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The SARS-CoV-2 outbreaks highlighted the need for effective, reliable, fast, easy-to-do and cheap diagnostics procedures. We pragmatically experienced that an early positive-case detection, inevitably coupled with a mass vaccination campaign, is a milestone to control the COVID-19 pandemic. Gold nanoparticles (AuNPs) can indeed play a crucial role in this context, as their physicochemical, optics and electronics properties are being extensively used in photothermal therapy (PTT), radiation therapy (RT), drug delivery and diagnostic. AuNPs can be synthesized by several approaches to obtain different sizes and shapes that can be easily functionalized with many kinds of molecules such as antibodies, proteins, probes, and lipids. In addition, AuNPs showed high biocompatibility making them useful tool in medicine field. We thus reviewed here the most relevant evidence on AuNPs as effective way to detect the presence of SARS-CoV-2 antigens. We trust future diagnostic efforts must take this 'old-fashioned' nanotechnology tool into consideration for the development and commercialization of reliable and feasible detection kits.

The quest for novel nanoscale materials for different applications necessitates that they are easy to obtain and have excellent physical properties and low toxicity. Moreover, considering the ongoing environmental impact of noxious chemical waste products, it is important to adopt eco-friendly approaches for nanoparticle synthesis. In this work, a natural polymer (medium molecular weight chitosan) derived from chitin was employed as a reducing agent to obtain gold nanoparticles (AuNPs) with a chitosan shell (AuNPs@CS) by a microwave oven. The chitosan is economically viable and cost-competitive in the market showing also nontoxic behavior in the environment and living organisms. The synthesized AuNPs@CS-FITC NPs were fully characterized by spectroscopic and microscopic characterization techniques. The size distribution of NPs was about 15 nm, which is a suitable dimension to use in biomedical applications due to their high tissue penetration, great circulation in blood, and optimal clearance as well as low toxicity. The prepared polymer-capped NPs were further functionalized with a fluorescent molecule, i.e., Fluorescein-5-isothiocyanate (FITC), to perform imaging in the cell. The results highlighted the goodness of the synthesis procedure, as well as the high internalization rate that resulted in an optimal fluorescence intensity. Thus, this work presents a good sustainable/green approach-mediated polymer nanocomposite for various applications in the field of diagnostic imaging.

Neurodegenerative disorders (NDs) affect a great number of people worldwide and also have a significant socio-economic impact on the aging population. In this context, nanomedicine applied to neurological disorders provides several biotechnological strategies and nanoformulations that improve life expectancy and the quality of life of patients affected by brain disorders. However, available treatments are limited by the presence of the blood–brain barrier (BBB) and the blood–cerebrospinal fluid barrier (B–CSFB). In this regard, nanotechnological approaches could overcome these obstacles by updating various aspects (e.g., enhanced drug-delivery efficiency and bioavailability, BBB permeation and targeting the brain parenchyma, minimizing side effects). The aim of this review is to carefully explore the key elements of different neurological disorders and summarize the available nanomaterials applied for neurodegeneration therapy looking at several types of nanocarriers. Moreover, nutraceutical-loaded nanoparticles (NPs) and synthesized NPs using green approaches are also discussed underling the need to adopt eco-friendly procedures with a low environmental impact. The proven antioxidant properties related to several natural products provide an interesting starting point for developing efficient and green nanotools useful for neuroprotection.

The increasingly widespread use of engineered nanomaterials in many applications increases the need to understand the mechanisms behind their toxicity [...]

The widespread use of nanotechnology in different application fields, resulting in the integration of nanostructures in a plethora of devices, has addressed the research toward novel and easy-to-setup nanofabrication techniques to realize nanostructures with high spatial resolution and reproducibility. Owing to countless applications in molecular electronics, data storage, nanoelectromechanical, and systems for the Internet of Things, in recent decades, the scientific community has focused on developing methods suitable for nanopattern polymers. To this purpose, Atomic Force Microscopy-based nanolithographic techniques are effective methods that are relatively less complex and inexpensive than equally resolute and accurate techniques, such as Electron Beam lithography and Focused Ion Beam lithography. In this work, we propose an evolution of nanoindentation, named Pulse-Atomic Force Microscopy, to obtain continuous structures with a controlled depth profile, either constant or variable, on a polymer layer. Due to the modulation of the characteristics of voltage pulses fed to the AFM piezo-scanner and distance between nanoindentations, it was possible to indent sample surface with high spatial control and fabricate highly resolved 2.5D nanogrooves. That is the real strength of the proposed technique, as no other technique can achieve similar results in tailor-made graded nanogrooves without the need for additional manufacturing steps.

In recent decades, great efforts have been made to develop innovative, effective, and accurate nanofabrication techniques stimulated by the growing demand for nanostructures. Nowadays, mechanical tip-based emerged as the most promising nanolithography technique, allowing the pattern of nanostructures with a sub-nanometer resolution, high reproducibility, and accuracy. Unfortunately, these nanostructures result in contoured pile-ups that could limit their use and future integration into high-tech devices. The removal of pile-ups is still an open challenge. In this perspective, two different AFM-based approaches, i.e., Force Modulation Mode imaging and force-distance curve analysis, were used to characterize the structure of pile-ups at the edges of nanogrooves patterned on PMMA substrate by means of Pulse-Atomic Force Lithography. Our experimental results showed that the material in pile-ups was less stiff than the pristine polymer. Based on this evidence, we have developed an effective strategy to easily remove pile-ups, preserving the shape and the morphology of nanostructures.

