Abstract: The ability to detect low concentrations of protein biomarkers is crucial for the early-stage detection of many diseases and therefore indispensable for improving diagnostic devices for healthcare. Here, we demonstrate that by integrating DNA nanotechnologies like DNA origami and aptamers, we can design innovative biosensing concepts for reproducible and sensitive detection of specific targets. DNA origami structures decorated with aptamers were studied as a novel tool to structure the biosensor surface with nanoscale precision in a digital detection bioassay, enabling control of the density, orientation, and accessibility of the bioreceptor to optimize the interaction between target and aptamer. DNA origami was used to control the spatial distribution of an in-house-generated aptamer on superparamagnetic microparticles, resulting in an origami-linked digital aptamer bioassay to detect the main peanut antigen Ara h1 with 2-fold improved signal-to-noise ratio and 15-fold improved limit of detection compared to a digital bioassay without DNA origami. Moreover, the sensitivity achieved was 4 orders of magnitude higher than commercially available and literature-reported enzyme-linked immunosorbent assay techniques. In conclusion, this novel and innovative approach to engineer biosensing interfaces will be of major interest to scientists and clinicians looking for new molecular insights and ultrasensitive detection of a broad range of targets, and, for the next generation of diagnostics.

Abstract: Eosin is a synthetic organic colorant prone to fading under the influence of light. On the basis of the growing interest in the understanding of the discoloration mechanism of eosin-based lakes, this study compares the ability of two ultrafast and ultrasensitive mass spectrometry techniques to detect eosin derivatives in complex matrices, such as oil media without the use of conventional separation columns or additional sample preparation protocols. Direct analysis in real time mass spectrometry (DART-MS) and direct infusion electrospray ionization mass spectrometry (DI-ESI-MS) were used to characterize the degradation pathway of eosin in oil media. The analysis protocols developed in this study are applied to discern the degradation mechanism of the lake pigment eosin (comprising the molecule per se complexed to an inorganic substrate) dispersed in linseed oil to create an oil paint. The analysis of oil paints by high resolution MS without an extraction methodology that modifies the system chemistry allowed us to identify the degradation forms without causing any additional fragmentation. Both techniques revealed the primary photodegradation pathway of eosin in linseed oil, and DI-ESI-MS provided additional information on the native conformation of the lake.

Abstract: MA-XRF is a novel macroscopic imaging technique originally developed for easel paintings and recently made available to glass conservators. This paper discusses the first real-life contribution of MA-XRF imaging to a conservation intervention of stained-glass panels. The six panels under study belong to the cathedral building since their creation in 1555-1559 AD. MA-XRF appeared an outstanding tool for first-line screening of stained-glass windows, providing readily interpretable information on glass type, coloring and alteration processes. In particular, the chemical imaging technique allowed distinguishing unambiguously the surviving original glass panes from later additions, thereby ensuring a correct historical understanding. From a more practical point of view, the experiments supplied accurate schemes that can be directly incorporated in condition reports and assist designing the ensuing conservation approach. (C0 2019 Elsevier Masson SAS. All rights reserved.

Abstract: Oil paints comprise pigments, drying oils, and additives that together confer desirable properties, but can react to form metal carboxylates (soaps) that may damage artworks over time. To obtain information on soap formation and aggregation, we introduce a new tapping-mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopy and imaging on highly heterogenous and rough paint thin sections. PTIR is used in combination with mu-computed tomography and IR microscopy to determine the distribution of metal carboxylates in a 23-year old oil paint of known formulation. Results show that heterogeneous agglomerates of Al-stearate and a Zn-carboxylate complex with Zn-stearate nano-aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al-stearate distribution. These measurements open a new chemically sensitive nanoscale observation window on the distribution of metal soaps that can bring insights for understanding soap formation in oil paint.

