HIV-1 Broadly Neutralizing Antibody Extracts Its Epitope from a Kinked gp41 Ectodomain Region on the Viral Membrane

SummaryAlthough rarely elicited during natural human infection, the most broadly neutralizing antibodies (BNAbs) against diverse human immunodeficiency virus (HIV)-1 strains target the membrane-proximal ectodomain region (MPER) of viral gp41. To gain insight into MPER antigenicity, immunogenicity, and viral function, we studied its structure in the lipid environment by a combination of nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and surface plasmon resonance (SPR) techniques. The analyses revealed a tilted N-terminal α helix (aa 664–672) connected via a short hinge to a flat C-terminal helical segment (675–683). This metastable L-shaped structure is immersed in viral membrane and, therefore, less accessible to immune attack. Nonetheless, the 4E10 BNAb extracts buried W672 and F673 after initial encounter with the surface-embedded MPER. The data suggest how BNAbs may perturb tryptophan residue-associated viral fusion involving the mobile N-terminal MPER segment and, given conservation of MPER sequences in HIV-1, HIV-2, and SIV, have important implications for structure-guided vaccine design

Fully Printed Ultraflexible Supercapacitor Supported by a Single-Textile Substrate

Textile-based supercapacitors have recently attracted much attention owing to their great potential as energy storage components in wearable electronics. However, fabrication of a high-performance, fully printed, and ultraflexible supercapacitor based on a single textile still remains a great challenge. Herein, a facile, low-cost, and textile-compatible method involving screen printing and transfer printing is developed to construct all-solid-state supercapacitors on a single silk fabric. The system exhibits a high specific capacitance of 19.23 mF cm^–2 at a current density of 1 mA cm^–2 and excellent cycling stability with capacitance retention of 84% after 2000 charging/discharging cycles. In addition, the device possesses superior mechanical stability with stable performance and structures after 100 times of bending and twisting. A butterfly-patterned supercapacitor was manufactured to demonstrate the compatibility of the printing approaches to textile aesthetics. This work may provide a facile and versatile approach for fabricating rationally designed ultraflexible textile-based power-storage elements for potential applications in smart textiles and stretchable/flexible electronics

Enhance electron transfer and performance of microbial fuel cells by perforating the cell membrane

In this study, a facile bacteria treatment approach by chemically "perforating" pores and channels on the bacterial membrane is developed to significantly improve the electron transfer rate and power density of microbial fuel cell (MFC). The enhancements are due to increased mediator excretion evidenced by UV–vis absorption measurements and enhanced direct electron transfer through the bacterial membrane as proved by the significantly increased bioelectrocatalytic currents measured with cyclic voltammograms

A Sandwich-Structured Piezoresistive Sensor with Electrospun Nanofiber Mats as Supporting, Sensing, and Packaging Layers

Electrospun nanofiber mats have been used as sensing elements to construct piezoresistive devices due to their large surface area and high porosity. However, they have not been utilized as skin-contact supporting layers to package conductive nanofiber networks for the fabrication of piezoresistive sensors. In this work, we developed a sandwich-structured pressure sensor, which can sensitively monitor human motions and vital signs, with electrospun nanofiber mats as supporting, sensing, and packaging layers. The nanofiber mats were prepared by electrospinning with biocompatible poly (l-lactide) (PLA), silk fibroin (SF), and collagen (COL) as raw materials. The synthesized PLA–SF–COL mat possesses a non-woven structure with a fiber diameter of 122 ± 28 nm and a film thickness of 37 ± 5.3 μm. Polypyrrole (PPy) nanoparticles were grown in-situ on the mat to form a conductive layer. After stacking the pristine and conductive mats to form a PLA–SF–COL mat/(PPy-coated mat)2 structure, another layer was electrospun to pack the multilayers for the construction of a sandwich-structured piezoresistive sensor. The as-prepared device can sensitively detect external pressures caused by coin loading and finger tapping/pressing. It can also tolerate more than 600 times of pressing without affecting its sensing capability. The human body-attached experiments further demonstrate that the sensor could real-time monitor finger/arm bending, arterial pulse, respiration rate, and speaking-caused throat vibration. The electrospinning-based fabrication may be used as a facile and low-cost strategy to produce flexible piezoresistive sensors with excellent skin-compatibility and great pressure sensing capability

Hierarchical Porous Carbon Fibers for Enhanced Interfacial Electron Transfer of Electroactive Biofilm Electrode

