Flow Monitoring in Microdialysis Systems for Continuous Sampling

2000 ◽  
Author(s):  
Herbert Ernst ◽  
Artur Jachimowicz ◽  
Gerald Urban
Keyword(s):  
Flow Measurement ◽  
Thermal Characteristics ◽  
Flow Sensor ◽  
Continuous Sampling ◽  
Flow Monitoring ◽  
Perfusate Flow ◽  
In Vivo Sampling

Abstract Continuous in vivo sampling of medically relevant substances using the microdialysis method requires the most exact possible knowledge about the involved perfusate flow. As this flow is typically in the range of few microliters per hour a flow sensor with a resolution of less than 1 microliter per hour is required. This paper will present such a sensor based on a calorimetrical measurement. The described principle of operation allows not only the flow measurement itself but also an additional detection of the involved fluids thermal characteristics, allowing the compensation of important interferents in this and similar micro fluidic applications, e.g. gas enclosures.

Regional blood flow measurement in vivo for a definable geometry

1964 ◽  
Vol 206 (5) ◽  
pp. 962-966 ◽  
Author(s):  
Marvin B. Bacaner ◽  
James S. Beck
Keyword(s):  
Blood Flow ◽  
Flow Measurement ◽  
Necessary Conditions ◽  
Regional Blood Flow ◽  
The Body ◽  
Continuous Measure ◽  
Radioisotope Method ◽  
Arterial Concentration ◽  
Regional Concentration

A radioisotope method for measuring regional blood flow in the intestine of the dog in vivo has been favorably compared with measurement by timed collection of total venous outflow. The necessary conditions are a continuous measure of arterial concentration and cumulative regional concentration of radioisotope, an experimentally definable region, and temporary complete retention of tracer. The derivation of the relations used suggests additional applications of the method to other regions of the body.

In vivo sampling of environmental organic contaminants in fish by solid-phase microextraction

2012 ◽  
Vol 32 ◽  
pp. 31-39 ◽  
Author(s):  
Xu Zhang ◽  
Ken D. Oakes ◽  
Shuang Wang ◽  
Mark R. Servos ◽  
Shufen Cui ◽  
...  
Keyword(s):  
Organic Contaminants ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
In Vivo Sampling

scholarly journals The potential of microdialysis to estimate rifampicin concentrations in the lung of guinea pigs

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245922
Author(s):  
Faye Lanni ◽  
Neil Burton ◽  
Debbie Harris ◽  
Susan Fotheringham ◽  
Simon Clark ◽  
...  
Keyword(s):  
Drug Development ◽  
Guinea Pigs ◽  
Sampling Technique ◽  
Tissue Fluid ◽  
Experimental Conditions ◽  
Continuous Sampling ◽  
Drug Concentrations ◽  
The Impact

Optimised pre-clinical models are required for TB drug development to better predict the pharmacokinetics of anti-tuberculosis (anti-TB) drugs to shorten the time taken for novel drugs and combinations to be approved for clinical trial. Microdialysis can be used to measure unbound drug concentrations in awake freely moving animals in order to describe the pharmacokinetics of drugs in the organs as a continuous sampling technique. The aim of this work was to develop and optimise the microdialysis methodology in guinea pigs to better understand the pharmacokinetics of rifampicin in the lung. In vitro experiments were performed before progressing into in vivo studies because the recovery (concentration of the drug in the tissue fluid related to that in the collected dialysate) of rifampicin was dependent on a variety of experimental conditions. Mass spectrometry of the dialysate was used to determine the impact of flow rate, perfusion fluid and the molecular weight cut-off and membrane length of probes on the recovery of rifampicin at physiologically relevant concentrations. Following determination of probe efficiency and identification of a correlation between rifampicin concentrations in the lung and skeletal muscle, experiments were conducted to measure rifampicin in the sacrospinalis of guinea pigs using microdialysis. Lung concentrations of rifampicin were estimated from the rifampicin concentrations measured in the sacrospinalis. These studies suggest the potential usefulness of the microdialysis methodology to determine drug concentrations of selected anti-TB drugs to support new TB drug development.

scholarly journals Microdialysis of skeletal muscle at rest

1999 ◽  
Vol 58 (4) ◽  
pp. 919-923 ◽  
Author(s):  
Jan Henriksson
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Human Skeletal Muscle ◽  
Human Metabolism ◽  
High Expectations ◽  
Perfusate Flow ◽  
Muscle Research ◽  
Interstitial Glucose

