35 research outputs found
6âRing Piperidine-Based Polymers with Both Upper and Lower Critical Solution Temperatures as Kinetic Hydrate Inhibitors
Kinetic hydrate inhibitors (KHIs) are a chemical method
of preventing
gas hydrate plugging of oil and gas production flow lines. The main
ingredient in a KHI formulation giving a high performance is one or
more water-soluble amphiphilic polymers. Many of these polymers exhibit
a cloud point or lower critical solution temperature (LCST) in water,
which can cause fouling problems if the polymer solution is above
this temperature. A few polymers exhibit an upper critical solution
temperature (UCST) such that the polymer is soluble only above this
temperature. This could be advantageous for use as a KHI to avoid
fouling issues at high temperatures, but only if the UCST was below
the minimum temperature encountered by the hydrate-forming fluids.
Here, we report the first study of a KHI polymer with a UCST in aqueous
solution, poly(N-acryloyl-nipecotamide) (PNANAm).
It gave a good KHI performance at 2500 ppm when screened using the
slow constant cooling (1.0 °C/h) test method in high-pressure
rocking cells with a synthetic natural gas blend, lowering the average
hydrate onset temperature by 5.3 °C relative to tests with no
additive. The related polymers poly(N-acryloylpiperidine)
(PAPip) and poly(N-acryloyl-N,N-diethylnipecotamide) (PNADNAm) lowered the hydrate onset
temperature by about 1 °C more, probably due to the increased
hydrophobicity of the amphiphilic side groups
Temperature-responsive culture surfaces for insect cell sheets to fabricate a bioactuator
High stability of thermoresponsive polymer-brush-grafted silica beads as chromatography matrices
Covalent Immobilization of Collagen Type I to a Polydimethylsiloxane Surface for Preventing Cell Detachment by Retaining Collagen Molecules under Uniaxial Cyclic Mechanical Stretching Stress
Surface modification of polydimethylsiloxane (PDMS) with
an extracellular
matrix (ECM) is useful for enhancing stable cell attachment. However,
few studies have investigated the correlation between the stability
of deposited ECM and cell behavior on the PDMS surfaces in external
stretched cell culture systems. Herein, covalent collagen type I (Col)-immobilized
PDMS surfaces were fabricated using 3-aminopropyl-trimethoxysilane,
glutaraldehyde, and Col molecules. The immobilized collagen molecules
on the PDMS surface were more stable and uniform than the physisorbed
collagen. The cells stably adhered to the Col-immobilized surface
and proliferated even under uniaxial cyclic mechanical stretching
stress (UnCyMSt), whereas the cells gradually detached from the Col-physisorbed
PDMS surface, accompanied by a decrease in the number of deposited
collagen molecules. Moreover, the immobilization of collagen molecules
enhanced cell alignment under the UnCyMSt. This study reveals that
cell adhesion, proliferation, and alignment under the UnCyMSt can
be attributed to the retention of collagen molecules on the PDMS surface
Effect of Temperature Changes on Serum Protein Adsorption on Thermoresponsive Cell-Culture Surfaces Monitored by A Quartz Crystal Microbalance with Dissipation
Thermoresponsive cell-culture polystyrene (PS) surfaces that are grafted with poly(N-isopropylacrylamide) (PIPAAm) facilitate the cultivation of cells at 37 °C and the detachment of cultured cells as a sheet with an underlying extracellular matrix (ECM) by reducing the temperature. However, the ECM and cell detachment mechanisms are still unclear because the detachment of cells from thermoresponsive surfaces is governed by complex interactions among the cells/ECM/surface. To explore the dynamic behavior of serum protein adsorption/desorption, thermoresponsive surfaces that correspond to thermoresponsive tissue-culture PS dishes were formed on sensor chips for quartz crystal microbalance with dissipation (QCM-D) measurements. X-ray photoelectron spectroscopy (XPS) measurements and temperature-dependent frequency and dissipation shifts, Δf and ΔD, using QCM-D revealed that the thermoresponsive polymers were successfully grafted onto oxidized, thin PS films on the surfaces of the sensor chips. Increased amounts of adsorbed bovine serum albumin (BSA) and fibronectin (FN) were observed on the thermoresponsive polymer-grafted surfaces at 37 °C when compared with those at 20 °C because of enhanced hydrophobic interactions with the hydrophobic, thermoresponsive surface. While the calculated masses of adsorbed BSA and FN using QCM-D were 3–5 times more than those that were obtained from radiolabeling, the values were utilized for relative comparisons among the same substrate. More importantly, the thermoresponsive, dynamic behavior of serum protein adsorption/desorption was monitored using the QCM-D technique. Observations of this dynamic behavior revealed that the BSA and FN that were adsorbed at 37 °C remained on both surfaces after decreasing the temperature to 20 °C
A combination of 7-ketocholesterol, lysosphingomyelin and bile acid-408 to diagnose Niemann-Pick disease type C using LC-MS/MS.
BackgroundNiemann-Pick disease type C (NPC) is an autosomal recessive disorder caused by mutations of NPC1 or NPC2, which encode the proteins that are responsible for intracellular cholesterol trafficking. Loss of this function results in the accumulation of cholesterol-related products, such as oxysterols, sphingolipids, and NPC-related bile acids, which were recently used as biochemical biomarkers for the diagnosis of NPC. Bile acid-408 is a new significant compound we found in Japanese NPC patients, and it likely belongs to the category of bile acids. However, the diagnosis of NPC using a single biomarker is not satisfactory for clinical application because of the high instance of false negatives or positives. Therefore, we proposed an application of NPC diagnosis using a combination of 7-ketocholesterol (7-KC), lysosphingomyelin (lysoSM), bile acid-408 and/or glucosylsphingosine (lysoGL-1).Methods and findings7-KC, lysoSM and lysoGL-1 in sera and bile acid-408 in dried blood spots (DBS) were quantified within 17 minutes using tandem mass spectrometry and high-resolution mass spectrometry, respectively. We measured these biomarkers in NPC patients (n = 19), X-linked adrenoleukodystrophy (X-ALD) patients (n = 5), patients with other lysosomal diseases (n = 300), newborns (n = 124) and healthy people (n = 74). Our results showed a promising accuracy (97%) for NPC diagnosis using the combination of 7-KC, lysoSM and bile acid-408. However, contrary to our expectations, lysoGL-1 levels did not present at a significantly greater amount in NPC patients than other patients and negative controls.ConclusionsThe combination of 7-KC, lysoSM and bile acid-408 improves the accuracy of NPC diagnosis and is feasible for mass screening due to its simple sample preparation and measurement. Future research should investigate the chemical structure of bile acid-408 to further facilitate its advantage in diagnosis