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Ancient glass objects typically show distinctive effects of deterioration as a result of environmentally induced physicochemical transformations of their surface over time. Iridescence is one of the distinctive signatures of aging that is most commonly found on excavated glass. In this work, we present an ancient glass fragment that exhibits structural color through surface weathering resulting in iridescent patinas caused by silica reprecipitation in nanoscale lamellae. This archaeological artifact reveals an unusual hierarchically assembled photonic crystal with extremely ordered nanoscale domains, high spectral selectivity, and reflectivity (~90%), that collectively behaves like a gold mirror. Optical characterization paired with nanoscale elemental analysis further underscores the high quality of this structure providing a window into this sophisticated natural photonic crystal assembled by time.
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The growth of pyramidal platinum nanocrystals is studied by a combination of synthesis/characterization experiments and density functional theory calculations. It is shown that the growth of pyramidal shapes is due to a peculiar type of symmetry breaking, which is caused by the adsorption of hydrogen on the growing nanocrystals. Specifically, the growth of pyramidal shapes is attributed to the size-dependent adsorption energies of hydrogen atoms on {100} facets, whose growth is hindered only if they are sufficiently large. The crucial role of hydrogen adsorption is further confirmed by the absence of pyramidal nanocrystals in experiments where the reduction process does not involve hydrogen.
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The ability of shape-controlled octahedral Pt nanoparticles to act as nanozyme mimicking glucose oxidase enzyme is reported. Extended {111} particle surface facets coupled with a size comparable to natural enzymes and easy-to-remove citrate coating give high affinity for glucose, comparable to the enzyme as proven by the steady-state kinetics of glucose electrooxidation. The easy and thorough removal of the citrate coating, demonstrated by X-ray photoelectron spectroscopy analysis, allows a highly stable deposition of the nanozymes on the electrode. The glucose electrochemical detection (at -0.2 V vs SCE) shows a linear response between 0.36 and 17 mM with a limit of detection of 110 µM. A good reproducibility has been achieved, with an average relative standard deviation (RSD) value of 9.1% (n = 3). Similarly, a low intra-sensor variability has been observed, with a RSD of 6.6% (n = 3). Moreover, the sensor shows a long-term stability with reproducible performances for at least 2 months (RSD: 7.8%). Tests in saliva samples show the applicability of Pt nanozymes to commercial systems for non-invasive monitoring of hyperglycemia in saliva, with recoveries ranging from 92 to 98%.
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Glucose Oxidase , Nanopartículas , Glucose Oxidase/química , Platina/química , Reprodutibilidade dos Testes , Nanopartículas/química , Glucose/análiseRESUMO
Redox imbalance and oxidative stress-related biomarkers are raising increasing consensus in the scientific community for their significant role in a wide range of human disorders. In this framework, the total antioxidant capacity (TAC), namely, the overall pattern of both enzymatic and nonenzymatic antioxidant compounds within the body, represents an important bioanalytical parameter. To date, however, antioxidant assays require costly instrumentations, laboratory setups, and reagents, and they are invasive. Yet, their accuracy typically suffers from strong sensitivity to interfering matrices and inability to detect the complete pattern of physiological antioxidant molecules, due to the use of reaction schemes and probes/substrates that are not sensitive to the diverse range of relevant target species. Here, we exploit the enzyme-mimetic properties of platinum nanoparticles combined with hydroxyl radical probes produced at the particle surface to develop an effective detection scheme that is sensitive to both single electron transfer (SET) and hydrogen atom transfer (HAT) reactions, thus covering all the physiologically relevant antioxidant species. Importantly, the nanozyme-enabled method allows fast (5 min), accurate, and noninvasive evaluation of the body TAC through saliva via simple naked-eye or smartphone-based inspection.
