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Peptide nucleic acids (PNAs) play a key role in prebiotic chemistry as a chimera between RNA and proteins. We developed an alternative synthesis of bioactive PNA's diaminopurine and guanine analogues from prebiotic compounds, such as aminomalononitrile (AMN), urea, and guanidine, using a two-step multicomponent microwave-assisted and solvent-free approach in the presence of selected amino acids. The novel derivatives showed selective inhibitory activity against influenza virus A/Puerto Rico/8/34 H1N1 encompassing the range of nanomolar activity. Derivatives decorated with the tyrosine residue showed the highest inhibitory activity against the virus.

The SARS-CoV-2 life cycle is strictly dependent on the environmental redox state that influences both virus entry and replication. A reducing environment impairs the binding of the spike protein (S) to the angiotensin-converting enzyme 2 receptor (ACE2), while a highly oxidizing environment is thought to favor S interaction with ACE2. Moreover, SARS-CoV-2 interferes with redox homeostasis in infected cells to promote the oxidative folding of its own proteins. Here we demonstrate that synthetic low molecular weight (LMW) monothiol and dithiol compounds induce a redox switch in the S protein receptor binding domain (RBD) toward a more reduced state. Reactive cysteine residue profiling revealed that all the disulfides present in RBD are targets of the thiol compounds. The reduction of disulfides in RBD decreases the binding to ACE2 in a cell-free system as demonstrated by enzyme-linked immunosorbent and surface plasmon resonance (SPR) assays. Moreover, LMW thiols interfere with protein oxidative folding and the production of newly synthesized polypeptides in HEK293 cells expressing the S1 and RBD domain, respectively. Based on these results, we hypothesize that these thiol compounds impair both the binding of S protein to its cellular receptor during the early stage of viral infection, as well as viral protein folding/maturation and thus the formation of new viral mature particles. Indeed, all the tested molecules, although at different concentrations, efficiently inhibit both SARS-CoV-2 entry and replication in Vero E6 cells. LMW thiols may represent innovative anti-SARS-CoV-2 therapeutics acting directly on viral targets and indirectly by inhibiting cellular functions mandatory for viral replication.

The preparation of three different functionalized PdNPs systems for room temperature BTX sensing detection and their morphostructural characterization is described. PdNPs are prepared through two-phase water/toluene wet chemical reduction method in the presence of bifunctional organic thiols as stabilizing agents suitable for the formation of covalently linked PdNPs networks: p-terphenyl-4,4”-dithiol (PdNPs-TR), biphenyl-4,4’-dithiol (PdNPs-BP), or with 9,9-didodecyl-2,7-bis(acetylthio)fluorene (PdNPs-FL). Comparing the hydrodynamic diameter values, TR and BP ligands allow to obtain networks consisting of spherical NPs of about 2 nm, in which each bifunctional ligand act as a bridge between PdNPs. In contrast, PdNPs-FL show a population centered at = 45 ± 5 nm. To perform preliminary gas sensing measurements, PdNPs networks are cast deposited on interdigitated electrodes to study their resistive response towards volatile organic compounds (VOCs) such as benzene (0-5%), toluene (0-1.7%), and p-xylene (0-0.4%) (BTX) and common interfering gases (H2S, NH3, SO2, and relative humidity, RH). PdNPs-FL show enhanced response to BTX with an appreciable response also toward H2S and RH. PdNPs-TR exhibit better ability to discriminate benzene gas with negligible response after H2S exposure. Moreover, all the PdNPs systems show little to no response to NH3 and SO2 gases, offering an interesting perspective in practical sensing applications.

COronaVIrus Disease 2019 (COVID-19) is a newly emerging infectious disease that spread across the world, caused by the novel coronavirus Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2). Despite the advancements in science that led to the creation of the vaccine, there is still an urgent need for new antiviral drugs effective against SARS-CoV-2. This study aimed to investigate the antiviral effect of Paulownia tomentosa Steud extract against SARS-CoV-2 and to evaluate its antioxidant properties, including respiratory smooth muscle relaxant effects. Our results showed that P. tomentosa extract can inhibit viral replication by directly interacting with both the 3-chymotrypsin-like protease and spike protein. In addition, the phyto complex does not reduce lung epithelial cell viability and exerts a protective action in those cells damaged by tert-butyl hydroperoxide , a toxic agent able to alter cells' functions via increased oxidative stress. These data suggest the potential role of P. tomentosa extract in COVID-19 treatment, since this extract is able to act both as an antiviral and a cyto-protective agent in vitro.

Nanomaterials such as gold nanoparticles employed as solid-state sensors have attracted attention in recent years due to their ability to detect poisonous elements in the indoor/outdoor environment. Herein, chemoresistive sensors based on gold nanoparticles (AuNPs) functionalized with mixed thiol ligands were tested as sensing materials. Specifically, the electrical response of gold nanoparticles-based sensors was tested against Hg0vap, H2S, SO2, NH3, and relative humidity (RH) at room temperature. Gold nanoparticles samples were synthesized by the wet reduction method and then deposited as thin films on suitable interdigitated transducers. Electrical conductivity measurements allowed evaluating a semiconducting behavior of the colloids. A selective and reproducible sensing behavior toward Hg0vap was observed in the range 0.1-1.0 ng/mL, allowing simple and reliable resistive devices to be obtained. An irreversible interaction mechanism, based on formation of an Au-Hg direct bond, was observed in the case of isolated AuNPs samples. Interconnected AuNPs exhibited a reversible behavior as assessed by Micro Raman, XRD, XPS, AFM, SEM, and UV-vis and FTIR spectroscopies together with DLS measurements. Broadening of the plasmonic band and an increase in the mean particle size upon contact with Hg0vap was observed. Morphological characterization revealed the formation of aggregates after interaction between Hg0vap and AuNPs. XRD and Micro Raman measurements collected on the nonexposed and Hg-exposed nanoparticles suggest their structural rearrangement at the surface and formation of an Au-Hg alloy with Hg mechanically trapped within the bulk material. The simple and cost-effective fabrication of these sensors has prospect in the future as nanodevices for real-time outdoor air quality monitoring.

