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Versatile, Multivalent Nanobody Cocktails for Highly Efficient SARS-CoV-2 Neutralization

The outbreak of COVID-19 has severely impacted global health and the economy. Cost-effective, highly efficacious therapeutics are urgently needed. Here, we used camelid immunization and proteomics to identify a large repertoire of highly potent neutralizing nanobodies (Nbs) to the SARS-CoV-2 spike (S) protein receptor-binding domain (RBD). We discovered multiple elite Nbs with picomolar to femtomolar affinities that inhibit viral infection at sub-ng/ml concentration, more potent than some of the best human neutralizing antibodies. We determined a crystal structure of such an elite neutralizing Nb in complex with RBD. Structural proteomics and integrative modeling revealed multiple distinct and non-overlapping epitopes and indicated an array of potential neutralization mechanisms. Structural characterization facilitated the bioengineering of novel multivalent Nb constructs into multi-epitope cocktails that achieved ultrahigh neutralization potency (IC50s as low as 0.058 ng/ml) and may prevent mutational escape. These thermostable Nbs can be rapidly produced in bulk from microbes and resist lyophilization, and aerosolization. These promising agents are readily translated into efficient, cost-effective, and convenient therapeutics to help end this once-in-a-century health crisis.

bioengineering↗

Modeling SARS-CoV-2 infection in vitro with a human intestine-on-chip device

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) has given rise to a global pandemic. The gastrointestinal symptoms of some COVID-19 patients are underestimated. There is an urgent need to develop physiologically relevant model that can accurately reflect human response to viral infection. Here, we report the creation of a biomimetic human intestine infection model on a chip system that allows to recapitulate the intestinal injury and immune response induced by SARS-CoV-2, for the first time. The microengineered intestine-on-chip device contains human intestinal epithelium (co-cultured human intestinal epithelial Caco-2 cells and mucin secreting HT-29 cells) lined in upper channel and vascular endothelium (human umbilical vein endothelial cells, HUVECs) in a parallel lower channel under fluidic flow condition, sandwiched by a porous PDMS membrane coated with extracellular matrix (ECM). At day 3 post-infection of SARS-CoV-2, the intestine epithelium showed high susceptibility to viral infection and obvious morphological changes with destruction of intestinal villus, dispersed distribution of mucus secreting cells and reduced expression of tight junction (E-cadherin), indicating the destruction of mucous layer and the integrity of intestinal barrier caused by virus. Moreover, the endothelium exhibited abnormal cell morphology with disrupted expression of adherent junction protein (VE-cadherin). Transcriptional analysis revealed the abnormal RNA and protein metabolism, as well as activated immune responses in both epithelial and endothelial cells after viral infection (e.g., up-regulated cytokine genes, TNF signaling and NF-kappa B signaling-related genes). This bioengineered in vitro model system can mirror the human relevant pathophysiology and response to viral infection at the organ level, which is not possible in existing in vitro culture systems. It may provide a promising tool to accelerate our understanding of COVID-19 and devising novel therapies.

bioengineering↗

Innervated adrenomedullary microphysiological system to model prenatal nicotine and opioid exposure

The transition to extrauterine life results in a critical surge of catecholamines necessary for increased cardiovascular, respiratory, and metabolic activity. The mechanisms mediating adrenomedullary catecholamine release are poorly understood, given the sympathetic adrenomedullary control systems functional immaturity. Important mechanistic insight is provided by newborns delivered by cesarean section or subjected to prenatal nicotine or opioid exposure, demonstrating the impaired release of adrenomedullary catecholamines. To investigate mechanisms regulating adrenomedullary innervation, we developed compartmentalized 3D microphysiological systems (MPS) by exploiting the meniscus pinning effect via GelPins, capillary pressure barriers between cell-laden hydrogels. The MPS comprises discrete 3D cultures of adrenal chromaffin cells and preganglionic sympathetic neurons within a contiguous bioengineered microtissue. Using this model, we demonstrate that adrenal chromaffin innervation plays a critical role in hypoxia-medicated catecholamine release. Furthermore, opioids and nicotine were shown to affect adrenal chromaffin cell response to a reduced oxygen environment, but neurogenic control mechanisms remained intact. GelPin containing MPS represent an inexpensive and highly adaptable approach to study innervated organ systems and improve drug screening platforms by providing innervated microenvironments.

