Twin-chain polymer hydrogels based on poly(vinyl alcohol) as new advanced tool for the cleaning of modern and contemporary art.

Conservation of our cultural heritage is fundamental for conveying to future generations our culture, traditions, and ways of thinking and behaving. Cleaning art, in particular modern/contemporary paintings, with traditional tools could be risky and impractical, particularly on large collections of important works to be transferred to future generations. We report on advanced cleaning systems, based on twin-chain polymer networks made of poly(vinyl alcohol) (PVA) chains, semiinterpenetrated (semi-IPN) with PVA of lower molecular weight (L-PVA). Interpenetrating L-PVA causes a change from gels with oriented channels to sponge-like semi-IPNs with disordered interconnected pores, conferring different gel (and solvent) dynamics. These features grant residue-free, time efficient cleaning capacity and effective dirt capture, defeating risks for the artifact, making possible a safer treatment of important collections, unconceivable with conventional methods. We report as an example the conservation of Jackson Pollock's masterpieces, cleaned in a controlled way, safety and selectivity with unprecedented performance.

In Vivo Radiobiological Investigations with the TOP-IMPLART Proton Beam on a Medulloblastoma Mouse Model.

Protons are now increasingly used to treat pediatric medulloblastoma (MB) patients. We designed and characterized a setup to deliver proton beams for in vivo radiobiology experiments at a TOP-IMPLART facility, a prototype of a proton-therapy linear accelerator developed at the ENEA Frascati Research Center, with the goal of assessing the feasibility of TOP-IMPLART for small animal proton therapy research. Mice bearing Sonic-Hedgehog (Shh)-dependent MB in the flank were irradiated with protons to test whether irradiation could be restricted to a specific depth in the tumor tissue and to compare apoptosis induced by the same dose of protons or photons. In addition, the brains of neonatal mice at postnatal day 5 (P5), representing a very small target, were irradiated with 6 Gy of protons with two different collimated Spread-Out Bragg Peaks (SOBPs). Apoptosis was visualized by immunohistochemistry for the apoptotic marker caspase-3-activated, and quantified by Western blot. Our findings proved that protons could be delivered to the upper part while sparing the deepest part of MB. In addition, a comparison of the effectiveness of protons and photons revealed a very similar increase in the expression of cleaved caspase-3. Finally, by using a very small target, the brain of P5-neonatal mice, we demonstrated that the proton irradiation field reached the desired depth in brain tissue. Using the TOP-IMPLART accelerator we established setup and procedures for proton irradiation, suitable for translational preclinical studies. This is the first example of in vivo experiments performed with a "full-linac" proton-therapy accelerator.

Characterization of Early and Late Damage in a Mouse Model of Pelvic Radiation Disease.

Pelvic radiation disease (PRD), a frequent side effect in patients with abdominal/pelvic cancers treated with radiotherapy, remains an unmet medical need. Currently available preclinical models have limited applications for the investigation of PRD pathogenesis and possible therapeutic strategies. In order to select the most effective irradiation protocol for PRD induction in mice, we evaluated the efficacy of three different locally and fractionated X-ray exposures. Using the selected protocol (10 Gy/day × 4 days), we assessed PRD through tissue (number and length of colon crypts) and molecular (expression of genes involved in oxidative stress, cell damage, inflammation, and stem cell markers) analyses at short (3 h or 3 days after X-ray) and long (38 days after X-rays) post-irradiation times. The results show that a primary damage response in term of apoptosis, inflammation, and surrogate markers of oxidative stress was found, thus determining a consequent impairment of cell crypts differentiation and proliferation as well as a local inflammation and a bacterial translocation to mesenteric lymph nodes after several weeks post-irradiation. Changes were also found in microbiota composition, particularly in the relative abundance of dominant phyla, related families, and in alpha diversity indices, as an indication of dysbiotic conditions induced by irradiation. Fecal markers of intestinal inflammation, measured during the experimental timeline, identified lactoferrin, along with elastase, as useful non-invasive tools to monitor disease progression. Thus, our preclinical model may be useful to develop new therapeutic strategies for PRD treatment.

