Developed Flow System Research Articles

A Simple Flow Injection System for Amperometric Detection of Ascorbic Acid Using Carbon Paste/Copper Schiff Base Composite Electrode

AbstractIn this paper, a simple, sensitive, and precise flow injection system was optimized and applied to ascorbic acid determination with a carbon paste electrode modified with the Schiff base copper complex. The modified sensor showed increased sensitivity toward ascorbic acid oxidation with a decrease of oxidation potential by 200 mV. Under optimized flow parameters, working potential, gasket thickness, sample and reaction coil volumes, and flow rate, the developed flow system gave a linear response from 5 to 75 μmol/L of ascorbic acid. The calculated limit of detection was 4.5 μmol/L, calculated as 3σ/s which corresponds to the absolute value of 40 ng for the 50 μL sample coil. The precision for six consecutive injections of 5 and 75 μmol/L ascorbic acid solutions was determined as a relative standard deviation of 5.8 % and 1.5 %, respectively. The flow injection system enabled up to 120 analyses per hour. An optimized flow system was applied to the determination of ascorbic acid in dietary supplements, after simple preparation.

An optoelectronic flow-through detectors for active ingredients determination in the pharmaceutical formulations

An optoelectronic flow-through detector for active ingredients determination in pharmaceutical formulations is explained. Two consecutive compact photodetector’s devices operating according to light-emitting diodes-solar cells concept where the LEDs acting as a light source and solar cells for measuring the attenuated light of the incident light at 180˚ have been developed. The turbidimetric detector, fabricated of ten light-emitting diodes and five solar cells only, integrated with a glass flow cell has been easily adapted in flow injection analysis manifold system. For active ingredients determination, the developed detector was successfully utilized for the development and validation of an analytical method for warfarin determination in pure and pharmaceutical preparations. The developed method is based on the forming of a white, turbid product as a result of a reaction between the warfarin and semicarbazide which was used as an oxidizing agent. The developed flow-through detector system is semi mechanized, economic in materials consumption, easy to operate and characterized by excellent analytical results. Both developed analytical devices used in two channels flow injection system allow for turbidimetric measurements of warfarin in 0.9–154 μg ml−1 and 123–1600 μg ml−1 ranges of concentration, with limits of detections 0.73 μg ml−1 and 24.66 μg ml−1 for photodetectors 1& 2 respectively. The turbidity measurement procedure for the current flow system offers to conduct 60 tests per hour of the warfarin which is the most needs of quality control analysis in industrial applications. To ensure the analytical usefulness of the flow system, the warfarin has been analyzed in the real samples with a fully acceptable agreement and a correlation between the results offered by the developed flow system and the official method.

Temperature-dependent schlieren effect in liquid flow for chemical analysis

In flow analysis, such as flow injection analysis, liquid lens is formed at the boundary between two adjacent liquid media which have different refractive indices. Light refraction at the liquid interface gives the so-called ‘schlieren signal’. Schlieren effect is both concentration-dependent and temperature-dependent. In this work, the schlieren signal from temperature difference was quantitatively investigated for application in enthalpimetric measurement. The schlieren phenomena was then exploited for chemical analysis. A thermal insulated single flow line manifold was constructed using deionized water at 23 °C as the carrier. Deionized water at various temperatures in the range of 5–85 °C was injected into the carrier flow. A correlation between the schlieren signal and sample temperature was observed. A heat exchanger unit (HEU), consisting of a small volume glass-reaction chamber with a surrounding water jacket, was constructed. The unit was thermally insulated in a double layer cylindrical PVC unit. For demonstrating the applicability of temperature-dependent schlieren effect in chemical analysis, the exothermic oxidation reaction between acid dichromate and ethanol or ascorbic acid was employed with heat transferring to the surrounding water layer. When an aliquot of water from the HEU is injected into the constant temperature flow line the observed schlieren signal was dependent on the analyte concentration. Linear calibration (r2 > 0.99) were obtained covering the concentration range of ethanol and ascorbic acid as found in samples. The developed flow system provides good precision (RSD < 5%) with sample throughput of 4 sample h−1. The system were applied to the determination of ethanol in Thai white spirit and ascorbic acid in vitamin C tablets, respectively. The quantitative results obtained from the schlieren method were in agreement with the comparative methods.

