Presence Of Microbubbles Research Articles

Aphron properties and application of surfactant drilling fluids in depleted reservoirs

Aphron drilling fluids (ADFs) are finding increasing application in science engineering fields because of their distinctive characteristic. As the interest in the application of aprons-based fluids continues to grow, there is a decisive need to advance a deeper understanding of the factors affecting their behavior and properties, especially for successful petroleum industries, such as drilling depleted reservoirs and production. This study delves into investigating the density, rheological behavior and properties, filtration properties, bubble size, and their distribution of Aphrons-drilling fluids utilizing two ionic surfactants. Sodium Dodecyl Benzene Sulfate (SDBS) as an anionic surfactant, Cetyl Trimethyl Ammonium Bromide (CTAB) as a cationic surfactant, described as environmentally friendly, in Iraqi depleted reservoirs drilling. With an emphasis on the concentrations balance between Aphron generator (SDBS) and Aphron stabilizer (CTAB), the study analyzes the behavior and characteristics of Aphron drilling fluid. The investigation demonstrates that adding SDBS and CTAB reduces system density by 28%, owing to microbubbles production which is utilized with near-balance drilling. Rheological testing reveals that shear-thinning behavior in all Aphron samples improved, and the presence of SDBS affects the fluid's internal friction, gel strength, and short-term gel structure. Filtering control characteristic study demonstrates that the presence of microbubbles significantly minimizes fluid loss by 33% with 0.20% SDBS during filtering. Bubble size and dispersion studies demonstrate that 0.20% SDBS concentration, along with 0.30% CTAB, gives the best microbubble size and distribution. These findings suggest that Aphron fluids will be a promising innovation in petroleum industries, during actual drilling operations in Iraqi depleted oilfields.

Effects of microbubbles and frother types on first-order flotation kinetics of coarse quartz: a Box–Behnken design study

ABSTRACT This study utilised a Box–Behnken experimental design to examine the influence of various frothers (MIBC, 2-Ethylhexanol, α-Terpineol, and AF-65), dodecylamine (DDA) collector, and microbubbles on coarse quartz flotation performance. The flotation efficiency was evaluated through two key parameters: maximum recovery (R∞) and first-order rate constant (k). The findings revealed that microbubbles substantially enhanced flotation kinetics through synergistic interactions, particularly in combination with aliphatic alcohol frothers. The effectiveness of cyclic alcohol and polyglycol-type frothers varied significantly, depending on microbubble presence, frother concentration, and DDA interactions. While 2-Ethylhexanol achieved the highest recovery (97.71%) in conventional flotation without microbubbles, α-Terpineol exhibited the most pronounced synergistic effect when combined with microbubbles and DDA, reaching 99.71% recovery. In terms of kinetic performance, AF-65 demonstrated exceptional results in the presence of microbubbles and DDA, achieving the highest rate constant of 2.12 min−1. The effectiveness of the bubble bridging mechanism showed considerable variation across different frother types, with aliphatic alcohols exhibiting notable improvements in the presence of microbubbles, particularly at lower concentrations. Although increased DDA concentrations generally resulted in decreased flotation rates, they enhanced overall recovery – an effect that was further amplified by the presence of microbubbles.

Transient Perivascular Inflammation of the Carotid Artery Syndrome: A Case Report with Diagnostic Insights from Vessel Wall Imaging and Contrast-enhanced Ultrasonography

Transient perivascular inflammation of the carotid artery (TIPIC) syndrome is a rare disease accompanied by acute neck pain and specific pathologic changes in the carotid artery and surrounding tissue. Here, we present a case diagnosed with typical imaging features, including extensive enhancement with luminal narrowing on vessel wall imaging and the presence of microbubbles on contrast-enhanced ultrasonography. These findings provide valuable insights into the pathophysiology of TIPIC syndrome and importance of imaging modalities for early detection and management.

