Perfusion based microfluidic system for pharmacological profiling of neuronal networks

This work presents the integration of a semi-automated microfluidic platform that utilizes calcium imaging to enable the pharmacological characterization of functionally connected, but environmentally isolated neuronal networks. This approach allows, for the first time, to assess the cause-effect relationship of neuronal communication following drug application, thus allowing the pharmacological characterisation of novel drugs proposed to influence communication between neuronal networks

In-line single-mode fiber variable optical attenuator based on electrically addressable microdroplets

We report an in-line, fiber optic, broadband variable optical attenuator employing a side-polished, single-mode optical fiber integrated on a digital microfluidics platform. The system is designed to electrically translate a liquid droplet along the polished surface of an optical fiber using electrowetting forces. This fiber optic device has the advantage of no moving mechanical parts and lends itself to miniaturization. A maximum attenuation of 25 dB has been obtained in the wavelength range between 1520 nm and 1560 nm

Modeling and characterization of an electrowetting based single mode fiber variable optical attenuator

We report an optofluidics-based variable optical attenuator (VOA) employing a tapered side-polished single-mode optical fiber attached to an electrowetting-on-dielectric (EWOD) platform. The side polishing of the fiber cladding gives access to the evanescent field of the guided mode, while the EWOD platform electrically controls the stepwise translation of a liquid droplet along the variable thickness polished cladding of the fiber. The penetration of the evanescent field into the droplet leads to tunneling of optical power from the fiber core to the droplet, from where it is radiatively lost. As a result of the variable cladding thickness, the position of the droplet along the length of the polished fiber determines the degree of penetration of the evanescent field into the droplet. The droplet position can be electrically changed; thus, controlling the optical power loss from the fiber. This approach has been used to demonstrate an optofluidic continuous-fiber VOA typically providing up to 26 dB of broadband attenuation in the 1550-nm transmission window, with a wavelength dependent loss less than 1.1 dB. In this paper, we present the theoretical modeling and experimental characterization of the system, discussing the influence of the design parameters on the performance of this VOA

Controlled delivery of membrane proteins to artificial lipid bilayers by nystatin-ergosterol modulated vesicle fusion

The study of ion channels and other membrane proteins and their potential use as biosensors and drug screening targets require their reconstitution in an artificial membrane. These applications would greatly benefit from microfabricated devices in which stable artificial lipid bilayers can be rapidly and reliably formed. However, the amount of protein delivered to the bilayer must be carefully controlled. A vesicle fusion technique is investigated where composite ion channels of the polyene antibiotic nystatin and the sterol ergosterol are employed to render protein-carrying vesicles fusogenic After fusion with an ergosterol-free artificial bilayer the nystatin-ergosterol channels do not dissociate immediately and thus cause a transient current signal that marks the vesicle fusion event. Experimental pitfalls of this method were identified, the influence of the nystatin and ergosterol concentration on the fusion rate and the shape of the fusion event marker was explored, and the number of different lipid was reduced. Under these conditions, the B-amyloid peptide could be delivered in a controlled manner to a standard planar bilayer. Additionally, the electrical recordings were obtained of vesicles fusing with a planar lipid bilayer in a microfabricated device, demonstrating the suitability of nystatin-ergosterol modulated vesicle fusion for protein delivery within microsystems

Time-lapse measurement of single-cell response to nanomaterial : a microfluidic approach

This work presents the successful application of a single-cell microfluidic platform for high-throughput, real-time screening of nanoparticle-cell interactions. Taking vaccine delivery as a proof-of-concept application, ovalbumin-conjugated gold nanorods were produced and controllably delivered to primary dendritic cells within the device. Time-lapse imaging enabled monitoring of hundreds of single-cells during exposure to a range of concentrations of nanoparticle conjugates and simultaneous quantification of specific cellular functions. This integrated system provides throughput and statistical data comparable to that obtained with flow cytometry but also offers a novel approach to determine the dynamics of nanoparticle-cell interactions and nanoparticle-mediated antigen delivery with single-cell resolution

A microfluidics tool for high-throughput, real-time multimodal imaging of nanoparticle-cell interactions

The increasing use of nanomaterials for biomedical applications has raised the need for efficient, robust and low-cost high-throughput assessment of nanotoxicity and cell-nanoparticle interactions. Microfluidics provides the tools for high-throughput single-cell functional monitoring, while gold nanorods have unique potential for intracellular tracking and can simultaneously be used as drug carriers. Presented here is a miniaturised platform that integrates these features with a multimodal approach to cell imaging. A microfluidic device allows for trapping of an array of singlecells, followed by the controlled delivery of nanoparticles into the cell array and subsequent real-time multimodal imaging of cellular interactions with functionalised nanoparticles. This system has been successfully used to assess cellnanoparticle interactions at the single-cell level