Development of gas flow reactor with on-line monitoring system for nitrogen dioxide removal

In this work, a new flow system was developed for investigating the efficiency of synthesized TiO2 photocatalysts for NO2 degradation. The system consists of two parts: the gas flow reactor and an on-line NO2 monitoring system. The latter is based on the conversion of NO2(g) to NO2−(aq) with subsequent spectrophotometric detection of the nitrite anion by the Griess-Saltzman reaction. Simplex optimization was employed to obtain the required sensitivity for the NO2 monitoring. The developed flow system was employed to measure the catalytic efficiency of photodegradation of NO2 by various types of TiO2-based synthesized photocatalysts and a commercial TiO2 photocatalyst, ‘P25’. The TiO2 photocatalysts were synthesized using titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT) and titanium oxysulfate (TiOSO4) as precursors. Glass beads, coated with the TiO2 photocatalyst, were packed in a quartz tube reactor. Standard NO2 gas mixture (50ppmv) was continuously flowed through the reactor under UV radiation. Residual NO2 from the outlet of the reactor was measured using the on-line NO2 monitoring system which employs a gas diffusion unit and an acceptor stream of triethanolamine solution. The NO2(g) was converted into NO2−(aq) which was measured spectrophotometrically at 540nm using the Griess-Saltzman reaction. The photocatalytic efficiency of the synthesized photocatalysts was compared. The effects of oxygen and humidity were also studied in order to investigate the mechanism of photodegradation of NO2by the TiO2 catalyst. We observed that at low humidity (12% RH), the OH• radical generated from moisture plays an important role for photooxidation process of NO2.

Optimization of sodium extraction from soil by using a central composite design (CCD) and determination of soil sodium content by ion selective electrodes

Rapid determination of sodium (Na) ions in soil samples using ion selective electrodes (ISE) was investigated in this study. The compatibility of ISEs with soil extraction solution is a challenging subject as various effects such as pH, ionic strength and other interferences have to be considered as well as efficiency of the extraction solution. Because almost every type of sodium salt is soluble in water, and the pH of water is suitable for ISE studies, it was chosen as the soil extractant. Firstly, the extraction parameters were optimized by using a central composite design (CCD), secondly thirty agricultural soil samples were extracted with water and the extracts were measured by Na-ISE in a previously developed flow system. The results were compared with ion chromatography (IC) as the reference method, and the regression analysis between IC and ISE results yielded a high correlation (R² = 0.9408). It was concluded that, ion selective electrodes can be used with water as an extraction solution for rapid determination of sodium in soil samples.

Formaldehyde vapor produced from hexamethylenetetramine and pesticide: Simultaneous monitoring of formaldehyde and ozone in chamber experiments by flow-based hybrid micro-gas analyzer

Simultaneous analysis of HCHO and O3 was performed by the developed flow analysis system to prove that HCHO vapor is produced from solid pesticide in the presence of O3. HCHO is produced in many ways, including as primary emissions from fuel combustion and in secondary production from anthropogenic and biogenic volatile organic compounds by photochemical reactions. In this work, HCHO production from pesticides was investigated for the first time. Commonly pesticide contains surfactant such as hexamethylenetetramine (HMT), which is a heterocyclic compound formed from six molecules of HCHO and four molecules of NH3. HMT can react with gaseous oxidants such as ozone (O3) to produce HCHO. In the present study, a flow analysis system was developed for simultaneous analysis of HCHO and O3, and this system was used to determine if solid pesticides produced HCHO vapor in the presence of O3. HMT or the pesticide jimandaisen, which contains mancozeb as the active ingradient and HMT as a stabilizer was placed at the bottom of a 20-L stainless steel chamber. Air in the chamber was monitored using the developed flow system. Analyte gases were collected into an absorbing solution by a honeycomb-patterned microchannel scrubber that was previously developed for a micro gas analysis system (μGAS). Subsequently, indigotrisulfonate, a blue dye, was added to the absorbing solution to detect O3, which discolored the solution. HCHO was detected after mixing with the Hantzsch reaction reagent. Both gases could be detected at concentrations ranging from parts per billion by volume (ppbv) to 1000ppbv with good linearity. Both HMT and jimandaisen emitted large amount of HCHO in the presence of O3.

RETRACTED ARTICLE: High Pulsatility Flow Promotes Vascular Fibrosis by Triggering Endothelial EndMT and Fibroblast Activation.