The molecular impact of sonoporation: A transcriptomic analysis of gene regulation profile

Sonoporation has long been known to disrupt intracellular signaling, yet the involved molecules and pathways have not been identified with clarity. In this study, we employed whole transcriptome shotgun sequencing (RNA-seq) to profile sonoporation-induced gene responses after membrane resealing has taken place. Sonoporation was achieved by microbubble-mediated ultrasound (MB-US) exposure in the form of 1 MHz ultrasound pulsing (0.50 MPa peak negative pressure, 10 % duty cycle, 30 s exposure period) in the presence of microbubbles (1:1 cell-to-bubble ratio). Using propidium iodide (PI) and calcein respectively as cell viability and cytoplasmic uptake labels, post-exposure flow cytometry was performed to identify three viable cell populations: 1) unsonoporated cells, 2) sonoporated cells with low uptake, and 3) sonoporated cells with high uptake. Fluorescence-activated cell sorting was then conducted to separate the different groups followed by RNA-seq analysis of the gene expressions in each group of cells. We found that sonoporated cells with low or high calcein uptake showed high similarity in the gene responses, including the activation of multiple heat shock protein (HSP) genes and immediate early response genes mediating apoptosis and transcriptional regulation. In contrast, unsonoporated cells exhibited a more extensive gene expression alteration that included the activation of more HSP genes and the upregulation of diverse apoptotic mediators. Four oxidative stress-related and three immune-related genes were also differentially expressed in unsonoporated cells. Our results provided new information for understanding the intracellular mobilization in response to sonoporation at the molecular level, including the identification of new molecules in the sonoporation-induced apoptosis regulatory network. Our data also shed light on the innovative therapeutic strategy which could potentially leverage the responses of viable unsonoporated cells as a synergistic effector in the microenvironment to favor tumor treatment.

Ultrasound-compatible 3D-printed Franz diffusion system for sonophoresis with microbubbles

Sonophoresis is a topical drug delivery approach that utilises ultrasound as a physical stimulus to enhance permeation of active pharmaceutical ingredients through the skin. Only limited research has however been conducted to evaluate the potential of ultrasound-responsive drug carriers, such as gas microbubbles, in sonophoresis. Franz diffusion cells have been extensively used for measuring drug permeation in vitro; however, traditional systems lack compatibility with ultrasound and only limited characterisation of their acoustical behaviour has been carried out in previous research. To overcome this limitation, we designed and manufactured a novel Franz cell donor compartment coupled with a conventional glass receptor, and performed a functional characterisation of the assembly for application in sonophoresis with ultrasound-responsive agents (specifically imiquimod-loaded gas microbubbles). The donor was fabricated using a photoreactive resin via 3D printing and was designed to enable integration with a therapeutically relevant ultrasound source. The assembly was capable of effectively retaining liquids during prolonged incubation and the absorption of imiquimod onto the 3D-printed material was comparable to the one of glass. Moreover, a predictable ultrasound field could be generated at a target surface without any significant spatial distortion. Finally, we demonstrated applicability of the developed assembly in sonophoresis experiments with StratM®, wherein ultrasound stimulation in the presence of microbubbles resulted in significantly enhanced drug permeation through and partitioning within the membrane (2.96 ± 0.25 μg and 3.84 ± 0.39 μg) compared to passive diffusion alone (1.74 ± 0.29 μg and 2.29 ± 0.32 μg), over 24 h.

Mesenchymal stem cell cryopreservation with cavitation-mediated trehalose treatment

Dimethylsulfoxide (DMSO) has conventionally been used for cell cryopreservation both in research and in clinical applications, but has long-term cytotoxic effects. Trehalose, a natural disaccharide, has been proposed as a non-toxic cryoprotectant. However, the lack of specific cell membrane transporter receptors inhibits transmembrane transport and severely limits its cryoprotective capability. This research presents a method to successfully deliver trehalose into mesenchymal stem cells (MSCs) using ultrasound in the presence of microbubbles. The optimised trehalose concentration was shown to be able to not only preserve membrane integrity and cell viability but also the multipotency of MSCs, which are essential for stem cell therapy. Confocal imaging revealed that rhodamine-labelled trehalose was transported into cells rather than simply attached to the membrane. Additionally, the membranes were successfully preserved in lyophilised cells. This study demonstrates that ultrasonication with microbubbles facilitated trehalose delivery, offering promising cryoprotective capability without the cytotoxicity associated with DMSO-based methods.

