14 research outputs found
Travelling Surface Acoustic Waves Microfluidics
AbstractIn this paper, we demonstrate the working principle of travelling surface acoustic waves (TSAWs) in a microfluidic system. The TSAWs were incorporated to separate polystyrene (PS) particles of variable diameters and perform controlled mixing of different chemicals for concentration gradient generation, both inside a polydimethylsiloxane (PDMS) microfluidic channel. The TSAWs generated an acoustic streaming flow (ASF) upon coupling with a liquid and exerted an acoustic radiation force (ARF) on the suspended particles. The ARF was theoretically estimated for PS microspheres suspended in water, and conditions for ARF dominance over ASF or vice versa were identified. Recently reported TSAW-based PS particles separation and gradient generation results by our group are summarized here
Endoscopic Pancreatic Sphincterotomy: Indications and Complications
Background/Aims: Although a few recent studies have reported the effectiveness of endoscopic pancreatic sphincterotomy (EPST), none has compared physicians' skills and complications resulting from the procedure. Thus, we examined the indications, complications, and safety of EPST performed by a single physician at a single center. Methods: Among 2,313 patients who underwent endoscopic retrograde cholangiopancreatography between January 1996 and March 2008, 46 patients who underwent EPST were included in this retrospective study. We examined the indications, complications, safety, and effectiveness of EPST, as well as the need for a pancreatic drainage procedure and the concomitant application of EPST and endoscopic sphincterotomy (EST). Results: Diagnostic indications for EPST were chronic pancreatitis (26 cases), pancreatic divisum (4 cases), and pancreatic cancer (8 cases). Therapeutic indications for EPST were removal of a pancreaticolith (10 cases), stent insertion for pancreatic duct stenosis (9 cases), nasopancreatic drainage (7 cases), and treatment of sphincter of Oddi dysfunction (1 case). The success rate of EPST was 95.7% (44/46). Acute complications of EPST included five cases (10.9%) of pancreatitis and one of cholangitis (2.2%). EPST with EST did not reduce biliary complications. Endoscopic pancreatic drainage procedures following EPST did not reduce pancreatic complications. Conclusions: EPST showed a low incidence of complications and a high rate of treatment success; thus, EPST is a relatively safe procedure that can be used to treat pancreatic diseases. Pancreatic drainage procedures and additional EST following EPST did not reduce the incidence of procedure-related complications
Differences in Clinical Characteristics between Patients with Non-Erosive Reflux Disease and Erosive Esophagitis in Korea
Gastroesophageal reflux disease (GERD) is caused by abnormal reflux of gastric contents into the esophagus. GERD can be divided into two groups, erosive esophagitis and non-erosive reflux disease (NERD). The aim of this study was to compare the clinical characteristics of patients with erosive esophagitis to those with NERD. All participating patients underwent an upper endoscopy during a voluntary health check-up. The NERD group consisted of 500 subjects with classic GERD symptoms in the absence of esophageal mucosal injury during upper endoscopy. The erosive esophagitis group consisted of 292 subjects with superficial esophageal erosions with or without typical symptoms of GERD. Among GERD patients, male gender, high body mass index, high obesity degree, high waist-to-hip ratio, high triglycerides, alcohol intake, smoking and the presence of a hiatal hernia were positively related to the development of erosive esophagitis compared to NERD. In multivariated analysis, male gender, waist-to-hip ratio and the presence of a hiatal hernia were the significant risk factors of erosive esophagitis. We suggest that erosive esophagitis was more closely related to abdominal obesity
Biocompatible Polyhydroxyethylaspartamide-based Micelles with Gadolinium for MRI Contrast Agents
Biocompatible poly-[N-(2-hydroxyethyl)-d,l-aspartamide]-methoxypoly(ethyleneglycol)-hexadecylamine (PHEA-mPEG-C16) conjugated with 1,4,7,10-tetraazacyclododecan-1,4,7,10-tetraacetic acid-gadolinium (DOTA-Gd) via ethylenediamine (ED) was synthesized as a magnetic resonance imaging (MRI) contrast agent. Amphiphilic PHEA-mPEG-C16-ED-DOTA-Gd forms micelle in aqueous solution. All the synthesized materials were characterized by proton nuclear magnetic resonance (1H NMR). Micelle size and shape were examined by dynamic light scattering (DLS) and atomic force microscopy (AFM). Micelles with PHEA-mPEG-C16-ED-DOTA-Gd showed higher relaxivities than the commercially available gadolinium contrast agent. Moreover, the signal intensity of a rabbit liver was effectively increased after intravenous injection of PHEA-mPEG-C16-ED-DOTA-Gd
Generation of Dynamic Free-Form Temperature Gradients in a Disposable Microchip
Temperature
gradients (TGs) provide an effective approach to controlling
solvated molecules and creating spatiotemporally varying thermal stimuli
for biochemical research. Methods developed to date for generating
TGs can only create a limited set of static temperature profiles.
