Search

Multielectrode arrays are fabricated from thin films of highly conductive and ductile metals, which cannot mimic the natural environment of biological tissues. These properties limit the conformability of the electrode to the underlying target tissue and present challenges in developing seamless interfaces. By introducing porous, hydrogel materials that are embedded with metal additives, highly conductive hydrogels can be formed. Tuning the hydrogel composition, % volume and aspect ratio of different additive(s), and the processing conditions of these composite materials can alter the mechanical and electrical properties. The resulting materials have a high surface area and can be used as biomaterial scaffolds to support the growth of macrophages for 5 days. Further optimization can enable the use of the materials for the electrodes in implantable arrays, or as living electrode platforms, to study and modulate various cellular cultures. These advancements would benefit both in vivo and in vitro applications of tissue engineering.

Partial cell reprogramming has been demonstrated in certain mouse tissues by in situ overexpression of Oct3/4, Klf4, Sox2 and cMyc (OKSM) transcription factors, and can trigger rejuvenation and/or augment regeneration of aged or injured tissues. In vivo reprogramming of adult mouse cardiomyocytes has been elusive, but success could overcome the lack of endogenous cardiomyocyte turnover that contributes to the poor resolution of heart disease. Here, we exploited cell type-specific Cre recombination and conditional, doxycycline-inducible, control of gene expression to generate cardiomyocyte-specific, inducible, reprogrammable mice. Eighteen days of doxycycline-induced OKSM expression in this model established a gene expression program characteristic of the pluripotent state and triggered the generation of teratomas of confirmed cardiomyocyte origin. These findings confirm that OKSM reprograms adult mouse cardiomyocytes to pluripotency and will enable studies of the contribution of reprogrammed cardiomyocytes to cardiac regeneration.

The coronavirus disease 2019 (COVID‐19) pandemic demonstrates the importance of generating safe and efficacious vaccines that can be rapidly deployed against emerging pathogens. Subunit vaccines are considered among the safest, but proteins used in these typically lack strong immunogenicity, leading to poor immune responses. Here, a biomaterial COVID‐19 vaccine based on a mesoporous silica rods (MSRs) platform is described. MSRs loaded with granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), the toll‐like receptor 4 (TLR‐4) agonist monophosphoryl lipid A (MPLA), and SARS‐CoV‐2 viral protein antigens slowly release their cargo and form subcutaneous scaffolds that locally recruit and activate antigen‐presenting cells (APCs) for the generation of adaptive immunity. MSR‐based vaccines generate robust and durable cellular and humoral responses against SARS‐CoV‐2 antigens, including the poorly immunogenic receptor binding domain (RBD) of the spike (S) protein. Persistent antibodies over the course of 8 months are found in all vaccine configurations tested and robust in vitro viral neutralization is observed both in a prime‐boost and a single‐dose regimen. These vaccines can be fully formulated ahead of time or stored lyophilized and reconstituted with an antigen mixture moments before injection, which can facilitate its rapid deployment against emerging SARS‐CoV‐2 variants or new pathogens. Together, the data show a promising COVID‐19 vaccine candidate and a generally adaptable vaccine platform against infectious pathogens., Mesoporous silica rods (MSRs) scaffolds are used as a platform to induce adaptive immunity against SARS‐CoV‐2 antigens. Sustained delivery of GM‐CSF, MPLA, and a variety of SARS‐CoV‐2 subunit immunogens from the MSR vaccine recruite immune cells into the scaffolds and consistently induce antigen‐specific long‐lasting antibodies, cytotoxic T lymphocyte responses (CTL), and viral neutralization in vitro.

Correction for ‘Actuated 3D microgels for single cell mechanobiology’ by Berna Özkale et al., Lab Chip, 2022, 22, 1962–1970, https://doi.org/10.1039/D2LC00203E.

