction patients, using manually traced MI contours from two independent observers as reference. Good agreement was observed between automatic and manual MI identification. Validation results showed that the average Dice indices, which describe the percentage of overlap between two regions, were 0.83 ± 0.07 and 0.79 ± 0.08 between the automatic identification and the manual tracing from observer 1 and observer 2, and the errors in estimated infarct percentage were 0.0 ± 1.9% and 3.8 ± 4.7% compared with observer 1 and observer 2. The difference between the automatic method and manual tracing is in the order of interobserver variation. In conclusion, the developed automatic method is accurate and robust in MI delineation, providing an objective tool for quantitative assessment of MI in LGE MR imaging. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Active microcoil tracking in the lungs using a semisolid rubber as signal source
Authors: Alt Stefan , Homagk Ann‐Kathrin , Umathum Reiner , Semmler Wolfhard , Bock Michael
Published: May 2010

A new method to localize and track medical devices in air‐filled body cavities is proposed that uses active microcoils with a semisolid filling. In air spaces, e.g., the lung, microcoils require an independent signal source, which should be made of a biocompatible, solid and sterilizable material with a long shelf time. In a measurement of the T1 and T*2 and the relative spin density of several semisolid materials, latex was identified as a suitable material from which a prototype catheter was constructed with a microcoil at its tip. In a dual‐echo tracking pulse sequence, the very short T*2 of the rubber material allowed suppressing the background signal from surrounding tissue with a subtraction technique and additional dephasing gradients. With a roadmapping reconstruction, the microcoil's trajectory could be visualized on a previously acquired reference image set with a tracking rate of up to 60 Hz at a spatial resolution of better than 2mm. In a real‐time tracking implementation, an image update rate of 4 Hz was achieved by combining the tracking with a fast real‐time imaging sequence. Both methods were successfully applied in vivo to track the catheter in the lung of a pig. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Simulation model for contrast agent dynamics in brain perfusion scans
Authors: Bredno Jörg , Olszewski Mark E. , Wintermark Max
Published: May 2010

Standardization efforts are currently under way to reduce the heterogeneity of quantitative brain perfusion methods. A brain perfusion simulation model is proposed to generate test data for an unbiased comparison of these methods. This model provides realistic simulated patient data and is independent of and different from any computational method. The flow of contrast agent solute and blood through cerebral vasculature with disease‐specific configurations is simulated. Blood and contrast agent dynamics are modeled as a combination of convection and diffusion in tubular networks. A combination of a cerebral arterial model and a microvascular model provides arterial‐input and time‐concentration curves for a wide range of flow and perfusion statuses. The model is configured to represent an embolic stroke in one middle cerebral artery territory and provides physiologically plausible vascular dispersion operators for major arteries and tissue contrast agent retention functions. These curves are fit to simpler template curves to allow the use of the simulation results in multiple validation studies. A γ‐variate function with fit parameters is proposed as the vascular dispersion operator, and a combination of a boxcar and exponential decay function is proposed as the retention function. Such physiologically plausible operators should be used to create test data that better assess the strengths and the weaknesses of various analysis methods. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Optimization of RF excitation to maximize signal and T2 contrast of tissues with rapid transverse relaxation
Authors: Carl Michael , Bydder Mark , Du Jiang , Takahashi Atsushi , Han Eric
Published: May 2010

Ultrashort echo time MRI requires specialized pulse sequences to overcome the short T2 of the MR signal encountered in tissues such as ligaments, tendon, or cortical bone. Theoretical work is presented, supported by simulations and experimental data on optimizing the radiofrequency excitation to maximize signal‐to‐noise ratio and contrast‐to‐noise ratio. The theoretical calculations and simulations are based on the classic Bloch equations and lead to a closed form expression for the optimal radiofrequency pulse parameters to maximize the MR signal in the presence of rapid T2 decay. In the steady state, the spoiled gradient recalled echo signal amplitude in response to the radiofrequency excitation pulses is not maximized by the classic Ernst angle but by a more general criterion we call “generalized Ernst angle.” Finally, it is shown that T2 contrast is maximized by flipping the magnetization at the Ernst angle with a radiofrequency pulse duration proportional to the targeted T2. Experimental studies on short T2 phantoms confirm these optimization criteria for both signal‐to‐noise ratio and contrast‐to‐noise ratio. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Simulated MR magnetic field induces steady‐state changes in brain dynamics: Implications for interpretation of functional MR studies
Authors: Marino Andrew A. , Carrubba Simona , Frilot Clifton , Chesson Andrew L. , Gonzalez‐Toledo Eduardo
Published: May 2010

We examined whether a magnetic field comparable to one of the fields produced during MRI induced steady‐state changes in brain electrical activity while the field was applied (called a presence effect to distinguish it from evoked potentials). The electroencephalogram was measured from standard scalp locations in the presence and absence of 100‐200 μT, 60 Hz, and the effect of the field was evaluated by nonlinear (recurrence analysis) and linear techniques; individual subjects served as their own controls. Using recurrence analysis, changes in brain activity lasting 1 sec (the longest interval considered) were found in 21 of 22 subjects (P < 0.05 for each subject). The presence effect was not detected using linear analysis and was reversible, as indicated by a return of brain activity to baseline levels in all subjects within 2 sec of field offset. The possible role of artifacts or systematic errors was ruled out by studies using electrical phantoms and by analyses of electroencephalograms recorded during sham exposure. It is reasonable to expect that actual scanner magnetic fields also produce nonlinear steady‐state perturbations of brain dynamical activity. The effect may influence the picture of brain connectivity inferred in some functional MR studies. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Reactions of young children to the MRI scanner environment
Authors: Malisza Krisztina L. , Martin Toby , Shiloff Deborah , Yu Dickie C. T.
Published: May 2010

Seventy children aged 2 to 7 years were exposed to the MRI environment through a series of steps typical of a research study. Their willingness to proceed through the process was used to estimate the prevalence of fear. Thirty‐seven children (53%; 95% confidence interval [41%, 65%]) completed the approach sequence. Although the correlation of child age in months (Mean (M) = 60.1, standard deviation = 16.5, N = 70) and highest successful step (M = 5.8, standard deviation = 2.6, 95% confidence interval [5.2, 6.4]) completed was not statistically significant at the 0.05 level, r (68) = 0.21, P = 0.08, 95% confidence interval [−0.03, 0.42], the proportion of children aged 6‐7 years who successfully completed all steps (14 of 21, 67%, 95% confidence interval [50%, 84%]) was significantly different from the proportion of children aged 2‐3 years who completed all steps (six of 23, 26%, 95% confidence interval [11%, 41%]) (Fisher's exact test, two‐tailed P = 0.0148). A failure rate of at least 50% should be included into group size calculations when performing studies with young children (2‐7 years), in addition to motion and other experimental factors. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.