Biology subjects

McGrath, J. L.

Publications and source records attributed to McGrath, J. L..

10 recordsLinked to original sources

bioRxiv2026

Design and Application of a μSiM Outer Blood-Retinal Barrier (OBRB) Model as a Drug Development Tool

The outer blood-retinal barrier (OBRB) is the primary interface through which systemically circulating drugs reach the retina. A tool that measures delivery across this barrier would support the development of targeted therapies as alternatives to repeated intravitreal injection, and the screening of drugs that reach the retina as an off-target toxicity. Such a tool should deliver drugs fluidically through a vascular compartment, measure transport across the retinal pigment epithelium (RPE), and display disease phenotypes relevant to efficacy. Here we adapt the SiM platform, which places epithelium and endothelium in direct juxtaposition across a permeable, optically transparent silicon nitride nanomembrane. ARPE-19 and human umbilical vein endothelial cells (HUVECs) were used as development cell sources. ARPE-19 monocultures reached a transepithelial electrical resistance of 68 {+/-} 26 {Omega} cm2 by 28 days, and ARPE-19 + HUVEC co-cultures reached a small-molecule permeability of 6.34 {+/-} 1.3 x 10-4 cm min-1 within 14 days, a state reported elsewhere only after longer culture. The barriers developed an intervening basement membrane. Drugs perfused through the basal vascular channel crossed into an open apical well, where sampling and mass spectrometry showed transport correlating with lipophilicity, as reported in vivo. The device also displayed two clinically relevant phenotypes. Digoxin at a clinically toxic concentration reduced viability in the co-barrier by about half and doubled permeability. In a vascularized configuration, VEGF drove endothelial invasion of the RPE layer, as seen in neovascular AMD. The SiM-OBRB therefore satisfies basic design criteria for measurement of drug bioavailability, toxicity, and efficacy.

bioengineering↗

bioRxiv2026

A human synovial tendon-on-a-chip models key features of peritendinous adhesions and offers a new approach methodology for testing anti-fibrotic drugs

Peritendinous adhesions are a debilitating complication of tendon injury characterized by excessive matrix deposition and chronic inflammation. Due to limitations of current preclinical models, the underlying mechanisms of adhesion pathogenesis remain poorly defined, and there are no approved drugs to prevent or resolve adhesions. Here, we develop a human synovial tendon-on-a-chip (synToC) that integrates synovial fibroblasts, tendon-resident fibroblasts, immune cells, and vascular endothelium to reconstruct the intrasynovial tendon microenvironment. We show that synovial fibroblast activation promoted tendon contraction and inflammatory cytokine secretion dominated by IL-6, leading to monocyte infiltration and formation of fibronectin- and collagen III-rich matrix bridges between tendon and synovial compartments resembling nascent peritendinous adhesions. These phenotypes emerged even in the absence of exogenous TGF-{beta}1, indicating that synovial fibroblast-mediated crosstalk is sufficient to initiate adhesion-like pathology. Importantly, pharmacological inhibition of the IL-6/JAK/STAT pathway suppressed synovial activation, blunted inflammatory cytokine signaling, and attenuated fibrotic matrix deposition and interfacial adhesion formation. These findings establish the synToC as a human-relevant new approach methodology (NAM) to interrogate the multicellular drivers of tendon adhesions and to accelerate the development of anti-fibrotic therapies.

bioengineering↗

bioRxiv2026

Modular Integration of Impedance Sensing for Real-Time Assessment of Barrier Integrity

Microphysiological systems (MPS) are essential for modeling tissue barriers, yet integrating electrical readouts often requires permanently sealed microfluidic architectures that limit access to open-well (direct-access) workflows used in bioscience laboratories. To resolve this issue, we present a modular approach in which functional components are added and removed from a standard MPS core using a magnetic interface. This design preserves compatibility with established open-well protocols for seeding and downstream analysis, while microfluidic perfusion or electrical sensing capabilities are added only when needed. We demonstrate this approach with an impedance-sensing module that enables continuous impedance measurements to assess barrier function. By fitting spectra to an equivalent circuit model, we quantify junctional and non-junctional electrical contributions to barrier integrity over time, alongside conventional single-frequency TEER, and complementary permeability and imaging readouts. We apply this platform across three representative use cases, including LPS-induced disruption, shear stress-mediated strengthening, and compatibility with barrier models formed above a 3D hydrogel matrix.

bioengineering↗

bioRxiv2026

Bacterial extracellular vesicles indirectly destabilize a human stem cell-derived blood-brain barrier on-chip through pro-inflammatory stimulation of immune cells

