Electrical Conductivity and In Situ SAXS Probing of Block Copolymer Nanocomposites Under Mechanical Stretching.

Elastomers based on block copolymers can self-organize into ordered nanoscale structures, making them attractive for use as flexible conductive nanocomposites. Understanding how ordered structures impact electrical properties is essential for practical applications. This study investigated the morphological evolution of flexible conductive elastomers based on polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymers with aligned single- or multi-wall carbon nanotubes (SWCNTs or MWCNTs) and their electrical conductivity under large deformations. Oriented nanocomposites were obtained through injection molding and characterized using two different setups: tensile testing monitored by in situ small-angle X-ray scattering (SAXS) and tensile testing with simultaneous electrical conductivity measurements. Our findings demonstrate that structural orientation significantly influences electrical conductivity, with higher conductivity in the longitudinal direction due to the preferred orientation of carbon nanotubes. Tensile testing demonstrated that carbon nanotubes accelerate the process of realignment of the ordered structure. As a consequence, higher deformations reduced the conductivity of samples with longitudinal alignment due to the disruption of percolation contacts between nanotubes, while in samples with a transverse alignment the process promoted the formation of a new conductive network, increasing electrical conductivity.

ZnO-Based Electrochemical Immunosensor to Assess Vaccine-Induced Antibody-Mediated Immunity against Wild-Type and Gamma SARS-CoV-2 Strains.

The evaluation of serological responses to COVID-19 is crucial for population-level surveillance, developing new vaccines, and evaluating the efficacy of different immunization programs. Research and development of point-of-care test technologies remain essential to improving immunity assessment, especially for SARS-CoV-2 variants that partially evade vaccine-induced immune responses. In this work, an impedimetric biosensor based on the immobilization of the recombinant trimeric wild-type spike protein (S protein) on zinc oxide nanorods (ZnONRs) was employed for serological evaluation. We successfully assessed its applicability using serum samples from spike-based COVID-19 vaccines: ChAdOx1-S (Oxford-AstraZeneca) and BNT162b2 (Pfizer-BioNTech). Overall, the ZnONRs/ spike-modified electrode displayed accurate results for both vaccines, showing excellent potential as a tool for assessing and monitoring seroprevalence in the population. A refined outcome of this technology was achieved when the ZnO immunosensor was functionalized with the S protein from the P.1 linage (Gamma variant). Serological responses against samples from vaccinated individuals were acquired with excellent performance. Following studies based on traditional serological tests, the ZnONRs/spike immunosensor data reveal that ChAdOx1-S vaccinated individuals present significantly less antibody-mediated immunity against the Gamma variant than the BNT162b2 vaccine, highlighting the great potential of this point-of-care technology for evaluating vaccine-induced humoral immunity against different SARS-CoV-2 strains.

Electrochemical Immunosensors Based on Zinc Oxide Nanorods for Detection of Antibodies Against SARS-CoV-2 Spike Protein in Convalescent and Vaccinated Individuals.

Even after over 2 years of the COVID-19 pandemic, research on rapid, inexpensive, and accurate tests remains essential for controlling and avoiding the global spread of SARS-CoV-2 across the planet during a potential reappearance in future global waves or regional outbreaks. Assessment of serological responses for COVID-19 can be beneficial for population-level surveillance purposes, supporting the development of novel vaccines and evaluating the efficacy of different immunization programs. This can be especially relevant for broadly used inactivated whole virus vaccines, such as CoronaVac, which produced lower titers of neutralizing antibodies. and showed lower efficacy for specific groups such as the elderly and immunocompromised. We developed an impedimetric biosensor based on the immobilization of SARS-CoV-2 recombinant trimeric spike protein (S protein) on zinc oxide nanorod (ZnONR)-modified fluorine-doped tin oxide substrates for COVID-19 serology testing. Due to electrostatic interactions, the negatively charged S protein was immobilized via physical adsorption. The electrochemical response of the immunosensor was measured at each modification step and characterized by scanning electron microscopy and electrochemical techniques. We successfully evaluated the applicability of the modified ZnONR electrodes using serum samples from COVID-19 convalescent individuals, CoronaVac-vaccinated with or without positive results for SARS-CoV-2 infection, and pre-pandemic samples from healthy volunteers as controls. ELISA for IgG anti-SARS-CoV-2 spike protein was performed for comparison, and ELISA for IgG anti-RBDs of seasonal coronavirus (HCoVs) was used to test the specificity of immunosensor detection. No cross-reactivity with HCoVs was detected using the ZnONR immunosensor, and more interestingly, the sensor presented higher sensitivity when compared to negative ELISA results. The results demonstrate that the ZnONRs/spike-modified electrode displayed sensitive results for convalescents and vaccinated samples and shows excellent potential as a tool for the population's assessment and monitoring of seroconversion and seroprevalence.