Living tissues are non-linearly elastic materials that exhibit viscoelasticity and plasticity. Man-made, implantable bioelectronic arrays mainly rely on rigid or elastic encapsulation materials and stiff films of ductile metals that can be manipulated with microscopic precision to offer reliable electrical properties. In this study, we have engineered a surface microelectrode array that replaces the traditional encapsulation and conductive components with viscoelastic materials. Our array overcomes previous limitations in matching the stiffness and relaxation behaviour of soft biological tissues by using hydrogels as the outer layers. We have introduced a hydrogel-based conductor made from an ionically conductive alginate matrix enhanced with carbon nanomaterials, which provide electrical percolation even at low loading fractions. Our combination of conducting and insulating viscoelastic materials, with top-down manufacturing, allows for the fabrication of electrode arrays compatible with standard electrophysiology platforms. Our arrays intimately conform to the convoluted surface of the heart or brain cortex and offer promising bioengineering applications for recording and stimulation., This work was supported in part by the Center for Nanoscale Systems at Harvard University, which is a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation under award no. 1541959. We thank the Weitz lab for the use of their rheometer, which is funded by the Materials Research Science and Engineering Center of Harvard University under National Science Foundation award no. DMR 14-20570. This work was supported by an NSF GRFP to C.M.T., as well as funding for C.M.T. through an NIH grant awarded to D.J.M. (RO1DE013033), NSF MRSEC award DMR 14-20570 and funding by the Wyss Institute for Biologically Inspired Engineering at Harvard University. I.d.L. was supported by the National Cancer Institute of the National Institutes of Health under award no. U01CA214369. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. H.W. gratefully acknowledges funding support from the Wyss Technology Development Fellowship. B.R.S. is supported by the National Institute of Dental and Craniofacial Research (R01DE013349) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (P2CHD086843). A.E.-A. received funding for this work from the European Union’s Horizon 2020 research and innovation programme through a Marie Sklodowska-Curie grant agreement no. 798504 (MECHANOSITY). K.K., C.C. and Y.S. were mainly funded by the EPSRC Programme Grant 2D-Health (EP/P00119X/1). C.C. acknowledges support by the EPSRC (EP/N010345/1). N.V., A.T., F.F. and S.P.L. were funded by the Bertarelli Foundation, the Wyss Center Geneva and SNSF Sinergia grant no. CRSII5_183519

In contrast to sintered calcium phosphates (CaPs) commonly employed as scaffolds to deliver mesenchymal stromal cells (MSCs) targeting bone repair, low temperature setting conditions of calcium deficient hydroxyapatite (CDHA) yield biomimetic topology with high specific surface area. In this study, the healing capacity of CDHA administering MSCs to bone defects is evaluated for the first time and compared with sintered beta-tricalcium phosphate (β-TCP) constructs sharing the same interconnected macroporosity. Xeno-free expanded human bone marrow MSCs attached to the surface of the hydrophobic β-TCP constructs, while infiltrating the pores of the hydrophilic CDHA. Implantation of MSCs on CaPs for 8 weeks in calvaria defects of nude mice exhibited complete healing, with bone formation aligned along the periphery of β-TCP, and conversely distributed within the pores of CDHA. Human monocyte-osteoclast differentiation was inhibited in vitro by direct culture on CDHA compared to β-TCP biomaterials and indirectly by administration of MSC-conditioned media generated on CDHA, while MSCs increased osteoclastogenesis in both CaPs in vivo. MSC engraftment was significantly higher in CDHA constructs, and also correlated positively with bone in-growth in scaffolds. These findings demonstrate that biomimetic CDHA are favorable carriers for MSC therapies and should be explored further towards clinical bone regeneration strategies. Statement of significance Delivery of mesenchymal stromal cells (MSCs) on calcium phosphate (CaP) biomaterials enhances reconstruction of bone defects. Traditional CaPs are produced at high temperature, but calcium deficient hydroxyapatite (CDHA) prepared at room temperature yields a surface structure more similar to native bone mineral. The objective of this study was to compare the capacity of biomimetic CDHA scaffolds with sintered β-TCP scaffolds for bone repair mediated by MSCs for the first time. In vitro, greater cell infiltration occurred in CDHA scaffolds and following 8 weeks in vivo, MSC engraftment was higher in CDHA compared to β-TCP, as was bone in-growth. These findings demonstrate the impact of material features such as surface structure, and highlight that CDHA should be explored towards clinical bone regeneration strategies.