Comparison of the Application Value of Transthoracic Echocardiography in Diagnosing Patent Foramen Ovale Under Different States of Stimulation: A Retrospective Study.

This study aims to evaluate the application value of contrast-enhanced transthoracic echocardiography (cTEE) in the diagnosis of patent foramen ovale (PFO) under different states of stimulation, with the goal of enhancing the accuracy and efficiency of PFO diagnosis. This research consecutively enrolled patients suspected of having PFO from October 2022 to February 2024, presenting primary clinical symptoms such as unexplained syncope, headache, dizziness, and stroke. Patients underwent standard transthoracic echocardiography (TTE) and cTEE under three different states of stimulation (resting state, coughing, and Valsalva maneuver). Based on the presence of microbubbles in the left heart and their initial appearance time, patients were classified into PFO and control groups, with further diagnostic confirmation via transesophageal echocardiography (TEE) or foramen ovale closure procedures. The study results revealed significant differences between the PFO and control groups regarding age (p = 0.034) and headache symptoms (p = 0.001). In the PFO group, TTE showed a higher positivity rate both at rest and during coughing, highlighting the association between PFO and specific clinical symptoms. The number of microbubbles observed during TTE increased significantly under various stimulation states, particularly during the Valsalva maneuver (p < 0.05). This increase became more pronounced as the duration of the maneuver was extended, underscoring the differential response of PFO patients under varied physiological testing conditions, especially during prolonged Valsalva maneuvers. The study confirms the significant value of cTEE in diagnosing PFO under different stimulation states, particularly emphasizing the application of the Valsalva maneuver to significantly improve the sensitivity and specificity of PFO detection. Thus, incorporating cTEE examinations under various stimulation states holds significant clinical importance for enhancing the accuracy and efficiency of PFO diagnosis.

Experimental study on the disturbance of microbubble liquid jets

The presence of microbubble significantly influences the rheological properties of a jet, thereby considerably increasing the complexity of the jet instability problem. However, the instability of microbubble jets has been rarely studied, and their breakup mechanism remains obscure. The present study was focused on conducting a comprehensive analysis of bubble jet flows. A high-precision experimental system was constructed to extract the time-series signals of each cross-sectional profile along the axial direction of a jet. Glycerol solutions with three different bubble volume fractions were prepared, and the standard deviation, spectral relationship, and nonlinear dynamical behavior (i.e., autocorrelation, phase space trajectory, Poincaré section, and Lyapunov exponent) were studied. The detailed development process of small surface disturbances in space was assessed, and the influence of variations in the bubble volume fraction on the nonlinear dynamics of the jet was examined. The results demonstrate that microbubbles can significantly change the energy transfer relationship between various sections of a jet and enhance the periodicity of the signal.

Alzheimer's disease brain endothelial-like cells reveal differential drug transporter expression and modulation by potentially therapeutic focused ultrasound

The blood-brain barrier (BBB) has a key function in maintaining homeostasis in the brain, partly modulated by transporters, which are highly expressed in brain endothelial cells (BECs). Transporters mediate the uptake or efflux of compounds to and from the brain and they can also challenge the delivery of drugs for the treatment of Alzheimer's disease (AD). Currently there is a limited understanding of changes in BBB transporters in AD. To investigate this, we generated brain endothelial-like cells (iBECs) from induced pluripotent stem cells (iPSCs) with familial AD (FAD) Presenilin 1 (PSEN1) mutation and identified AD-specific differences in transporter expression compared to control (ctrl) iBECs. We first characterized the expression levels of 12 BBB transporters in AD-, Ctrl-, and isogenic (PSEN1 corrected) iBECs to identify any AD specific differences. We then exposed the cells to focused ultrasound (FUS) in the absence (FUSonly) or presence of microbubbles (MB) (FUS+MB), which is a novel therapeutic method that can be used to transiently open the BBB to increase drug delivery into the brain, however its effects on BBB transporter expression are largely unknown. Following FUSonly and FUS+MB, we investigated whether the expression or activity of key transporters could be modulated. Our findings demonstrate that PSEN1 mutant FAD (PSEN1AD) possess phenotypical differences compared to control iBECs in BBB transporter expression and function. Additionally, we show that FUSonly and FUS+MB can modulate BBB transporter expression and functional activity in iBECs, having potential implications on drug penetration and amyloid clearance. These findings highlight the differential responses of patient cells to FUS treatment, with patient-derived models likely providing an important tool for modelling therapeutic effects of FUS.

