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This work proposes a novel method to determine the Cd(II) and Cr(III) content in commercial sugar samples. It is based on the extraction of the analytes (as ammonium pyrrolidine dithiocarbamate complexes) into a semipermeable membrane device (SPMD) filled with CHCl3. After extraction, the SPMD was deployed and opened, and the analytes were recovered from the organic phase by back extraction with a 4.2 mol L-1 HNO3 solution. The analytes present in the acid extract were measured with graphite furnace atomic absorption spectrometry. Under optimized conditions, the limit of quantification of the method was 1.2 and 3.1 ng g-1 for Cd(II) and Cr(III), respectively. Twelve samples of different types of sugar were analyzed. In addition, a recovery test was performed to evaluate the accuracy of the method. The recovery percentage was 90 %-102 % for Cd(II) and 85.2 %-103 % for Cr(III).

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Natural rubber originates from the coagulation of rubber particles (RP) from Hevea brasiliensis latex. The size distribution of Hevea RP is bimodal with the presence of small rubber particles (SRP) and large rubber particles (LRP). This study aims at getting a better understanding of the early coagulation steps of Hevea RP taking into account the particle size. SRP and LRP were obtained by centrifugation of freshly tapped ammonia-free latex from RRIM600 clone. Size and zeta potential measurements showed that both RP fractions were efficiently separated and stable in basic buffer. SRP and LRP dispersions were placed in a Langmuir trough and RP were let to adsorb at the air-liquid interface to form interfacial films. Surface tension and ellipsometry indicate that the formation kinetics and the stabilization of the film at the air-liquid interface are faster for SRP than LRP. Moreover, the arrangement of RP at the interface differs between SRP and LRP, as shown by Brewster angle microscopy, atomic force microscopy and confocal laser scanning microscopy. First, the RP membrane and cis-1,4-polyisoprene core spread at the air-liquid interface before clustering. Then, while the SRP fuse, the LRP keep their structure in individual particles in floating aggregate. The role of the non-isoprene molecules on the different organization of SRP and LRP films is discussed, the one of the two major RP proteins, SRPP1 (Small Rubber Particle Protein) and Rubber Elongation Factor (REF1) in the early coagulation steps.

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CONTEXT: Exploring potential energy surfaces (PES) is fundamental in computational chemistry, as it provides insights into the relationship between molecular energy, geometry, and chemical reactivity. We introduce Kick-MEP, a hybrid method for exploring the PES of atomic and molecular clusters, particularly those dominated by non-covalent interactions. Kick-MEP computes the Coulomb integral between the maximum and minimum electrostatic potential values on a 0.001 a.u. electron density isosurface for two interacting fragments. This approach efficiently estimates interaction energies and selects low-energy configurations at reduced computational cost. Kick-MEP was evaluated on silicon-lithium clusters, water clusters, and thymol encapsulated within Cucurbit[7]uril, consistently identifying the lowest energy structures, including global minima and relevant local minima. METHODS: Kick-MEP generates an initial population of molecular structures using the stochastic Kick algorithm, which combines two molecular fragments (A and B). The molecular electrostatic potential (MEP) values on a 0.001 a.u. electron density isosurface for each fragment are used to compute the Coulomb integral between them. Structures with the lowest Coulomb integral are selected and refined through gradient-based optimization and DFT calculations at the PBE0-D3/Def2-TZVP level. Molecular docking simulations for the thymol-Cucurbit[7]uril complex using AutoDock Vina were performed for benchmarking. Kick-MEP was validated across different molecular systems, demonstrating its effectiveness in identifying the lowest energy structures, including global minima and relevant local minima, while maintaining a low computational cost.

