Conjugation to gold nanoparticles of methionine gamma-lyase, a cancer-starving enzyme. Physicochemical characterization of the nanocomplex for prospective nanomedicine applications.

The pyridoxal 5'-dependent enzyme methionine γ-lyase (MGL) catalyzes the degradation of methionine. This activity has been profitable to develop an antitumor agent exploiting the strict dependence of most malignant cells on the availability of methionine. Indeed, methionine depletion blocks tumor proliferation and leads to an increased susceptibility to anticancer drugs. Here, we explore the conjugation of MGL to gold nanoparticles capped with citrate (AuNPs) as a novel strategy to deliver MGL to cancer cells. Measurements of Transmission Electron Microscopy, Dynamic Light Scattering, Asymmetrical Flow Field-Flow Fractionation, X-ray Photoelectron Spectroscopy, and Circular Dichroism allowed to achieve an extensive biophysical and biochemical characterization of the MGL-AuNP complex including particle size, size distribution, MGL loading yield, enzymatic activity, and impact of gold surface on protein structure. Noticeably, we found that activity retention was improved over time for the enzyme adsorbed to AuNPs with respect to the enzyme free in solution. The acquired body of knowledge on the nanocomplex properties and this encouraging stabilizing effect upon conjugation are the necessary basis for further studies aimed at the evaluation of the therapeutic potential of MGL-AuNP complex in a biological milieu.

Analytical Ultracentrifugation Detects Quaternary Rearrangements and Antibody-Induced Conformational Selection of the SARS-CoV-2 Spike Trimer.

Analytical ultracentrifugation (AUC) analysis shows that the SARS-CoV-2 trimeric Spike (S) protein adopts different quaternary conformations in solution. The relative abundance of the "open" and "close" conformations is temperature-dependent, and samples with different storage temperature history have different open/close distributions. Neutralizing antibodies (NAbs) targeting the S receptor binding domain (RBD) do not alter the conformer populations; by contrast, a NAb targeting a cryptic conformational epitope skews the Spike trimer toward an open conformation. The results highlight AUC, which is typically applied for molecular mass determination of biomolecules as a powerful tool for detecting functionally relevant quaternary protein conformations.

Differences in Physico-Chemical Properties and Immunological Response in Nanosimilar Complex Drugs: The Case of Liposomal Doxorubicin.

This study aims to highlight the impact of physicochemical properties on the behaviour of nanopharmaceuticals and how much carrier structure and physiochemical characteristics weigh on the effects of a formulation. For this purpose, two commercially available nanosimilar formulations of Doxil and their respective carriers were compared as a case study. Although the two formulations were "similar", we detected different toxicological effects (profiles) in terms of in vitro toxicity and immunological responses at the level of cytokines release and complement activation (iC3b fragment), that could be correlated with the differences in the physicochemical properties of the formulations. Shedding light on nanosimilar key quality attributes of liposome-based materials and the need for an accurate characterization, including investigation of the immunological effects, is of fundamental importance considering their great potential as delivery system for drugs, genes, or vaccines and the growing market demand.

Detection and formation mechanisms of secondary nanoplastic released from drinking water bottles.

Since nanoplastics are currently considered potentially hazardous to the environment and human health, reliability of studies on nanoplastic exposure becomes crucial. However, analytical challenges limit our understanding of their formation and detection, thus hampering their biological interactions assessment. Here we provide a combined approach to quantitatively and qualitatively detect the release of nanoplastics in water matrix and, in particular, to measure direct exposure of consumers by simulated use of drinking water plastic bottles. We measured that the polyethylene sealing of the bottles released particles with a size distribution ranging from few hundreds nanometers up to about one micron and estimated a mass release in the order of few tenths of nanograms per opening/closing cycle. We observe that mechanical stress alters the physical-chemical characteristics of the generated secondary nanoplastics and degrades the material properties compared to the original bulk source, thus complicating their spectroscopic chemical identification. Our findings demonstrate that understanding material degradation processes is therefore crucial for identifying and quantifying nanoplastics in real samples. Moreover, methods allowing quantitative studies on the release of nanoplastic as a source of exposure are considered essential for proper assessment of their potential health hazards and to promote improvements in consumer products plastic packaging design.

In Vitro High-Throughput Toxicological Assessment of Nanoplastics.