Preparation and performance of laminated anti‐fire glass using the K2O·nSiO2‐based ultrathin and flexible membrane

AbstractWe present a new method for synthesizing cold‐resistant laminated anti‐fire glass using a K2O·nSiO2‐based ultrathin flexible membrane, which is prepared by vacuum surface treatment method with ball‐milled core–shell SiO2 emulsion (55 wt%). We systemically characterize the mechanical, optical, rheological, cold‐resistant, fire‐resistant, and weather‐resistant performances of this glass. The formation mechanism of K2O·nSiO2‐based ultrathin membrane is studied in detail using multispeckle diffusing–wave spectroscopy and scanning electron microscopy. Then, the tensile strength, plasticity, and rheological behavior of the materials with different moduli are characterized. Combined with thermal gravity analysis, we characterize the compositions of K2O·nSiO2‐based materials with different moduli. For the K2O·nSiO2‐based ultrathin flexible membrane, the appearance of air‐conducting microchannels is designed, resembling the Wu Zhu coin morphology (a square hole circular coin in ancient China) or honeycomb wall morphology. These structures endow the visible region of the anti‐fire glass with a reduced presence of microbubbles. As a type of building safety glass, the spongelike microporous insulation layer can increase the heat‐insulating time in the event of a fire. Furthermore, the weather‐resistant performance of this glass is demonstrated to be more than 3000 h through an ultraviolet test. This work also provides a new routine for synthesizing high‐quality anti‐fire glass with different shapes, including curved surfaces.

Ultrasonic therapies for seizures and drug-resistant epilepsy.

Ultrasonic therapy is an increasingly promising approach for the treatment of seizures and drug-resistant epilepsy (DRE). Therapeutic focused ultrasound (FUS) uses thermal or nonthermal energy to either ablate neural tissue or modulate neural activity through high- or low-intensity FUS (HIFU, LIFU), respectively. Both HIFU and LIFU approaches have been investigated for reducing seizure activity in DRE, and additional FUS applications include disrupting the blood-brain barrier in the presence of microbubbles for targeted-drug delivery to the seizure foci. Here, we review the preclinical and clinical studies that have used FUS to treat seizures. Additionally, we review effective FUS parameters and consider limitations and future directions of FUS with respect to the treatment of DRE. While detailed studies to optimize FUS applications are ongoing, FUS has established itself as a potential noninvasive alternative for the treatment of DRE and other neurological disorders.

The effect of microbubbles on coarse particle anionic flotation: analysis and optimization

Since the grinding and chemical reagents required for flotation are expensive, coarse particle flotation reduces grinding costs and makes the subsequent process more accessible and cheaper. Recent studies suggest that the flotation of coarse particles using microbubbles has some advantages. However, a thorough analysis of the effectiveness of various flotation parameters and the impact of their interactions on the recovery of coarse particles in the presence and absence of microbubbles has yet to be fully understood. In the current study, the two-level factorial and Box-Behnken experimental designs were performed to characterize, assess, and optimize the implications of seven numerical (sodium oleate, collector; calcium oxide, activator; MIBC, frother; impeller speed; froth depth; pulp concentration; fine particles) and one categorical (microbubbles) independent parameters on the coarse quartz particles. Characterization revealed that froth depth did not significantly affect the flotation recovery of coarse particles in the mechanical laboratory cell. The effects of the variables in the presence of microbubbles revealed that sodium oleate and impeller speed significantly impacted recovery, followed by calcium oxide and fine particles, both of which had a medium influence, and MIBC and pulp concentration, which had a minimal impact. The recovery of coarse particles increased by 92.714% when microbubbles were used, compared to the estimated maximum recovery under ideal conditions of 62.258% without them. From this, it can be concluded that a high coarse particle flotation recovery is possible by optimizing the hydrodynamic conditions and the chemical environment using microbubbles.