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We fabricated ultrathin metal - oxide - semiconductor (MOS) nanocapacitors using atomic layer deposition. The capacitors consist of a bilayer of Al2O3 and Y2O3 with a total thickness of ~10 nm, deposited on silicon substrate. The presence of the two materials, each slab being ~5 nm thick and uniform over a large area, was confirmed with Transmission Electron Microscopy and X-ray photoelectron spectroscopy (XPS). The capacitance in accumulation varied from 1.6 nF (at 1MHz) to ~2.8 nF (at 10 kHz), which is one to two orders of magnitude higher than other nanocapacitors. This high capacitance is attributed to the synergy between the dielectric properties of ultrathin Al2O3 and Y2O3 layers. The electrical properties of the nanocapacitor are stable within a wide range of temperatures, from 25 °C to 150 °C, as indicated by capacitance-voltage (C - V). Since the thickness-to-area ratio is negligible, the nanocapacitor could be simulated as a single parallel plate capacitor in COMSOL Multiphysics, with good agreement between experimental and simulation data. As a proof-of-concept we simulated a MOSFET device with the nanocapacitor gate dielectric, whose drain current is sufficiently high for micro and nanoelectronics integrated circuits, including for applications in sensing.

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We searched for an extraction method that would allow a precise quantification of metal(loid)s in milligram-size samples using high-resolution graphite furnace atomic absorption spectrometry (HR-GFAAS). We digested biological (DORM-4, DOLT-5 and TORT-3) and sediment (MESS-4) certified reference materials (CRMs) using nitric acid in a drying oven, aqua regia in a drying oven, or nitric acid in a microwave. In addition, we digested MESS-4 using a mixture of nitric and hydrofluoric acids in a drying oven. We also evaluated the effect of sample size (100 and 200 mg) on the extraction efficiency. Nitric acid extraction in a drying oven yielded the greatest recovery rates for all metal(loid)s in all tested CRMs (80.0 %-100.0 %) compared with the other extraction methods tested (67.3 %-99.2 %). In most cases, the sample size did not have a significant effect on the extraction efficiency. Therefore, we conclude that nitric acid digestion in a drying oven is a reliable extraction method for milligram-size samples to quantify metal(loid)s with HR-GFAAS. This validated method could provide substantial benefits to environmental quality monitoring programs by significantly reducing the time and costs required for sample collection, storage, transport and preparation, as well as the amount of hazardous chemicals used during sample extraction and analysis. •Sample digestion with nitric acid in a drying oven yielded the greatest recovery rates of metal(loid)s from biological and sediment certified reference materials.•The recovery rates of metal(loid)s from biological and sediment certified reference materials using nitric acid digestion in a drying oven ranged from 73 % to 100 %.•Digestion with nitric acid in a drying oven is a simple and reliable method to extract small size environmental samples for metal(loid)s quantification by high-resolution graphite furnace atomic absorption spectrometry.

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The objective of this work was to prepare and characterize liposomes containing co-encapsulated ascorbic acid (AA) and ascorbyl palmitate (AP), as well as to evaluate their stability, cytotoxicity, antioxidant, and antimicrobial activity. Through the pre-formulation studies, it was possible to improve the formulation, as leaving it more stable and with a greater antioxidant activity, resulting in a formulation designated LIP-AAP, with 161 nm vesicle size, 0.215 polydispersity index, -31.7 mV zeta potential, and pH of 3.34. Encapsulation efficiencies were 37% for AA and 79% for AP, and the content was 1 mg/mL for each compound. The optimized liposomes demonstrated stability under refrigeration for 60 days, significant antioxidant activity (31.4 µMol of TE/mL), and non-toxicity, but no antimicrobial effects against bacteria and fungi were observed. These findings confirm that the co-encapsulated liposomes are potent, stable antioxidants that maintain their physical and chemical properties under optimal storage conditions.

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Synthetic plastic polymers are causing considerable emerging ecological hazards. Starch-based biofilms are a potential alternative. However, depending on the natural source and extraction method, the properties of starch can vary, affecting the physicochemical characteristics of the corresponding casted films generated from it. These differences might entail morphological changes at the nanoscale, which can be explored by inspecting their surfaces. Potato (Solanum tuberosum) is a well-known tuber containing a high amount of starch, but the properties of the biofilms extracted from it are dependent on the specific variety. In this research, four Ecuadorian potato varieties (Leona Blanca, Única, Chola, and Santa Rosa) were analyzed and blended with different glycerol concentrations. The amylose content of each extracted starch was estimated, and biofilms obtained were characterized at both macroscopic and nanoscopic levels. Macroscopic tests were conducted to evaluate their elastic properties, visible optical absorption, water vapor permeability, moisture content, and solubility. It was observed that as the glycerol percentage increased, both moisture content and soluble matter increased, while tensile strength decreased, especially in the case of the Chola variety. These results were correlated to a surface analysis using atomic force microscopy, providing a possible explanation based on the topography and phase contrast observations made at the nanoscale.

