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BACKGROUND. Weeks after SARS-CoV-2 infection or exposure, some children develop a severe, life-threatening illness called multisystem inflammatory syndrome in children (MIS-C). Gastrointestinal (GI) symptoms are common in patients with MIS-C, and a severe hyperinflammatory response ensues with potential for cardiac complications. The cause of MIS-C has not been identified to date. METHODS. Here, we analyzed biospecimens from 100 children: 19 with MIS-C, 26 with acute COVID-19, and 55 controls. Stools were assessed for SARS-CoV-2 by reverse transcription PCR (RT-PCR), and plasma was examined for markers of breakdown of mucosal barrier integrity, including zonulin. Ultrasensitive antigen detection was used to probe for SARS-CoV-2 antigenemia in plasma, and immune responses were characterized. As a proof of concept, we treated a patient with MIS-C with larazotide, a zonulin antagonist, and monitored the effect on antigenemia and the patient's clinical response. RESULTS. We showed that in children with MIS-C, a prolonged presence of SARS-CoV-2 in the GI tract led to the release of zonulin, a biomarker of intestinal permeability, with subsequent trafficking of SARS-CoV-2 antigens into the bloodstream, leading to hyperinflammation. The patient with MIS-C treated with larazotide had a coinciding decrease in plasma SARSCoV-2 spike antigen levels and inflammatory markers and a resultant clinical improvement above that achieved with currently available treatments. CONCLUSION. These mechanistic data on MIS-C pathogenesis provide insight into targets for diagnosing, treating, and preventing MIS-C, which are urgently needed for this increasingly common severe COVID-19-related disease in children., Introduction Most children who are acutely infected with SARS-CoV-2 develop mild upper respiratory symptoms or experience asymptomatic infection. Several days to weeks after resolution of the initial infection, some of [...]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins were measured in longitudinal plasma samples collected from 13 participants who received two doses of mRNA-1273 vaccine. Eleven of 13 participants showed detectable levels of SARS-CoV-2 protein as early as day 1 after first vaccine injection. Clearance of detectable SARS-CoV-2 protein correlated with production of immunoglobulin G (IgG) and immunoglobulin A (IgA). [ABSTRACT FROM AUTHOR]

The virus bioresistor (VBR) is a chemiresistor that directly transfers information from virus particles to an electrical circuit. Specifically, the VBR enables the label-free detection of a target protein that is recognized and bound by filamentous M13 virus particles, each with dimensions of 6 nm (w) × 1 μm (l), entrained in an ultrathin (~250 nm) composite virus-polymer resistor. Signal produced by the specific binding of virus to target molecules is monitored using the electrical impedance of the VBR: The VBR presents a complex impedance that is modeled by an equivalent circuit containing just three circuit elements: a solution resistance (Rsoln), a channel resistance (RVBR), and an interfacial capacitance (CVBR). The value of RVBR, measured across 5 orders of magnitude in frequency, is increased by the specific recognition and binding of a target protein to the virus particles in the resistor, producing a signal ΔRVBR. The VBR concept is demonstrated using a model system in which human serum albumin (HSA, 66 kDa) is detected in a phosphate buffer solution. The VBR cleanly discriminates between a change in the electrical resistance of the buffer, measured by Rsoln, and selective binding of HSA to virus particles, measured by RVBR. The ΔRVBR induced by HSA binding is as high as 200 Ω, contributing to low sensor-to-sensor coefficients-of-variation (<15%) across the entire calibration curve for HSA from 7.5 nM to 900 nM. The response time for the VBR is 3-30 s. [ABSTRACT FROM AUTHOR]

The label-free detection of human serum albumin (HSA) in aqueous buffer is demonstrated using a simple, monolithic, two-electrode electrochemical biosensor. In this device, both millimeter-scale electrodes are coated with a thin layer of a composite containing M13 virus particles and the electronically conductive polymer poly(3,4-ethylenedioxy thiophene) or PEDOT. These virus particles, engineered to selectively bind HSA, serve as receptors in this biosensor. The resistance component of the electrical impedance, Zre, measured between these two electrodes provides electrical transduction of HSA binding to the virus-PEDOT film. The analysis of sample volumes as small as 50 μL is made possible using a microfluidic cell. Upon exposure to HSA, virus-PEDOT films show a prompt increase in Zre within 5 s and a stable Zre signal within 15 min. HSA concentrations in the range from 100 nM to 5 μM are detectable. Sensor-to-sensor reproducibility of the HSA measurement is characterized by a coefficient-of-variance (COV) ranging from 2% to 8% across this entire concentration range. In addition, virus-PEDOT sensors successfully detected HSA in synthetic urine solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrodeposition and electropolymerization have emerged as versatile tools for the fabrication of chemical and biosensors. The literature in this area, published since 2017, is the main focus of this review. Electropolymerization has played a particularly prominent role in sensor development since its discovery in 1980 by Diaz at IBM. The ability to entrain receptors such as antibodies, engineered virus particles, and metal chelating agents into a conductive polymer sensing element during electropolymerization has proven to be a powerful means of preparing chemiresistors for a variety of analyses. Electrodeposition has also been used to prepare nanostructured metal indicator microelectrodes, enabling of a new modality for transducing biosensors. Electrodeposited metal nanowires have formed the basis for rapid and sensitive sensors for hydrogen gas. Electrodeposition has also been exploited as a powerful means for amplifying weak biosensor signals, extending their dynamic range. Opportunities for the application of electrodeposition and electropolymerization for chemical and biological sensor fabrication and function are discussed. [ABSTRACT FROM AUTHOR]