The nanoporous carbon fiber materials derived from electrospun polyacrylonitrile (PAN) fibers doped with zeolitic imidazolate framework are developed here and applied in the microbe fuel cell anode for enhanced interfacial electron transfer. Zeolitic imidazolate fram-8 (ZIF-8) could introduce a large number of mesopores into fibers, which significantly promote indirect electron transfer mediated by flavins (IET). Moreover, it is noted that thinner fibers are more suitable for cytochromes-based direct electron transfer (DET). Furthermore, the enlarged fiber interspace strengthens the amount of biofilm loading but a larger interspace between thick fibers would hinder the formation of continuous biofilm. Consequently, the nanoporous carbon fiber derived from PAN/ZIF-8 composite with a 1:1 wt ratio shows the best performance according to its suitable mesoporous structure and optimal fiber diameter, which delivers a 10-fold higher maximum power density in microbial fuel cells compared to carbon fabric. In this work, we reveal that the proportion of IET and DET in the interfacial electron transfer process varies with different porous structures and fiber diameters, which may provide some insights for designing porous fiber electrodes for microbial fuel cells and also other devices of bioelectrochemical systems

Hierarchical Porous Carbon Fibers for Enhanced Interfacial Electron Transfer of Electroactive Biofilm Electrode

The nanoporous carbon fiber materials derived from electrospun polyacrylonitrile (PAN) fibers doped with zeolitic imidazolate framework are developed here and applied in the microbe fuel cell anode for enhanced interfacial electron transfer. Zeolitic imidazolate fram-8 (ZIF-8) could introduce a large number of mesopores into fibers, which significantly promote indirect electron transfer mediated by flavins (IET). Moreover, it is noted that thinner fibers are more suitable for cytochromes-based direct electron transfer (DET). Furthermore, the enlarged fiber interspace strengthens the amount of biofilm loading but a larger interspace between thick fibers would hinder the formation of continuous biofilm. Consequently, the nanoporous carbon fiber derived from PAN/ZIF-8 composite with a 1:1 wt ratio shows the best performance according to its suitable mesoporous structure and optimal fiber diameter, which delivers a 10-fold higher maximum power density in microbial fuel cells compared to carbon fabric. In this work, we reveal that the proportion of IET and DET in the interfacial electron transfer process varies with different porous structures and fiber diameters, which may provide some insights for designing porous fiber electrodes for microbial fuel cells and also other devices of bioelectrochemical systems

Cobalt valence modulating in CoOx incorporated carbon nanofiber for enhanced glucose electrooxidation

Glucose fuel cells (GFCs) driven by abiotic catalysts are promising green power sources for portable or wearable devices. In this work, a CoOx incorporated carbon nanofiber (CoOx@CNF) catalyst with mixed valences cobalt oxides have been developed through partial oxidation of pyrolyzed electrospun Co2+/poly acrylonitrile fibers. The cobalt valence modulating could be achieved via regulating the incorporation ratio of cobalt acetate in precursors or the oxidation temperature of the pyrolyzed fibers. Electrocatalytic analyses show that the presence of CoO in CoOx@CNF will provide more active sites for glucose electrooxidation, and thus enhance the electrocatalytic performance significantly. As a result, the glucose fuel cell built with the CoOx@CNF anode containing both CoO and Co3O4 delivered a maximum power density of 270 μW cm−2, which is higher than that of other reported Co3O4 based GFCs. This work provides a simple strategy to develop excellent transition metal catalysts for GFCs to expand their applications in portable and wearable energy devices

Polydopamine-Functionalization of Graphene Oxide to Enable Dual Signal Amplification for Sensitive Surface Plasmon Resonance Imaging Detection of Biomarker

Surface plasmon resonance imaging (SPRi) is one of the powerful tools for immunoassays with advantages of label-free, real-time, and high-throughput; however, it often suffers from limited sensitivity. Herein we report a dual signal amplification strategy utilizing polydopamine (PDA) functionalization of reduced graphene oxide (PDA-rGO) nanosheets for sensitive SPRi immunoassay in serum. The PDA-rGO nanosheet is synthesized by oxidative polymerization of dopamine in a gentle alkaline solution in the presence of graphene oxide (GO) sheets and then is antibody-conjugated via a spontaneous reaction between the protein and the PDA component. In the dual amplification mode, the first signal comes from capture of the antibody-conjugated PDA-rGO to form sandwiched immunocomplexes on the SPRi chip, followed by a PDA-induced spontaneous gold reductive deposition on PDA-rGO to further enhance the SPRi signal. The detection limit as low as 500 pg mL^–1 is achieved on a nonfouling SPRi chip with high specificity and a wide dynamic range for a model biomarker, carcinoembryonic antigen (CEA) in 10% human serum