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The Hertz-Sneddon elastic indentation model is widely adopted in the biomechanical investigation of living cells and other soft materials using atomic force microscopy despite the explicit viscoelastic nature of these materials. In this work, we demonstrate that an exact analytical viscoelastic force model for power-law materials, can be interpreted as a time-dependent Hertz-Sneddon-like model. Characterizing fibroblasts (L929) and osteoblasts (OFCOLII) demonstrates the model's accuracy. Our results show that the difference between Young's modulus EY obtained by fitting force curves with the Hertz-Sneddon model and the effective Young's modulus derived from the viscoelastic force model is less than 3%, even when cells are probed at large forces where nonlinear deformation effects become significant. We also propose a measurement protocol that involves probing samples at different indentation speeds and forces, enabling the construction of the average viscoelastic relaxation function of samples by conveniently fitting the force curves with the Hertz-Sneddon model.

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Modern imaging strategies are paramount to studying living systems such as cells, bacteria, and fungi and their response to pathogens, toxicants, and nanomaterials (NMs) as modulated by exposure and environmental factors. The need to understand the processes and mechanisms of damage, healing, and cell survivability of living systems continues to motivate the development of alternative imaging strategies. Of particular interest is the use of label-free techniques (microscopy procedures that do not require sample staining) that minimize interference of biological processes by foreign marking substances and reduce intense light exposure and potential photo-toxicity effects. This review focuses on the synergic capabilities of atomic force microscopy (AFM) as a well-developed and robust imaging strategy with demonstrated applications to unravel intimate details in biomedical applications, with the label-free, fast, and enduring Holotomographic Microscopy (HTM) strategy. HTM is a technique that combines holography and tomography using a low intensity continuous illumination laser to investigate (quantitatively and non-invasively) cells, microorganisms, and thin tissue by generating three-dimensional (3D) images and monitoring in real-time inner morphological changes. We first review the operating principles that form the basis for the complementary details provided by these techniques regarding the surface and internal information provided by HTM and AFM, which are essential and complimentary for the development of several biomedical areas studying the interaction mechanisms of NMs with living organisms. First, AFM can provide superb resolution on surface morphology and biomechanical characterization. Second, the quantitative phase capabilities of HTM enable superb modeling and quantification of the volume, surface area, protein content, and mass density of the main components of cells and microorganisms, including the morphology of cells in microbiological systems. These capabilities result from directly quantifying refractive index changes without requiring fluorescent markers or chemicals. As such, HTM is ideal for long-term monitoring of living organisms in conditions close to their natural settings. We present a case-based review of the principal uses of both techniques and their essential contributions to nanomedicine and nanotoxicology (study of the harmful effects of NMs in living organisms), emphasizing cancer and infectious disease control. The synergic impact of the sequential use of these complementary strategies provides a clear drive for adopting these techniques as interdependent fundamental tools.

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The cornea is a fundamental ocular tissue for the sense of sight. Thanks to it, the refraction of two-thirds of light manages to participate in the visual process and protect against mechanical damage. Because it is transparent, avascular, and innervated, the cornea comprises five main layers: Epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. Each layer plays a key role in the functionality and maintenance of ocular tissue, providing unique ultrastructural and biomechanical properties. Bullous Keratopathy (BK) is an endothelial dysfunction that leads to corneal edema, loss of visual acuity, epithelial blisters, and severe pain, among other symptoms. The corneal layers are subject to changes in their biophysical properties promoted by Keratopathy. In this context, the Atomic Force Microscopy (AFM) technique in air was used to investigate the anterior epithelial surface and the posterior endothelial surface, healthy and with BK, using a triangular silicone tip with a nominal spring constant of 0.4 N/m. Six human corneas (n = 6) samples were used for each analyzed group. Roughness data, calculated by third-order polynomial adjustment, adhesion, and Young's modulus, were obtained to serve as a comparison and identification of morphological and biomechanical changes possibly associated with the pathology, such as craters and in the epithelial layer and exposure of a fibrotic layer due to loss of the endothelial cell wall. Endothelial cell membrane area and volume data were calculated, obtaining a relevant comparison between the control and patient. Such results may provide new data on the physical properties of the ocular tissue to understand the physiology of the cornea when it has pathology.

