A polymer-based microfluidic device for immunosensing biochips

This paper describes the design, fabrication, and test of a PDMS/PMMA-laminated microfluidic device for an immunosensing biochip. A poly(dimethyl siloxane)(PDMS) top substrate molded by polymer casting and a poly(methyl methacrylate)(PMMA) bottom substrate fabricated by hot embossing are bonded with pressure and hermetically sealed. Two inlet ports and an air vent are opened through the PDMS top substrate, while gold electrodes for electrochemical biosensing are patterned onto the PMMA bottom substrate. The analyte sample is loaded from the sample inlet port to the detection chamber by capillary force, without any external intervening forces. For this and to control the time duration of sample fluid in each compartment of the device, including the inlet port, diffusion barrier, reaction chamber, flow-delay neck, and detection chamber, the fluid conduit has been designed with various geometries of channel width, depth, and shape. Especially, the fluid path has been designed so that the sample flow naturally stops after filling the detection chamber to allow sufficient time for biochemical reaction and subsequent washing steps. As model immunosensing tests for the microfluidic device, functionalizations of ferritin and biotin to the sensing surfaces on gold electrodes and their biospecific interactions with antiferritin antiserum and streptavidin have been investigated. An electrochemical detection method for immunosensing by biocatalyzed precipitation has been developed and applied for signal registration. With the biochip, the whole immunosensing processes could be completed within 30 min.     

Ketalizations of aryl ω-(2-imidazolyl)alkyl ketones by glycerol and 3-mercapto-1,2-propanediol. synthesis and characterization of cis- and trans-{2-aryl-2-[ω-(2-imidazolyl)alkyl](1,3-dioxolan-4-yl and 1,3-oxathiolan-5-yl)}methanols

Aryl 2-[(2-imidazolyl)ethyl or 3-(2-imidazolyl)propyl]ketones were ketalized by glycerol or 3-mercapto-1,2-propanediol in boiling benzene in the presence of 4-toluenesulfonic acid to provide the title compounds. The aryl substituents are 4-chloro-, 4-bromo-, 4-fluoro-, or 2,4-dichlorophenyl. While aryl (2-imidazolyl)methyl ketones condensed with glycerol to form cis- and trans-{2-aryl-2-[(2-imidazolyl)methyl]-4-(hydroxymethyl)}-1,3-dioxolanes, related condensations with 3-mercapto-1,2-propanediol, under similar, or even more stringent reaction conditions, produced no 1,3-oxathiolane analogs, with the starting ketones being recovered. Separation and structure determination of these racemic cis and trans isomeric products are described. The structure of these stereoisomers was established by means of ¹H and ¹³C nmr correlation and nOe experiments. Selective methylation of the N-unsubstituted 2-imidazolyl alcohols with one equivalent sodium hydride and methyl iodide provided the corresponding N-methyl alcohols in excellent yields. With excess benzoyl chloride, N-unsubstituted 2-imidazolyl alcohols were initially converted to O, N-dibenzoates from which the N-benzoyl group was easily cleaved by ammonium hydroxide in ethanol to provide benzoate esters.     