bioengineering↗

A Two-Step Bioreactor for Lung Recellularization

Bioreactors for reseeding of decellularized lung scaffolds have evolved with a wide variety of advancements. These include biomimetic mechanical stimulation, constant nutrient flow, multi-output monitoring, and large mammal scaling. Although dynamic bioreactors are not new to the field of bioengineered lungs, ideal conditions during cell seeding have not been extensively studied or controlled. To address the lack of cell dispersal in traditional seeding methods, we have designed a two-step bioreactor. The first step rotates a seeded lung every 20 minutes at different angles to ensure 20 percent of cells are anchored to a particular location based on the known rate of attachment. The second step involves perfusion culture to ensure nutrient dispersion and cellular growth. Compared to statically seeded lungs followed by conventional perfusion, rotationally seeded lungs followed by perfusion had significantly increased dsDNA content and more uniform cellular distribution. This new bioreactor system will aid in recellularizing the lung and other geometrically complex organs for tissue engineering.

bioengineering↗

Distinguishing dopamine and calcium responses using XNA-nanotube sensors for improved neurochemical sensing

To date, the engineering of single-stranded DNA-SWCNT (DNA-SWCNT) optical biosensors have largely focused on creating sensors for new applications with little focus on optimising existing sensors for in vitro and in vivo conditions. Recent studies have shown that nanotube fluorescence can be severely impacted by changes in local cation concentrations. This is particularly problematic for neurotransmitter sensing applications as spatial and temporal fluctuations in the concentration of cations, such as Na+, K+, or Ca2+, play a central role in neuromodulation. This can lead to inaccuracies in the determination of neurotransmitter concentrations using DNA-SWCNT sensors, which limits their use for detecting and treating neurological diseases. Herein, we present new approaches using locked nucleic acid (LNA) to engineer SWCNT sensors with improved stability towards cation-induced fluorescence changes. By incorporating LNA bases into the (GT)15-DNA sequence, we create sensors that are not only more resistant towards undesirable fluorescence modulation in the presence of Ca2+ but that also retain their capabilities for the label-free detection of dopamine. The synthetic biology approach presented in this work therefore serves as a complementary means for enhancing nanotube optoelectronic behavior, unlocking previously unexplored possibilities for developing nano-bioengineered sensors with augmented capabilities.

bioengineering↗

Pre-Clinical Application of Functional Human Induced Pluripotent Stem Cell-Derived Airway Epithelial Grafts

Airway pathologies including cancer, trauma and stenosis lack effective treatments, meanwhile airway transplantation and available tissue engineering approaches fail due to epithelial dysfunction. Autologous progenitors do not meet the clinical need for regeneration due to their insufficient expansion and differentiation, for which human induced pluripotent stem cells (hiPSCs) are promising alternatives. Airway epithelial grafts are engineered by differentiating hiPSC-derived airway progenitors into physiological proportions of ciliated (73.9{+/-}5.5%) and goblet (2.1{+/-}1.4%) cells on a Silk Fibroin-Collagen Vitrigel Membrane (SF-CVM) composite biomaterial for transplantation in porcine tracheal defects ex vivo and in vivo. Evaluation of ex vivo tracheal repair using hiPSC-derived SF-CVM grafts demonstrate native-like tracheal epithelial metabolism and maintenance of mucociliary epithelium to day 3. In vivo studies reveal SF-CVM integration, maintenance of airway patency, showing 80.8{+/-}3.6% graft coverage with an hiPSC-derived pseudostratified epithelium and 70.7{+/-}2.3% coverage with viable cells, 3 days post-operatively. We demonstrate the utility of bioengineered, hiPSC-derived epithelial grafts for airway repair in a pre-clinical survival model, providing a significant leap for airway reconstruction approaches.