Vascular fibrosis, the formation of excess fibrous tissue on the blood vessel wall, is characterized by unmitigated proliferation of fibroblasts or myofibroblast-like cells exhibiting α-smooth-muscle-actin in vessel lumen and other vascular layers. It likely contributes to vascular unresponsiveness to conventional therapies. This paper demonstrates a new flow-induced vascular fibrosis mechanism. Using our developed flow system which simulates the effect of vessel stiffening and generates unidirectional high pulsatility flow (HPF) with the mean shear flow at a physiological level, we have shown that HPF caused vascular endothelial dysfunction. Herein, we further explored the role of HPF in vascular fibrosis through endothelial-to-mesenchymal transdifferentiation (EndMT). Pulmonary arterial endothelial cells (ECs) were exposed to steady flow and HPF, which have the same physiological mean fluid shear but different in flow pulsatility. Cells were analyzed after being conditioned with flows for 24 or 48h. HPF was found to induce EndMT of cells after 48h stimulation; cells demonstrated drastically decreased expression in EC marker CD31, as well as increased transforming growth factor β, α-SMA, and collagen type-I, in both gene and protein expression profiles. Using the flow media from HPF-conditioned endothelial culture to cultivate arterial adventitial fibroblasts (AdvFBs) and ECs respectively, we found that the conditioned media respectively enhanced migration, proliferation and α-SMA expression of AdvFBs, and induced EndMT of ECs. It was further revealed that cells exposed to HPF exhibited much higher percentage of caspase-positive cells compared to those exposed to steady flow. Apoptotic cells together with remaining, caspase-negative cells suggested the presence of apoptosis-resistant dysfunctional ECs which likely underwent EndMT process and perpetuated fibrosis throughout vascular tissues. Therefore, our results indicate that prolonged HPF stimuli induce vascular fibrosis through triggering EndMT and EC-mediated AdvFB activation and migration, which follows initial endothelial inflammation, dysfunction and apoptosis.

Determination of europium(III) in environmental samples using a flow injection analysis system with on-line preconcentration and spectrophotometric detection

A simple and accurate flow injection analysis system coupled with spectrophotometric detector was developed for preconcentration and determination of europium(III) in aqueous samples. The developed flow system includes a europium preconcentration step in a column packed with Amberlite XAD-4 resin impregnated with nalidixic acid at pH 7.0. The europium complex was desorbed from the resin by 0.1 mol L−1 HCl and mixed with arsenazo-III solution (0.05 % solution in 0.1 mol L−1 HCl) and taken to the flow through cell of spectrophotometer where its absorbance was measured at 661 nm. The optimum preconcentration system, chemical and FIA variables were investigated. The preconcentration factors obtained were 115 and 500, detection limits of 0.43 and 0.1 μg L−1, sample throughputs of 40 and 10 were obtained for preconcentration time of 60 and 300 s respectively. The proposed system showed good precision and accuracy with relative standard deviation of 1.5 %. The method has been applied to the determination of europium(III) in real water samples and certified reference material IAEA-SL-1 (Lake sediment).

PH-sensitive spectrophotometric control of nilutamide in an automatic micro-flow system

The drug nilutamide belongs to the pharmacological group of antiandrogens, clinically used to prevent tumor development observed in the first phase of the administration of analogues of gonadotrophin-releasing hormone in patients with prostate cancer. Due to the high toxicity of this drug, the chemical control in pharmaceutical formulations is extremely important. The aim of this work was to develop an automatic procedure, based on flow analysis, for the quantification of the drug nilutamide that could constitute a simpler alternative for routine quality control in industry that is normally performed by a chromatographic method. A new, very simple and high-throughput methodology was developed based on the spectrophotometric monitoring of the drug at the wavelength of 438 nm in a solution of sodium hydroxide, the only reagent used in this method. It was verified through spectrophotometric studies that by varying the pH conditions, electronic transitions from bonding orbitals π to anti-bonding orbitals π* occur in the molecular structure of nilutamide. In this work, the potentialities of the pulsed flow in the multipumping methodology were exploited taking into account the high viscosity of the sodium hydroxide solutions that impaired the flow of reagents and the development of reaction was expedited through a stopped-flow approach. The developed flow system allowed us to perform 24 determinations per hour, and the limit of detection was 2.26 mg L−1.