MP-453088-3 PULSED FIELD ABLATION USING A NOVEL INSULATED ELECTRODE DESIGN REDUCES MICROBUBBLE FORMATION WHILE CREATING LARGE AND HOMOGENEOUS LESIONS IN VITRO

Pulsed Field ablation (PFA) is a promising strategy for treatment of cardiac arrhythmias. But there are unresolved issues pertaining to its safety and efficacy, specifically microbubbles and lesion homogeneity. Conventional electrode designs result in the ablation electrode surface to be largely in contact with blood, leading to electrolysis and microbubbles during PFA. Additionally, the blood in contact with the electrodes provides a conductive path for the energy, directing it away from the targeted tissue. This in turn can result in non-homogeneous application of energy, thereby, impacting lesion size and durability. We hypothesized that PFA using a novel ablation catheter with an insulated electrode design (Sirona Medical Technologies, SMT) (Figure), in vitro could achieve large, homogeneous lesions while minimizing microbubbles by reducing exposure to the blood path. In total, 18 single-shot, bipolar (2.2 kV) pulsed field applications were delivered using the SMT PFA catheter for 3, 6, and 10 bursts in a potato model. The potato model is considered a relevant and well-accepted model for in vitro study of irreversible electroporation (IRE) due to its similar response to IRE as mammalian cells. Applications were closely observed for presence of microbubbles. Lesion were assessed for thermal injury and the dimensions were analyzed and reported (diameter x depth) 24 h post-ablation. There was no discernible microbubbling observed during PFA at 20 pulses/burst, and only minor microbubbling was encountered at 40 and 60 pulses/bursts. All the lesions were large and homogeneous. With 3 bursts of PFA, lesions measured 7 mm x 3 mm (20 pulses/burst), 10 mm x 4 mm (40 pulses/burst), and 12 mm x 4 mm (60 pulses/burst), respectively. With 6 bursts of PFA, lesions measured 14 mm x 5 mm (20 pulses/burst), 15 mm x 6 mm (40 pulses/burst), and 17 mm x 6 mm (60 pulses/burst), respectively. Lastly, with 10 bursts of PFA, lesions measured 18 mm x 8 mm (20 pulses/burst), 19 mm x 9 mm (40 pulses/burst), and 21 mm x 10 mm (10 pulses/burst), respectively. As such, there was a direct dose response as a function of the number of pulses/burst and the duration of applications. Furthermore, there was no evidence of thermal injury. PFA with the SMT catheter utilizing a novel, insulated electrode design in vitro can create large, homogenous lesions with no discernible/minimal microbubbles. These findings have significant safety and efficacy implications.

Inactivation and removal of Klebsiella michiganensis biofilm attached to the inner surfaces of piping by plasma-activated microbubble water (PMBW)