bioengineering↗

Engineered small extracellular vesicles as a FGL1/PD-L1 dual-targeting delivery system for alleviating immune rejection

There is an urgent need for developing new immunosuppressive agents due to the toxicity of long-term use of broad immunosuppressive agents post organ transplantation. Comprehensive sample analysis revealed dysregulation of FGL1/LAG-3 and PD-L1/PD-1 immune checkpoints in allogeneic heart transplantation mice and clinical kidney transplant patients. In order to enhance these two immunosuppressive signal axes, we developed a bioengineering strategy to simultaneously display FGL1/PD-L1 (FP) on the surface of small extracellular vesicles (sEVs). Among various cell sources, FP sEVs derived from mesenchymal stem cells (MSCs) not only enriched FGL1/PD-L1 expression but also maintained the immunomodulatory properties of unmodified MSC sEVs. Next, we confirmed that FGL1 and PD-L1 on sEVs were specifically bound to their receptors LAG-3 and PD-1 on target cells. Importantly, FP sEVs significantly inhibited T cell activation and proliferation in vitro and a heart allograft model. Furthermore, FP sEVs encapsulated with low-dose FK506 (FP sEVs@FK506) exerted stronger effects on inhibiting T cell proliferation, reducing CD8+ T cell density and cytokine production in the spleens and heart grafts, inducing regulatory T cells in lymph nodes, and extending graft survival. Taken together, dual-targeting sEVs have the potential to boost the immune inhibitory signalings in synergy and slow down transplant rejection.

bioengineering↗

Embedded 3D printing in self-healing annealable composites for functional patterning of human neural constructs

Human in vitro models of neural tissue with controllable cellular identity, tunable microenvironment, and defined spatial arrangement are needed to facilitate studies of brain development and disease. Towards this end, embedded printing in jammed microgel supports (i.e., granular gels) holds great promise as it allows precise and programmable patterning of extremely soft and compliant tissue constructs. However, in contrast to the vast material landscape available for bulk hydrogels, granular printing support formulations are restricted to a handful of materials without the ability for facile adjustment of biofunctional properties of the cellular microenvironment. Therefore, there has been a need for novel materials that take advantage of versatile biomimicry of bulk hydrogels while providing high-fidelity support for embedded printing akin to granular gels. To address this need, we present a modular platform for bioengineering of neuronal networks via direct embedded 3D printing of human stem cells inside Self-Healing Annealable Particle-Extracellular matrix (SHAPE) composites. SHAPE composites consist of soft microgels immersed in viscous extracellular-matrix solution to enable precise freeform patterning of human stem cells and consequent generation and long-term maintenance of mature subtype-specific neurons that extend projections within the volume of the annealed support. The developed approach further allows multi-ink deposition, live spatial and temporal monitoring of oxygen levels, as well as creation of vascular channels. Due to its modularity, SHAPE biomanufacturing toolbox not only offers a solution for functional modeling of mechanically sensitive neural constructs, but also has potential to be applied to a wide range of biomaterials with different crosslinking mechanisms to model tissues and diseases where recapitulation of complex architectural features and topological cues is essential.