New membraneless vaporization unit coupled with flow systems for analysis of ethanol

This work presents the development of a new design for a membraneless vaporization (MBL-VP) unit, called dual chamber MBL-VP for measurement of volatile compounds. With this unit, exact volumes of sample and reagent are introduced into their respective cone-shaped chambers from the base of the cones. Diffusion of volatile analyte then takes place. After an appropriate time interval, the acceptor solution is withdrawn from the chamber into the detector flow-cell, while the sample solution is withdrawn to waste. Unlike the previous MBL-VP design, problems with overflow of solutions are eliminated by precise control of the input volume to be less than the volume of the chamber. The developed flow system with the dual chamber MBL-VP unit was applied to the determination of the ethanol content of various liquid samples, using the oxidation reaction between potassium dichromate and the diffused ethanol. In addition, in order to accelerate the gas diffusion process, the donor chamber was aerated. As the result, relatively short analysis time of 144s was achieved for ethanol content in the range of 5–50% (v/v). The proposed method was successfully validated against a gas chromatographic method for 17 alcoholic samples. Percentage recovery was in the range of 96–109%.

Endothelial Cell Sensing of Flow Direction

Atherosclerosis-prone regions of arteries are characterized by complex flow patterns where the magnitude of shear stress is low and direction rapidly changes, termed disturbed flow. How endothelial cells sense flow direction and how it impacts inflammatory effects of disturbed flow are unknown. We therefore aimed to understand how endothelial cells respond to changes in flow direction. Using a recently developed flow system capable of changing flow direction to any angle, we show that responses of aligned endothelial cells are determined by flow direction relative to their morphological and cytoskeletal axis. Activation of the atheroprotective endothelial nitric oxide synthase pathway is maximal at 180° and undetectable at 90°, whereas activation of proinflammatory nuclear factor-κB is maximal at 90° and undetectable at 180°. Similar effects were observed in randomly oriented cells in naive monolayers subjected to onset of shear. Cells aligned on micropatterned substrates subjected to oscillatory flow were also examined. In this system, parallel flow preferentially activated endothelial nitric oxide synthase and production of nitric oxide, whereas perpendicular flow preferentially activated reactive oxygen production and nuclear factor-κB. These data show that the angle between flow and the cell axis defined by their shape and cytoskeleton determines endothelial cell responses. The data also strongly suggest that the inability of cells to align in low and oscillatory flow is a key determinant of the resultant inflammatory activation.

Reagent-free analytical flow methods for the soft drink industry: Efforts for environmentally friendly chemical analysis

The evolution of an entirely green analytical system for industrial quality control of carbonated drinks is described. The developed flow system is capable of providing analytical data of the dissolved CO2, sucrose, and color of a sample consecutively in real-time. The system has been carefully designed on the basis of “reagent-free”, meaning that no added chemicals are required for the analysis. The system first vaporizes CO2 from the soft drink in a gas–liquid separation chamber, with a channel for a flow of pure water as the CO2 acceptor. The dissolved CO2 alters the conductivity of the water stream, which is directly related to the concentration of CO2 in the soft drink. The sucrose content is measured based on the “schlieren effect”, the sample plug flows out of the vaporization chamber into a colorimeter with a near-infrared/light-emitting diode (NIR/LED) as light source. The schlieren effect arises at the boundary of pure water and soft drink with refraction of light in proportion to the sugar concentration. The system also measures the absorbance of the sample using an RGB-LED. The related principles and preliminary experiments as proof of concept are described as well as the construction of the flow system for this completely reagent-free analyzer. A simple flow injection system using the schlieren effect was also developed for rapid quantitative analysis of sugar in noncarbonated soft drinks.

Computer controlled-flow injection potentiometric system based on virtual instrumentation for the monitoring of metal-biosorption processes

A completely automated flow-injection system was developed for the monitoring of biosorption studies of Cu(II) ion on vegetable waste by-products. The system employed flow-through Cu(II)-selective electrodes, of epoxy-resin-CuS/Ag 2S heterogeneous crystalline type, and computer controlled pumps and valves for the flow operation. Computer automation was done through a specially devised virtual instrument, which commanded and periodically calibrated the system, allowing for the monitoring of Cu(II) ions between 0.6 and 6530 mg L −1 at a typical frequency of 15 h −1. Grape stalk wastes were used as biosorbent to remove Cu(II) ions in a fixed-bed column with a sorption capacity of 5.46 mg g −1, obtained by the developed flow system, while the reference determination performed by FAAS technique supplied a comparable value of 5.41 mg g −1.

A Multicommutated Flow System Based on an Opened‐Loop with Micropump Propulsion

A multicommutated flow system using an opened‐loop configuration and incorporating micropump propulsion was developed and applied in the determination of highly concentrated species in wastewater samples. The developed flow system enabled a suitable dilution level to be attained and continuously monitoring of the analytical process. A synergetic effect was also obtained with the continuous removal of the dispersed front and trailing zones of the sample plug. The developed strategy was evaluated on the determination of iron in high concentrated wastewater samples without any pre‐treatment. The continuous sample recirculation permitted an increase in linear range up to 10 g · l−1.