Targeted immunomodulation of dendritic cells (DCs) in vivo will enable manipulation of T-cell priming and amplification of anticancer immune responses, but a general strategy has been lacking. Here we show that DCs concentrated by a biomaterial can be metabolically labelled with azido groups in situ, which allows for their subsequent tracking and targeted modulation over time. Azido-labelled DCs were detected in lymph nodes for weeks, and could covalently capture dibenzocyclooctyne (DBCO)-bearing antigens and adjuvants via efficient Click chemistry for improved antigen-specific CD8+ T-cell responses and antitumour efficacy. We also show that azido labelling of DCs allowed for in vitro and in vivo conjugation of DBCO-modified cytokines, including DBCO–IL-15/IL-15Rα, to improve priming of antigen-specific CD8+ T cells. This DC labelling and targeted modulation technology provides an unprecedented strategy for manipulating DCs and regulating DC–T-cell interactions in vivo. Dendritic cells concentrated in vivo within a hydrogel have been metabolically tagged with azido groups to enable tracking as well as delivery of antigens, adjuvants and cytokines, thereby facilitating targeted immunomodulation.

Myelofibrosis (MF) is a progressive, myeloid malignancy characterized by deposition of collagen and reticulin fibers in the bone marrow (BM). Previous studies have shown that monocytosis is associated with poor prognosis in MF, highlighting a potential pathogenic role for monocytes in MF. Although many studies have addressed the role of cell-intrinsic and soluble extracellular factors in MF development, it is currently unknown if mechanical properties of fibrotic BM contribute to aberrant differentiation of myeloid cells and of monocytes in particular. We first defined the stiffness and viscoelastic properties of healthy and fibrotic BM. Stiffness is defined as the resistance of a matrix to deformation, while viscoelasticity is the rate of dissipation of an applied stress over time. Independent of stiffness, an applied stress relaxes rapidly in a more viscous, liquid-like matrix, whereas in a more elastic, solid-like material, stress relaxes slowly. We next generated a cohort of fibrotic and non-fibrotic mice by transplanting retrovirally transduced JAK2V617F or empty vector (EV) control hematopoietic stem and progenitor cells (HSPCs) into lethally irradiated recipients. Femurs from these mice were harvested seven months post-transplant, as well as from age- and sex-matched healthy primary mice. Nanoindentation was performed to measure BM stiffness and viscoelasticity. Fibrotic BM showed higher stiffness, as well as trending higher elastic, solid-like properties, compared to BM of control mice. We then aimed to study the effect of matrix stiffness and viscoelasticity on monocytes. Human BM-derived monocytes were encapsulated in stiff, viscous or stiff, elastic hydrogels and cultured in the presence of GM-CSF, IL-4, and PGE2 for 3 days, followed by nanoString and flow cytometry analyses. Cells in elastic gels upregulated gene sets associated with co-stimulatory molecules and cytokine receptor signaling, MHC class II antigen presentation, and regulation of extracellular matrix (ECM), compared to cells in viscous gels of the same stiffness. The fraction of dendritic cells (DCs) was significantly upregulated, as indicated by double-positive CD11c+CD1c+ (40.9% viscous vs 69.5% elastic of CD11b+HLA-DR+ cells) and CD80+ cells (20.9% viscous vs 62.7% elastic of CD11b+HLA-DR+ cells), and surface expression of HLA-DR (gMFI 2587 viscous vs 6334 elastic). Consistent with these findings, the fraction of pro-fibrotic SLAMF7+ cells (4.2% viscous vs 17.3% elastic) were also significantly higher in elastic gels. Together, these data suggest that stiff, elastic ECM drives pro-inflammatory polarization and differentiation of monocytes into antigen-presenting cells. Next, we examined the role of the cytoskeleton on human monocyte differentiation. Cortical F-actin was significantly upregulated in cells in stiff, elastic gels compared to viscous gels. Cells were exposed to a highly selective small molecular inhibitor of the γ-isoform of PI3K. Treatment with the PI3Ky