This article describes a method for establishing dynamic free-form
TGs in polydimethylsiloxane (PDMS) as well as in gases and liquids
in contact with the PDMS. The heating mechanism relies on the efficient
acoustic absorption by the PDMS of high-frequency (5–200 MHz)
surface acoustic waves (SAWs). MATLAB-aided actuation of a transducer
enabled the generation and propagation of SAWs in a controlled fashion,
which permitted spatiotemporal control over the temperature in the
PDMS microstructures. This technique is exploited to perform one-shot
high-resolution melting (HRM) analysis to detect single nucleotide
polymorphisms (SNPs) in DNA. The experimental results displayed a
10-fold higher resolution and an enhanced signal-to-noise ratio compared
to the results obtained using a conventional real-time PCR machine
Generation of Dynamic Free-Form Temperature Gradients in a Disposable Microchip
Temperature
gradients (TGs) provide an effective approach to controlling
solvated molecules and creating spatiotemporally varying thermal stimuli
for biochemical research. Methods developed to date for generating
TGs can only create a limited set of static temperature profiles.
This article describes a method for establishing dynamic free-form
TGs in polydimethylsiloxane (PDMS) as well as in gases and liquids
in contact with the PDMS. The heating mechanism relies on the efficient
acoustic absorption by the PDMS of high-frequency (5–200 MHz)
surface acoustic waves (SAWs). MATLAB-aided actuation of a transducer
enabled the generation and propagation of SAWs in a controlled fashion,
which permitted spatiotemporal control over the temperature in the
PDMS microstructures. This technique is exploited to perform one-shot
high-resolution melting (HRM) analysis to detect single nucleotide
polymorphisms (SNPs) in DNA. The experimental results displayed a
10-fold higher resolution and an enhanced signal-to-noise ratio compared
to the results obtained using a conventional real-time PCR machine
Microchannel Anechoic Corner for Size-Selective Separation and Medium Exchange via Traveling Surface Acoustic Waves
We demonstrate a miniaturized acoustofluidic
device composed of
a pair of slanted interdigitated transducers (SIDTs) and a polydimethylsiloxane
microchannel for achieving size-selective separation and exchange
of medium around polystyrene particles in a continuous, label-free,
and contactless fashion. The SIDTs, deposited parallel to each other,
produce tunable traveling surface acoustic waves (TSAWs) at desired
locations, which, in turn, yield an anechoic corner inside the microchannel
that is used to selectively deflect particles of choice from their
streamlines. The TSAWs with frequency <i>f</i><sub>R</sub> originating from the right SIDT and propagating left toward the
microchannel normal to the fluid flow direction, laterally deflect
larger particles with diameter <i>d</i><sub>1</sub> from
the hydrodynamically focused sample fluid that carries other particles
as well with diameters <i>d</i><sub>2</sub> and <i>d</i><sub>3</sub>, such that <i>d</i><sub>1</sub> > <i>d</i><sub>2</sub> > <i>d</i><sub>3</sub>. The deflected
particles (<i>d</i><sub>1</sub>) are pushed into the top-left
corner of the microchannel. Downstream, the TSAWs with frequency <i>f</i><sub>L</sub>, such that <i>f</i><sub>L</sub> > <i>f</i><sub>R</sub>, disseminating from the left SIDT, deflect
the medium-sized particles (<i>d</i><sub>2</sub>) rightward,
leaving behind the larger particles (<i>d</i><sub>1</sub>) unaffected in the top-left anechoic corner and the smaller particles
(<i>d</i><sub>3</sub>) in the middle of the microchannel,
thereby achieving particle separation. A particle not present in the
anechoic corner could be deflected rightward to realize twice the
medium exchange. In this work, the three-way separation of polystyrene
particles with diameters of 3, 4.2, and 5 μm and 3, 5, and 7
μm is achieved using two separate devices. Moreover, these devices
are used to demonstrate multimedium exchange around polystyrene particles
∼5 μm and 7 μm in diameter