Person:

Seo, Bo Ri

Living tissues are non-linearly elastic materials that exhibit viscoelasticity and plasticity1,2. Man-made, implantable bioelectronics mainly rely on rigid or elastic encapsulation materials and brittle thin films of metal that can be manipulated with microscopic precision to offer reliable electrical properties3–7. Here, we engineer a surface microelectrode array that replaces both the traditional encapsulation and conductive components with viscoelastic materials. Our entirely viscoelastic array overcomes previous limitations in matching the stiffness and relaxation behavior of soft biological tissues by using hydrogels as the outer layers. We introduce a novel hydrogel-based conductor made from an ionically conductive alginate matrix enhanced with carbon nanomaterials (graphene, carbon nanotubes). These high aspect ratio additives provide electrical percolation even at low loading fractions, and we fabricate ultra-soft viscoelastic conductive electrodes and electrical tracks that intimately conform to the convoluted surface of the heart or the brain cortex. Our combination of conducting and insulating viscoelastic materials, with top-down manufacturing, allows for the versatile fabrication of electrode arrays compatible with standard electrophysiology platforms, and offer promising applications in bioengineering and nanomedicine.

Ischemic diseases are a leading cause of mortality and can result in autoamputation of lower limbs. We explored the hypothesis that implantation of an antigen-releasing scaffold, in animals previously vaccinated with the same antigen, can concentrate TH2 T cells and enhance vascularization of ischemic tissue. This approach may be clinically relevant, as all persons receiving childhood vaccines recommended by the Centers for Disease Control and Prevention have vaccines that contain aluminum, a TH2 adjuvant. To test the hypothesis, mice with hindlimb ischemia, previously vaccinated with ovalbumin (OVA) and aluminum, received OVA-releasing scaffolds. Vaccinated mice receiving OVA-releasing scaffolds locally concentrated antigen-specific TH2 T cells in the surrounding ischemic tissue. This resulted in local angiogenesis, increased perfusion in ischemic limbs, and reduced necrosis and enhanced regenerating myofibers in the muscle. These findings support the premise that antigen depots may provide a treatment for ischemic diseases in patients previously vaccinated with aluminum-containing adjuvants.

While mechanical stimulation is known to regulate a wide range of biological processes at the cellular and tissue level, its medical use for tissue regeneration and rehabilitation has been limited by the availability of suitable devices. Here we present a mechanically active gel-elastomer-nitinol tissue adhesive (MAGENTA) that generates and delivers muscle contraction mimicking stimulation to a target tissue with programmed strength and frequency. MAGENTA consists of shape memory alloy spring that enables actuation up to 40% strain, and an adhesive that efficiently transmits the actuation to the underlying tissue. MAGENTA activates mechanosensing pathways involving yes-associated protein (YAP) and myocardin related transcription factor A (MRTFA) and increases the muscle rate of protein synthesis. Disuse muscles treated with MAGENTA exhibit greater size and weight, and generate higher forces compared to untreated muscles, demonstrating prevention of atrophy. MAGENTA has thus promising applications in the treatment of muscle atrophy and regenerative medicine.