inhibitor significantly reduced F-actin staining of cells in elastic gels, upregulated immature monocyte markers, reduced surface expression of HLA-DR, and downregulated the cytokines IL6, IL8, CCL4, which have previously been associated with disease progression in myelofibrosis. In line with the above human ex vivo data, BM isolated from fibrotic mice (described above) showed skewing towards Ly6G-Ly6C+ monocytes (a population enriched for inflammatory monocytes) within the CD11b myeloid compartment compared to control transplanted mice or to non-fibrotic mice that were transplanted with endogenously expressing Jak2V617F cells. Additionally, the percentage of conventional DCs (cDCs) was increased in fibrotic Jak2V617F mice compared to control mice. Importantly, 16 day in vivo treatment with the PI3Ky inhibitor significantly reduced the fraction of Ly6G-Ly6C+ monocytes within the CD11b compartment as well as the fraction of cDCs, compared to vehicle-treated Jak2V617F mice. In summary, fibrotic BM is stiffer and more elastic than normal BM. Our studies show that a stiff, elastic BM environment drives monocytes towards a more pro-inflammatory state which can in part be suppressed by PI3K-γ inhibition. Our results have relevance for human MF by demonstrating that a fibrotic BM niche is not just a consequence of chronic inflammation but is also inflammation-promoting. KHV and AEM contributed equally to this work. Disclosures Pozdnyakova: Scopio Labs: Consultancy. Mullally: Janssen, PharmaEssentia, Constellation and Relay Therapeutics: Consultancy. Wucherpfennig: Novartis: Research Funding; Nextechinvest: Membership on an entity's Board of Directors or advisory committees; Immunitas Therapeutics: Current holder of individual stocks in a privately-held company; TScan Therapeutics: Membership on an entity's Board of Directors or advisory committees; TCR2 Therapeutics: Membership on an entity's Board of Directors or advisory committees; SQZ Biotech: Membership on an entity's Board of Directors or advisory committees. Mooney: Novartis: Patents & Royalties: Licensed IP, Research Funding; Sirenex: Patents & Royalties: Licensed IP; Samyang Corp: Membership on an entity's Board of Directors or advisory committees; IVIVA: Membership on an entity's Board of Directors or advisory committees; Attivare: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Revela: Membership on an entity's Board of Directors or advisory committees; Amend Surgical: Patents & Royalties: Licensed IP; Lyell: Current equity holder in publicly-traded company, Patents & Royalties.

Auditory brainstem implants (ABIs) provide sound awareness to deaf individuals who are not candidates for the cochlear implant. The ABI electrode array rests on the surface of the cochlear nucleus (CN) in the brainstem and delivers multichannel electrical stimulation. The complex anatomy and physiology of the CN, together with poor spatial selectivity of electrical stimulation and inherent stiffness of contemporary multichannel arrays, leads to only modest auditory outcomes among ABI users. Here, we hypothesized that a soft ABI could enhance biomechanical compatibility with the curved CN surface. We developed implantable ABIs that are compatible with surgical handling, conform to the curvature of the CN after placement, and deliver efficient electrical stimulation. The soft ABI array design relies on precise microstructuring of plastic-metal-plastic multilayers to enable mechanical compliance, patterning, and electrical function. We fabricated soft ABIs to the scale of mouse and human CN and validated them in vitro. Experiments in mice demonstrated that these implants reliably evoked auditory neural activity over 1 month in vivo. Evaluation in human cadaveric models confirmed compatibility after insertion using an endoscopic-assisted craniotomy surgery, ease of array positioning, and robustness and reliability of the soft electrodes. This neurotechnology offers an opportunity to treat deafness in patients who are not candidates for the cochlear implant, and the design and manufacturing principles are broadly applicable to implantable soft bioelectronics throughout the central and peripheral nervous system.