Nanodiamond Effects on Cancer Cell Radiosensitivity: The Interplay between Their Chemical/Physical Characteristics and the Irradiation Energy.

Nanoparticles are being increasingly studied to enhance radiation effects. Among them, nanodiamonds (NDs) are taken into great consideration due to their low toxicity, inertness, chemical stability, and the possibility of surface functionalization. The objective of this study is to explore the influence of the chemical/physical properties of NDs on cellular radiosensitivity to combined treatments with radiation beams of different energies. DAOY, a human radioresistant medulloblastoma cell line was treated with NDs-differing for surface modifications [hydrogenated (H-NDs) and oxidized (OX-NDs)], size, and concentration-and analysed for (i) ND internalization and intracellular localization, (ii) clonogenic survival after combined treatment with different radiation beam energies and (iii) DNA damage and apoptosis, to explore the nature of ND-radiation biological interactions. Results show that chemical/physical characteristics of NDs are crucial in determining cell toxicity, with hydrogenated NDs (H-NDs) decreasing either cellular viability when administered alone, or cell survival when combined with radiation, depending on ND size and concentration, while OX-NDs do not. Also, irradiation at high energy (γ-rays at 1.25 MeV), in combination with H-NDs, is more efficient in eliciting radiosensitisation when compared to irradiation at lower energy (X-rays at 250 kVp). Finally, the molecular mechanisms of ND radiosensitisation was addressed, demonstrating that cell killing is mediated by the induction of Caspase-3-dependent apoptosis that is independent to DNA damage. Identifying the optimal combination of ND characteristics and radiation energy has the potential to offer a promising therapeutic strategy for tackling radioresistant cancers using H-NDs in conjunction with high-energy radiation.

Lysozyme is Sterically Trapped Within the Silica Cage in Bioinspired Silica-Lysozyme Composites: A Multi-Technique Understanding of Elusive Protein-Material Interactions.

Lysozyme is widely known to promote the formation of condensed silica networks from solutions containing silicic acid, in a reproducible and cost-effective way. However, little is known about the fate of the protein after the formation of the silica particles. Also, the relative arrangement of the different components in the resulting material is a matter of debate. In this study, we investigate the nature of the protein-silica interactions by means of solid-state nuclear magnetic resonance spectroscopy, small-angle X-ray scattering, and electron microscopy. We find that lysozyme and silica are in intimate contact and strongly interacting, but their interaction is neither covalent nor electrostatic: lysozyme is mostly trapped inside the silica by steric effects.

2-Butanol Aqueous Solutions: A Combined Molecular Dynamics and Small/Wide-Angle X-ray Scattering Study.

Structural properties of 2-butanol aqueous solutions at different concentrations have been studied using small- and wide-angle X-ray scattering and molecular dynamics simulations. The experimental structure factors have been accurately reproduced by the simulations, allowing one to explain their variation with concentration and to achieve a detailed description of the structural and dynamic properties of the studied systems. The analysis of experimental and computational data has shown that 2-butanol, the simplest aliphatic chiral alcohol, tends to form aggregates at a concentration above 1 M, affecting also both the structural and dynamic properties of the solvent.

Unraveling the role of male reproductive tract and haemolymph in cantharidin-exuding Lydus trimaculatus and Mylabris variabilis (Coleoptera: Meloidae): a comparative transcriptomics approach.