Sub-micrometer particles derived from the fragmentation of plastics in the environment can enter the food chain and reach humans, posing significant health risks. To date, there is a lack of adequate toxicological assessment of the effects of nanoplastics (NPs) in mammalian systems, particularly in humans. In this work, we evaluated the potential toxic effects of three different NPs in vitro: two NPs obtained by laser ablation (polycarbonate (PC) and polyethylene terephthalate (PET1)) and one (PET2) produced by nanoprecipitation. The physicochemical characterization of the NPs showed a smaller size, a larger size distribution, and a higher degree of surface oxidation for the particles produced by laser ablation. Toxicological evaluation performed on human cell line models (HePG2 and Caco-2) showed a higher toxic effect for the particles synthesized by laser ablation, with PC more toxic than PET. Interestingly, on differentiated Caco-2 cells, a conventional intestinal barrier model, none of the NPs produced toxic effects. This work wants to contribute to increase knowledge on the potential risks posed by NPs.

Detecting Micro- and Nanoplastics Released from Food Packaging: Challenges and Analytical Strategies.

Micro- and nanoplastic (pMP and pNP, respectively) release is an emerging issue since these particles constitute a ubiquitous and growing pollutant, which not only threatens the environment but may have potential consequences for human health. In particular, there is concern about the release of secondary pMP and pNP from the degradation of plastic consumer products. The phenomenon is well-documented in relation to plastic waste in the environment but, more recently, reports of pMP generated even during the normal use of plastic food contact materials, such as water bottles, tea bags, and containers, have been published. So far, a validated and harmonized strategy to tackle the issue is not available. In this study, we demonstrate that plastic breakdown to pMP and pNP can occur during the normal use of polyethylene (PE) rice cooking bags and ice-cube bags as well as of nylon teabags. A multi-instrumental approach based on Raman microscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and particular attention on the importance of sample preparation were applied to evaluate the chemical nature of the released material and their morphology. In addition, a simple method based on Fourier transform infrared (FT-IR) spectroscopy is proposed for pNP mass quantification, resulting in the release of 1.13 ± 0.07 mg of nylon 6 from each teabag. However, temperature was shown to have a strong impact on the morphology and aggregation status of the released materials, posing to scientists and legislators a challenging question: are they micro- or nanoplastics or something else altogether?

Large-Sized Nanocrystalline Ultrathin ß-Ga2O3 Membranes Fabricated by Surface Charge Lithography.

Large-sized 2D semiconductor materials have gained significant attention for their fascinating properties in various applications. In this work, we demonstrate the fabrication of nanoperforated ultrathin ß-Ga2O3 membranes of a nanoscale thickness. The technological route includes the fabrication of GaN membranes using the Surface Charge Lithography (SCL) approach and subsequent thermal treatment in air at 900 °C in order to obtain ß-Ga2O3 membranes. The as-grown GaN membranes were discovered to be completely transformed into ß-Ga2O3, with the morphology evolving from a smooth topography to a nanoperforated surface consisting of nanograin structures. The oxidation mechanism of the membrane was investigated under different annealing conditions followed by XPS, AFM, Raman and TEM analyses.

Microplastic retention in small and medium municipal wastewater treatment plants and the role of the disinfection.

Wastewater treatment plants (WWTPs) efficiently retain microplastic particles (MPs) generated within urban areas. Among the wastewater treatment steps, disinfection has not been characterized for its potential MPs retention activity, although it has been reported that processes used to abate the bacterial load could also affect MPs concentration. For this reason, we evaluated the MPs concentration across the overall wastewater treatment process and before and after the disinfection step in four small/medium WWTPs located in the north of Italy. Most of the MPs found in the samples were fibers or fragments, smaller than 500 µm, mainly composed of polyethylene, polypropylene, or polyethylene terephthalate. The retention efficiency at the outlets was higher than 94% in all the plants analyzed. More interestingly, the disinfection treatments adopted by the different WWTPs reduced MPs concentration from a minimum of 9.1% (UV treatment) to a maximum of 67.6% (chlorination), promoting a further increase of the overall retention efficiency of the WWTPs from 0.4 to 0.7%. Quantitatively, the disinfection contributes to the MPs reduction in the outlets by retaining 0.5-6.7 million MPs per day, in WWTPs that discharge 2.7-12 million MPs per day. The results of the present work underline the importance of a careful choice of the steps that constitute the wastewater treatment, including disinfection, in order to minimize MPs discharge into the natural ecosystems.

TiO2@BSA nano-composites investigated through orthogonal multi-techniques characterization platform.