Plasma-activated microbubble water (PMBW) is an environmentally friendly sanitizer that possesses potent antimicrobial activities and imparts substantial shear stress to food contact surfaces. In this study, PMBW, plasma-activated water (PAW), microbubble water (MBW), and chlorine water (100 mg/L) were used to clean PVC tubing inoculated by Klebsiella michiganensis. The sanitizer flow with microbubble was numerically simulated by COMSOL Multiphysics® and the shear stress imparted to the bacteria was calculated. The presence of microbubbles in the flow increased the shear stress imparted to the bacteria. The number of K. michiganensis on the inner surfaces of the pipes was ∼7.4 log CFU/cm2 before washing. PMBW showed the most potent antimicrobial effect, which reduced the number of bacteria by 3.1 log CFU/cm2 at a flow velocity of 1 m/s. PAW, MBW, and chlorine water reduced a similar number of bacteria (2.4 log CFU/ cm2 to 2.6 log CFU/ cm2) at all the selected flow velocities. DI water only reduced the number of K. michiganensis by 0.7 log CFU/ cm2 at 1 m/s flow velocity. Industrial relevancePMBW can potentially be an environmentally friendly sanitizer, which can be employed by food processors to clean their food processing equipment with minimized usage of chemical sanitizers. The technology developed in this study will benefit the food industry by mitigating potential risks of foodborne pathogens without generating environmental hazards.

Characterization of a Modular Microfluidic Section for Seeded Nucleation in Multiphase Flow

We present a proof-of-concept modular nucleation section for seeded multiphase flow crystallization of an active pharmaceutical ingredient. The setup can be used in four different modes of operation (with or without off-line prepared seeds and with or without a stream of microbubbles). The setup is characterized to provide insights into the design and operation of crystallization processes. First, the performance of the off-line continuous seeding platform is established via the seed delivery efficiency for constant and oscillatory flows. Second, the yields of seeded and unseeded crystallization are evaluated in the presence and absence of microbubbles. A statistically significant increase in the net crystal mass and net yield was measured when comparing unseeded and seeded crystallization, which can be attributed to the increased nucleation rates as a result of secondary nucleation. Third, the clogging behavior of the presented continuous microcrystallizer is discussed. Finally, also the crystal size distribution is analyzed: the mean crystal size decreases for both single- and two-phase flow when seeds are introduced. The presence of microbubbles resulted in a higher net yield and slightly smaller crystals compared to that of the single-phase flow. This work highlights the importance of a holistic characterization approach for continuous microfluidic crystallizers.

Scaling mitigation in direct contact membrane distillation using air microbubbles

Membrane distillation (MD) is a promising process for high-salinity waters. However, water recovery in MD treatments of these feed waters is often limited by their high scaling potential, which results in the need for extensive pre-treatment or the use of antiscalants for scaling control. In this study, we show the potential of using air microbubbles (MB) for scaling mitigation in MD. Addition of MB in the feed was found to reduce membrane scaling, which was confirmed by electron microscopy and quantification of salt deposits on the membrane. In the presence of MB, scaling-induced flux decline was observed at a critical concentration factor of 2.70, compared to 1.97 in the absence of MBs. Scaling mitigation by MB was found to be dependent on the MD operating conditions, with better performance at lower feed temperatures (50 °C) and flow rate (0.4 L/min). Continuous MB injection was more effective in preventing scaling than a periodic on/off MB regime, which emphasized that MB mitigate scaling by preventing salt crystal formation on the membrane instead of dislodging the scaling layer formed on the surface. These results highlight the potential of air MB as a chemical-free scaling control strategy for MD treatment of high scaling potential waters.

Structural and mechanical properties of folded protein hydrogels with embedded microbubbles.

Globular folded proteins are powerful building blocks to create biomaterials with mechanical robustness and inherent biological functionality. Here we explore their potential as advanced drug delivery scaffolds, by embedding microbubbles (MBs) within a photo-activated, chemically cross-linked bovine serum albumin (BSA) protein network. Using a combination of circular dichroism (CD), rheology, small angle neutron scattering (SANS) and microscopy we determine the nanoscale and mesoscale structure and mechanics of this novel multi-composite system. Optical and confocal microscopy confirms the presence of MBs within the protein hydrogel, their reduced diffusion and their effective rupture using ultrasound, a requirement for burst drug release. CD confirms that the inclusion of MBs does not impact the proportion of folded proteins within the cross-linked protein network. Rheological characterisation demonstrates that the mechanics of the BSA hydrogels is reduced in the presence of MBs. Furthermore, SANS reveals that embedding MBs in the protein hydrogel network results in a smaller number of clusters that are larger in size (∼16.6% reduction in number of clusters, 17.4% increase in cluster size). Taken together, we show that MBs can be successfully embedded within a folded protein network and ruptured upon application of ultrasound. The fundamental insight into the impact of embedded MBs in protein scaffolds at the nanoscale and mesoscale is important in the development of future platforms for targeted and controlled drug delivery applications.