Pathogenic bacterial extracellular vesicles (BEVs) can disrupt the blood-brain barrier (BBB), leading to neuroinflammation. Prior in vitro studies of this process were performed in simple models that may have lacked important physiological factors. We sought to determine if treatment with Escherichia coli-derived BEVs could directly compromise the integrity of a BBB lab-on-chip model or if an immune component was required. Our device featured isogenic human induced pluripotent stem cell-derived brain microvascular endothelial-like cells (BMECs) and pericytes separated by an ultrathin, porous silicon nitride membrane. BEVs and free lipopolysaccharide (LPS) were capable of causing upregulation of intercellular adhesion molecule-1 on the BMEC surfaces, which is important for immune cell recruitment. However, neither BEVs nor LPS at physiological doses caused pronounced loss of BMEC tight junction proteins, nor did they increase barrier permeability to small dye molecules. In contrast, stimulating THP-1 macrophages with BEVs led to increased production of pro-inflammatory cytokines, and conditioned media from the stimulated macrophages disrupted BMEC tight junctions and increased barrier permeability. Our work demonstrates the importance of incorporating an immune component in studies of BEV-mediated disruption of BBB models.

cell biology↗

bioRxiv2025

Pericytes Repair Engineered Defects in the Basement Membrane to Restore Barrier Integrity in an in vitro Model of the Blood-Brain Barrier.

Pericytes play a key role in the brain where they support the blood-brain barrier (BBB). Their loss has been reported in response to systemic inflammation and neurodegenerative disease. We recently demonstrated that iPSC-derived brain pericyte-like cells (BPLCs) and brain microvascular endothelial cell (BMEC)-like cells collaboratively form a nascent, 3D basement membrane when cultured across a nanoporous membrane1. Building on this, we aimed to engineer defects in the basement membrane to investigate whether pericytes could facilitate its repair. In BMEC monocultures, we observed that micropore patterns in nanomembranes created discontinuities in laminin, which destabilized barrier function. Remarkably, the addition of pericytes to the basal side of the membrane restored both laminin integrity and barrier function. Our results align with the role of pericytes as support cells for microvasculature and encourage the use of our tissue barrier platform (the {micro}SiM) to model neurological disorders involving pericyte dysfunction and/or disruption of basement membrane.

bioengineering↗

bioRxiv2024

Fluid Flow Impacts Endothelial-Monocyte Interactions in a Model of Vascular Inflammatory Fibrosis

The aberrant vascular response associated with tendon injury results in circulating immune cell infiltration and a chronic inflammatory feedback loop leading to poor healing outcomes. Studying this dysregulated tendon repair response in human pathophysiology has been historically challenging due to the reliance on animal models. To address this, our group developed the human tendon-on-a-chip (hToC) to model cellular interactions in the injured tendon microenvironment; however, this model lacked the key element of physiological flow in the vascular compartment. Here, we leveraged the modularity of our platform to create a fluidic hToC that enables the study of circulating immune cell and vascular crosstalk in a tendon injury model. Under physiological shear stress consistent with postcapillary venules, we found a significant increase in the endothelial leukocyte activation marker intercellular adhesion molecule 1 (ICAM-1), as well as enhanced adhesion and transmigration of circulating monocytes across the endothelial barrier. The addition of tissue macrophages to the tendon compartment further increased the degree of circulating monocyte infiltration into the tissue matrix. Our findings demonstrate the importance of adding physiological flow to the human tendon-on-a-chip, and more generally, the significance of flow for modeling immune cell interactions in tissue inflammation and disease.

bioengineering↗

bioRxiv2024

Rapid Assessment of Biomarkers on Single Extracellular Vesicles Using 'Catch and Display' on Ultrathin Nanoporous Silicon Nitride Membranes

Extracellular vesicles (EVs) are particles secreted by all cells that carry bioactive cargo and facilitate intercellular communication with roles in normal physiology and disease pathogenesis. EVs have tremendous diagnostic and therapeutic potential and accordingly, the EV field has grown exponentially in recent years. Bulk assays lack the sensitivity to detect rare EV subsets relevant to disease, and while single EV analysis techniques remedy this, they are undermined by complicated detection schemes often coupled with prohibitive instrumentation. To address these issues, we propose a microfluidic technique for EV characterization called catch and display for liquid biopsy (CAD-LB). CAD-LB rapidly captures fluorescently labeled EVs in the similarly-sized pores of an ultrathin silicon nitride membrane. Minimally processed sample is introduced via pipette injection into a simple microfluidic device which is directly imaged using fluorescence microscopy for a rapid assessment of EV number and biomarker colocalization. In this work, nanoparticles were first used to define the accuracy and dynamic range for counting and colocalization by CAD-LB. Following this, the same assessments were made for purified EVs and for unpurified EVs in plasma. Biomarker detection was validated using CD9 in which Western blot analysis confirmed that CAD-LB faithfully recapitulated differing expression levels among samples. We further verified that CAD-LB captured the known increase in EV-associated ICAM-1 following the cytokine stimulation of endothelial cells. Finally, to demonstrate CAD-LBs clinical potential, we show that EV biomarkers indicative of immunotherapy responsiveness are successfully detected in the plasma of bladder cancer patients undergoing immune checkpoint blockade.