On-chip formation of 3D spheroids for patient-derived tissue screening

Three-dimensional (3D) multicellular spheroids have been identified as a suitable model of solid tumours for drug screening and cancer research [1]. However, creating and monitoring a large number of spheroids using conventional methods remains labour-intensive. This work reports a novel double-layer microfluidic device for the generation and culture of 3D multicellular spheroids and its use with biopsy samples. The system enables drug concentration-response curves to be obtained from a limited amount of sample material by applying a drug concentration gradient using an integrated passive microchannel network

An in vitro microfluidic model of microglia migration after stroke

Objectives: Microglia migrate to the site of ischemic insult in response to mediators such as glutamate and ADP being released from damaged or stressed cells and can exert both protective and detrimental effects1. Our present objective is to characterise microglia migration in vitro using a microfluidic model which allows precise chemical concentration gradients to be established over time, mimicking the release of mediators after stroke in vivo. Methods: Microglial cell line, SIM-A9, were seeded in microfluidic culture chambers at 2.5 × 106 cells/ml for 24 hrs prior to exposure to concentration gradients of glutamate (100 µM) or vehicle (DMEM, control), with and without direct LPS (1µg/ml). Real time time-lapse imaging and cell tracking software were used to quantify cell migration velocity, and accumulated and Euclidean distance. Preliminary experiments analysed an average of 24 cell tracks per group (mean ± SD). Results: Microglia were observed to migrate towards increasing chemical concentration gradients compared to control. This directionality effect was supported by an increased average number of cells entering the microchannels and an increased Euclidean distance towards the glutamate gradient versus control (170.36 ± 108.19 µM vs 35.5 ± 36.9 µm, respectively). Interestingly, the addition of direct LPS dampened down the increased Euclidean distance to 75.26 ± 53.5 µm. Compared to vehicle, a concentration gradient of glutamate induced a substantial increase in velocity which was further increased by the additional direct application of LPS (0.33 ± 0.18 µm/min vs 0.58 ± 0.15 µm/min vs 0.65 ± 0.18 µm/min, respectively). A similar pattern was observed for accumulated distance (372.8 ± 203.12 µm vs 651.02 ± 169.4 µm vs 730.4 ± 205.47 µm, respectively). Conclusions: These results suggest that a pro-inflammatory environment limits glutamate-induced directionality and provide novel insight into dynamics of microglia responses after stroke

Microfluidic technologies for immunotherapy studies on solid tumours

Immunotherapy is a powerful and targeted cancer treatment that exploits the body's immune system to attack and eliminate cancerous cells. This form of therapy presents the possibility of long-term control and prevention of recurrence due to the memory capabilities of the immune system. Various immunotherapies are successful in treating haematological malignancies and have dramatically improved outcomes in melanoma. However, tackling other solid tumours is more challenging, mostly because of the immunosuppressive tumour microenvironment (TME). Current in vitro models based on traditional 2D cell monolayers and animal models, such as patient-derived xenografts, have limitations in their ability to mimic the complexity of the human TME. As a result, they have inadequate translational value and can be poorly predictive of clinical outcome. Thus, there is a need for robust in vitro preclinical tools that more faithfully recapitulate human solid tumours to test novel immunotherapies. Microfluidics and lab-on-a-chip technologies offer opportunities, especially when performing mechanistic studies, to understand the role of the TME in immunotherapy, and to expand the experimental throughput when using patient-derived tissue through its miniaturization capabilities. This review first introduces the basic concepts of immunotherapy, presents the current preclinical approaches used in immuno-oncology for solid tumours and then discusses the underlying challenges. We provide a rationale for using microfluidic-based approaches, highlighting the most recent microfluidic technologies and methodologies that have been used for studying cancer–immune cell interactions and testing the efficacy of immunotherapies in solid tumours. Ultimately, we discuss achievements and limitations of the technology, commenting on potential directions for incorporating microfluidic technologies in future immunotherapy studies

A modular microfluidic platform to enable complex and customisable in vitro models for neuroscience

Disorders of the central nervous system (CNS) represent a global health challenge and an increased understanding of the CNS in both physiological and pathophysiological states is essential to tackle the problem. Modelling CNS conditions is difficult, as traditional in vitro models fail to recapitulate precise microenvironments and animal models of complex disease often have limited translational validity. Microfluidic and organ-on-chip technologies offer an opportunity to develop more physiologically relevant and complex in vitro models of the CNS. They can be developed to allow precise cellular patterning and enhanced experimental capabilities to study neuronal function and dysfunction. To improve ease-of-use of the technology and create new opportunities for novel in vitro studies, we introduce a modular platform consisting of multiple, individual microfluidic units that can be combined in several configurations to create bespoke culture environments. Here, we report proof-of-concept experiments creating complex in vitro models and performing functional analysis of neuronal activity across modular interfaces. This platform technology presents an opportunity to increase our understanding of CNS disease mechanisms and ultimately aid the development of novel therapies