Abstract: Electrochemical strategies to selectively detect heroin in street samples without the use of complicated electrode modifications were developed for the first time. For this purpose, heroin, mixing agents (adulterants, cutting agent, and impurities), and their binary mixtures were subjected to square wave voltammetry measurements at bare graphite electrodes at pH 7.0 and pH 12.0, in order to elucidate the unique electrochemical fingerprint of heroin and mixing agents as well as possible interferences or reciprocal influences. Adjusting the pH from pH 7.0 to pH 12.0 allowed a more accurate detection of heroin in the presence of most common mixing agents. Furthermore, the benefit of introducing a preconditioning step prior to running square wave voltammetry on the electrochemical fingerprint enrichment was explored. Mixtures of heroin with other drugs (cocaine, 3,4-methylenedioxymethamphetamine, and morphine) were also tested to explore the possibility of their discrimination and simultaneous detection. The feasibility of the proposed electrochemical strategies was tested on realistic heroin street samples from forensic cases, showing promising results for fast, on-site detection tools of drugs of abuse.

Abstract: This research is aimed to the study and application of an electrochemical immunosensor for the detection of ovalbumin (OVA) from egg white (or albumen) used as a binder in some works of art, such as some historical photographic prints and tempera paintings. The immunosensor takes advantage of the interesting biodetection capabilities offered by nanoelectrode ensembles (NEEs). The NEEs used to this aim are prepared by template deposition of gold nanoelectrodes within the pores of track-etched polycarbonate (PC) membranes. The affinity of polycarbonate for proteins is exploited to capture OVA from the aqueous extract obtained by incubation in phosphate buffer of a small sample fragment (<1 mg). The captured protein is reacted selectively with anti-OVA antibody, labelled with glucose oxidase (GOx). In the case of positive response, the addition of the GOx substrate (i.e. glucose) and a suitable redox mediator (a ferrocenyl derivative) reflects in the up rise of an electrocatalytic oxidation current, which depends on the OVA amount captured on the NEE, this amount correlating with OVA concentration in the extract. After optimization, the sensor is successfully applied to identify OVA in photographic prints dating back to the late 19th century, as well as in ancient tempera paintings from the 15th and 18th centuries.

Abstract: The darkening due to chemical alteration of chrome yellows (PbCrO4/PbCr1-xSxO4) is a phenomenon threatening a large number of 19th-20th century paintings, including the Amsterdam Sunflowers by Vincent van Gogh. Our earlier studies have proven that the alteration is due to a Cr(VI) -> Cr(III) reduction with Cr(V)-species that are formed as long-lived intermediates and that bCr(1-x)S(x)O(4) (0 < x <= 0.8) types undergo reduction more readily than monoclinic, S-free, PbCrO4. In this context, there is still lack of knowledge about the effects of the chemical properties of the binding medium (i.e., chemical composition and drying process) and the solubility of chrome yellows on the overall reduction pathways. Here, we study a series of naturally and photochemically aged mock-up paints prepared by mixing chrome yellow powders (PbCrO4/PbCr0.2S0.8O4) with either linseed oil or a water-based acrylic emulsion as the binding medium. Equivalent paints made up of the highly soluble K2CrO4 were also investigated and used as benchmarks to provide a more in-depth understanding of the influence of the solubility on the chromate reduction pathways in the two different binders. A combination of synchrotron radiation-based Cr K-edge X-ray absorption near edge structure (XANES), electron paramagnetic resonance (EPR), and UV-Visible spectroscopy measurements shows that: (1) the Cr(VI) reduction results from the interaction between the pigment and the binder; (2) the process is more significant in oil, giving rise to Cr(V)- and Cr(III)-species as well as oxidized organic compounds; (3) the lightfastness of the chrome yellow pigment is enhanced in the acrylic binder; and (4) the tendency toward chromium reduction increases with increasing solubility of the pigment. Based on our findings, we propose a scheme for the mechanism of the (photo)reduction process of chrome yellows in the oil and acrylic binder. Overall, our results provide new insights into the factors driving the degradation of lead chromate-based paints in artworks and contribute to the development of strategies for preserving them over time.