Techniques in human skeletal muscle research are by necessity predominantly 'descriptive'.Microdialysis has raised high expectations that it could meet the demand for a method that allows 'mechanistic' investigations to be performed in human skeletal muscle. In the present review, some views are given on how well the initial expectations on the use of the microdialysis technique in skeletal muscle have been fulfilled, and the areas in which additional work is needed in order to validate microdialysis as an important metabolic technique in this tissue. The microdialysis catheter has been equated to an artificial blood vessel, which is introduced into the tissue. By means of this 'vessel' the concentrations of compounds in the interstitial space can be monitored. The concentration of substances in the collected samples is dependent on the rate of perfusate flow. When perfusate flow is slow enough to allow complete equilibration between interstitial and perfusate fluids, the concentration in the perfusate is maximal and identical to the interstitial concentration. Microdialysis data may be influenced by changes in blood flow, especially in instances where the tissue diffusivity limits the recovery in vivo, i.e. when recovery in vitro is 100 %, whereas the recovery in vivo is less than 100 %. Microdialysis data indicate that a significant arterial-interstitial glucose concentration gradient exists in skeletal muscle but not in adipose tissue at rest. While the concentrations of glucose and lactate in the dialysate from skeletal muscle are close to the expected values, the glycerol values obtained for muscle are still puzzling. Ethanol added to the perfusate will be cleared by the tissue at a rate that is determined by the nutritive blood flow (the microdialysis ethanol technique). It is concluded that microdialysis of skeletal muscle has become an important technique for mechanistic studies in human metabolism and nutrition.

Solid-Phase Microextraction: A Complementary In Vivo Sampling Method to Microdialysis

2013 ◽  
Vol 125 (46) ◽  
pp. 12346-12348 ◽  
Author(s):  
Erasmus Cudjoe ◽  
Barbara Bojko ◽  
Inés de Lannoy ◽  
Victor Saldivia ◽  
Janusz Pawliszyn
Keyword(s):  
Solid Phase Microextraction ◽  
Sampling Method ◽  
Solid Phase ◽  
In Vivo Sampling

scholarly journals Ingestible Osmotic Pill for In Vivo Sampling of Gut Microbiomes

2019 ◽  
Vol 1 (5) ◽  
pp. 1900053 ◽  
Author(s):  
Hojatollah Rezaei Nejad ◽  
Bruno C. M. Oliveira ◽  
Aydin Sadeqi ◽  
Amin Dehkharghani ◽  
Ivanela Kondova ◽  
...  
Keyword(s):  
In Vivo Sampling

scholarly journals Piezoresistive Carbon Nanofiber-Based Cilia-Inspired Flow Sensor

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 211 ◽  
Author(s):  
Debarun Sengupta ◽  
Duco Trap ◽  
Ajay Giri Prakash Kottapalli
Keyword(s):  
Carbon Nanofiber ◽  
Detection Threshold ◽  
Flow Sensor ◽  
Oxygen Intake ◽  
Mems Devices ◽  
Flow Sensors ◽  
Flow Monitoring ◽  
Flow Sensing ◽  
Artificial Cilia ◽  
Lower Detection

Evolving over millions of years, hair-like natural flow sensors called cilia, which are found in fish, crickets, spiders, and inner ear cochlea, have achieved high resolution and sensitivity in flow sensing. In the pursuit of achieving such exceptional flow sensing performance in artificial sensors, researchers in the past have attempted to mimic the material, morphological, and functional properties of biological cilia sensors, to develop MEMS-based artificial cilia flow sensors. However, the fabrication of bio-inspired artificial cilia sensors involves complex and cumbersome micromachining techniques that lay constraints on the choice of materials, and prolongs the time taken to research, design, and fabricate new and novel designs, subsequently increasing the time-to-market. In this work, we establish a novel process flow for fabricating inexpensive, yet highly sensitive, cilia-inspired flow sensors. The artificial cilia flow sensor presented here, features a cilia-inspired high-aspect-ratio titanium pillar on an electrospun carbon nanofiber (CNF) sensing membrane. Tip displacement response calibration experiments conducted on the artificial cilia flow sensor demonstrated a lower detection threshold of 50 µm. Furthermore, flow calibration experiments conducted on the sensor revealed a steady-state airflow sensitivity of 6.16 mV/(m s−1) and an oscillatory flow sensitivity of 26 mV/(m s−1), with a lower detection threshold limit of 12.1 mm/s in the case of oscillatory flows. The flow sensing calibration experiments establish the feasibility of the proposed method for developing inexpensive, yet sensitive, flow sensors; which will be useful for applications involving precise flow monitoring in microfluidic devices, precise air/oxygen intake monitoring for hypoxic patients, and other biomedical devices tailored for intravenous drip/urine flow monitoring. In addition, this work also establishes the applicability of CNFs as novel sensing elements in MEMS devices and flexible sensors.

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