Synthesis of bioluminescent gold nanoparticle-luciferase hybrid systems for technological applications.

Bioluminescent gold nanoparticles (AuNPs) were synthesized in situ using dithiol-terminated polyethylene glycol (PEG(SH)2) as reducer and stabilizing agents. Hybrid Au/F3O4 nanoparticles were also produced in a variation of synthesis, and both types of nanostructures had the polymer capping replaced by L-cysteine (Cys). The four types of nanoparticles, PEG(SH)2AuNPs, PEG(SH)2Au/F3O4NPs, CysAuNPs, and CysAu/F3O4NPs were associated with purified recombinant Pyrearinus termitilluminans green emitting click beetle luciferase (PyLuc) and Phrixotrix hirtus (RELuc) red-emitting railroad worm luciferase. Enzyme association with PEG(SH)2 was also investigated as a control. Luciferases were chosen because they catalyze bioluminescent reactions used in a wide range of bioanalytical applications, including ATP assays, gene reporting, high-throughput screening, bioluminescence imaging, biosensors and other bioluminescence-based assays. The immobilization of PyLuc and RELuc promoted partial suppression of the enzyme luminescence activity in a functionalization-dependent way. Association of PyLuc and RELuc with AuNPs increased the enzyme operational stability in relation to the free enzyme, as evidenced by the luminescence intensity from 0 to 7 h after substrate addition. The stability of the immobilized enzymes was also functionalization-dependent and the association with CysAuNPs was the condition that combined more sustained luminescent activity with a low degree of luminescence quenching. The higher enzymatic stability and sustained luminescence of luciferases associated with nanoparticles may improve the applicability of bioluminescence for bioimaging and biosensing purposes.

Promising Nanostructured Materials against Enveloped Virus.

The development of self-disinfectant devices is highly needed to prevent and control infections, mainly caused by virus. In the past years, coronaviruses have been a threat to humanity, causing severe epidemics of respiratory infections such as severe acute respiratory syndrome (SARS), in 2003, and Middle East respiratory syndrome (MERS) in 2012, and presently the SARS-CoV2 is causing the COVID-19 pandemic. Previous studies have demonstrated that surface contamination play a significant role in the spreading of viruses. These studies demonstrated that the production of highly reactive species by copper alloys contributes to rapid elimination of viruses. Nanostructured materials such as semiconductors TiO2, Co3O4 CuO, NiO, and TiO2, and silver nanoparticles can decrease the virus viability on the surfaces when associated with polymers and textiles, especially in conditions of light exposure. In addition, graphene oxide is rising as a promising material for inactivation of viruses due to its capacity of destroying the viral envelope and capsid. The virucidal property of these materials can be enhanced by increasing their functionalization with photosensitizers. The present mini-review brings subsidies for the development of new advanced self-disinfectant materials that can be used in the manufacture of gloves, masks, and a variety of other devices.

Gold nanochannels oxidation by confined water.

Confined and interstitial water has a key role in several chemical, physical and biological processes. It is remarkable that many aspects of water behavior in this regime (e.g., chemical reactivity) remain obscure and unaddressed. In particular for gold surfaces, results from simulations indicated that the first wetting layer would present hydrophilic behavior in contrast to the overall hydrophobic character of the bulk water on this surface. In the present work we investigate the properties of confined water on Au 〈111〉 nanochannels. Our findings, based on a large set of morphological, structural and spectroscopic experimental data and ab initio computer simulations, strongly support the hypothesis of hydrophilicity of the first wetting layer of the Au 〈111〉 surface. A unique oxidation process was also observed in the nanochannels driven by confined water. Our findings indicated that the oxidation product is Au(OH)3. Therefore, the Au surface reactivity against confined water needs to be considered for nanoscopic applications such as, e.g., catalysis in fine chemicals, pharmaceuticals, and the food industry green processes.

Proteins and Peptides at the Interfaces of Nanostructures.

The present review focuses on the proteins and peptides at the interfaces of nanostructured metals and semiconductors as a result of their use in synthesis in-situ and functionalization of nanostructures. We start the review with an introduction about the peculiar properties of nanostructured materials and their applications. In the following, the chemical and structural properties of peptides and proteins that allow their use as reducing, stabilizing, and functionalization agents are discussed. Proteins and peptides have not only the chemical groups for the metal ion reducing but also provide templates for directing the crystalline growing of nanostructures to the desired shapes and sizes. Proteins and peptides are also used mainly for the stabilization and functionalization of a diversity of nanostructured materials providing properties such as biocompatibility, plasmon-enhanced catalysis, sensing, micro/nanomotors, spin filters, and others. Nanostructured materials of metal oxides have mainly been functionalized with proteins and peptides to gain specific properties such as light harvesting and spin filters. Herein, we described the synthesis and functionalization of some types of nanostructured materials by using peptides and proteins. In the last part of the review, it is discussed the perspectives and challenges for the use of proteins and peptides in Nanotechnology.

pH-Dependent Synthesis of Anisotropic Gold Nanostructures by Bioinspired Cysteine-Containing Peptides.