bioengineering↗

Development of Permanent Artificial Bowel Replacement Substrates

Short bowel syndrome (SDS) is a malabsorption disorder caused by loss of function of the small intestine, either by trauma or innately. Current treatment options include parenteral nutrition (PN) or allograft transplants. Long term PN dependence can lead to complications due to line infections and toxicity from the formula itself. A lack of healthy donors results in long waiting lists and high mortality rates. With allograft transplants, long-term graft and patient survival rates are poor (48% and 39% respectively at 5 years); graft loss occurs due to rejection (48%), thrombosis (28%), sepsis (12%); main causes of death are due to bacterial infection (94%) and rejection. Costs associated with PN annually per patient approximate to {pound}40,000, whereas one allograft procedure costs approximately {pound}80,000; not including intervention due to complications. Interest in developing an off-the-shelf bioengineered alternative have been expressed. Autologous transplants could be a more beneficial route to improving survival rates, enabling the transplant of patients healthy cells back to them. We describe here the development of a synthetic poly(ethylene terephthalate) scaffold using electrospinning, which showed excellent physical and chemical characteristics; high surface area:volume ratio, high mechanical strength, high porosity, and the ability to be chemically/physically functionalised without losing integrity in structure and physical properties. The cost of electrospinning is far lower in comparison to the current available treatment options, potentially providing a stable, off-the-shelf, ready-to-culture product as the need arises for applications in tissue engineered small intestine (TESI), or 3D models for small bowel research.

bioengineering↗

The role of extracellular matrix biomolecules on endometrial epithelial cell attachment and cytokeratin 18 expression on gelatin hydrogels

The endometrium undergoes profound changes in tissue architecture and composition, both during the menstrual cycle as well as in the context of pregnancy. Dynamic remodeling processes of the endometrial extracellular matrix (ECM) are a major element of endometrial homeostasis, including changes across the menstrual cycle. A critical element of this tissue microenvironment is the endometrial basement membrane, a specialized layer of proteins that separates the endometrial epithelium from the underlying endometrial ECM. Bioengineering models of the endometrial microenvironment that present an appropriate endometrial ECM and basement membrane may provide an improved environment to study endometrial epithelial cell (EEC) function. Here, we exploit a tiered approach using two-dimensional high throughput microarrays and three-dimensional gelatin hydrogels to define patterns of EEC attachment and cytokeratin 18 (CK18) expression in response to combinations of endometrial basement membrane proteins. We identify combinations (collagen IV + tenascin C; collagen I + collagen III; hyaluronic acid + tenascin C; collagen V; collagen V + hyaluronic acid; collagen III; collagen I) that facilitate increased EEC attachment, increased CK18 intensity, or both. We also identify significant EEC mediated remodeling of the GelMA matrix environment via analysis of nascent protein deposition. Together, we report efforts to tailor the localization of basement membrane-associated proteins and proteoglycans in order to investigate tissue engineered models of the endometrial microenvironment.

bioengineering↗

Experimental analysis and biaxial biomechanical behaviour of ex-vivo sheep trachea

PurposeThe purpose of this study is to investigate the mechanical behaviour of the tracheal tissue under biaxial tensile loading. Furthermore, the study examines the material properties of the tissue through a study of the model parameters for six constitutive models. Materials and methodsThe fourteen (n = 13) trachea sheep (Vleis Merino) pieces of tissues measured to be ~ 30 x 20 mm where only the effective area subjected to engineering strain was ~ 25 x 16 mm. In this study, we assume that the tracheal tissue is anisotropic and incompressible, therefore we apply and study the material parameters from six models namely the Fung, Choi-Vito, Holzapfel (2000), Holzapfel (2005), Polynomial (Anisotropic) and Four-Fiber Family models. ResultsThe results show that the trachea tissue is twice as stiff along the circumferential direction as it is along the longitudinal direction. It is also observed that the material properties are different (non-homogeneous) along the trachea. ConclusionsThe findings of this study will benefit computational models for the study of tracheal diseases or injuries. Furthermore, these findings will assist in the development of regenerative medicine for different tracheal pathologies and in the bioengineering of replacement tissue in cases of damage.

bioengineering↗

Imaging-Guided Bioreactor for De-Epithelialization and Long-Term Cultivation of Ex Vivo Rat Trachea