Biocompatible coating based on bovine serum albumin (BSA) was applied on two different TiO2 nanoparticles (aeroxide P25 and food grade E171) to investigate properties and stability of resulting TiO2@BSA composites, under the final perspective to create a "Safe-by-Design" coating, able to uniform, level off and mitigate surface chemistry related phenomena, as naturally occurring when nano-phases come in touch with proteins enriched biological fluids. The first step towards validating the proposed approach is a detailed characterization of surface chemistry with the quantification of amount and stability of BSA coating deposited on nanoparticles' surfaces. At this purpose, we implemented an orthogonal multi-techniques characterization platform, providing important information on colloidal behavior, particle size distribution and BSA-coating structure of investigated TiO2 systems. Specifically, the proposed orthogonal approach enabled the quantitative determination of bound and free (not adsorbed) BSA, a key aspect for the design of intentionally BSA coated nano-structures, in nanomedicine and, overall, for the control of nano-surface reactivity. In fact, the BSA-coating strategy developed and the orthogonal characterisation performed can be extended to different designed nanomaterials in order to further investigate the protein-corona formation and promote the implementation of BSA engineered coating as a strategy to harmonize the surface reactivity and minimize the biological impact.

Photoelectrochemical water splitting by hybrid organic-inorganic systems: setting the path from 2% to 20% solar-to-hydrogen conversion efficiency.

Promoting solar fuels as a viable alternative to hydrocarbons calls for technologies that couple efficiency, durability, and low cost. In this work we elucidate how hybrid organic-inorganic systems employing hybrid photocathodes (HPC) and perovskite solar cells (PSC) could eventually match these needs, enabling sustainable and clean hydrogen production. First, we demonstrate a system comprising an HPC, a PSC, and a Ru-based oxygen evolution catalyst reaching a solar-to-hydrogen (STH) efficiency above 2%. Moving from this experimental result, we elaborate a perspective for this technology by adapting the existing models to the specific case of an HPC-PSC tandem. We found two very promising scenarios: one with a 10% STH efficiency, achievable using the currently available semiconducting polymers and the widely used methylammonium lead iodide (MAPI) PSC, and the other one with a 20% STH efficiency, requiring dedicated development for water-splitting applications of recently reported high-performing organic semiconductors and narrow band-gap perovskites.

Role of Self-Assembled Surface Functionalization on Nucleation Kinetics and Oriented Crystallization of a Small-Molecule Drug: Batch and Thin-Film Growth of Aspirin as a Case Study.

The present paper assesses the heterogeneous nucleation of a small-molecule drug and its relationship with the surface chemistry of engineered heteronucleants. The nucleation of aspirin (ASA) was tuned by different functional groups exposed by self-assembled monolayers (SAMs) immobilized on glass surfaces. Smooth topographies and defect-free surface modification allowed the deconvolution of chemical and topographical effects on nucleation. The nucleation induction time of ASA in batch crystallization was mostly enhanced by methacrylate and amino groups, whereas it was repressed by thiol groups. In this perspective, we also present a novel strategy for the evaluation of surface-drug interactions by confining drug crystallization to thin films and studying the preferential growth of crystal planes on different surfaces. Crystallization by spin coating improved the study of oriented crystallization, enabling reproducible sample preparation, minimal amounts of drug required, and short processing time. Overall, the acid surface tension of SAMs dictated the nucleation kinetics and the extent of relative growth of the ASA crystal planes. Moreover, the face-selective action of monolayers was investigated by force spectroscopy and attributed to the preferential interaction of exposed groups with the (100) crystal plane of ASA.

Combining microcavity size selection with Raman microscopy for the characterization of Nanoplastics in complex matrices.

Nanoplastic particulates (pNP) are widely considered as being potentially harmful to the environment and living organisms while also being technically difficult to detect and identify in the presence of biological matrices. In this study, we describe a method for the extraction and subsequent Raman analysis of pNP present in the tissues of salt-water mussels. The process combines a step of enzymatic digestion/filtering to eliminate the biological matrix with a detection/identification procedure, which uses a micro-machined surface, composed of arrays of cavities with well-defined sub-micron depths and diameters. This sensor surface, exploits capillary forces in a drying droplet of analyte solution to drive the self-assembly of suspended nanoparticles into the cavities leaving the individual particles isolated from each other over the surface. The resulting array, when analysed using confocal Raman microscopy, permits the size selective analysis of the individual sub-micron pNP trapped in the cavities structure.

Detection of Metal-Doped Fluorescent PVC Microplastics in Freshwater Mussels.

