Sterilizable and Reusable UV-Resistant Graphene-Polyurethane Elastomer Composites.

Shortages of personal protective equipment (PPE) at the start of the COVID-19 pandemic caused medical workers to reuse medical supplies such as N95 masks. While ultraviolet germicidal irradiation (UVGI) is commonly used for sterilization, UVGI can also damage the elastomeric components of N95 masks, preventing effective fit and thus weakening filtration efficacy. Although PPE shortage is no longer an acute issue, the development of sterilizable and reusable UV-resistant elastomers remains of high interest from a long-term sustainability and health perspective. Here, graphene nanosheets, produced by scalable and sustainable exfoliation of graphite in ethanol using the polymer ethyl cellulose (EC), are utilized as UV-resistant additives in polyurethane (PU) elastomer composites. By increasing the graphene/EC loading up to 1 wt %, substantial UV protection is imparted by the graphene nanosheets, which strongly absorb UV light and hence suppress photoinduced degradation of the PU matrix. Additionally, graphene/EC provides mechanical reinforcement, such as increasing Young's modulus, elongation at break, and toughness, with negligible changes following UV exposure. These graphene/EC-PU composites remain mechanically robust over at least 150 sterilization cycles, enabling safe reuse following UVGI. Beyond N95 masks, these UVGI-compatible graphene/EC-PU composites have potential utility in other PPE applications to address the broader issue of single-use waste.

Aerosol-jet-printed graphene electrochemical immunosensors for rapid and label-free detection of SARS-CoV-2 in saliva.

Rapid, inexpensive, and easy-to-use coronavirus disease 2019 (COVID-19) home tests are key tools in addition to vaccines in the world-wide fight to eliminate national and local shutdowns. However, currently available tests for SARS-CoV-2, the virus that causes COVID-19, are too expensive, painful, and irritating, or not sufficiently sensitive for routine, accurate home testing. Herein, we employ custom-formulated graphene inks and aerosol jet printing (AJP) to create a rapid electrochemical immunosensor for direct detection of SARS-CoV-2 Spike Receptor-Binding Domain (RBD) in saliva samples acquired non-invasively. This sensor demonstrated limits of detection that are considerably lower than most commercial SARS-CoV-2 antigen tests (22.91 ± 4.72 pg/mL for Spike RBD and 110.38 ± 9.00 pg/mL for Spike S1) as well as fast response time (~30 mins), which was facilitated by the functionalization of printed graphene electrodes in a single-step with SARS-CoV-2 polyclonal antibody through the carbodiimide reaction without the need for nanoparticle functionalization or secondary antibody or metallic nanoparticle labels. This immunosensor presents a wide linear sensing range from 1 to 1000 ng/mL and does not react with other coexisting influenza viruses such as H1N1 hemagglutinin. By combining high-yield graphene ink synthesis, automated printing, high antigen selectivity, and rapid testing capability, this work offers a promising alternative to current SARS-CoV-2 antigen tests.

Persistent polyamorphism in the chiton tooth: From a new biomineral to inks for additive manufacturing.

Engineering structures that bridge between elements with disparate mechanical properties are a significant challenge. Organisms reap synergy by creating complex shapes that are intricately graded. For instance, the wear-resistant cusp of the chiton radula tooth works in concert with progressively softer microarchitectural units as the mollusk grazes on and erodes rock. Herein, we focus on the stylus that connects the ultrahard and stiff tooth head to the flexible radula membrane. Using techniques that are especially suited to probe the rich chemistry of iron at high spatial resolution, in particular synchrotron Mössbauer and X-ray absorption spectroscopy, we find that the upper stylus of Cryptochiton stelleri is in fact a mineralized tissue. Remarkably, the inorganic phase is nano disperse santabarbaraite, an amorphous ferric hydroxyphosphate that has not been observed as a biomineral. The presence of two persistent polyamorphic phases, amorphous ferric phosphate and santabarbaraite, in close proximity, is a unique aspect that demonstrates the level of control over phase transformations in C. stelleri dentition. The stylus is a highly graded material in that its mineral content and mechanical properties vary by a factor of 3 to 8 over distances of a few hundred micrometers, seamlessly bridging between the soft radula and the hard tooth head. The use of amorphous phases that are low in iron and high in water content may be key to increasing the specific strength of the stylus. Finally, we show that we can distill these insights into design criteria for inks for additive manufacturing of highly tunable chitosan-based composites.

Fully Inkjet-Printed, Mechanically Flexible MoS2 Nanosheet Photodetectors.

Solution-processed two-dimensional materials offer a scalable route toward next-generation printed devices. In this report, we demonstrate fully inkjet-printed photodetectors using molybdenum disulfide (MoS2) nanosheets as the active material and graphene as the electrodes. Percolating films of semiconducting MoS2 with high electrical conductivity are achieved with an ethyl cellulose-based ink formulation. Two classes of photodetectors are fabricated, including thermally annealed devices on glass with fast photoresponse of 150 µs and photonically annealed devices on flexible polyimide with high photoresponsivity exceeding 50 mA/W. The photonically annealed photodetector also reduces the curing time to milliseconds and maintains functionality over 500 bending cycles.

Three-Dimensional Printing of Cytocompatible, Thermally Conductive Hexagonal Boron Nitride Nanocomposites.