Recent synergistic advances in organ-on-chip and tissue engineering technologies offer opportunities to create in vitro-grown tissue or organ constructs that can faithfully recapitulate their in vivo counterparts. Such in vitro tissue or organ constructs can be utilized in multiple applications, including rapid drug screening, high-fidelity disease modeling, and precision medicine. Here, we report an imaging-guided bioreactor that allows in situ monitoring of the lumen of ex vivo airway tissues during controlled in vitro tissue manipulation and cultivation of isolated rat trachea. Using this platform, we demonstrated selective removal of the rat tracheal epithelium (i.e., de-epithelialization) without disrupting the underlying subepithelial cells and extracellular matrix. Through different tissue evaluation assays, such as immunofluorescent staining, DNA/protein quantification, and electron beam microscopy, we showed that the epithelium of the tracheal lumen can be effectively removed with negligible disruption in the underlying tissue layers, such as cartilage and blood vessel. Notably, using a custom-built micro-optical imaging device integrated with the bioreactor, the trachea lumen was visualized at the cellular level in real time, and removal of the endogenous epithelium and distribution of locally delivered exogenous cells were demonstrated in situ. Moreover, the de-epithelialized trachea supported on the bioreactor allowed attachment and growth of exogenous cells seeded topically on its denuded tissue surface. Collectively, the results suggest that our imaging-enabled rat trachea bioreactor and selective cell replacement method can facilitate creating of bioengineered in vitro airway tissue that can be used in different biomedical applications.

bioengineering↗

Which lower-limb joints compensate for destabilising energy during walking in humans

Maintaining stability during perturbed locomotion requires coordinated responses across multiple levels of organization (e.g., legs, joints, muscle-tendon units). However, current approaches to investigating such responses lack a "common currency" that is both shared across scales and can be directly related to perturbation demands. We used mechanical energetics to investigate the demands imposed on a leg by a transient increase in unilateral treadmill belt speed targeted to either early or late stance. We collected full body kinematics and kinetics from 7 healthy participants during 222 total perturbations. From across-subject means, we found early stance perturbations elicited no change in net work exchanged between the perturbed leg and the treadmill but net positive work at the overall leg level, and late stance perturbations elicited positive work at the leg/treadmill interface but no change in net work at the overall leg level. Across all perturbations, changes in ankle and knee work from steady state best reflected changes in overall leg work on the perturbed and contralateral sides, respectively. Broadening this paradigm to include joint level (vs. leg level) perturbations and including muscle-tendon unit mechanical energetics may reveal neuromechanical responses used in destabilizing environments which could inform design of balance-assisting devices and interventions. Subject Areasbiomechanics, biomedical engineering, bioengineering

bioengineering↗

3D bioprinting of an implantable xeno-free vascularized human skin graft

Bioengineered tissues or organs produced using matrix proteins or components derived from xenogeneic sources pose risks of allergic responses, immune rejection, or even autoimmunity. Here, we report successful xeno-free isolation, expansion, and cryopreservation of human endothelial cells, fibroblasts, pericytes and keratinocytes from a single donor. We further demonstrate the bioprinting of a human skin substitute with a dermal layer containing xeno-free cultured human endothelial cells (EC), fibroblasts, and pericytes in a xeno-free bioink containing human collagen type I and fibronectin layered in a biocompatible polyglycolic acid (PGA) mesh and subsequently seeded with xeno-free human keratinocytes to form an epidermal layer. Following implantation of such bilayered skin grafts on the dorsum of immunodeficient mice, keratinocytes form a mature stratified epidermis with rete ridge-like structures. The ECs and pericytes form human EC-lined perfused microvessels within 2 weeks after implantation, preventing graft necrosis, and eliciting further perfusion of the graft by angiogenic host microvessels. In summary, we describe the fabrication of a bioprinted vascularized bilayered skin substitute under completely xeno-free culture conditions demonstrating feasibility of a xeno-free approach to complex tissue engineering.

bioengineering↗

Combining SLA 3D printing and soft lithography for fast, versatile, and accessible high-resolution fabrication of customised multiscale cell culture devices with complex designs