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Atomic layer deposition (ALD) offers unique capabilities to fabricate atomically engineered porous materials with precise pore tuning and multi-functionalization for diverse applications like advanced membrane separations towards sustainable energy-water systems. However, current ALD technique is inhibited on most non-polar polymeric membranes due to lack of accessible nucleation sites. Here, we report a facile method to efficiently promote ALD coating on hydrophobic surface of polymeric membranes via novel protein activation/sensitization. As a proof of concept, TiO2 ALD-coated membranes activated by bovine serum albumin exhibit remarkable superhydrophilicity, ultralow underwater crude oil adhesion, and robust tolerance to rigorous environments including acid, alkali, saline, and ethanol. Most importantly, excellent cyclable crude oil-in-water emulsion separation performance can be achieved. The mechanism for activation/sensitization is rooted in reactivity for a particular set of amino acids. Furthermore, the universality of protein-sensitized ALD is demonstrated using common egg white, promising numerous potential usages in biomedical engineering, environmental remediation, low-carbon manufacturing, catalysis, and beyond.

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We conducted a comprehensive analysis of the surface microtexture of kefir biofilms grown on Theobroma grandiflorum Shum (cupuaçu) juice using atomic force microscopy. Our goal was to investigate the unique monofractal and multifractal spatial patterns of these biofilms to complement the existing limited literature. The biofilms were prepared dispersing four different concentrations of kefir grains in cupuaçu juice. Our morphological analysis showed that the surface of the obtained biofilms is essentially formed by the presence of cupuaçu fibers and microorganisms like lactobacilli and yeast. The topographic height-based parameter analysis reveals that there is a dependence between surface roughness and the concentration of kefir grains used. The strongly anisotropic well-centralized topographical height distribution of the biofilms also exhibited a quasi-symmetrical and platykurtic pattern. The biofilms exhibit comparable levels of spatial complexity, surface percolation and surface homogeneity, which can be attributed to their similar topographic uniformity. This aspect was further supported by the presence of similar multifractality in the biofilms, suggesting that despite their varying topographic roughness, their vertical growth dynamics follow a similar pattern. Our findings demonstrate that the surface roughness of kefir biofilms cultivated on cupuaçu juice is influenced by the concentration of kefir grains in the precursor solution. However, this dependence follows a consistent pattern across different concentrations. Graphical Abstract.

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The internal topography of the root canal is complex, especially for the permanent molar's mesial root. In response to such issues, improved irrigation techniques have been created, which use laser pulses to agitate fluids and improve microbial deposit removal. Objective: To assess the effectiveness of the Er,Cr:YSGG laser with a wavelength of 2,780 nm via photon-induced photoacoustic streaming (PIPS) protocol which agitated of 2% chlorohexidine (CHX) in removing mature Enterococcus faecalis (E. faecalis) biofilm in root canal systems of lower molars. Material and Methods: The mesial roots of lower first and second molars were separated and inoculated with E. faecalis bacterial suspension for 30 days. The roots were irrigated with CHX, some of them were agitated with a passive ultrasonic device (PUI), while the other roots were agitated by an Er,Cr:YSGG laser in PIPS at 60 µs/pulse, 5 Hz, (0.25, 0.5, 0.75, and 1) W. An atomic force microscope (AFM) was used as a new method to get the results in the isthmus area; the obtained results from each group were compared with each other. Results: Based on the AFM and SEM analyses, laser and ultrasonic activation groups showed higher antimicrobial efficacy than the conventional syringe irrigation group (P<0.05). Conclusion: Based on the investigation's findings, the activation of 2% CHX solution by Er,Cr:YSGG laser in PIPS and PUI offers better mature bacterial biofilm removal in the mesial root of lower human molars than the same irrigant with the SI technique (AU)

