A multi-chamber microfluidic intestinal barrier model using Caco-2 cells for drug transport studies

This paper presents the design and fabrication of a multi-layer and multi-chamber microchip system using thiol-ene 'click chemistry' aimed for drug transport studies across tissue barrier models. The fabrication process enables rapid prototyping of multi-layer microfluidic chips using different thiol-ene polymer mixtures, where porous Teflon membranes for cell monolayer growth were incorporated by masked sandwiching thiol-ene-based fluid layers. Electrodes for trans-epithelial electrical resistance (TEER) measurements were incorporated using low-melting soldering wires in combination with platinum wires, enabling parallel real-time monitoring of barrier integrity for the eight chambers. Additionally, the translucent porous Teflon membrane enabled optical monitoring of cell monolayers. The device was developed and tested with the Caco-2 intestinal model, and compared to the conventional Transwell system. Cell monolayer differentiation was assessed via in situ immunocytochemistry of tight junction and mucus proteins, P-glycoprotein 1 (P-gp) mediated efflux of Rhodamine 123, and brush border aminopeptidase activity. Monolayer tightness and relevance for drug delivery research was evaluated through permeability studies of mannitol, dextran and insulin, alone or in combination with the absorption enhancer tetradecylmaltoside (TDM). The thiol-ene-based microchip material and electrodes were highly compatible with cell growth. In fact, Caco-2 cells cultured in the device displayed differentiation, mucus production, directional transport and aminopeptidase activity within 9-10 days of cell culture, indicating robust barrier formation at a faster rate than in conventional Transwell models. The cell monolayer displayed high TEER and tightness towards hydrophilic compounds, whereas co-administration of an absorption enhancer elicited TEER-decrease and increased permeability similar to the Transwell cultures. The presented cell barrier microdevice constitutes a relevant tissue barrier model, enabling transport studies of drugs and chemicals under real-time optical and functional monitoring in eight parallel chambers, thereby increasing the throughput compared to previously reported microdevices

Development of a lab on a chip for nerve agent detection

An escalating number of threats in terrorist activities had led to an urgent demand for innovative devices for on-site detection of chemical and biological agents as well as explosive materials. Rapid and sensitive detection of chemical and biological warfare agents (CWA) could provide an early ‘alarm’ of their release, therefore minimizing civilian casualties. Point-of-care diagnosis of individuals who are potentially exposed to chemical warfare agents will allow first-responder health providers to react quickly and efficiently. Health authority can then provide optimal, case-appropriate health care, and convince the unexposed individuals of their health safety. Such devices are required to encompass powerful analytical performance, low energy consumption and high portability. Lab-on-a-Chip (LOC) devices offer great promise for converting large and sophisticated instruments into powerful field-deployable analyzers where liquids are manipulated in a network of microchannels. Designing and fabricating miniaturized field-deployable devices whilst retaining the high sensitivity and selectivity of sophisticated laboratory-based instruments present multiple challenges. In this work, the components and systems for detection the presence of CWA or its degraded by-products in aqueous mediums were developed.MASTER OF ENGINEERING (MAE

What can microfluidics do for human microbiome research?

Dysregulation of the human microbiome has been linked to various disease states, which has galvanized the efforts to modulate human health through microbiomes. Currently, human microbiome research is going through several phases to identify the constituent components of the microbiome, associate microbiome changes with physiological and pathological states, understand causative relationships, and finally translate this knowledge into therapeutics and diagnostics. The convergence of microfluidic technologies with molecular and cell profiling, microbiology, and tissue engineering can potentially be applied to these different phases of microbiome research to overcome the existing challenges faced by conventional approaches. The goal of this paper is to discuss and highlight the opportunities of applying different microfluidic technologies to specific areas of microbiome research as well as unique challenges that microfluidics must overcome when working with microbiome-relevant biological materials, e.g., micro-organisms, host tissues, and fluids. We will discuss the applicability of integrated microfluidic systems for processing biological samples for genomic sequencing analyses. For functional analysis of the microbiota, we will cover state-of-the-art microfluidic devices for microbiota cultivation and functional measurements. Finally, we highlight the use of organs-on-chips to model various microbiome-host tissue interactions. We envision that microfluidic technologies may hold great promise in advancing the knowledge on the interplay between microbiome and human health, as well as its eventual translation into microbiome-based diagnostics and therapeutics.</p

A reliable method for bonding polydimethylsiloxane (PDMS) to polymethylmethacrylate (PMMA) and its application in micropumps