Abstract: During the conservation treatment of Memling’s Christ with Singing and Music-making Angels, three panel paintings that are among the most monumental works in early Netherlandish art, the conservators came across insoluble surface layers containing calcium oxalates. A very thin and irregular layer of this type, hardly visible to the naked eye, was spread across the surface of all three panels. A much thicker layer forming an opaque and highly disfiguring crust that obscured the composition (Figs. 15.1 and 15.7) was locally present on areas of dark copper-containing paint, where multiple layers of old discolored coatings and accretions remained in place before the most recent cleaning. This article describes the application of a wide range of analytical techniques in order to fully understand the stratigraphy and composition of the crusts on the Memling paintings. FTIR spectroscopy in transmission and reflection mode, micro-ATR-FTIR imaging and macro-rFTIR scanning, SEM-EDX, mobile XRD, and SR-μXRD showed that the crusts contained two related Ca-based oxalate salts, whewellite and weddellite, and were separated from the original paint surface by varnish, indicating that they did not originate from degradation of the original paint but from a combination of microbial action and a thick accumulation of dirt. Supported by the results from these different analytical techniques, which when used together proved to be very effective in providing complementary information that addressed this specific conservation problem, and aided by the presence of the intermediate varnish layer(s), the conservators were able to remove most of the crusts with spectacular results.

Abstract: We present a decision-support system that guides heritage guardians in selecting mitigation actions to improve the indoor air quality and thus the preservation conditions of indoor collections in heritage buildings. This contribution shows that it is feasible to build a decision support system dedicated to preventive conservation when the following barriers are overcome: 1) simultaneous measurement of a wide range of environmental parameters in order to detect a larger number of undesired situations; 2) development of an algorithm to perform reproducible indoor air quality assessments; and 3) transformation of the air quality assessment into a graph that can be read intuitively without causing a wide variation of interpretations among stakeholders. An important aspect of the decision support system is that it reduces several sources of uncertainty that hamper reliable indoor air quality assessments. The possibilities of such a system are illustrated with a measurement campaign in a church where a heating system has been installed and used for the first time.

Abstract: Novel synthetic protocols based on both template and multi-step methods were developed for phenyl-substituted pyrazinoporphyrazine complexes of rare-earth elements (Y, Eu, Gd, Dy, Er and Lu). p-Hydroquinone was employed as a reaction medium and as a reducing agent in the process of porphyrazine macrocycle formation. Both thermal and microwave irradiation techniques were successfully applied for activation of the template macrocyclization process. An alternative multi-step approach involving the initial stage of free-base ligand formation was realized for the lutetium compound. The target complexes were identified by high-resolution mass spectrometry, infrared spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Electrochemical behavior in solution and UV-vis absorbance in solutions and films were studied as well. Shifts in the position of the Q band and oxidationreduction potentials in comparison with corresponding phthalocyanine analogues were noticed. Using the IR absorption spectra recorded in the temperature range of 170300 K, the position of the Fermi level of −4.7 ± 0.1 eV and a characteristic energy diagram were obtained for the erbium complex.