The use of silver nanoparticles (Ag NPs) in the biomedical field deserves a mindful analysis of the possible inflammatory response which could limit their use in the clinic. Despite the anti-cancer properties of Ag NPs having been widely demonstrated, there are still few studies concerning their involvement in the activation of specific inflammatory pathways. The inflammatory outcome depends on the synthetic route used in the NPs production, in which toxic reagents are employed. In this work, we compared two types of Ag NPs, obtained by two different chemical routes: conventional synthesis using sodium citrate and a green protocol based on leaf extracts as a source of reduction and capping agents. A careful physicochemical characterization was carried out showing spherical and stable Ag NPs with an average size between 20 nm and 35 nm for conventional and green Ag NPs respectively. Then, we evaluated their ability to induce the activation of inflammation in Human Leukemic Monocytes (THP-1) differentiated into M0 macrophages using 1 µM and 2 µM NPs concentrations (corresponded to 0.1 µg/mL and 0.2 µg/mL respectively) and two-time points (24 h and 48 h). Our results showed a clear difference in Nuclear Factor ?B (NF-?b) activation, Interleukins 6–8 (IL-6, IL-8) secretion, Tumor Necrosis Factor-? (TNF-?) and Cyclooxygenase-2 (COX-2) expression exerted by the two kinds of Ag NPs. Green Ag NPs were definitely tolerated by macrophages compared to conventional Ag NPs which induced the activation of all the factors mentioned above. Subsequently, the exposure of breast cancer cell line (MCF-7) to the green Ag NPs showed that they exhibited antitumor activity like the conventional ones, but surprisingly, using the MCF-10A line (not tumoral breast cells) the green Ag NPs did not cause a significant decrease in cell viability. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Among all the inorganic nanomaterials used in commercial products, industry, and medicine, the amorphous silica nanoparticles (SiO2 NPs) appeared to be often tolerated in living organisms. However, despite several toxicity studies, some concerns about the exposure to high doses of SiO2 NPs with different sizes were raised. Then, we used the microemulsion method to obtain stable SiO2 NPs having different sizes (110 nm, 50 nm, and 25 nm). In addition, a new one-pot green synthetic route using leaves extract of Laurus nobilis was performed, obtaining monodispersed ultrasmall SiO2 NPs without the use of dangerous chemicals. The NPs achieved by microemulsion were further functionalized with amino groups making the NPs surface positively charged. Then, high doses of SiO2 NPs (1 mg/mL and 3 mg/mL) achieved from the two routes, having different sizes and surface charges, were used to assess their impact on human alveolar cells (A549), being the best cell model mimicking the inhalation route. Cell viability and caspase-3 induction were analyzed as well as the cellular uptake, obtaining that the smallest (25 nm) and positive-charged NPs were more able to induce cytotoxicity, reaching values of about 60% of cell death. Surprisingly, cells incubated with green SiO2 NPs did not show strong toxicity, and 70% of them remained vital. This result was unusual for ultrasmall nanoobjects, generally highly toxic. The actin reorganization, nuclear morphology alteration, and cell membrane elasticity analyses confirmed the trend achieved from the biological assays. The obtained data demonstrate that the increase in cellular softness, i.e., the decrease in Young’s modulus, could be associated with the smaller and positive NPs, recording values of about 3 kPa. On the contrary, green NPs triggered a slight decrease of stiffness values (c.a. 6 kPa) compared to the untreated cells (c.a. 8 kPa). As the softer cells were implicated in cancer progression and metastasization, this evidence strongly supported the idea of a link between the cell elasticity and physicochemical properties of NPs that, in turn, influenced the interaction with the cell membrane. Thus, the green SiO2 NPs compromised cells to a lesser extent than the other SiO2 NPs types. In this scenario, the elasticity evaluation could be an interesting tool to understand the toxicity of NPs with the aim of predicting some pathological phenomena associated with their exposure.

In recent years, Atomic Force Microscope (AFM)-based nanolithography techniques have emerged as a very powerful approach for the machining of countless types of nanostructures. However, the conventional AFM-based nanolithography methods suffer from low efficiency, low rate of patterning, and high complexity of execution. In this frame, we first developed an easy and effective nanopatterning technique, termed Pulse-Atomic Force Lithography (P-AFL), with which we were able to pattern 2.5D nanogrooves on a thin polymer layer. Indeed, for the first time, we patterned nanogrooves with either constant or varying depth profiles, with sub-nanometre resolution, high accuracy, and reproducibility. In this paper, we present the results on the investigation of the effects of P-AFL parameters on 2.5D nanostructures’ morphology. We considered three main P-AFL parameters, i.e., the pulse’s amplitude (setpoint), the pulses’ width, and the distance between the following indentations (step), and we patterned arrays of grooves after a precise and well-established variation of the aforementioned parameters. Optimizing the nanolithography process, in terms of patterning time and nanostructures quality, we realized unconventional shape nanostructures with high accuracy and fidelity. Finally, a scanning electron microscope was used to confirm that P-AFL does not induce any damage on AFM tips used to pattern the nanostructures.

Natural halloysite clay nanotubes (HNTs) are versatile inorganic reinforcing materials for creating hybrid composites. Upon doping HNTs with polymers, coating, or loading them with bioactive molecules, the production of novel nanocomposites is possible, having specific features for several applications. To investigate HNTs composites nanostructures, AFM is a very powerful tool since it allows for performing nano-topographic and morpho-mechanical measurements in any environment (air or liquid) without treatment of samples, like electron microscopes require. In this review, we aimed to provide an overview of recent AFM investigations of HNTs and HNT nanocomposites for unveiling hidden characteristics inside them envisaging future perspectives for AFM as a smart device in nanomaterials characterization.