BACKGROUND: Meloidae (blister beetles) are known to synthetize cantharidin (CA), a toxic and defensive terpene mainly stored in male accessory glands (MAG) and emitted outward through reflex-bleeding. Recent progresses in understanding CA biosynthesis and production organ(s) in Meloidae have been made, but the way in which self-protection is achieved from the hazardous accumulation and release of CA in blister beetles has been experimentally neglected. To provide hints on this pending question, a comparative de novo assembly transcriptomic approach was performed by targeting two tissues where CA is largely accumulated and regularly circulates in Meloidae: the male reproductive tract (MRT) and the haemolymph. Differential gene expression profiles in these tissues were examined in two blister beetle species, Lydus trimaculatus (Fabricius, 1775) (tribe Lyttini) and Mylabris variabilis (Pallas, 1781) (tribe Mylabrini). Upregulated transcripts were compared between the two species to identify conserved genes possibly involved in CA detoxification and transport. RESULTS: Based on our results, we hypothesize that, to avoid auto-intoxication, ABC, MFS or other solute transporters might sequester purported glycosylated CA precursors into MAG, and lipocalins could bind CA and mitigate its reactivity when released into the haemolymph during the autohaemorrhaging response. We also found an over-representation in haemolymph of protein-domains related to coagulation and integument repairing mechanisms that likely reflects the need to limit fluid loss during reflex-bleeding. CONCLUSIONS: The de novo assembled transcriptomes of L. trimaculatus and M. variabilis here provided represent valuable genetic resources to further explore the mechanisms employed to cope with toxicity of CA in blister beetle tissues. These, if revealed, might help conceiving safe and effective drug-delivery approaches to enhance the use of CA in medicine.

Functionalised nanoclays as microstructure modifiers for calcium and magnesium silicate hydrates.

Calcium silicate hydrate (C-S-H) is the main binding product of ordinary Portland concrete (OPC). Unfortunately, OPC production generates ∼5% of all anthropomorphic CO2. Among the most promising green alternatives, magnesium silicate hydrate (M-S-H) is a colloidal gel equivalent to C-S-H which exhibits weaker mechanical properties. Here we investigated the effect of the inclusion of aluminosilicate nanoclays (HNTs) on the microstructure of the silicate hydrate gels as a strategy to ultimately improve their mechanical properties. The microstructure of C-S-H and M-S-H gels synthesized with and without carboxylic or polycarboxylic functionalised HNTs (HNT-COOH, HNT-PAA) was investigated by a multi-technique approach including small- and wide-angle X-ray scattering (SWAXS) and scanning electron microscopy (SEM). The results indicate that, during C-S-H formation in solution, HNTs decrease the size of the disk-like globules with little influence on the spacing of calcium silicate layers. In the case of M-S-H, the presence of functionalised HNTs has a reduced effect on the hydrate structure as a result of the weaker interaction of the carboxylic moieties with Mg2+ ions. SEM investigation on the synthesized composites shows that HNT-PAA are better included in the hydration products. Moreover, in the proximity of the PAA functionalised surfaces, less extended aggregates are formed. The morphology at the micron scale for M-S-H and C-S-H with HNT-COOH is conserved.

(+)-Catechin-assisted graphene production by sonochemical exfoliation in water. A new redox-active nanomaterial for electromediated sensing.

A new green and effective sonochemical liquid-phase exfoliation (LPE) is proposed wherein a flavonoid compound, catechin (CT), promotes the formation of conductive, redox-active, water-phase stable graphene nanoflakes (GF). To maximize the GF-CT redox activity, the CT concentration and sonication time have been studied, and the best performing nanomaterial-fraction selected. Physicochemical and electrochemical methods have been employed to characterize the morphological, structural, and electrochemical features of the GF-CT nanoflakes. The obtained GF intercalated with CT exhibits fully reversible electrochemistry (ΔEp = 28 mV, ipa/ipc = ⁓1) because of the catecholic adducts. GF-CT-integrated electrochemistry was generated directly during LPE of graphite, with no need of graphene oxide production, nor activation steps, electropolymerization, or ex-post functionalization. The GF-CT electro-mediator ability has been proven towards hydrazine (HY) and ß-nicotinamide adenine dinucleotide (NADH) by simply drop-casting the redox-material onto screen-printed electrodes. GF-CT-based electrodes by using amperometry exhibited high sensitivity and extended linear ranges (HY: LOD = 0.1 µM, L.R. 0.5-150 µM; NADH: LOD = 0.6 µM, L.R. 2.5-200 µM) at low overpotential (+ 0.15 V) with no electrode fouling. The GF-CT electrodes are performing significantly better than commercial graphite electrodes and graphene nanoflakes exfoliated with a conventional surfactant, such as sodium cholate. Recoveries of 94-107% with RSD ≤ 8% (n = 3) for determination of HY and NADH in environmental and biological samples were achieved, proving the material functionality also in challenging analytical media. The presented GF-CT is a new functional redox-active material obtainable with a single-pot sustainable strategy, exhibiting standout properties particularly prone to (bio)sensors and cutting-edge device development.