The large-scale production of plastic and the resulting release of waste is leading to a huge accumulation of micro-sized particles in the environment that could have an impact on not only aquatic organisms but also on humans. Despite the extensive literature on the subject, there is still an insufficient harmonization of methodologies for the collection and analysis of microplastics (MPs) in complex matrices; especially for high density polymers; such as polyvinyl chloride (PVC), which tend to sink and accumulate in sediments, becoming available to benthonic organisms. In this article, mussels have been chosen as model for microplastic accumulation due to their extensive filtering activity and their wide distribution in both fresh and salt water basins. To facilitate the identification and quantification of microplastics taken up by mussels, novel fluorescent and metal-doped PVC microplastics (PVC-Platinum octaethylporphyrin (PtOEP) MPs in the size range of 100 µm) have been synthesized and characterized. For the analysis of the mussels following exposure, an enzymatic protocol using amylase, lipase, papain, and SDS for organic material digestion and a sucrose-ZnCl2 density gradient for the selective separation of ingested microplastics has been developed. The final identification of MPs was performed by fluorescence microscopy. This work can greatly benefit the scientific community by providing a means to study the behavior of PVC MPs, which represent an example of a very relevant yet poorly studied high density polymeric contaminant commonly found in complex environmental matrices.

Synthesis of Citrate-Stabilized Silver Nanoparticles Modified by Thermal and pH Preconditioned Tannic Acid.

Silver nanoparticles (AgNPs) may be synthesized by many different methods, with those based on the thermal reduction of silver salts by citric acid or citric acid/tannic acid being amongst the most commonly used. These methods, although widely used and technically simple, can produce particles in which the size, polydispersivity and morphology can vary greatly. In this work nearly mono-dispersed spherical AgNPs have been synthesized via a one-step reduction method by using sodium citrate and varying quantities of Tannic Acid (TA), which was thermally conditioned prior to use in the growth process. It was found that the final size can be further tailored by controlling the amount of TA and the thermal conditioning of the TA at 60 °C at different time points, which changes the size and polydispersivity of AgNPs. To better understand the origin of this effect, optical spectroscopic analysis and 1H NMR of the TA following mild thermal conditioning of the solution have been done. Comparison of thermally conditioned TA and TA exposed to basic pH shows that similar chemical modifications occur and consequently produce similar effects on growth when used in the synthesis of AgNPs. It is proposed that thermal preconditioning of the TA introduces either chemical or structural changes, which decrease the final particle size under a given total silver content.

Non-Equilibrium Synthesis of Highly Active Nanostructured, Oxygen-Incorporated Amorphous Molybdenum Sulfide HER Electrocatalyst.

Molybdenum sulfide emerged as promising hydrogen evolution reaction (HER) electrocatalyst thanks to its high intrinsic activity, however its limited active sites exposure and low conductivity hamper its performance. To address these drawbacks, the non-equilibrium nature of pulsed laser deposition (PLD) is exploited to synthesize self-supported hierarchical nanoarchitectures by gas phase nucleation and sequential attachment of defective molybdenum sulfide clusters. The physics of the process are studied by in situ diagnostics and correlated to the properties of the resulting electrocatalyst. The as-synthesized architectures have a disordered nanocrystalline structure, with nanodomains of bent, defective S-Mo-S layers embedded in an amorphous matrix, with excess sulfur and segregated molybdenum particles. Oxygen incorporation in this structure fosters the creation of amorphous oxide/oxysulfide nanophases with high electrical conductivity, enabling fast electron transfer to the active sites. The combined effect of the nanocrystalline pristine structure and the surface oxidation enhances the performance leading to small overpotentials, very fast kinetics (35.1 mV dec-1 Tafel slope) and remarkable long-term stability for continuous operation up to -1 A cm-2. This work shows possible new avenues in catalytic design arising from a non-equilibrium technique as PLD and the importance of structural and chemical control to improve the HER performance of MoS-based catalysts.

General and adaptive synthesis protocol for high-quality organosilane self-assembled monolayers as tunable surface chemistry platforms for biochemical applications.

The controlled modification of surface properties represents a pervasive requirement to be fulfilled when developing new technologies. In this paper, we propose an easy-to-implement protocol for the functionalization of glass with self-assembled monolayers (SAMs). The adaptivity of the synthesis route was demonstrated by the controlled anchoring of thiol, amino, glycidyloxy, and methacrylate groups onto the glass surface. The optimization of the synthetic pathway was mirrored by extremely smooth SAMs (approximately 150 pm roughness), layer thickness comparable to the theoretical molecule length, absence of silane islands along the surface, quasi-unitary degree of packing, and tailored wettability and charge. The functionalization kinetics of two model silanes, 3-mercapto- and 3-amino-propyltrimethoxysilane, was determined by cross-comparing x-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry data. Our SAMs with tailored physicochemical attributes will be implemented as supports for the crystallization of pharmaceuticals and biomolecules in upcoming studies. Here, the application to a small molecule drug model, namely aspirin, was discussed as a proof of concept.