Adsorption and detection of environmental total gaseous mercury (TGM) was studied by using gold nanoparticles (AuNPs) on purpose functionalized with dithiol ligands, i.e. Biphenyl-4,4′-dithiol (BI) or p-Terphenyl-4,4′′-dithiol (TR), suitable for nanoparticles based network formation. AuNPs-BI and AuNPs-TR with size 6–8 nm were deposited onto quartz fibres and used as adsorbent materials for the detection of TGM, both indoor for adsorption studies, at defined concentrations (∼4.5 ng m−3 Hg), and outdoor, at the vapour mercury concentration of the environmental countryside (∼1.5 ng m−3 Hg). The role of relative humidity (RH) in the absorption process has been observed. A high Hg adsorption capability, also when exposed to sub ppb concentration, has been observed. A cold vapour atomic fluorescence spectroscopy (CVAFS) detector was used to determine gaseous mercury concentrations lower than 2 ng m−3, with a robust and reproducible procedure. Moreover, the use of quartz fibres substrate covered with AuNPs-BI or AuNPs-TR, and used for more than thirty times during the experiments, makes them competitive in the use in large-scale measurement campaigns.

Enzyme immobilization on nanocarriers is nowadays considered a useful tool for improving activity and maintaining biocatalysts stability while facilitating their recovery and reuse. In this work we prepared Au and Ag based nanoparticles (AuNPs or AgNPs) stabilized with two different ligands, the organometallic dinuclear complex trans,trans-[dithiodibis(tributylphosphine)diplatinum(II)-4,4′-diethynylbiphenyl] (Pt-DEBP) and the organic dithiol 4,4′-dithiol-biphenyl (BI), able to link the NPs in 3D networks. We investigated the ability of these nanocarriers to interact with a model lipolytic enzyme from Pseudomonas fluorescens and maintain its activity, both in aqueous as well as in organic media. In particular, our results highlighted that the nature of the metal plays a role in enzyme adsorption, while enzyme activity is mostly influenced by the chemistry of the organic spacer. The obtained bioconjugate, between lipase and the most promising carrier, AgNPs-Pt-DEBP, was stable in a wide temperature range (25–55 °C) and it showed good activity retention both in aqueous (50%) as well as in organic media (75%), compared to the lipase used in soluble form.

Amyloid protein misfolding results in a self-assembling aggregation process, characterized by the formation of typical aggregates. The attention is focused on pre-fibrillar oligomers (PFOs), formed in the early stages and supposed to be neurotoxic. PFOs structure may change due to their instability and different experimental protocols. Consequently, it is difficult to ascertain which aggregation species are actually neurotoxic. We used salmon Calcitonin (sCT) as an amyloid model whose slow aggregation rate allowed to prepare stable samples without photochemical cross-linking. Intracellular Ca2+ rise plays a fundamental role in amyloid protein-induced neurodegerations. Two paradigms have been explored: (i) the “membrane permeabilization” due to the formation of amyloid pores or other types of membrane damage; (ii) “receptor-mediated” modulation of Ca2+ channels. In the present paper, we tested the effects of native sCT PFOs- with respect to Monomer-enriched solutions in neurons characterized by an increasing degree of differentiation, in terms of -Ca2+-influx, cellular viability, -Long-Term Potentiation impairment, Post-Synaptic Densities and synaptophysin expression. Results indicated that PFOs-, but not Monomer-enriched solutions, induced abnormal -Ca2+-influx, which could only in part be ascribed to NMDAR activation. Thus, we propose an innovative neurotoxicity mechanism for amyloid proteins where “membrane permeabilization” and “receptor-mediated” paradigms coexist.

Amyloid protein misfolding results in a self-assembling aggregation process, characterized by the formation of typical aggregates. The attention is focused on pre-fibrillar oligomers (PFOs), formed in the early stages and supposed to be neurotoxic. PFOs structure may change due to their instability and different experimental protocols. Consequently, it is difficult to ascertain which aggregation species are actually neurotoxic. We used salmon Calcitonin (sCT) as an amyloid model whose slow aggregation rate allowed to prepare stable samples without photochemical cross-linking. Intracellular Ca2+ rise plays a fundamental role in amyloid protein-induced neurodegerations. Two paradigms have been explored: (i) the “membrane permeabilization” due to the formation of amyloid pores or other types of membrane damage; (ii) “receptor-mediated” modulation of Ca2+ channels. In the present paper, we tested the effects of native sCT PFOs- with respect to Monomer-enriched solutions in neurons characterized by an increasing degree of differentiation, in terms of -Ca2+-influx, cellular viability, -Long-Term Potentiation impairment, Post-Synaptic Densities and synaptophysin expression. Results indicated that PFOs-, but not Monomer-enriched solutions, induced abnormal -Ca2+-influx, which could only in part be ascribed to NMDAR activation. Thus, we propose an innovative neurotoxicity mechanism for amyloid proteins where “membrane permeabilization” and “receptor-mediated” paradigms coexist.