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Antioxidantes/análise , Colorimetria/métodos , Nanopartículas Metálicas/química , Platina/química , Saliva/química , Adulto , Antioxidantes/química , Materiais Biomiméticos/química , Elétrons , Humanos , Hidrogênio/química , Radical Hidroxila/química , Pessoa de Meia-Idade , Saliva/metabolismo , Adulto JovemRESUMO
We present a fast and sensitive nanosensor that can detect organic mercury, exploiting the combination of the catalytic and plasmonic properties of gold nanoparticles (AuNPs). The method is one-step and completely instrument-free, and has a colorimetric readout clearly detectable by simple visual inspection. The AuNPs catalyze efficient organic mercury reduction to the metallic form (Hg0 ), allowing its nucleation and amalgam formation on particle surface, with consequent aggregation-induced plasmon shift. This leads to very rapid (1â min) and specific colorimetric detection of mercury species. The achieved limit of detection (20â ppb) is compliant with current regulatory limits in food.
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Oxidative stress-dependent inflammatory diseases represent a major concern for the population's health worldwide. Biocompatible nanomaterials with enzymatic properties could play a crucial role in the treatment of such pathologies. In this respect, platinum nanoparticles (PtNPs) are promising candidates, showing remarkable catalytic activity, able to reduce the intracellular reactive oxygen species (ROS) levels and impair the downstream pathways leading to inflammation. This review reports a critical overview of the growing evidence revealing the anti-inflammatory ability of PtNPs and their potential applications in nanomedicine. It provides a detailed description of the wide variety of synthetic methods recently developed, with particular attention to the aspects influencing biocompatibility. Special attention has been paid to the studies describing the toxicological profile of PtNPs with an attempt to draw critical conclusions. The emerging picture suggests that the material per se is not causing cytotoxicity, while other physicochemical features related to the synthesis and surface functionalization may play a crucial role in determining the observed impairment of cellular functions. The enzymatic activity of PtNPs is also summarized, analyzing their action against ROS produced by pathological conditions within the cells. In particular, we extensively discuss the potential of these properties in nanomedicine to down-regulate inflammatory pathways or to be employed as diagnostic tools with colorimetric readout. A brief overview of other biomedical applications of nanoplatinum is also presented.
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Nanopartículas Metálicas/química , Nanomedicina , Platina/química , Humanos , Tamanho da PartículaRESUMO
A rapid point-of-care method for the colorimetric detection of cisplatin was developed, exploiting the efficient conversion of the chemotherapeutic drug into a high-performance nanocatalyst with peroxidase enzyme mimics. This assay provides high specificity and ppb-detection sensitivity with the naked eye or a smartphone-based readout, outperforming many standard laboratory-based techniques. The nanocatalyst-enabled colorimetric assay can be integrated with machine-learning methods, providing accurate quantitative measurements. Such a combined approach opens interesting perspectives for the on-site monitoring of both chemotherapeutic patients to achieve optimal treatments and healthcare workers to prevent their unsafe exposure.
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Cisplatino , Colorimetria , Colorimetria/métodos , Humanos , Limite de Detecção , SmartphoneRESUMO
Counterfeiting is a worldwide issue affecting many industrial sectors, ranging from specialized technologies to retail market, such as fashion brands, pharmaceutical products, and consumer electronics. Counterfeiting is not only a huge economic burden (>$ 1 trillion losses/year), but it also represents a serious risk to human health, for example, due to the exponential increase of fake drugs and food products invading the market. Considering such a global problem, numerous anticounterfeit technologies have been recently proposed, mostly based on tags. The most advanced category, based on encryption and cryptography, is represented by physically unclonable functions (PUFs). A PUF tag is based on a unique physical object generated through chemical methods with virtually endless possible combinations, providing remarkable encoding capability. However, most methods adopted nowadays are based on expensive and complex technologies, relying on instrumental readouts, which make them not effective in real-world applications. To achieve a simple yet cryptography-based anticounterfeit method, herein we exploit a combination of nanotechnology, chemistry, and artificial intelligence (AI). Notably, we developed platinum nanocatalyst-enabled visual tags, exhibiting the properties of PUFs (encoding capability >10300) along with fast (1 min) ON/OFF readout and full reversibility, enabling multiple onsite authentication cycles. The development of an accurate AI-aided algorithm powers the system, allowing for smartphone-based PUF authentications.