Hexagonal boron nitride (hBN) is a thermally conductive yet electrically insulating two-dimensional layered nanomaterial that has attracted significant attention as a dielectric for high-performance electronics in addition to playing a central role in thermal management applications. Here, we report a high-content hBN-polymer nanocomposite ink, which can be 3D printed to form mechanically robust, self-supporting constructs. In particular, hBN is dispersed in poly(lactic- co-glycolic acid) and 3D printed at room temperature through an extrusion process to form complex architectures. These constructs can be 3D printed with a composition of up to 60% vol hBN (solids content) while maintaining high mechanical flexibility and stretchability. The presence of hBN within the matrix results in enhanced thermal conductivity (up to 2.1 W K-1 m-1) directly after 3D printing with minimal postprocessing steps, suggesting utility in thermal management applications. Furthermore, the constructs show high levels of cytocompatibility, making them suitable for use in the field of printed bioelectronics.

Combustion-Assisted Photonic Annealing of Printable Graphene Inks via Exothermic Binders.

High-throughput and low-temperature processing of high-performance nanomaterial inks is an important technical challenge for large-area, flexible printed electronics. In this report, we demonstrate nitrocellulose as an exothermic binder for photonic annealing of conductive graphene inks, leveraging the rapid decomposition kinetics and built-in energy of nitrocellulose to enable versatile process integration. This strategy results in superlative electrical properties that are comparable to extended thermal annealing at 350 °C, using a pulsed light process that is compatible with thermally sensitive substrates. The resulting porous microstructure and broad liquid-phase patterning compatibility are exploited for printed graphene microsupercapacitors on paper-based substrates.

A population of selected renal cells augments renal function and extends survival in the ZSF1 model of progressive diabetic nephropathy.

New treatment paradigms that slow or reverse progression of chronic kidney disease (CKD) are needed to relieve significant patient and healthcare burdens. We have shown that a population of selected renal cells (SRCs) stabilized disease progression in a mass reduction model of CKD. Here, we further define the cellular composition of SRCs and apply this novel therapeutic approach to the ZSF1 rat, a model of severe progressive nephropathy secondary to diabetes, obesity, dyslipidemia, and hypertension. Injection of syngeneic SRCs into the ZSF1 renal cortex elicited a regenerative response that significantly improved survival and stabilized disease progression to renal structure and function beyond 1 year posttreatment. Functional improvements included normalization of multiple nephron structures and functions including glomerular filtration, tubular protein handling, electrolyte balance, and the ability to concentrate urine. Improvements to blood pressure, including reduced levels of circulating renin, were also observed. These functional improvements following SRC treatment were accompanied by significant reductions in glomerular sclerosis, tubular degeneration, and interstitial inflammation and fibrosis. Collectively, these data support the utility of a novel renal cell-based approach for slowing renal disease progression associated with diabetic nephropathy in the setting of metabolic syndrome, one of the most common causes of end-stage renal disease.

Isolation, characterization, and expansion methods for defined primary renal cell populations from rodent, canine, and human normal and diseased kidneys.

Chronic kidney disease (CKD) is a global health problem; the growing gap between the number of patients awaiting transplant and organs actually transplanted highlights the need for new treatments to restore renal function. Regenerative medicine is a promising approach from which treatments for organ-level disorders (e.g., neurogenic bladder) have emerged and translated to clinics. Regenerative templates, composed of biodegradable material and autologous cells, isolated and expanded ex vivo, stimulate native-like organ tissue regeneration after implantation. A critical step for extending this strategy from bladder to kidney is the ability to isolate, characterize, and expand functional renal cells with therapeutic potential from diseased tissue. In this study, we developed methods that yield distinct subpopulations of primary kidney cells that are compatible with process development and scale-up. These methods were translated to rodent, large mammal, and human kidneys, and then to rodent and human tissues with advanced CKD. Comparative in vitro studies demonstrated that phenotype and key functional attributes were retained consistently in ex vivo cultures regardless of species or disease state, suggesting that autologous sourcing of cells that contribute to in situ kidney regeneration after injury is feasible, even with biopsies from patients with advanced CKD.

Tubular cell-enriched subpopulation of primary renal cells improves survival and augments kidney function in rodent model of chronic kidney disease.

Established chronic kidney disease (CKD) may be identified by severely impaired renal filtration that ultimately leads to the need for dialysis or kidney transplant. Dialysis addresses only some of the sequelae of CKD, and a significant gap persists between patients needing transplant and available organs, providing impetus for development of new CKD treatment modalities. Some postulate that CKD develops from a progressive imbalance between tissue damage and the kidney's intrinsic repair and regeneration processes. In this study we evaluated the effect of kidney cells, delivered orthotopically by intraparenchymal injection to rodents 4-7 wk after CKD was established by two-step 5/6 renal mass reduction (NX), on the regeneration of kidney function and architecture as assessed by physiological, tissue, and molecular markers. A proof of concept for the model, cell delivery, and systemic effect was demonstrated with a heterogeneous population of renal cells (UNFX) that contained cells from all major compartments of the kidney. Tubular cells are known contributors to kidney regeneration in situ following acute injury. Initially tested as a control, a tubular cell-enriched subpopulation of UNFX (B2) surprisingly outperformed UNFX. Two independent studies (3 and 6 mo in duration) with B2 confirmed that B2 significantly extended survival and improved renal filtration (serum creatinine and blood urea nitrogen). The specificity of B2 effects was verified by direct comparison to cell-free vehicle controls and an equivalent dose of non-B2 cells. Quantitative histological evaluation of kidneys at 6 mo after treatment confirmed that B2 treatment reduced severity of kidney tissue pathology. Treatment-associated reduction of transforming growth factor (TGF)-ß1, plasminogen activator inhibitor (PAI)-1, and fibronectin (FN) provided evidence that B2 cells attenuated canonical pathways of profibrotic extracellular matrix production.