Aero-Ga2O3 Nanomaterial Electromagnetically Transparent from Microwaves to Terahertz for Internet of Things Applications.

In this paper, fabrication of a new material is reported, the so-called Aero-Ga2O3 or Aerogallox, which represents an ultra-porous and ultra-lightweight three-dimensional architecture made from interconnected microtubes of gallium oxide with nanometer thin walls. The material is fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods followed by decomposition of sacrificial ZnO and oxidation of GaN which according to the results of X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) characterizations, is transformed gradually in ß-Ga2O3 with almost stoichiometric composition. The investigations show that the developed ultra-porous Aerogallox exhibits extremely low reflectivity and high transmissivity in an ultrabroadband electromagnetic spectrum ranging from X-band (8-12 GHz) to several terahertz which opens possibilities for quite new applications of gallium oxide, previously not anticipated.

Large area porous 1D photonic crystals comprising silicon hierarchical nanostructures grown by plasma-assisted, nanoparticle jet deposition.

In this contribution, we describe a room-temperature, template-free, single-step approach for the growth of functional crystalline silicon nanostructures with tailored porosity and photonic properties. The method employs a plasma-assisted nanoparticle synthesis reactor in combination with a supersonic jet deposition stage, in what we call nanoparticle jet deposition or plasma-assisted, supersonic aerosol jet deposition. The relationship between plasma parameters, nanoparticle impaction conditions and the resulting silicon material structural characteristics is investigated. This understanding is successfully employed for the production of porous 1D photonic crystals obtained by periodically modulating the density of the hierarchical silicon nanostructures and hence their local refractive index. The open porosity of this device is then exploited in a proof of concept optical chemical sensor.

Multi-layered hierarchical nanostructures for transparent monolithic dye-sensitized solar cell architectures.

Monolithic dye-sensitized solar cell (DSC) architectures hold great potential for building-integrated photovoltaics applications. They indeed benefit from lower weight and manufacturing costs as they avoid the use of a transparent conductive oxide (TCO)-coated glass counter electrode. In this work, a transparent monolithic DSC comprising a hierarchical 1D nanostructure stack is fabricated by physical vapor deposition techniques. The proof of concept device comprises hyperbranched TiO2 nanostructures, sensitized by the prototypical N719, as photoanode, a hierarchical nanoporous Al2O3 spacer, and a microporous indium tin oxide (ITO) top electrode. An overall 3.12% power conversion efficiency with 60% transmittance outside the dye absorption spectral window is demonstrated. The introduction of a porous TCO layer allows an efficient trade-off between transparency and power conversion. The porous ITO exhibits submicrometer voids and supports annealing temperatures above 400 °C without compromising its optoelectronical properties. After thermal annealing at 500 °C, the resistivity, mobility, and carrier concentration of the 800 nm-thick porous ITO layer are found to be respectively 2.3 × 10-3 Ω cm-1, 11 cm2 V-1 s-1, and 1.62 × 1020 cm-3, resulting in a series resistance in the complete device architecture of 45 Ω. Electrochemical impedance and intensity-modulated photocurrent/photovoltage spectroscopy give insight into the electronic charge dynamic within the hierarchical monolithic DSCs, paving the way for potential device architecture improvements.

Stable hybrid organic/inorganic photocathodes for hydrogen evolution with amorphous WO3 hole selective contacts.

Photoelectrochemical H2 production through hybrid organic/inorganic interfaces exploits the capability of polymeric absorbers to drive photo-induced electron transfer to an electrocatalyst in a water environment. Photoelectrode architectures based on solution-processed organic semiconductors are now emerging as low-cost alternatives to crystalline inorganic semiconductors based on Si, oxides and III-V alloys. In this work, we demonstrate that the stability of a hybrid organic/inorganic photocathode, employing a P3HT:PCBM blend as photoactive material, can be considerably improved by introducing an electrochemically stable WO3 hole selective layer, paired with a TiO2 electron selective layer. This hybrid photoelectrode exhibits a photocurrent of 2.48 mA cm-2 at 0 VRHE, +0.56 VRHE onset potential and a state-of the art operational activity of more than 10 hours. This work gives the perspective that photoelectrodes based on organic semiconductors, coupled with proper inorganic selective contacts, represent a sound new option for the efficient and durable photoelectrochemical conversion of solar energy into fuels.