Cell culture devices, such as microwells and microfluidic chips, are designed to increase the complexity of cell-based models whilst retaining control over culture conditions and have become indispensable platforms for biological systems modelling. From microtopography, microwells, plating devices and microfluidic systems to larger constructs for specific applications such as live imaging chamber slides, a wide variety of culture devices with different geometries have become indispensable in biology laboratories. However, while their application in biological projects is increasing exponentially, due to a combination of the techniques and tools required for their manufacture, and the physical science background sometimes needed, the design and fabrication of such devices directly by biological labs remains a relatively high investment in terms of costs, use of facilities, needed collaborations and time. Whilst commercially available systems are available, these are also often costly, and importantly lack the potential for customisation by each single lab. This combination of factors still limits widespread application of microfabricated custom devices in most biological wet labs. Capitalising on recent important advancements in the fields of bioengineering and microfabrication, and taking advantage of low-cost, high-resolution desktop resin 3D printers combined with PDMS soft lithography, we have developed an optimised low-cost and highly reproducible microfabrication pipeline, capable of generating a wide variety of customisable devices for cell culture and tissue engineering in an easy, fast reproducible way for a fraction of the cost of conventional microfabrication or commercial alternatives. This protocol is designed specifically to be a resource for biological labs with little to none prior exposure to these fields technique and enables the manufacture of complex devices across the {micro}m to cm scale. We provide a ready-to-go pipeline for the efficient treatment of resin-based 3D printed constructs for PDMS curing, using a combination of curing steps, washes and surface treatments. Together with the extensive characterisation of the fabrication pipeline, we show the utilization of this system to a variety of applications and use cases relevant to biological experiments, ranging from micro topographies for cell alignments to complex multi-part hydrogel culturing systems. This methodology can be easily adopted by any wet lab, irrespective of prior expertise or resource availability and will enable the wide adoption of tailored microfabricated devices across many fields of biology.

bioengineering↗

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↗

Efficient algorithms for designing maximally sized orthogonal DNA sequence libraries

Orthogonal sequence library design is an essential task in bioengineering. Typical design approaches scale quadratically in the size of the candidate sequence space. As such, exhaustive searches of sequence space to maximize library size are computationally intractable with existing methods. Here, we present SeqWalk, a time and memory efficient method for designing maximally-sized orthogonal sequence libraries using the sequence symmetry minimization heuristic. SeqWalk encodes sequence design constraints in a de Bruijn graph representation of sequence space, enabling the application of efficient graph traversal techniques to the problem of orthogonal DNA sequence design. We demonstrate the scalability of SeqWalk by designing a provably maximal set of > 106 orthogonal 25nt sequences in less than 20 seconds on a single standard CPU core. We additionally derive fundamental bounds on orthogonal sequence library size under a variety of design constraints.

bioengineering↗

An off-the-shelf multi-well scaffold-supported platform for tumour organoid-based tissues

Complex 3D bioengineered tumour models provide the opportunity to better capture the heterogeneity of patient tumours. Patient-derived organoids are emerging as a useful tool to study tumour heterogeneity and variation in patient responses. Organoid cultures typically require a 3D microenvironment that can be manufactured easily to facilitate screening. Here we set out to create a high-throughput, "off-the-shelf" platform which permits the generation of organoid-containing microtissues for standard phenotypic bioassays and image-based readings. To achieve this, we developed the Scaffold-supported Platform for Organoid-based Tissues (SPOT) platform. SPOT is a 3D gel-embedded in vitro platform that can be produced in a 96- or 384-well plate format and enables the generation of flat, thin and dimensionally-defined microgels. SPOT has high potential for adoption due to its reproducible manufacturing methodology, compatibility with existing instrumentation, and reduced within-sample and between-sample variation, which can pose challenges to both data analysis and interpretation. Using SPOT we generate cultures from patient derived pancreatic ductal adenocarcinoma organoids and assess the cellular response to standard-of-care chemotherapeutic compounds, demonstrating our platforms usability for drug screening. We envision 96/384-SPOT will provide a useful tool to assess drug sensitivity of patient-derived organoids and easily integrate into the drug discovery pipeline.

bioengineering↗