Mesenchymal stem cell (MSC) therapies demonstrate particular promise in ameliorating diseases of immune dysregulation but are hampered by short in vivo cell persistence and inconsistencies in phenotype. Here, we demonstrate that biomaterial encapsulation into alginate using a microfluidic device could substantially increase in vivo MSC persistence after intravenous (i.v.) injection. A combination of cell cluster formation and subsequent cross-linking with polylysine led to an increase in injected MSC half-life by more than an order of magnitude. These modifications extended persistence even in the presence of innate and adaptive immunity-mediated clearance. Licensing of encapsulated MSCs with inflammatory cytokine pretransplantation increased expression of immunomodulatory-associated genes, and licensed encapsulates promoted repopulation of recipient blood and bone marrow with allogeneic donor cells after sublethal irradiation by a ∼2-fold increase. The ability of microgel encapsulation to sustain MSC survival and increase overall immunomodulatory capacity may be applicable for improving MSC therapies in general.

Brain function depends on simultaneous electrical, chemical and mechanical signaling at the cellular level. This multiplicity has confounded efforts to simultaneously measure or modulate these diverse signals in vivo. Here we present fiber probes that allow for simultaneous optical stimulation, neural recording and drug delivery in behaving mice with high resolution. These fibers are fabricated from polymers by means of a thermal drawing process that allows for the integration of multiple materials and interrogation modalities into neural probes. Mechanical, electrical, optical and microfluidic measurements revealed high flexibility and functionality of the probes under bending deformation. Long-term in vivo recordings, optogenetic stimulation, drug perturbation and analysis of tissue response confirmed that our probes can form stable brain-machine interfaces for at least 2 months. We expect that our multifunctional fibers will permit more detailed manipulation and analysis of neural circuits deep in the brain of behaving animals than achievable before.

Reversible deformation is a unique property of elastic materials. Here, we design and fabricate highly stretchable multilayered films by patterning Y-shaped motifs through films of non- elastic materials, e.g. plastics, metals, ceramics. By adjusting the geometry and density of the motif, as well as the thickness of the film(s), the effective spring constant of the engineered film(s) can be tuned. Three-dimensional bending of the patterned film(s) enables macroscopic stretchability and minimizes local film strain fields. The engineered films demonstrate no preferential direction of stretching and the proposed design is versatile. Furthermore our approach is compatible with thin-film processing. We demonstrate the Y-shaped motifs allow for the design of stretchable plastic foils coated with metallic and metal oxide conductors. We anticipate the patterned motifs can be scaled down to offer a wider range of elastic electronic materials to use in stretchable electronics and to create soft bioelectronics. (c) 2017 Elsevier Ltd. All rights reserved.

We present a new cell culture technology for large-scale mechanobiology studies capable of generating and applying optically controlled uniform compression on single cells in 3D. Mesenchymal stem cells (MSCs) are individually encapsulated inside an optically triggered nanoactuator-alginate hybrid biomaterial using microfluidics, and the encapsulating network isotropically compresses the cell upon activation by light. The favorable biomolecular properties of alginate allow cell culture in vitro up to a week. The mechanically active microgels are capable of generating up to 15% compressive strain and forces reaching 400 nN. As a proof of concept, we demonstrate the use of the mechanically active cell culture system in mechanobiology by subjecting singly encapsulated MSCs to optically generated isotropic compression and monitoring changes in intracellular calcium intensity.