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Inteligência Artificial , Medicamentos Falsificados , Algoritmos , Humanos , Nanotecnologia , SmartphoneRESUMO
Ultrasmall (<5 nm diameter) noble metal nanoparticles with a high fraction of {111} surface domains are of fundamental and practical interest as electrocatalysts, especially in fuel cells; the nanomaterial surface structure dictates its catalytic properties, including kinetics and stability. However, the synthesis of size-controlled, pure Pt-shaped nanocatalysts has remained a formidable chemical challenge. There is an urgent need for an industrially scalable method for their production. Here, a one-step approach is presented for the preparation of single-crystal pyramidal nanocatalysts with a high fraction of {111} surface domains and a diameter below 4 nm. This is achieved by harnessing the shape-directing effect of citrate molecules, together with the strict control of oxidative etching while avoiding polymers, surfactants, and organic solvents. These catalysts exhibit significantly enhanced durability while, providing equivalent current and power densities to highly optimized commercial Pt/C catalysts at the beginning of life (BOL). This is even the case when they are tested in full polymer electrolyte membrane fuel cells (PEMFCs), as opposed to rotating disk experiments that artificially enhance electrode kinetics and minimize degradation. This demonstrates that the {111} surface domains in pyramidal Pt nanoparticles (as opposed to spherical Pt nanoparticles) can improve aggregation/corrosion resistance in realistic fuel cell conditions, leading to a significant improvement in membrane electrode assembly (MEA) stability and lifetime.
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Synthesizing metal nanoparticles with fine control of size, shape and surface properties is of high interest for applications such as catalysis, nanoplasmonics, and fuel cells. In this contribution, we demonstrate that the citrate-coated surfaces of palladium (Pd) and platinum (Pt)@Pd nanocubes with a lateral length <5 nm and low polydispersity in shape achieve superior catalytic properties. The synthesis achieves great control of the nanoparticle's physico-chemical properties by using only biogenic reagents and bromide ions in water while being fast, easy to perform and scalable. The role of the seed morphology is pivotal as Pt single crystal seeds are necessary to achieve low polydispersity in shape and prevent nanorods formation. In addition, electrochemical measurements demonstrate the abundancy of Pd{100} surface facets at a macroscopic level, in line with information inferred from TEM analysis. Quantum density functional theory calculations indicate that the kinetic origin of cubic Pd nanoshapes is facet-selective Pd reduction/deposition on Pd(111). Moreover, we underline both from an experimental and theoretical point of view that bromide alone does not induce nanocube formation without the synergy with formic acid. The superior performance of these highly controlled nanoparticles to perform the catalytic reduction of 4-nitrophenol was proved: polymer-free and surfactant-free Pd nanocubes outperform state-of-the-art materials by a factor >6 and a commercial Pd/C catalyst by more than one order of magnitude.