Epileptic seizures and oxidative stress in a mouse model over-expressing spermine oxidase.

Several studies have demonstrated high polyamine levels in brain diseases such as epilepsy. Epilepsy is the fourth most common neurological disorder and affects people of all ages. Excitotoxic stress has been associated with epilepsy and it is considered one of the main causes of neuronal degeneration and death. The transgenic mouse line Dach-SMOX, with CD1 background, specifically overexpressing spermine oxidase in brain cortex, has been proven to be highly susceptible to epileptic seizures and excitotoxic stress induced by kainic acid. In this study, we analysed the effect of spermine oxidase over-expression in a different epileptic model, pentylenetetrazole. Behavioural evaluations of transgenic mice compared to controls showed a higher susceptibility towards pentylentetrazole. High-performance liquid chromatography analysis of transgenic brain from treated mice revealed altered polyamine content. Immunoistochemical analysis indicated a rise of 8-oxo-7,8-dihydro-2'-deoxyguanosine, demonstrating an increase in oxidative damage, and an augmentation of system xc- as a defence mechanism. This cascade of events can be initially linked to an increase in protein kinase C alpha, as shown by Western blot. This research points out the role of spermine oxidase, as a hydrogen peroxide producer, in the oxidative stress during epilepsy. Moreover, Dach-SMOX susceptibility demonstrated by two different epileptic models strongly indicates this transgenic mouse line as a potential animal model to study epilepsy.

Colorimetric determination of polyphenols via a gold nanoseeds-decorated polydopamine film.

A polystyrene ELISA plate (EP) modified with a thin film based on gold nanoseeds (AuSDs) assembled onto polydopamine (PDA) is proposed. The nanodecorated film (PDA@AuSD) allows to evaluate the polyphenols antioxidant capacity (AOC) through a colorimetric approach based on a seed-mediated growth strategy. Polyphenols, in the presence of the nanodecorated (PDA@AuSD) surfaces are able to drive an increase in size of the AuSDs according to their AOC; this produces an increase of the localized surface plasmon resonance (LSPR; maximum at λ ~ 550 nm) that is taken as analytical signal. The PDA@AuSD EP manufacturing shows good intraplates repeatability (RSD ≤ 6.6%, n = 96 wells) and interplates reproducibility (RSD ≤ 7.4%, n = 748 wells), resulting stable for 1 year. The AuSDs growth kinetic has been studied using 11 polyphenols belonging to different chemical classes and 4 different food samples. The PDA@AuSD film is able to return quantitative information on the AOC of food polyphenols. Good repeatability (RSD ≤ 5.7%, n = 12 EP wells) and reproducibility (RSD ≤ 8.1%, n = 12 EP wells) was achieved, with acceptable linear correlation coefficients (R2 ≥ 0.990) and useful limits of detection (LODs ≤ 2.5 10-5 mol L-1). The samples analyzed with the PDA@AuSD device have been successfully ordered according to their AOC in agreement with conventional optical methods. The PDA@AuSD plate allows multiple measurements (96 wells per EP) with a one-step strategy, overcoming the limitations related to the use of colloidal nanoparticles; in addition, since absorbance is measured after washing, it is not affected by sample color or turbidity. Graphical abstract Schematic representation of ELISA plate (EP) modified with polydopamine (PDA) film decorated with gold nanoseeds (AuSD). The colorimetric assay, to evaluate the antioxidant capacity, is based on the AuSD growth mediated by polyphenols, resulting in absorbance increase at 550 nm (ΔAbs550), which is employed as analytical signal.

