Perforated red blood cells enable compressible and injectable hydrogels as therapeutic vehicles

Hydrogels engineered for medical use within the human body need to be delivered in a minimally invasive fashion without altering their biochemical and mechanical properties to maximize their therapeutic outcomes. In this regard, key strategies applied for creating such medical hydrogels include formulating precursor solutions that can be crosslinked in situ with physical or chemical cues following their delivery or forming macroporous hydrogels at sub-zero temperatures via cryogelation prior to their delivery. Here, we present a new class of injectable composite materials with shape recovery ability. The shape recovery is derived from the physical properties of red blood cells (RBCs) that are first modified via hypotonic swelling and then integrated into the hydrogel scaffolds before polymerization. The RBCs' hypotonic swelling induces the formation of nanometer-sized pores on their cell membranes, which enable fast liquid release under compression. The resulting biocomposite hydrogel scaffolds display high deformability and shape-recovery ability. The scaffolds can repeatedly compress up to ~87% of their original volumes during injection and subsequent retraction through syringe needles of different sizes; this cycle of injection and retraction can be repeated up to ten times without causing any substantial mechanical damage to the scaffolds. Our biocomposite material system and fabrication approach for injectable materials will be foundational for the minimally invasive delivery of drug-loaded scaffolds, tissue-engineered constructs, and personalized medical platforms that could be administered to the human body with conventional needle-syringe systems

Dynamic control of high-voltage actuator arrays by light-pattern projection on photoconductive switches

The ability to control high-voltage actuator arrays relies, to date, on expensive microelectronic processes or on individual wiring of each actuator to a single off-chip high-voltage switch. Here we present an alternative approach that uses on-chip photoconductive switches together with a light projection system to individually address high-voltage actuators. Each actuator is connected to one or more switches that are nominally OFF unless turned ON using direct light illumination. We selected hydrogenated amorphous silicon as our photoconductive material, and we provide complete characterization of its light to dark conductance, breakdown field, and spectral response. The resulting switches are very robust, and we provide full details of their fabrication processes. We demonstrate that the switches can be integrated in different architectures to support both AC and DC-driven actuators and provide engineering guidelines for their functional design. To demonstrate the versatility of our approach, we demonstrate the use of the photoconductive switches in two distinctly different applications control of micrometer-sized gate electrodes for patterning flow fields in a microfluidic chamber, and control of centimeter-sized electrostatic actuators for creating mechanical deformations for haptic displays

Biohybrid nanointerfaces for neuromodulation

Neural prostheses are bio-hybrid devices that interface electrodes with human tissue to stimulate neurons or record their activity. Conventional neural interfaces require surgical insertion of electrodes into the tissue to form contact with target cells and do not coherently integrate with the surrounding tissue. To overcome these limitations, advanced micro/nano-implants are proposed, which incorporate soft and nanomaterials featuring biophysical responsiveness, biocompatibility, and compliant design. In this review, we describe how stimuli-responsive nanotechnology and deformable materials have contributed to miniaturization, high-resolution operation, and biocompatibility in neuromodulation strategies, with a focus on nanoscaled neurotechnologies that affect neural tissue growth and functionality. We conclude by highlighting future directions for biocompliant and translatable neuromodulation across a combination of nanotransducers, soft implantable materials, and computationally guided interface design.ISSN:1748-0132ISSN:1878-044

Perfusable Biohybrid Designs for Bioprinted Skeletal Muscle Tissue

Engineered, centimeter-scale skeletal muscle tissue (SMT) can mimic muscle pathophysiology to study development, disease, regeneration, drug response, and motion. Macroscale SMT requires perfusable channels to guarantee cell survival, and support elements to enable mechanical cell stimulation and uniaxial myofiber formation. Here, stable biohybrid designs of centimeter-scale SMT are realized via extrusion-based bioprinting of an optimized polymeric blend based on gelatin methacryloyl and sodium alginate, which can be accurately coprinted with other inks. A perfusable microchannel network is designed to functionally integrate with perfusable anchors for insertion into a maturation culture template. The results demonstrate that i) coprinted synthetic structures display highly coherent interfaces with the living tissue, ii) perfusable designs preserve cells from hypoxia all over the scaffold volume, iii) constructs can undergo passive mechanical tension during matrix remodeling, and iv) the constructs can be used to study the distribution of drugs. Extrusion-based multimaterial bioprinting with the inks and design realizes in vitro matured biohybrid SMT for biomedical applications.ISSN:2192-2640ISSN:2192-265

Targeted gene editing by transfection of <i>in vitro</i> reconstituted <i>Streptococcus thermophilus</i> Cas9 nuclease complex

Targeted gene editing by transfection of <i>in vitro</i> reconstituted <i>Streptococcus thermophilus</i> Cas9 nuclease comple