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Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes grown by surface-initiated polymerization from a polyanionic macroinitiator adsorbed at the sapphire-water interface have been used as a substrate to study the interaction between the weak polyelectrolyte PDMAEMA and the oppositely charged surfactant sodium dodecyl sulfate (SDS) with neutron reflectivity. At pH 3, multilayered structures are formed in which the interlayer separation (â¼40 Å) is comparable to the dimensions of a SDS bilayer or micelle. The number of repeating layers that form depends on brush thickness, ranging from three layers in a relatively thin brush (5 nm dry thickness) to 15 layers in a relatively thick brush (17 nm dry thickness). In the 5 nm brush, addition of 0.01 mM SDS leads to brush deswelling, and the distinct layered structure only forms when the SDS concentration reaches 1 mM, with the brush reswelling slightly at 5 mM SDS. In the thicker (11 and 17 nm) brushes, distinct layered structures form at 0.1 mM SDS, in which the molar SDS/DMAEMA ratio is greater than unity. Exposing the 17 nm brush/SDS complex to 1 M NaNO(3) results in the complete removal of the surfactant and recovery of the bare brush structure. At pH 9, there is significant surfactant uptake by the brush, but no multilayer structures are formed. The brush presents a high concentration of DMAEMA segments that are localized to within 500-1000 Å of the sapphire interface. At pH 9 the high local concentration of hydrocarbon segments in the brush screens the hydrophobic tails of the surfactants from the unfavorable interaction with water, leading to significant surfactant uptake by the brush. At pH 3 the high local concentration of charges inside the brush additionally screens the repulsive interactions between the surfactant headgroups, making surfactant uptake even more favorable, leading to the formation of multilayered surfactant aggregates confined within the brush.
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Metacrilatos/química , Nanoestruturas/química , Nylons/química , Polimerização , Tensoativos/química , Óxido de Alumínio , Difração de Nêutrons , Polieletrólitos , Polímeros , ÁguaRESUMO
Introduction: Cerebrovascular diseases encompass various disorders of the brain vasculature, such as ischemic/hemorrhagic strokes, aneurysms, and vascular malformations, also affecting the central nervous system leading to a large variety of transient or permanent neurological disorders. They represent major causes of mortality and long-term disability worldwide, and some of them can be inherited, including Cerebral Cavernous Malformation (CCM), an autosomal dominant cerebrovascular disease linked to mutations in CCM1/KRIT1, CCM2, or CCM3/PDCD10 genes.Areas covered: Besides marked clinical and etiological heterogeneity, some commonalities are emerging among distinct cerebrovascular diseases, including key pathogenetic roles of oxidative stress and inflammation, which are increasingly recognized as major disease hallmarks and therapeutic targets. This review provides a comprehensive overview of the different clinical features and common pathogenetic determinants of cerebrovascular diseases, highlighting major challenges, including the pressing need for new diagnostic and therapeutic strategies, and focusing on emerging innovative features and promising benefits of nanomedicine strategies for early detection and targeted treatment of such diseases.Expert opinion: Specifically, we describe and discuss the multiple physico-chemical features and unique biological advantages of nanosystems, including nanodiagnostics, nanotherapeutics, and nanotheranostics, that may help improving diagnosis and treatment of cerebrovascular diseases and neurological comorbidities, with an emphasis on CCM disease.
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Transtornos Cerebrovasculares , Hemangioma Cavernoso do Sistema Nervoso Central , Transtornos Cerebrovasculares/diagnóstico , Transtornos Cerebrovasculares/genética , Transtornos Cerebrovasculares/terapia , Hemangioma Cavernoso do Sistema Nervoso Central/diagnóstico , Hemangioma Cavernoso do Sistema Nervoso Central/genética , Hemangioma Cavernoso do Sistema Nervoso Central/terapia , Humanos , Inflamação , Mutação , NanomedicinaRESUMO
Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes have been grown by surface-initiated atom transfer radical polymerization (SI-ATRP) from a polyanionic macroinitiator adsorbed at the sapphire-water interface, and neutron reflectivity has been used to characterize the structures and pH response of the brushes. The polymer brushes are well-described by Gaussian density profiles with an additional thin, dense layer close to the solid-liquid interface for the thicker brushes at pH 7 and 9, which produces a spike in the density profile. The spike in the distribution accounts for less than 5% of the polymer and disappears as the brushes swell at pH 3. The observed swelling behavior has been used in combination with the predictions of scaling theory and previous experimental measurements to determine the grafted density of PDMAEMA chains.