Suicide Gene Delivery System Mediated by Ultrasound-Targeted Microbubble Destruction: A Promising Strategy for Cancer Therapy.

The treatment of malignant tumors has always been one of the challenges that have plagued researchers and clinicians. The ideal status in cancer treatment is to eliminate tumor cells while avoiding damage to normal tissues. Different approaches have been investigated to achieve such a goal, and suicide gene therapy has emerged as a novel mode of cancer treatment. This approach involves the delivery of genes encoding enzymes that activate non-toxic prodrugs into cytotoxic metabolites that cause the death of transfected cancer cells. Despite promising results obtained both in vitro and in vivo, this innovative approach has long been stalled in the clinic due to the lack of a suitable delivery system to introduce the suicide gene into cancer cells. Ultrasound-targeted microbubble destruction (UTMD) represents a valuable non-viral vector system for site-specific and noninvasive gene therapy. Ultrasound promotes intracellular uptake of therapeutic agents by increasing vascular and cell membrane permeability, especially in the presence of microbubbles. In this scenario, the true potential of suicide genes can be translated into clinically valuable treatments for patients. This review provides background information on suicide gene therapy and UTMD technology, summarizes the current state of knowledge about UTMD-mediated suicide gene delivery in cancer treatment, and presents an outlook on its future development.

Heat transfer with single- and dual-gas distribution in a pressurised bubble column

The effects of the heat transfer coefficient variance on microbubble formation in a pressurised bubble column and its variance in the dual gas distribution were investigated. The tests were performed with a cylindrical column with an inner diameter of 0.097 m and a height of 1.8 m with air–kerosene media. The heat transfer coefficient was measured using various distributors with different numbers of orifices, and its size was fixed. For an opening fraction of 0.223 %, the heat-transfer coefficient increased with increasing superficial gas velocity (Ug) under all pressure conditions in the tested range. The amount of microbubble generation increased with an increase in pressure and Ug when the opening fraction decreased. To analyse the effect of the kinetic energy rate at the orifice on the number of microbubbles, the gas holdup was measured according to the increase in Ug and system pressure. When the total kinetic energy rate was equal to or higher than 1 J/s, the gas holdup rapidly increased owing to microbubble generation. To increase the heat transfer coefficient in the presence of microbubbles, a dual gas distribution was applied by inserting a single nozzle with different orifice hole diameters (1.7, 2.0, 2.5, and 3.46 mm). In this system, the heat transfer coefficient increased by approximately 25 % compared with the dispersion in a single distributor.

Advances in Trans-Epithelial Electrical Resistance (TEER) monitoring integration in an Intestinal Barrier-on-Chip (IBoC) platform with microbubbles-tolerant analytical method

Trans-epithelial resistance (TEER) is one of the most widely performed analysis in vitro methods for monitoring barrier tissue development, formation and functional maturation. It is a basic and important tool for the reproduction of an artificial human epithelium. However, in the design and construction of organ on chip devices, the reliable TEER measurements still remain a challenge, in spite of their efficacy in providing real time information on tissue integrity and function. The observed limitations often concern the nature of the selected electrodes, made with opaque or metal materials that prevent microscopic investigation, their correct and stable reposition that affect the impedance spectroscopy analysis and microbubbles interference. Here, we present a method to perform real time TEER analysis on an Intestinal Barrier-on-Chip (IBoC) using integrated transparent electrodes, by means of impedance spectroscopy analysis and supported by a microbubble-tolerant calculation method. The human Caco-2 cells were used as an in vitro model of the intestinal epithelial cell barrier. Measurements can be carried out even in presence of microbubbles during the analysis, thus allowing application of this analytical method in microfluidic organ on chip devices that must perform in continuum for a long time.