A topografia interna do canal radicular é complexa, especialmente para a raiz mesial do molar permanente. Em resposta a esses problemas, foram criadas técnicas aprimoradas de irrigação, que utilizam pulsos de laser para agitar fluidos e melhorar a remoção de depósitos microbianos. Objetivo: Avaliar a eficácia do laser Er,Cr:YSGG com comprimento de onda de 2.780 nm via protocolo de streaming fotoacústico induzido por fótons (PIPS) que agitou clorohexidina a 2% (CHX) na remoção de Enterococcus faecalis maduro (E. faecalis) biofilme em sistemas de canais radiculares de molares inferiores. Material e Métodos: As raízes mesiais de 28 primeiros e segundos molares inferiores foram separadas e inoculadas com suspensão bacteriana de E. faecalis por 30 dias. As raízes foram irrigadas com CHX, sendo algumas delas agitadas com aparelho ultrassônico passivo (PUI), enquanto as demais raízes foram agitadas com laser Er,Cr:YSGG em PIPS a 60 µs/pulso, 5 Hz (0,25, 0,5, 0,75 e 1) W. Um microscópio de força atômica (AFM) foi utilizado como um novo método para obter os resultados na área do istmo; os resultados obtidos de cada grupo foram comparados entre si. Resultados: Com base nas análises de AFM e SEM, os grupos de ativação por laser e ultrassom apresentaram maior eficácia antimicrobiana do que o grupo de irrigação com seringa convencional (P<0.05). Conclusão: Com base nos achados da investigação, a ativação da solução de CHX a 2% pelo laser Er,Cr:YSGG em PIPS a (60 µs/pulso, 5 Hz, 0,75 W) oferece melhor remoção de biofilme (AU)

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In the presented study, a novel approach for thermal atomic layer deposition (ALD) of Al2O3 thin films using plasma-activated water (PAW) as a co-reactant, replacing traditionally employed deionized (DI) water, is introduced. Utilizing ex situ PAW achieves up to a 16.4% increase in the growth per cycle (GPC) of Al2O3 films, consistent with results from plasma-enhanced atomic layer deposition (PEALD). Time-resolved mass spectrometry (TRMS) revealed disparities in CH4 partial pressures between TMA reactions with DI water and PAW, with PAW demonstrating enhanced reactivity. Reactive oxygen species (ROS), namely H2O2 and O3, are posited to activate Si(100) substrate sites, thereby improving GPC and film quality. Specifically, Al2O3 films grown with PAW pH = 3.1 displayed optimal stoichiometry, reduced carbon content, and an expanded bandgap. This study thus establishes "PAW-ALD" as a descriptor for this ALD variation and highlights the significance of comprehensive assessments of PAW in ALD processes.

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Hair is good bioindicator of exposure, due to its ability to store and retain trace elements for long periods of time. But it can be especially useful when hair dyes are used since they may contain potentially toxic salts in their composition. In this context, analytical methods for the determination of bismuth, cadmium, lead, and silver in scalp human hair by electrothermal atomic absorption spectrometry were successfully validated. A total of 60 samples obtained from women between 18 and 60 years were analyzed: 34 dyed hairs and 26 untreated hairs (control). Average results expressed in dry weight (dyed/control) for each element were 2.34/0.49 µg g-1 (silver), 0.142/0.139 µg g-1 (bismuth), 0.055/0.054 µg g-1 (cadmium), and 2.09/0.99 µg g-1 (lead), respectively. These results agreed with those previously reported for non-exposed populations. A statistically significant higher Ag concentration in dyed hairs was observed, suggesting the bioaccumulation of this element. The associations between metal concentration and variables of interest (age, education, smoking habit, dye brand, use of dietary supplements) were investigated. A strong Pearson correlation was found for the pair Ag/Pb (r = 0.494, p < 0.05). Also, strong associations between lead levels and all the selected variables were observed (p < 0.05), while strong associations between silver levels with age and dye brand and association between cadmium levels and smoking habit were found. Furthermore, several commercial hair dye brands were analyzed to verify compliance with cosmetic regulations. This constitutes the first study of such characteristics performed in Uruguay, with worldwide relevance.