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The fundamental interactions underlying citrate-mediated chemical stability of metal nanoparticles, and their surface characteristics dictating particle dispersion/aggregation in aqueous solutions, are largely unclear. Here, we developed a theoretical model to estimate the stoichiometry of small, charged ligands (like citrate) chemisorbed onto spherical metallic nanoparticles and coupled it with atomistic molecular dynamics simulations to define the uncovered solvent-accessible surface area of the nanoparticle. Then, we integrated coarse-grained molecular dynamics simulations and two-body free energy calculations to define dispersion state phase diagrams for charged metal nanoparticles in a range of medium's ionic strength, a known trigger for aggregation. Ultraviolet-visible spectroscopy experiments of citrate-capped nanocolloids validated our predictions and extended our results to nanoparticles up to 35 nm. Altogether, our results disclose a complex interplay between the particle size, its surface charge density, and the ionic strength of the medium, which ultimately clarifies how these variables impact colloidal stability.
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Green and scalable methodologies for the preparation of metal nanoparticles with fine control of shape and size are of high interest in many areas including catalysis, nanomedicine, and nanodiagnostics. In this contribution, we describe a new synthetic method for the production of palladium (Pd) penta-twinned nanowires and nanorods utilizing sodium citrate, formic acid, ascorbic acid, and potassium bromide (KBr) in water, without the use of surfactants or polymers. The synthesis is green, fast, and without the need of complex setups. Interestingly, a microwave-assisted scale-up process has been developed. The combination of a synthetic protocol for seeds and the seed-mediated growth process allows us to synthesize nanorods and nanowires by modulating the concentration of KBr. The synthesized nanomaterials have been physicochemically characterized. High-resolution transmission electron microscopy shows that the nanorods and nanowires have a penta-twinned structure enclosed by {100} lateral facets. Moreover, the absence of sticky molecules or toxic byproducts guarantees the biocompatibility of the nanomaterials, while leaving the surface clean to perform enzymatic activities.
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A method for the aqueous synthesis of stable and biocompatible citrate-coated palladium nanoparticles (PdNPs) in the size range comparable to natural enzymes (4-8 nm) has been developed. The toxicological profile of PdNPs was assessed by different assays on several cell lines demonstrating their safety in vitro also at high particle concentrations. To elucidate their cellular fate upon uptake, the localization of PdNPs was analyzed by Transmission Electron Microscopy (TEM). Moreover, crucial information about their intracellular stability and oxidation state was obtained by Sputtering-Enabled Intracellular X-ray Photoelectron Spectroscopy (SEI-XPS). TEM/XPS results showed significant stability of PdNPs in the cellular environment, an important feature for their biocompatibility and potential for biomedical applications. On the catalytic side, these PdNPs exhibited strong and broad antioxidant activities, being able to mimic the three main antioxidant cellular enzymes, i.e., peroxidase, catalase, and superoxide dismutase. Remarkably, using an experimental model of a human oxidative stress-related disease, we demonstrated the effectiveness of PdNPs as antioxidant nanozymes within the cellular environment, showing that they are able to completely re-establish the physiological Reactive Oxygen Species (ROS) levels in highly compromised intracellular redox conditions.
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Platinum nanoparticles (PtNPs) attract great attention due to their efficient catalysis and good degree of cytocompatibility, but information about their effects on the human immune system is still missing. Monocytes are key cells of the innate immune system and the understanding of their reactions to PtNPs is crucial in view of any feasible application to human pathologies. Here, we evaluate the internalization of citrate-coated PtNPs into THP-1 monocytes and its consequences on immune cell responses. We found that the presence of intracellular PtNPs efficiently reduce reactive oxygen species (ROS) without affecting cell viability. The physiological expression of the immune receptors Cluster of Differentiation 14 (CD14), CD11b, CC-Chemokine Receptor 2 (CCR2) and CCR5 and the expression of cytokines and chemokines are not compromised by the presence of PtNPs within THP-1 cells. On the other hand, the treatment with PtNPs modulates the transcription of sixty genes, some of them involved in lipopolysaccharide (LPS) signaling in different cells. However, the treatment with PtNPs of monocytes does not compromise the LPS-induce increase of cytokines in THP-1 monocytes in vitro. Our results demonstrate that citrate-coated PtNPs are non-toxic, perform efficient intracellular reactive oxygen species (ROS) scavenging activity and possess good immune-compatibility, suggesting them as feasible synthetic enzymes for applications in nanomedicine.
