Impact of Formulation of Photocurable Precursor Mixtures on the Performance and Dimensional Stability of Hierarchical Cation Exchange Membranes.

This work presents a systematic approach to formulating UV curable ionomer coatings that can be used as ion-exchange membranes when they are applied on porous substrates. Ion-exchange membranes fabricated in this way can be a cost-effective alternative to perfluorosulfonic acid membranes, such as Nafion and similar thin ionomer film membranes. Hierarchically structured coated membranes find applications for energy storage and conversion (organic redox flow batteries and artificial photosynthesis cells) and separation processes (electrodialysis). Designing the ionomer precursor for membrane formulation requires the introduction of compounds with drastically different properties into a liquid mixture. Hansen solubility theory was used to find the solvents to compatibilize main formulation components: acrylic sulfone salt (3-sulfopropyl methacrylate potassium salt) and hexafunctional polyester acrylate cross-linker (Ebecryl 830), otherwise nonmiscible or mutely soluble. Among the identified suitable solvents, acrylic acid and acetic acid allowed for optimal mixing of the components and reaching the highest levels of sulfonic group content, providing the desired ion-exchange capacity. Interestingly, they represented a case of a reactive and nonreactive solvent since acrylic acid was built into the ionomer during the UV curing step. Properties of the two membrane variants were compared. Samples fabricated with acetic acid exhibit improved handleability compared with the case of acrylic acid. Acetic acid yielded a lower area-specific resistance (6.4 ± 0.17 Ohm·cm2) compared to acrylic acid (12.1 ± 0.16 Ohm·cm2 in 0.5 M NaCl). This was achieved without severely suppressing the selectivity of the membrane, which was standing at 93.4 and 96.4% for preparation with acetic and acrylic acid, respectively.

Performance of electrochemical immunoassays for clinical diagnostics of SARS-CoV-2 based on selective nucleocapsid N protein detection: Boron-doped diamond, gold and glassy carbon evaluation.

The 21st century has already brought us a plethora of new threats related to viruses that emerge in humans after zoonotic transmission or drastically change their geographic distribution or prevalence. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first spotted at the end of 2019 to rapidly spread in southwest Asia and later cause a global pandemic, which paralyzes the world since then. We have designed novel immunosensors targeting conserved protein sequences of the N protein of SARS-CoV-2 based on lab-produced and purified anti-SARS-CoV-2 nucleocapsid antibodies that are densely grafted onto various surfaces (diamond/gold/glassy carbon). Titration of antibodies shows very strong reactions up to 1:72 900 dilution. Next, we showed the mechanism of interactions of our immunoassay with nucleocapsid N protein revealing molecular recognition by impedimetric measurements supported by hybrid modeling results with both density functional theory and molecular dynamics methods. Biosensors allowed for a fast (in less than 10 min) detection of SARS-CoV-2 virus with a limit of detection from 0.227 ng/ml through 0.334 ng/ml to 0.362 ng/ml for glassy carbon, boron-doped diamond, and gold surfaces, respectively. For all tested surfaces, we obtained a wide linear range of concentrations from 4.4 ng/ml to 4.4 pg/ml. Furthermore, our sensor leads to a highly specific response to SARS-CoV-2 clinical samples versus other upper respiratory tract viruses such as influenza, respiratory syncytial virus, or Epstein-Barr virus. All clinical samples were tested simultaneously on biosensors and real-time polymerase chain reactions.

Electrochemical Immunosensors Based on Screen-Printed Gold and Glassy Carbon Electrodes: Comparison of Performance for Respiratory Syncytial Virus Detection.

This paper presents the development and comparison of label-free electrochemical immunosensors based on screen-printed gold and glassy carbon (GC) disc electrodes for efficient and rapid detection of respiratory syncytial virus (RSV). Briefly, the antibody specific to the F protein of RSV was successfully immobilized on modified electrodes. Antibody coupling on the Au surface was conducted via 4-aminothiophenol (4-ATP) and glutaraldehyde (GA). The GC surface was modified with poly-L-lysine (PLL) for direct anti-RSV conjugation after EDC/NHS (1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-Hydroxysuccinimide) activation. Electrochemical characterizations of the immunosensors were carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). GC-based immunosensors show a dynamic range of antigen detection from 1.0 × 105 PFU/mL to 1.5×107 PFU/mL, more than 1.0 × 105 PFU/mL to 1.0 × 107 PFU/mL for the Au-based sensor. However, the GC platform is less sensitive and shows a higher detection limit (LOD) for RSV. The limit of detection of the Au immunosensor is 1.1 × 103 PFU/mL, three orders of magnitude lower than 2.85 × 106 PFU/mL for GC. Thus, the Au-based immunosensor has better analytical performance for virus detection than a carbon-based platform due to high sensitivity and very low RSV detection, obtained with good reproducibility.