Class-selective voltammetric determination of hydroxycinnamic acids structural analogs using a WS2/catechin-capped AuNPs/carbon black-based nanocomposite sensor.

A high-performance screen-printed electrode (SPE) based nanocomposite sensor integrating tungsten disulfide (WS2) flakes decorated with catechin-capped gold nanoparticles (AuNP-CT) and carbon black (CB) has been developed. The excellent antifouling properties of WS2 decorated with AuNP-CT into a high conductivity network of CB results in high selectivity, sensitivity, and reproducibility for the simultaneous determination of hydroxycinnamic acid (hCN) structural analogs: caffeic (CF), sinapic (SP), and p-coumaric acids (CM). Using differential pulse voltammetry (DPV), the target hCNs resulted in three well-resolved oxidation peaks at SPE-CB-WS2/AuNP-CT sensor. Excellent antifouling performance (RSD ip,a ≤ 3%, n = 15 for three analytes' simultaneous measure) and low detection limits (CF 0.10 µmol L-1; SP, 0.40 µmol L-1; CM, 0.40 µmol L-1) are obtained despite the analyzed compounds having a high passivation tendency towards carbon-based sensors. The SPE-CB-WS2/AuNP-CT sensor was successfully applied to determine CF, SP, and CM in food samples with good precision (RSD ≤ 4%, n = 3) and recoveries (86-109%; RSD ≤ 5%, n = 3). The proposed sensor is the first example exploiting the simultaneous determination of these compounds in food samples. Given its excellent electrochemical performance, low cost, disposability, and ease of use, this SPE-CB-WS2/AuNP-CT nanocomposite sensor represents a powerful candidate for the realization of electrochemical devices for the determination of (bio)compounds with high passivation tendency. Graphical abstract.

Nanohybrid carbon black-molybdenum disulfide transducers for preconcentration-free voltammetric detection of the olive oil o-diphenols hydroxytyrosol and oleuropein.

A new hybrid nanomaterial is used in a screen-printed electrode (SPE) for sensing of the ortho-diphenols oleuropein (OLEU) and hydroxytyrosol (HYT) in extra virgin olive oil (EVOO) and related samples. The hybrid material consists of carbon black (CB) and molybdenum disulfide (MoS2). In comparison with individual nanomaterials, CB-MoS2 exhibits improved charge-transfer ability, low charge-transfer resistance, high electrical conductivity and enhanced electrocatalysis. The sensor is also characterized by (a) high sensitivity that avoids the need for adsorptive voltammetry, (b) reduced analysis time, and (c) high anti-fouling ability (electrode RSDOLEU < 8%, for n = 10). OLEU can be detected in the 0.3 to 30 µM concentration range with a 0.1 µM LOD, and HYT in the 2-100 µM range with a 1 µM LOD. A comparison of the data obtained by this sensor and by HPLC-UV exhibited high correlation (r = 0.995, p < 0.05). These data revealed the reliability of CB-MoS2 for analysis of complex EVOO and related samples. Graphical abstract CB-MoS2-based electrochemical sensor for fast and reliable assessment of total ortho-diphenols antioxidants in olive oils.

Tales of the Unexpected: The Case of Zirconium(IV) Complexes with Desferrioxamine.