Poly(methylmethacrylate) (PMMA) attracts growing interest in microfluidics research community due to its low cost, high transparency, good mechanical and chemical properties. The more flexible polydimethylsiloxane (PDMS) is well suited for pneumatic actuation. However, PDMS is permeable to gases and absorbs molecules from the sample liquids. Combining PMMA with PDMS would allow a microfluidic device to utilize advantages of both materials. Bonding PMMA to PDMS is a critical step for this hybrid approach. In this paper, we present a simple, fast and reliable technique for bonding PMMA to PDMS. A 25 μm thick adhesive film (ARclear® Optically clear adhesive 8154, Adhesive Research, Glen Rock, PA USA) was laminated onto a clean PMMA surface. Subsequently, pre-cured PDMS mixture was spin coated onto the adhesive film. After curing, the adhesive and the PDMS layer form a hybrid membrane. The bonding quality and the strength of the PDMS/adhesive membrane was tested using a precision pressure source. A peristaltic micropump was fabricated by bonding a PDMS part with microchannels to the PDMS/PMMA part. The PDMS/adhesive membrane acts as the pneumatic actuator for the micropump. Pressurized air was switched to the three pneumatic actuators by solenoid valves and control electronics. The micropumps can achieve a flow rate as high as 96 μl/min. The techniques reported in this paper allow the integration of microfluidic components made of both PMMA and PDMS in a single device.Accepted versio

A lab-on-a-chip for detection of nerve agent sarin in blood

Sarin (C4H10FO2P,O-isopropyl methylphosphonofluoridate) is a colourless, odourless and highly toxic phosphonate that acts as a cholinesterase inhibitor and disrupts neuromuscular transmission. Sarin and related phosphonates are chemical warfare agents, and there is a possibility of their application in a military or terrorist attack. This paper reports a lab-on-a-chip device for detecting a trace amount of sarin in a small volume of blood. The device should allow early detection of sarin exposure during medical triage to differentiate between those requiring medical treatment from mass psychogenic illness cases. The device is based on continuous-flow microfluidics with sequential stages for lysis of whole blood, regeneration of free nerve agent from its complex with blood cholinesterase, protein precipitation, filtration, enzyme-assisted reaction and optical detection. Whole blood was first mixed with a nerve gas regeneration agent, followed by a protein precipitation step. Subsequently, the lysed product was filtered on the chip in two steps to remove particulates and fluoride ions. The filtered blood sample was then tested for trace levels of regenerated sarin using immobilised cholinesterase on the chip. Activity of immobilised cholinesterase was monitored by the enzyme-assisted reaction of a substrate and reaction of the end-product with a chromophore. Resultant changes in chromophore-induced absorbance were recorded on the chip using a Z-shaped optical window. Loss of enzyme activity obtained prior and after passage of the treated blood sample, as shown by a decrease in recorded absorbance values, indicates the presence of either free or regenerated sarin in the blood sample. The device was fabricated in PMMA (polymethylmethacrylate) using CO2-laser micromachining. This paper reports the testing results of the different stages, as well as the whole device with all stages in the required assay sequence. The results demonstrate the potential use of a field-deployable hand-held device for point-of-care triage of suspected nerve agent casualties.Accepted versio

An Air Particulate Pollutant Induces Neuroinflammation and Neurodegeneration in Human Brain Models

10.1002/advs.202101251Advanced Science821210125

Metabolic co-culture of adipose tissue, skeletal muscle, and liver on a recirculatory microfluidic platform

In this work, we present a triple-organ co-culture between 3 metabolic organs (Skeletal Muscle, Adipose Tissue, Liver) within a recirculatory microfluidic Organ-on-Chip (OoC) set-up as a potential platform for metabolic disease modelling and drug testing applications.</p

Muscle on chip with a mechanically tunable 3D microenvironment

'Muscle-on-Chip' technologies have been developed to serve as physiologically relevant animal substitutes for in-vitro screening of drugs and study of myogenesis. The formation of 3D suspended myo-bundles within a contractable hydrogel in 'Muscle-on-Chip' devices has been well-established thus far. However, very limited studies have elucidated (i) The effect of physiological shear stresses and (ii) The mechanical properties of the 3D hydrogel microenvironment in myo-bundle formation and their subsequent myogenesis. As such, we have developed a perfusable 'Muscle-on-Chip' device which will enable us to study the effect of these dynamic stimuli on myo-bundle formation and maturation.</p