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• Noble-metal nanoparticles stabilized with different organic ligands were prepared. • A microbial lipase was immobilized on the nanocarriers through physical adsorption. • Lipolytic and esterasic activity tests of the samples were performed. • Au and AgNPs afforded different interactions with the lipase, affecting its activity. 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. [ABSTRACT FROM AUTHOR]

The preparation of three different functionalized palladium nanoparticles (PdNPs) systems for room temperature BTX (benzene, toluene, p‐xylene) sensing detection and their morphostructural characterization is described. PdNPs are prepared through a 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 help 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 <2RH> = 45 ± 5 nm. To perform preliminary gas sensing measurements, PdNPs networks are cast deposited on interdigitated electrodes to study their resistive response toward 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 a better ability to discriminate benzene gas with a 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Amino and sulfonate ending groups thiols are used as functionalizing agents to stabilize of gold nanoparticles (AuNPs), obtaining hydrophilic AuNPs with a 10–20 nm diameter range and tunable surface charge. The nanomaterial is extensively characterized from a physicochemical point of view by UV–Vis and Fourier‐transform infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, synchrotron radiation X‐ray photoelectron spectroscopy (XPS), and dynamic light scattering to investigate the bonding between the two thiols and the metal surface. Systems are also biologically characterized on human multiforme glioblastoma T98G cells to understand their behavior in cell culture for biomedical applications. NMR and XPS studies evidence the presence of amino ending thiols with different chain lengths, 6‐amino‐1‐hexanethiol hydrochloride (6EA) or cysteamine (CY) and sodium 3‐mercapto‐1‐propanesulfonate (3MPS) on the metal surface: the relative molar ratio between the thiols bound to the AuNPs (3MPS/6EA or 3MPS/CY) is measured. On selected samples, the anti‐PD‐L1 antibody is loaded using AuNPs/antibody combination in a 2:1 weight ratio. Comparing different AuNPs concentrations (10 and 50 µg mL−1), the effect on colony‐forming capacity after 24 h exposure is evaluated. The synthesized AuNPs are nontoxic, and they do not affect cell proliferation. These small particles can be used for targeting, opening tangible and interesting perspectives for further biomedical studies. [ABSTRACT FROM AUTHOR]

Natural products are a rich source of bioactive molecules that have potential pharmacotherapeutic applications. In this study, we focused on Artemisia annua (A. annua) and its enriched extracts which were biologically evaluated in vitro as virucidal, antiviral, and antioxidant agents, with a potential application against the COVID-19 infection. The crude extract showed virucidal, antiviral and antioxidant effects in concentrations that did not affect cell viability. Scopoletin, arteannuin B and artemisinic acid (single fractions isolated from A. annua) exerted a considerable virucidal and antiviral effect in vitro starting from a concentration of 50 µg/mL. Data from Surface Plasmon Resonance (SPR) showed that the inhibition of the viral infection was due to the interaction of these compounds with the 3CLpro and Spike proteins of SARS-CoV-2, suggesting that the main interaction of compounds may interfere with the viral pathways during the insertion and the replication process. The present study suggests that natural extract of A. annua and its components could have a key role as antioxidants and antiviral agents and support the fight against SARS-CoV-2 variants and other possible emerging Coronaviruses. [Display omitted] • A.annua extract play a significant role as antioxidant agent. • Scopoletin, arteannuin B and artemisinic acid inhibit SARS-CoV-2 viral replication. • Surface Plasmon Resonance confirms interaction of A. annua fraction with Spike and 3CLpro proteins of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

To investigate the interaction between amyloid assemblies and "lipid-rafts", we performed functional and structural experiments on salmon calcitonin (sCT) solutions rich in prefibrillar oligomers, proto- and mature-fibers interacting with liposomes made of monosialoganglioside-GM1 (4%), DPPC (48%) and cholesterol (48%). To focus on the role played by electrostatic forces and considering that sCT is positive and GM1 is negative at physiologic pH, we compared results with those relative to GM1-free liposomes while, to assess membrane fluidity effects, with those relative to cholesterol-free liposomes. We investigated functional effects by evaluating Ca2+-influx in liposomes and viability of HT22-DIFF neurons. Only neurotoxic solutions rich in unstructured prefibrillar oligomers were able to induce Ca2+-influx in the "lipid-rafts" model, suggesting that the two phenomena were correlated. Thus, we investigated protein conformation and membrane modifications occurring during the interaction: circular dichroism showed that "lipid-rafts" fostered the formation of β-structures and energy filtered-transmission electron microscopy that prefibrillar oligomers formed pores, similar to Aβ did. We speculate that electrostatic forces between the positive prefibrillar oligomers and the negative GM1 drive the initial binding while the hydrophobic profile and flexibility of prefibrillar oligomers, together with the membrane fluidity, are responsible for the subsequent pore formation leading to Ca2+-influx and neurotoxicity. [ABSTRACT FROM AUTHOR]

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 cytoprotective agent in vitro. [Display omitted] • The study conducted on Paulownia tomentosa Steud (PTS) extract confirms its relevant properties. • PTS extract showed antiviral and virucidal activity against SARS-CoV-2 in vitro. • Antioxidant properties and respiratory smooth muscle relaxant effects of PTS extract were proved. • PTS extract is able to act both as an antiviral and a cytoprotective agent in in vitro models. • The data presented suggest the potential role of PTS in COVID-19 treatment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]