Abstract: Over the past several decades the painting An Old Man in Military Costume by Rembrandt Harmensz van Rijn (ca. 1630-31; J. Paul Getty Museum, 78.PB.246) has been the subject of a number of investigations carried out in order to better visualize a second painting beneath the surface figure. The underlying image – the head and shoulders of a man wearing a cloak – is oriented 180 degrees from the upper image and appears to be fairly complete. Scanning macro x-ray fluorescence (XRF) spectroscopy reveals the face is painted with lead white and a mercury-containing pigment (likely vermilion), and the cloak is painted with a copper-containing pigment. Following the revelation and digital color reconstruction of the underlying figure, a number of questions still remained. Here, through the use of infrared reflectance imaging spectroscopy (i.e., hyperspectral imaging) and macro-XRF imaging spectroscopy, together with cross-sections taken from targeted areas, the sequence of painting in both compositions was explored. Of particular interest was the discovery of evidence of multiple attempts to situate the lower figure, and the subsequent application of a blocking-out layer over the lower figure before the artist rotated the panel and executed the upper figure. In addition, examination of the placement of the two images on the panel adds to our understanding of the subtle complexities of Rembrandt's working process. RESUMEAu cours des dernieres decennies, la peinture Le vieil homme en costume militaire de Rembrandt Harmensz van Rijn (ca. 1630-31; J. Paul Getty Museum, 78.PB.246) a fait l'objet de nombreuses investigations menees dans le but de mieux visualiser une seconde peinture dissimulee sous la surface. L'image sous-jacente – la tete et les epaules d'un homme vetu d'une cape – est orientee a 180 degres de de l'image du vieil homme, et elle semble assez complete. La spectroscopie a macro-balayage de fluorescence X (MA-XRF) revele que le visage est peint avec du blanc de plomb et un pigment contenant du mercure (comme le vermillon), et que la cape est peinte avec un pigment a base de cuivre. Plusieurs questions restaient en suspens suite a cette decouverte et a la reconstruction numerique en couleur de l'image sous-jacente. Grace a l'emploi de techniques d'imagerie comme la spectroscopie proche infrarouge (ex., imagerie hyperspectrale) et l'imagerie MA-XRF, combinees a l'analyse de coupes stratigraphiques prelevees a des endroits cibles, on a pu explorer la sequence d'application des couches picturales de chacune des deux compositions. Une decouverte particulierement interessante est la preuve que l'artiste a fait plusieurs tentatives pour positionner la figure sous-jacente puis, a ensuite applique une couche pour la recouvrir completement avant de faire pivoter le panneau et peindre la figure du vieil homme. De plus, l'examen du positionnement des deux images sur le panneau ajoute a notre comprehension de la subtile complexite du processus de creation de Rembrandt. Traduit par Elisabeth Forest. RESUMONas ultimas decadas, a pintura Um Velho em Traje Militar, de Rembrandt Harmensz van Rijn (ca. 1630-31; J. Paul Getty Museum, 78.PB.246), foi objeto de uma serie de investigacoes realizadas para visualizar melhor uma segunda pintura abaixo da figura aparente. A imagem subjacente – a cabeca e os ombros de um homem usando uma capa – e orientada a 180 graus da imagem superior e parece estar bastante completa. O macro mapeamento de imagem por espectroscopia de fluorescencia de raios X (FRX) revela que a face e pintada com branco de chumbo e um pigmento contendo mercurio (provavelmente vermelhAo), e a capa e pintada com um pigmento contendo cobre. Apos a descoberta e reconstrucAo digital da cor da figura subjacente, uma serie de questoes ainda permanecem. EntAo, atraves da utilizacAo do mapeamento por imagem de espectroscopia de refletancia por infravermelhos (i.e. mapeamento hiperespectral) e macro mapeamento por imagem de FRX, juntamente com cortes estratigraficos de amostras retiradas de areas de interesse, a pintura em ambas as composicoes foi explorada. De particular interesse foi a descoberta de evidencias de multiplas tentativas de posicionar a figura subjacente, e a subsequente aplicacAo de uma camada intermediaria de separacAo sobre a figura inferior antes do artista girar o painel e executar a figura superior. Alem disso, o exame da colocacAo das duas imagens no painel aumenta nossa compreensAo das sutis complexidades do processo de trabalho de Rembrandt. Traduzido por Marcia Rozzi e Beatriz Haspo. RESUMENA lo largo de las ultimas decadas, la pintura Un anciano con traje militar de Rembrandt Harmensz van Rijn (ca. 1630-31; J. Paul Getty Museum, 78.PB.246) ha sido objeto de varias investigaciones realizadas con el fin de visualizar mejor una segunda pintura debajo de la figura de la superficie. La imagen subyacente, la cabeza y los hombros de un hombre que lleva una capa, esta orientada a 180 grados de la imagen superior y parece estar bastante completa. La espectroscopia de fluorescencia de rayos X (XRF) de barrido revela que la cara esta pintada con blanco de plomo y un pigmento que contiene mercurio (probablemente bermellon), y la capa esta pintada con un pigmento que contiene cobre. Tras la revelacion y la reconstruccion digital del color de la figura subyacente, aun quedaban algunas preguntas. Aqui, por medio del uso de la espectroscopia de imagenes de reflectancia infrarroja (es decir, imagenes hiperespectrales) e imagenes macro-XRF, junto con las secciones transversales tomadas de areas especificas, se exploro la secuencia de pintura en ambas composiciones. De particular interes fue el descubrimiento de evidencia de multiples intentos de situar la figura inferior, y la aplicacion posterior de una capa de bloqueo sobre la figura inferior antes de que el artista rotara el panel y ejecutara la figura superior. Ademas, el examen de la colocacion de las dos imagenes en el panel contribuye a nuestra comprension de las sutiles complejidades del proceso de trabajo de Rembrandt. Traduccion: Amparo Rueda.