Strength of fibers from wholly aromatic polyesters

A theory of the strength (or the tenacity) of highly oriented Liquid Crystal Polymer (LCP) fibers was developed, and its results were compared with existing tensile strength data of fibers of a copolymer of 1,4-oxybenzoate and 6,2-oxynaphthoate. A basic premise of the theory is that the mechanical load transfer between polymer chains is through intermolecular interaction which acts in a manner similar to that of shear stress, and that the fiber strength is primarily governed by the intermolecular adhesion strength. The theory also incorporates the effects of MW, MW distribution, and the chain orientation distribution. Analysis of the experimental tenacity data demonstrates that the present theory can quantitatively describe the variation of the tenacity of LCP fibers with MW both in the as-spun and in the heat-treated states. The theory further predicts that the predominant factor governing the tenacity of LCP fibers is primarily due to MW increase due to solid-state polymerization. It is also demonstrated that the intermolecular adhesion between LCP chains is relatively weak and does not improve with heat treatment. The absence of factors that limit the MW increase (i.e, imbalanced end-groups and side reactions of end groups) is a prerequisite for fast heat treatment of a LCP fiber to a high tenacity.Symbols A _f the cross-sectional area of a single polymer chain - E _f the theoretical modulus of a polymer chain - G _m the shear modulus of fiber - h(l) the chain length distribution function - l the chain length - l the number average chain length - l _c the length of chain units that are bonded to adjacent polymer chains - n ² 4G _m/CE_f - N _c the number of polymer chains per unit area perpendicular to the fiber axis - P _b the probability that a chain does not have a chain end in the fracture zone - P _e the probability that a chain has, at least, a chain end in the fracture zone - q _e,q _b the probability of finding an ending and a bridging polymer chain, respectively, in the fracture zone - l the length of fracture zone - the elongation of a polymer chain - the chain orientation angle - _f the normal stress that acts on a polymer chain - _fu the fiber tenacity - _e the shear stress that acts on a polymer chain surface Dedicated to Prof. Dr. rer. nat. Wolfgang Hilger, Chairman of Hoechst A.G. in honor of his 60th birthday     

Differential 3ω calorimeter

We have developed a new dynamic calorimeter using the differential 3ω detection method. The differential 3ω calorimeter is capable of measuring dynamic heat capacity of liquid samples. The new calorimeter consists of a Wheatstone bridge made of two identical heater/sensors, and is based on the sensitive null detection method. The balancing is done automatically at all frequencies and is independent of temperature; once a sample is placed on one heater/sensor, a third harmonic signal is produced due to the difference in the two arms of the bridge. The differential 3ω calorimeter provides enhancements over traditional dynamic methods in dynamic range (up to 30 kHz), resolution, and ease of operation.     

Identification of New Non-BBB Permeable Tryptophan Hydroxylase Inhibitors for Treating Obesity and Fatty Liver Disease

Serotonin (5-hydroxytryptophan) is a hormone that regulates emotions in the central nervous system. However, serotonin in the peripheral system is associated with obesity and fatty liver disease. Because serotonin cannot cross the blood-brain barrier (BBB), we focused on identifying new tryptophan hydroxylase type I (TPH1) inhibitors that act only in peripheral tissues for treating obesity and fatty liver disease without affecting the central nervous system. Structural optimization inspired by para-chlorophenylalanine (pCPA) resulted in the identification of a series of oxyphenylalanine and heterocyclic phenylalanine derivatives as TPH1 inhibitors. Among these compounds, compound 18i with an IC₅₀ value of 37 nM was the most active in vitro. Additionally, compound 18i showed good liver microsomal stability and did not significantly inhibit CYP and Herg. Furthermore, this TPH1 inhibitor was able to actively interact with the peripheral system without penetrating the BBB. Compound 18i and its prodrug reduced body weight gain in mammals and decreased in vivo fat accumulation.     

Tomatidine-stimulated maturation of human embryonic stem cell-derived cardiomyocytes for modeling mitochondrial dysfunction

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) have been reported to exhibit immature embryonic or fetal cardiomyocyte-like phenotypes. To enhance the maturation of hESC-CMs, we identified a natural steroidal alkaloid, tomatidine, as a new substance that stimulates the maturation of hESC-CMs. Treatment of human embryonic stem cells with tomatidine during cardiomyocyte differentiation stimulated the expression of several cardiomyocyte-specific markers and increased the density of T-tubules. Furthermore, tomatidine treatment augmented the number and size of mitochondria and enhanced the formation of mitochondrial lamellar cristae. Tomatidine treatment stimulated mitochondrial functions, including mitochondrial membrane potential, oxidative phosphorylation, and ATP production, in hESC-CMs. Tomatidine-treated hESC-CMs were more sensitive to doxorubicin-induced cardiotoxicity than the control cells. In conclusion, the present study suggests that tomatidine promotes the differentiation of stem cells to adult cardiomyocytes by accelerating mitochondrial biogenesis and maturation and that tomatidine-treated mature hESC-CMs can be used for cardiotoxicity screening and cardiac disease modeling.Subject terms: Heart failure, Embryonic stem cells, Stem-cell differentiation