In the present study, alkaline peptides AAAXCX (X = lysine or arginine residues) were designed based on the conserved motif of the enzyme thioredoxin and used for the synthesis of gold nanoparticles (GNPs) in the pH range of 2-11. These peptides were compared with free cysteine, the counterpart acidic peptides AAAECE and γ-ECG (glutathione), and the neutral peptide AAAACA. The objective was to investigate the effect of the amino acids neighboring a cysteine residue on the pH-dependent synthesis of gold nanocrystals. Kohn-Sham density functional theory (KS-DFT) calculations indicated an increase in the reducing capacity of AAAKCK favored by the successive deprotonation of their ionizable groups at increasing pH values. Experimentally, it was observed that gold speciation and the peptide structure also have a strong influence on the synthesis and stabilization of GNPs. AAAKCK produced GNPs at room temperature, in the whole investigated pH range. By contrast, alkaline pH was the best condition for the synthesis of GNP assisted by the AAARCR peptide. The acidic peptides produced GNPs only in the presence of polyethylene glycol, and the synthesis using AAAECE and γ-ECG also required heating. The ionization state of AAAKCK had a strong influence on the preferential growth of the GNPs. Therefore, pH had a remarkable effect on the synthesis, kinetics, size, shape, and polydispersity of GNPs produced using AAAKCK. The AAAKCK peptide produced anisotropic decahedral and platelike nanocrystals at acidic pH values and spherical GNPs at alkaline pH values. Both alkaline peptides were also efficient capping agents for GNPs, but they produced a significant difference in the zeta potential, probably because of different orientations on the gold surface.

UV-light effects on cytochrome c modulated by the aggregation state of phenothiazines.

The present study shows the factors that modulate the photodamage promoted by phenothiazines. Cytochrome c was irradiated with UV light for 120 min, over a pH range from 4.0 to 8.0, in the absence and in the presence of different concentrations of thioridazine (TR) and fluphenazine (FP). In the absence of phenothiazines, the maximal rate of a Soret band blue shift (nm/min) from 409 to 406 nm was obtained at pH 4.0 (0.028 nm/min). The presence of phenothiazines at the concentration range 10-25 µmol/L amplified and accelerated a cytochrome c blue shift (409 to 405 nm, at a rate = 0.041 nm/min). Above 25 µmol/L, crescent concentrations of phenothiazines contributed to cytochrome c protection with (maximal at 2500 µmol/L). Scanning electronic microscopy revealed the formation of nanostructures. The pH also influenced the effect of low phenothiazine concentrations on cytochrome c. Thus, the predominance of phenothiazine-promoted cytochrome c damage or protection depends on a balance of the following factors: the yield of photo-generated drug cation radicals, which is favored by acidic pH; the stability of the cation radicals, which is favored by the drug aggregation; and the cytochrome c structure, modulated by the pH.

Electron-phonon scattering in Sn-doped In2O3 FET nanowires probed by temperature-dependent measurements.

We report on the structural and electrical characterization of individual Sn-doped In(2)O(3) nanowires. Key information on the nanowire's electron transport such as the carrier's mobility and density are presented. The mobility data was found to decrease as the temperature increases, providing direct evidence of the electron-phonon interaction as the dominant scattering mechanism in this oxide system. The results were confirmed by resistivity measurements and additionally the electron density could be directly calculated providing n = 5 x 10(24) cm(-3), confirming the samples' metallic character.

Electron dephasing and weak localization in Sn doped In(2)O(3) nanowires.

We report on (magneto-) transport measurements of individual In2O3 nanowires. We observed that the presence of a weak disorder arising from doping and electron-boundary collisions leads to weak localization of electrons as revealed by the positive magnetoconductivity in a large range of temperatures ( approximately 77 K). From temperature-dependent resistance and magnetoconductivity data, the electron-electron interaction was pointed out as the mechanism responsible for the increase of resistance in the low temperature range and the dominant source of the dephasing at low temperatures. The experimental data provided the phase coherence time tau(phi) approximately T(-2/3) expected for 1D systems, giving consistent support to the mechanisms underlying the weak-localization and electron-electron scattering theories.