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By using a simple device architecture along with a simple process design and a low thermal-budget of a maximum of 100 °C for passivating metal/semiconductor interfaces, a Schottky barrier MOSFET device with a low subthreshold slope of 70 mV dec-1could be developed. This device is enabled after passivation of the metal/silicon interface (found at the source/drain regions) with ultra-thin SiOxfilms, followed by the e-beam evaporation of high- quality aluminum and by using atomic-layer deposition for HfO2as a gate oxide. All of these fabrication steps were designed in a sequential process so that a gate-last recipe could minimize the defect density at the aluminum/silicon and HfO2/silicon interfaces, thus preserving the Schottky barrier height and ultimately, the outstanding performance of the transistor. This device is fully integrated into silicon after standard CMOS-compatible processing, so that it could be easily adopted into front-end-of-line or even in back-end-of-line stages of an integrated circuit, where low thermal budget is required and where its functionality could be increased by developing additional and fast logic.

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Snakebite envenoming is one of the most significantly neglected tropical diseases in the world. The lack of diagnosis/prognosis methods for snakebite is one of our motivations to develop innovative technological solutions for Brazilian health. The objective of this work was to evaluate the protein and metallic ion composition of Crotalus durissus terrificus, Bothrops jararaca, B. alternatus, B. jararacussu, B. moojeni, B. pauloensis, and Lachesis muta muta snake venoms. Brazilian snake venoms were subjected to the shotgun proteomic approach using mass spectrometry, and metal ion analysis was performed by atomic spectrometry. Shotgun proteomics has shown three abundant toxin classes (PLA2, serine proteases, and metalloproteinases) in all snake venoms, and metallic ions analysis has evidenced that the Cu2+ ion is present exclusively in the L. m. muta venom; Ca2+ and Mg2+ ions have shown a statistical difference between the species of Bothrops and Crotalus genus, whereas the Zn2+ ion presented a statistical difference among all species studied in this work. In addition, Mg2+ ions have shown 42 times more in the C. d. terrificus venom when compared to the average concentration in the other genera. Though metal ions are a minor fraction of snake venoms, several venom toxins depend on them. We believe that these non-protein fractions are capable of assisting in the development of unprecedented diagnostic devices for Brazilian snakebites.

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IMPORTANCE: In this work, we characterized the composition, structure, and functional potential for biofilm formation of Exiguobacterium strains isolated from the Salar de Huasco in Chile in the presence of arsenic, an abundant metalloid in the Salar that exists in different oxidation states. Our results showed that the Exiguobacterium strains tested exhibit a significant capacity to form biofilms when exposed to arsenic, which would contribute to their resistance to the metalloid. The results highlight the importance of biofilm formation and the presence of specific resistance mechanisms in the ability of microorganisms to survive and thrive under adverse conditions.

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Cowpea chlorotic mottle virus (CCMV) and brome mosaic virus (BMV) are naked plant viruses with similar characteristics; both form a T = 3 icosahedral protein capsid and are members of the bromoviridae family. It is well known that these viruses completely disassemble and liberate their genome at a pH around 7.2 and 1 M ionic strength. However, the 1 M ionic strength condition is not present inside cells, so an important question is how these viruses deliver their genome inside cells for their viral replication. There are some studies reporting the swelling of the CCMV virus using different techniques. For example, it is reported that at a pH~7.2 and low ionic strength, the swelling observed is about 10% of the initial diameter of the virus. Furthermore, different regions within the cell are known to have different pH levels and ionic strengths. In this work, we performed several experiments at low ionic strengths of 0.1, 0.2, and 0.3 and systematically increased the pH in 0.2 increments from 4.6 to 7.4. To determine the change in virus size at the different pHs and ionic strengths, we first used dynamic light scattering (DLS). Most of the experiments agree with a 10% capsid swelling under the conditions reported in previous works, but surprisingly, we found that at some particular conditions, the virus capsid swelling could be as big as 20 to 35% of the original size. These measurements were corroborated by atomic force microscopy (AFM) and transmission electron microscopy (TEM) around the conditions where the big swelling was determined by DLS. Therefore, this big swelling could be an easier mechanism that viruses use inside the cell to deliver their genome to the cell machinery for viral replication.

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