bioengineering↗

bioRxiv2022

The Modular μSiM: a Mass Produced, Rapidly Assembled, and Reconfigurable Platform for the Study of Barrier Tissue Models In Vitro

Advanced in vitro tissue chip models can reduce and replace animal experimentation and may eventually support on-chip clinical trials. To realize this potential, however, tissue chip platforms must be both mass-produced and reconfigurable to allow for customized design. To address these unmet needs, we introduce an extension of our {micro}SiM (microdevice featuring a silicon-nitride membrane) platform. The modular {micro}SiM (m-{micro}SiM) uses mass-produced components to enable rapid assembly and reconfiguration by laboratories without knowledge of microfabrication. We demonstrate the utility of the m-{micro}SiM by establishing an hiPSC-derived blood-brain barrier (BBB) in bioengineering and non-engineering, brain barriers focused laboratories. We develop and validate in situ and sampling-based assays of small molecule diffusion as a measure of barrier function. BBB properties show excellent interlaboratory agreement and match expectations from literature, validating the m-{micro}SiM as a platform for barrier models and demonstrating successful dissemination of components and protocols. We then demonstrate the ability to quickly reconfigure the m-{micro}SiM for co-culture and immune cell transmigration studies through addition of accessories and/or quick exchange of components. Because the development of modified components and accessories is easily achieved, custom designs of the m-{micro}SiM should be accessible to any laboratory desiring a barrier-style tissue chip platform.

bioengineering↗

bioRxiv2022

The Modular μSiM Reconfigured: Integration of Microfluidic Capabilities to Study in vitro Barrier Tissue Models under Flow

Microfluidic approaches to study tissue barriers have emerged to address the lack of fluid flow in conventional "open-well" Transwell-like devices. However, microfluidic techniques have not achieved widespread usage in bioscience laboratories because they are not fully compatible with traditional, tried-and-true experimental protocols. To advance barrier tissue research, there is a need for a platform that combines the advantages of both conventional open-well and microfluidic systems. Here, we develop a plug-and-play flow module to add on-demand microfluidic capabilities to a modular microfluidic system featuring a silicon membrane "m-SiM" as an open-well device with live-cell imaging capabilities. The magnetic latching assembly of our design enables bi-directional reconfiguration between open-well and fluidic modes. This design feature allows users to conduct an experiment in an open-well format with established protocols and then add or remove microfluidic capabilities as desired. Our work also provides an experimentally-validated flow model to help select desired flow conditions based on the experimental needs. As a proof-of-concept, we demonstrate flow-induced alignment of endothelial cells and visualize different phases of neutrophil transmigration across an endothelial monolayer under flow. We anticipate that our reconfigurable design will be adopted by both engineering and bioscience laboratories due to the compatibility with standard open-well protocols and the simple flow addition capabilities.

bioengineering↗

bioRxiv2019

Tangential flow microfluidics for the capture and release of nanoparticles and extracellular vesicles on conventional and ultrathin membranes

Membranes have been used extensively for the purification and separation of biological species. A persistent challenge is the purification of species from concentrated feed solutions such as extracellular vesicles (EVs) from biological fluids. We investigated a new method to isolate micro- and nano-scale species termed tangential flow for analyte capture (TFAC), which is an extension of traditional tangential flow filtration (TFF). Initially, EV purification from plasma on ultrathin nanomembranes was compared between both normal flow filtration (NFF) and TFF. NFF resulted in rapid formation of a protein cake which completely obscured any captured EVs and also prevented further transport across the membrane. On the other hand, TFF showed capture of CD63 positive EVs with minimal contamination. We explored the use of TFF to capture target species over membrane pores, wash and then release in a physical process that does not rely upon affinity or chemical interactions. This process of TFAC was studied with model particles on both ultrathin nanomembranes and conventional thickness membranes (polycarbonate track-etch). Successful capture and release of model particles was observed using both membranes. Ultrathin nanomembranes showed higher efficiency of capture and release with significantly lower pressures indicating that ultrathin nanomembranes are well-suited for TFAC of delicate nanoscale particles such as EVs.

bioengineering↗