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Platinum nanoparticles (PtNPs) are antioxidant enzyme-mimetic nanomaterials with significant potential for the treatment of complex diseases related to oxidative stress. Among such diseases, Cerebral Cavernous Malformation (CCM) is a major cerebrovascular disorder of genetic origin, which affects at least 0.5% of the general population. Accumulated evidence indicates that loss-of-function mutations of the three known CCM genes predispose endothelial cells to oxidative stress-mediated dysfunctions by affecting distinct redox-sensitive signaling pathways and mechanisms, including pro-oxidant and antioxidant pathways and autophagy. A multitargeted combinatorial therapy might thereby represent a promising strategy for the effective treatment of this disease. Herein, we developed a multifunctional nanocarrier by combining the radical scavenging activity of PtNPs with the autophagy-stimulating activity of rapamycin (Rapa). Our results show that the combinatorial targeting of redox signaling and autophagy dysfunctions is effective in rescuing major molecular and cellular hallmarks of CCM disease, suggesting its potential for the treatment of this and other oxidative stress-related diseases.
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The investigation of the toxicological profile and biomedical potential of nanoparticles (NPs) requires a deep understanding of their intracellular fate. Various techniques are usually employed to characterize NPs upon cellular internalization, including high-resolution optical and electron microscopies. Here, we show a versatile method, named sputtering-enabled intracellular X-ray photoelectron spectroscopy, proving that it is able to provide valuable information about the behavior of metallic NPs in culture media as well as within cells, directly measuring their internalization, stability/degradation, and oxidation state, without any preparative steps. The technique can also provide nanoscale vertical resolution along with semiquantitative information about the cellular internalization of the metallic species. The proposed approach is easy-to-use and can become a standard technique in nanotoxicology/nanomedicine and in the rational design of metallic NPs. Two model cases were investigated: silver nanoparticles (AgNPs) and platinum nanoparticles (PtNPs) with the same size and coating. We observed that, after 48 h incubation, intracellular AgNPs were almost completely dissolved, forming nanoclusters as well as AgO, AgS, and AgCl complexes. On the other hand, PtNPs were resistant to the harsh endolysosomal environment, and only some surface oxidation was detected after 48 h.
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Nanopartículas Metálicas/análise , Platina/análise , Prata/análise , Células HeLa , Humanos , Oxirredução , Tamanho da Partícula , Espectroscopia Fotoeletrônica , Platina/metabolismo , Prata/metabolismo , Propriedades de Superfície , Células Tumorais CultivadasRESUMO
The development of green and scalable syntheses for the preparation of size- and shape-controlled metal nanocrystals is of high interest in many areas, including catalysis, electrocatalysis, nanomedicine, and electronics. In this work, a new synthetic approach based on the synergistic action of physical parameters and reagents produces size-tunable octahedral Pt nanocrystals, without the use of catalyst-poisoning reagents and/or difficult-to-remove coatings. The synthesis requires sodium citrate, ascorbic acid, and fine control of the reduction rate in aqueous environment. Pt octahedral nanocrystals with particle size as low as 7 nm and highly developed {111} facets have been achieved, as demonstrated by transmission electron microscopy, X-ray diffraction, and electrochemical methods. The absence of sticky molecules together with the high quality of the surface makes these nanocrystals ideal candidates in electrocatalysis. Notably, 7 nm bismuth-decorated octahedral nanocrystals exhibit superior performance for the electrooxidation of formic acid in terms of both specific and mass activities.