Determination of Rh, Pd and Pt in urine samples using a pre-concentration sequential injection analysis system coupled to a quadrupole-inductively coupled plasma-mass spectrometer

The proposed flow system was developed in order to minimize the drawbacks related to the PGEs determination by quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS). It was intended not only to lower the limits of detection (LODs) but also to eliminate the interferences originating from some atomic and molecular ions produced in the argon plasma. This was accomplished by means of an on-line sample clean-up/pre-concentration step, using a chelating resin (Metalfix™ Chelamine™) in which Rh, Pd and Pt were preferably retained when compared with the interfering species. The results obtained by using the developed flow system in the analysis of urine samples are presented. With a sampling rate of 9 samples h −1 (i.e., 27 determinations) and a sample consumption of ca. 10 mL, the developed flow system allowed linear calibration plots up to 100 ng L −1 with detection limits of 1.2 ng L −1 (Rh), 0.4 ng L −1 (Pd) and 0.9 ng L −1 (Pt). Repeatability studies showed good precision (R.S.D.%, n = 5): 3.7% (Rh); 2.6% (Pd) and 2.4% (Pt), for 10 ng L −1; 2.4% (Rh); 1.4% (Pd) and 1.9% (Pt), for 50 ng L −1; and 1.3% (Rh); 0.58% (Pd) and 0.62% (Pt), for 100 ng L −1. By spiking human urine samples, recovery tests were performed, and the values obtained ranged between 89% and 105% (Rh); 90% and 104% (Pd); and 93% and 105% (Pt).

Automatic flow system for the sequential determination of copper in serum and urine by flame atomic absorption spectrometry

In this work, a fully automated flow system exploiting the advantages of the association of multi-pumping, multicommutation, binary sampling and merging zones, to accomplish the sequential determination of copper in serum and urine by flame atomic absorption spectrometry, is described. The developed flow system allowed multiple tasks, such as serum samples preparation (samples and standard solutions viscosity adjustment), serum copper (SCu) measurement, urine copper (UCu) pre-concentration and its subsequent elution and measurement, to be carried out sequentially. The implemented flow manifold presented a modular configuration consisting on two quasi-independent modules, each one accountable for a specific sample manipulation and whose combined operation under computer control enabled the determination of copper in a wide concentrations range. Once optimised and with a sample consumption of about 0.250 mL of serum and 7 mL of urine, the developed flow system allowed linear calibration plots up to 5 mg L −1 with a detection limit of 0.035 mg L −1 for SCu and linear calibration plots up to 300 μg L −1 with a detection limit of 0.67 μg L −1 for UCu. The sampling rate varied according to the module employed and was about 360 determinations h −1 (SCu module), 12 determinations h −1 (UCu module) or 24 determinations h −1 (12 urine and 12 serum samples; UCu and SCu modules simultaneously). Repeatability studies (R.S.D.%, n = 10) showed good precision for UCu at concentrations of 25 μg L −1 (2.54%), 50 μg L −1 (0.90%) and 100 μg L −1 (1.62%) as well as for SCu at concentrations of 0.25 mg L −1 (8.11%), 1 mg L −1 (3.11%) and 5 mg L −1 (0.90%). A comparative evaluation showed a good agreement between the results obtained in the analysis of UCu and SCu ( n = 18) by both the developed methodology and the reference procedures. Accuracy was further evaluated by means of the analysis of reference samples (Seronorm™ Trace Elements Urine and Seronorm™ Trace Elements Serum) and the obtained results complied with the certified values.

Flow Injection Potentiometric System for the Simultaneous Determination of Inositol Phosphates and Phosphate: Phosphorus Nutritional Evaluation on Seeds and Grains

A simple flow injection potentiometric (FIP) system, which uses a tubular cobalt electrode, has been developed for phosphorus nutritional evaluation of seeds and grains. Inorganic phosphorus, P(i), is determined using a 1 x 10(-2) mol.L(-1) potassium phthalate buffer solution adjusted at pH 4. A sensitivity of 47 mV/decade and an operating range from 10 to 1000 mg.L(-1) (1 x 10(-4)-1 x 10(-2) M) of dihydrogen phosphate are obtained. The inositol phosphates amount, which is referred to the organic phosphorus, P(org), is directly determined from extracts using a 1 x 10(-2) mol.L(-1) Tris-HCl buffer solution adjusted at pH 8. A sensitivity of 127 mV/decade and an operating range of 10-1000 mg.L(-1) (2.5 x 10(-4)-5 x 10(-3) M) of P(org) (expressed as inositol hexakisphosphoric acid monocalcium) are achieved. Some samples of seed and grain are analyzed by an ICP-OES and a spectrophotometric method to compare results to the developed flow system; no significant differences at the 95% confidence level are observed using a paired t test. Other samples such as animal nursing feed, soybean meal, and corn are also analyzed with the proposed FIP system, showing a good correlation to the ICP-OES values.