Single-molecule-enzymology (SME) methods have enabled the observation of heterogeneous catalytic activities within a single enzyme population. Heterogeneous activity is hypothesized to originate from conformational changes in the enzyme that result from changes in the local environment leading to catalytically active substates. Here, we use SME to investigate the mechanisms of heterogeneous activity exhibited by tissue nonspecific alkaline phosphatase (TNSALP), which reveals two subpopulations with different catalytic activities. We show the effect of pH and temperature on the distribution of TNSALP activity and confirm the presence of two subpopulations attributed to half- and fully active TNSALP substates. We provide mechanistic insight about protein structure using molecular dynamic simulations and show pH- and temperature-dependent conformational transitions that corroborate experimentally observed changes in TNSALP activity. These results show the utility of SME to understand heterogeneous enzyme activity and demonstrate a simple approach using pH and temperature to tune catalytic activity within an enzyme population., (Copyright © 2022 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Humoral immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during acute infection and convalescence has been widely studied since March 2020. In this review, the authors summarize literature on humoral responses to SARS-CoV-2 antigens with a focus on spike, nucleocapsid, and the receptor-binding domain as targets of antibody responses. They highlight serologic studies during acute SARS-CoV-2 infection and discuss the clinical relevance of antibody levels in COVID-19 progression. Antibody responses in pediatric COVID-19 patients are also reviewed. Finally, the authors discuss antibody responses during convalescence and their role in protection from SARS-CoV-2 reinfection., Competing Interests: Disclosure D.R. Walt has a financial interest in Quanterix Corporation, a company that develops an ultrasensitive digital immunoassay platform. He is an inventor of the Simoa technology, founder of the company, and serves on its Board of Directors. Dr D.R. Walt’s interests were reviewed and are managed by Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict-of-interest policies., (Copyright © 2021 Elsevier Inc. All rights reserved.)

DJ-1, a 20.7 kDa protein, is overexpressed in people who have bladder cancer (BC). Its elevated concentration in urine allows it to serve as a marker for BC. However, no biosensor for the detection of DJ-1 has been demonstrated. Here, we describe a virus bioresistor ( VBR ) capable of detecting DJ-1 in urine at a concentration of 10 pM in 1 min. The VBR consists of a pair of millimeter-scale gold electrodes that measure the electrical impedance of an ultrathin (≈ 150-200 nm), two-layer polymeric channel. The top layer of this channel (90-105 nm in thickness) consists of an electrodeposited virus-PEDOT (PEDOT is poly(3,4-ethylenedioxythiophene)) composite containing embedded M13 virus particles that are engineered to recognize and bind to the target protein of interest, DJ-1. The bottom layer consists of spin-coated PEDOT-PSS (poly(styrenesulfonate)). Together, these two layers constitute a current divider. We demonstrate here that reducing the thickness of the bottom PEDOT-PSS layer increases its resistance and concentrates the resistance drop of the channel in the top virus-PEDOT layer, thereby increasing the sensitivity of the VBR and enabling the detection of DJ-1. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise ( S / N > 100) and excellent sensor-to-sensor reproducibility characterized by coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a concentration of 30 pM, near the 10 pM limit of detection (LOD), encompassing four orders of magnitude in concentration.

Protein-metal-organic frameworks (p-MOFs) are a prototypical example of how synthetic biological hybrid systems can be used to develop next-generation materials. Controlling p-MOF formation enables the design of hybrid materials with enhanced biological activity and high stability. However, such control is yet to be fully realized due to an insufficient understanding of the governing nucleation and growth mechanisms in p-MOF systems. The structural evolution of p-MOFs was probed by cryo-transmission electron microscopy, revealing nonclassical pathways via dissolution-recrystallization of highly hydrated amorphous particles and solid-state transformation of a protein-rich amorphous phase. On the basis of these data, we propose a general description of p-MOF crystallization which is best characterized by particle aggregation and colloidal theory for future synthetic strategies.