The Zr4+ complexes with desferrioxamine (H3DFO) and its derivatives are the only 89Zr-based imaging agents for proton emission tomography (PET) that have been used so far in clinical trials. Nevertheless, a complete speciation of the Zr4+/H3DFO system in solution has never been performed and the stability constants of the relevant complexes are still unknown. Here we report, for the first time, the speciation of this system in water, performed by potentiometric titrations, and the determination of the stability constants of all complexes formed in the pH range 2.5-11.5. Surprisingly, although desferrioxamine gives rise to very stable 1:1 complexes with Zr4+ (logK = 36.14 for Zr4+ + DFO3- = [ZrDFO]+), 2:2 and 2:3 ones are also formed in solution. Depending on the conditions, these binuclear complexes can be main species in solution. These results were corroborated by small-angle X-ray scattering (SAXS) and MALDI mass spectrometry analyses of complex solutions. Information on complex structures was obtained by means of density functional theory (DFT) calculations.

Nonaqueous Microemulsion in the Bmim Tf2N/Brij 30/ n-Nonane System: Structural Investigation and Application as Gold Nanoparticle Microreactor.

Microemulsions based on ionic liquids (ILs) are being increasingly studied in many different areas of physical chemistry because of the attractive properties of ILs. In particular, waterless microemulsions where the IL represents the polar phase can be of interest for those applications that demand the nanosegregation of polar substances, but in which the absence of water is a strict requirement. In this work, we prepared a reverse, nonaqueous microemulsion based on the low-viscosity room-temperature IL, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide , the surfactant Brij 30, and n-nonane. The systems were characterized by dynamic light scattering and small-angle X-ray scattering; the IL/oil microemulsion was further employed as a templating system for the synthesis of gold nanoparticles from hydrogen tetrachloroaurate(III), HAuCl4, by UV-photoreduction technique.

Water as a Probe of the Colloidal Properties of Cement.

Cement is produced by mixing mineral phases based on calcium silicates and aluminates with water. The hydration reaction of the mixture leads to a synthetic material with outstanding properties that can be used as a binder for construction applications. Despite the importance of cement in society, for a long time, the chemical reactions involved in its hydration remained poorly understood as a result of the complexity of hydration processes, nanostructure, and transport phenomena. This feature article reviews the recently obtained results using water as a probe to detail the essential features in the setting process. By examining the peculiar physicochemical properties of water, fundamental information on the evolving inorganic colloid matrix can be deduced, ranging from the fractal nanostructure of the inorganic silicate framework to the transport phenomena inside the developing porosity. A similar approach can be transferred to the investigation of a plethora of other complex systems, where water plays the main role in determining the final structural and transport properties (i.e., biomaterials, hydrogels, and colloids).

Organogels from Double-Chained Vitamin†C Amphiphilic Derivatives.

The syntheses and physicochemical characterization of double-chained amphiphilic compounds obtained from vitamin C are reported: dialkanoyl-5,6-O-ascorbic acid esters (Di-ASCn, n=8, 10, and 12). The acetyl-5-dodecanoyl-6-ascorbic acid ester is synthesized and investigated for comparison. These products are quite insoluble in water and in polar solvents, although they form homogeneous dispersions in cyclohexane. Upon cooling, these dispersions turn into a gel-like phase. Differential scanning calorimetry, FTIR spectroscopy, and small- and wide-angle X-ray scattering experiments are performed to investigate the properties of pure solids and their liquid dispersions. Di-ASCn retain the same redox properties of the parent molecule and represent a valid candidate for the production of nanosized protective carriers for valuable guests that are sensitive to oxidative radical attack. Moreover, the contribution of the vitamin C hydroxyl group in position 5 to the overall hydration properties of single- and double-chained amphiphilic derivatives is discussed.

Influence of high energy electron irradiation on the network structure of gelatin hydrogels as investigated by small-angle X-ray scattering (SAXS).