Abstract: Titanium dioxide (TiO2) is a popular material as host matrix for enzymes. We now evidence that TiO2 can accumulate and retain reactive oxygen species after treatment by hydrogen peroxide (H2O2) and support redox cycling of a phenolic analyte between horseradish peroxidase (HRP) and an electrode. The proposed detection scheme is identical to that of second generation biosensors, but the measuring solution requires no dissolved H2O2. This significantly simplifies the analysis and overcomes issues related to H2O2 being present (or generated) in the solution. The modified electrodes showed rapid stabilization of the baseline, a low noise level, fast realization of a steady-state current response, and, in addition, improved sensitivity and limit of detection compared to the conventional approach, i.e. in the presence of H2O2 in the measuring solution. Hydroquinone, 4-aminophenol, and other phenolic compounds were successfully detected at sub-μM concentrations. Particularly, a linear response in the concentration range between 0.025 and 2 μM and LOD of 24 nM was demonstrated for 4-aminophenol. The proposed sensor design goes beyond the traditional concept with three sensors generations offering a new possibility for the development of enzymatic sensors based on peroxidases and the formation of ROS on titania after treatment with H2O2.

Abstract: This paper presents a previously unexplored biosensing strategy for detecting gliadin which exploits the crosslinking of gliadin with collagen, catalyzed by transglutaminase at the interfacial electron transfer rate, on a modified electrode. The process is monitored by electrochemical impedance spectroscopy using a glassy carbon electrode coated with a collagen layer. To validate the specificity of the response as well as to eliminate possible interferences from other proteins, such as soy protein or casein, the captured gliadin is further reacted with a specific anti-gliadin antibody. Changes in charge transfer resistance, measured from the Nyquist plots, scale linearly with the gliadin concentration in the range 5-20 mg/L, a range suitable for testing the gliadin concentration in gluten-free food commodities.

Abstract: Airborne particulate matter (PM) includes semi-volatile organic compounds (SVOCs), which can be deposited on vegetation matrices such as plant leaves. In alternative to air-point measurements or artificial passive substrates, leaf monitoring offers a cost-effective, time-integrating means of assessing local air quality. In this study, leaf washing solutions from ivy (Hedera hibernica) leaves exposed during one-month at different land use classes were explored via comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS). The composition of leaf-deposited SVOCs, corrected for those of unexposed leaves, was compared against routinely monitored pollutants concentrations (PM10, PM2.5, O3, NO2, SO2) measured at co-located air monitoring stations. The first study on leaf-deposited SVOCs retrieved from washing solutions, herein reported, delivered a total of 911 detected compounds. While no significant land use (rural, urban, industrial, traffic, mixed) effects were observed, increasing exposure time (from one to 28 days) resulted in a higher number and diversity of SVOCs, suggesting cumulative time-integration to be more relevant than local source variations between sites. After one day, leaf-deposited SVOCs were mainly due to alcohols, N-containing compounds, carboxylic acids, esters and lactones, while ketones, diketones and hydrocarbons compounds gained relevance after one week, and phenol compounds after one month. As leaf-deposited SVOCs became overall more oxidized throughout exposure time, SVOCs transformation or degradation at the leaf surface is suggested to be an important phenomenon. This study confirmed the applicability of GCxGC-TOFMS to analyze SVOCs from leaf washing solutions, further research should include validation of the methodology and comparison with atmospheric organic pollutants.