A wet chemical process involving two electrodeposition steps followed by a solution casting step, the "EESC" process, is described for the fabrication of electroluminescent, radial junction wires. EESC is demonstrated by assembling three well-studied nanocrystalline (or amorphous) materials: Au, CdSe, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The tri-layered device architecture produced by EESC minimizes the influence of an electrically resistive CdSe emitter layer by using a highly conductive gold nanowire that serves as both a current collector and a negative electrode. Hole injection, at a high barrier CdSe-PEDOT:PSS interface (ϕ h ≈ 1.1 V), is facilitated by a contact area that is 1.9-4.7-fold larger than the complimentary gold-CdSe electron-injecting contact (ϕ e ≈ 0.6 V), contributing to low-voltage thresholds (1.4-1.7 V) for electroluminescence (EL) emission. Au@CdSe@PEDOT:PSS wire EL emitters are 25 μm in length, amongst the longest so far demonstrated to our knowledge, but the EESC process is scalable to nanowires of any length, limited only by the length of the central gold nanowire that serves as a template for the fabrication process. Radial carrier transport within these multishell wires conforms to the back-to-back diode model.

Pd based alloy materials with hollow nanostructures are ideal hydrogen (H 2 ) sensor building blocks because of their double-H 2 sensing active sites (interior and exterior side of hollow Pd alloy) and fast response. In this work, for the first time, we report a simple fabrication process for preparing hollow Pd-Ag alloy nanowires (Pd@Ag HNWs) by using the electrodeposition of lithographically patterned silver nanowires (NWs), followed by galvanic replacement reaction (GRR) to form palladium. By controlling the GRR time of aligned Ag NWs within an aqueous Pd 2+ -containing solution, the compositional transition and morphological evolution from Ag NWs to Pd@Ag HNWs simultaneously occurred, and the relative atomic ratio between Pd and Ag was controlled. Interestingly, a GRR duration of 17 h transformed Ag NWs into Pd@Ag HNWs that showed enhanced H 2 response and faster sensing response time, reduced 2.5-fold, as compared with Ag NWs subjected to a shorter GRR period of 10 h. Furthermore, Pd@Ag HNWs patterned on the colorless and flexible polyimide (cPI) substrate showed highly reversible H 2 sensing characteristics. To further demonstrate the potential use of Pd@Ag HNWs as sensing layers for all-transparent, wearable H 2 sensing devices, we patterned the Au NWs perpendicular to Pd@Ag HNWs to form a heterogeneous grid-type metallic NW electrode which showed reversible H 2 sensing properties in both bent and flat states.

The oxygen, O 2 , in air interferes with the detection of H 2 by palladium (Pd)-based H 2 sensors, including Pd nanowires (NWs), depressing the sensitivity and retarding the response/recovery speed in air-relative to N 2 or Ar. Here, we describe the preparation of H 2 sensors in which a nanofiltration layer consisting of a Zn metal-organic framework (MOF) is assembled onto Pd NWs. Polyhedron particles of Zn-based zeolite imidazole framework (ZIF-8) were synthesized on lithographically patterned Pd NWs, leading to the creation of ZIF-8/Pd NW bilayered H 2 sensors. The ZIF-8 filter has many micropores (0.34 nm for gas diffusion) which allows for the predominant penetration of hydrogen molecules with a kinetic diameter of 0.289 nm, whereas relatively larger gas molecules including oxygen (0.345 nm) and nitrogen (0.364 nm) in air are effectively screened, resulting in superior hydrogen sensing properties. Very importantly, the Pd NWs filtered by ZIF-8 membrane (Pd NWs@ZIF-8) reduced the H 2 response amplitude slightly (ΔR/R 0 = 3.5% to 1% of H 2 versus 5.9% for Pd NWs) and showed 20-fold faster recovery (7 s to 1% of H 2 ) and response (10 s to 1% of H 2 ) speed compared to that of pristine Pd NWs (164 s for response and 229 s for recovery to 1% of H 2 ). These outstanding results, which are mainly attributed to the molecular sieving and acceleration effect of ZIF-8 covered on Pd NWs, rank highest in H 2 sensing speed among room-temperature Pd-based H 2 sensors.

The influence of hexamethylenetetraamine (HMTA) on the morphology of δ-MnO 2 and its properties for electrical energy storage are investigated-specifically for ultrathick δ-MnO 2 layers in the micron scale. Planar arrays of gold@δ-MnO 2 , core@shell nanowires, were prepared by electrodeposition with and without the HMTA and their electrochemical properties were evaluated. HMTA alters the MnO 2 in three ways: First, it creates a more open morphology for the MnO 2 coating, characterized by "petals" with a thickness of 6 to 9 nm, rather than much thinner δ-MnO 2 sheets seen in the absence of HMTA. Second, the electronic conductivity of the δ-MnO 2 is increased by an order of magnitude. Third, δ-MnO 2 prepared in HMTA shows a (001) interlayer spacing that is expanded by ≈30% possibly accelerating Li transport. The net effect of "HTMA doping" is to dramatically improve high rate performance, culminating in an increase in the specific capacity for the thickest MnO 2 shells examined here by a factor of 15 at 100 mV/s.