The impact of high energy crosslinking on the network structure of gelatin hydrogels was investigated in comparison to physically entangled gels by small-angle X-ray scattering (SAXS). Physically entangled gelatin of increasing concentration exhibited a nearly constant correlation length of several nanometers. These gels had scattering behavior close to that of polymer coils swollen in a good solvent, as evidenced by the Porod exponent of 1.8. The mass fractal dimension decreased towards 1, indicating increased formation of semiflexible gelatin triple helices and rod-like structures as a function of the gelatin concentration. In contrast, electron irradiation lead to a decrease in the correlation length at doses above 20 kGy. Covalent crosslinking induced by electron irradiation lead to increased branching and formation of globular structures, as observed by a steady increase of both the Porod exponent and mass fractal dimension. Furthermore, the network mesh size systematically decreased from approximately 45 nm to under 20 nm with both additional physical and chemical crosslinking. These mesh sizes as obtained by SAXS were used to estimate the network shear modulus using several polymer models and were compared to macroscopic rheology measurements. Finally, SEM images of freeze-dried samples revealed changes in the microstructure of the irradiated hydrogels. Overall, fundamental differences in the network structures stemming from the crosslinking method were observed across a wide range of length scales.

Pore Size Effect on Methane Adsorption in Mesoporous Silica Materials Studied by Small-Angle Neutron Scattering.

Methane adsorption in model mesoporous silica materials with the size range characteristic of shale is studied by small-angle neutron scattering (SANS). Size effect on the temperature-dependent gas adsorption at methane pressure about 100 kPa is investigated by SANS using MCM-41 and SBA-15 as adsorbents. Above the gas-liquid condensation temperature, the thickness of the adsorption layer is found to be roughly constant as a function of the temperature. Moreover, the gas adsorption properties, such as the adsorbed layer thickness and the specific amount of adsorbed gas, have little dependence on the pore size being studied, i.e., pore radius of 16.5 and 34.1 Å, but are mainly affected by the roughness of the pore surfaces. Hence, the surface properties of the pore wall are more dominant than the pore size in determining the methane gas adsorption of pores at the nanometer size range. Not surprisingly, the gas-liquid condensation temperature is observed to be sensitive to pore size and shifts to higher temperature when the pore size is smaller. Below the gas-liquid condensation temperature, even though the majority of gas adsorption experiments/simulations have assumed the density of confined liquid to be the same as the bulk density, the measured methane mass density in our samples is found to be appreciably smaller than the bulk methane density regardless of the pore sizes studied here. The mass density of liquid/solid methane in pores with different sizes shows different temperature dependence below the condensation temperature. With decreasing temperature, the methane density in larger pores (SBA-15) abruptly increases at approximately 65 K and then plateaus. In contrast, the density in smaller pores (MCM-41) monotonically increases with decreasing temperature before reaching a plateau at approximately 30 K.

Improving impedimetric nucleic acid detection by using enzyme-decorated liposomes and nanostructured screen-printed electrodes.

Sensitive impedimetric detection of miR-222, a miRNA sequence found in many lung tumors, was investigated by using gold-nanostructured disposable carbon electrodes and enzyme-decorated liposomes. The proposed method was based on the immobilization of thiolated DNA capture probes onto gold-nanostructured carbon surfaces. Afterwards, the capture probes were allowed to hybridize to the target miRNAs. Finally, enzyme-decorated liposomes were used as labels to amplify the miRNA sensing, by their association with the probe-miRNA hybrids generated on the nanostructured transducer. By using this amplification route a limit of detection of 0.400 pM, a limit of quantification of 1.70 pM, and an assay range spanning three orders of magnitude (1.70-900 pM) were obtained (RSD % = 13). This limit of quantification was 20 times lower than that obtained using a simple enzyme conjugate for the detection. A comparison was also made with gold screen-printed transducers. In this case, a limit of quantification approximately 70 times lower was found by using the nanostructured transducers. Application of the optimized assay in serum samples was also demonstrated. Graphical abstract Alkaline Phosphatase-decorated liposomes and Au nanostructured screen-printed electrodes have been used for the impedimetric detection of miRNAs, via the bio-catalyzed precipitation of an insulating product onto the electrode surface.