A flow system for the spectrophotometric determination of lead in different types of waters using ion-exchange for pre-concentration and elimination of interferences

A flow system for the spectrophotometric determination of lead in natural and waste waters is proposed. The determination is based on the colorimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between those reagents and lead cations. The developed flow system includes a lead pre-concentration step in a column packed with a cationic resin (Chelex 100) operating in a sequential injection mode. To improve the mixture of sample and reagents, a flow injection approach was adopted for the colorimetric determination. This way a hybrid flow system, involving both sequential and flow injection concepts was designed. Another feature of the proposed system is the efficient elimination of major interferent species, such as cadmium and copper. The elimination of cadmium interference is obtained by complexing Cd 2+ with chloride and retaining the formed negatively charged complexes in an anionic resin, AG1 X-8. As for copper, with the presence of both ionic resins as well as the conditions for cadmium elimination, it no longer acts as an interferent. Different ranges of lead concentration (50–300 and 300–1000 μg l −1) can be determined with minor changes in the controlling software, useful for application to both natural and waste waters. Therefore, a detection limit of 25 μg l −1 was achieved. Repeatability was evaluated from 10 consecutive determinations being the results better than 4%. The recoveries of lead spikes added to the samples ranged from 93 to 102%. The sampling frequency was 17 and 24 determinations per hour, for 50–300 and 300–1000 μg l −1 ranges, respectively.

Sampling strategies exploiting multi-pumping flow systems.

In this work new strategies were exploited to implement multi-pumping flow systems relying on the utilisation of multiple devices that act simultaneously as sample-insertion, reagent-introduction, and solution-propelling units. The solenoid micro-pumps that were initially used as the only active elements of multi-pumping systems, and which were able to produce pulses of 3 to 25 microL, were replaced by syringe pumps with the aim of producing pulses between 1 and 4 microL. The performance of the developed flow system was assessed by using distinct sample-insertion strategies like single sample volume, merging zones, and binary sampling in the spectrophotometric determination of isoniazid in pharmaceutical formulations upon reaction with 1,2-naphthoquinone-4-sulfonate, in alkaline medium. The results obtained showed that enhanced sample/reagent mixing could be obtained with binary sampling and by using a 1 microL per step pump, even in limited dispersion conditions. Moreover, syringe pumps produce very reproducible flowing streams and are easily manipulated and controlled by a computer program, which is greatly simplified since they are the only active manifold component. Linear calibration plots up to 18.0 microg mL(-1), with a relative standard deviation of less than 1.48% (n=10) and a throughput of about 20 samples per hour, were obtained.

Cardiovascular tissue engineering: a new laminar flow chamber for in vitro improvement of mechanical tissue properties.

A new in vitro flow system was developed to investigate the impact of laminar flow on extracellular matrix formation and tissue development. The dynamic in vitro system was designed to provide a cross flow arrangement of main flow induced by a dialysis roller pump (500 ml/min), and nutrition flow by a perfusion pump (3 ml/hr). Poly-L-lysine precoated polyglycolic acid (PGA) scaffolds (3.14 cm2) were seeded with myofibroblasts of human aortic origin (3.0 x 10(6) cells/ mesh) and incubated for 14 days under static conditions. The tissue was exposed to shear stress over a time period of 14 days (n = 4). The control group was seeded under static conditions (n = 4). To obtain a CO2 independent medium, 25 mM HEPES and 1 mM bicarbonate buffer was supplemented to modified MEM without bicarbonate. Gas samples were collected from the medium, and hydroxyproline assay was performed as a marker of collagen production. The newly developed flow system maintained stable cell culture conditions, with the hydroxyproline concentration significantly higher in group F (p < 0.05). These preliminary experiences with a new in vitro tissue culture system demonstrate the feasibility of using flow induced mechanical stress to enhance extracellular matrix formation.