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Micro, Volume 3, Issue 1 (March 2023) – 25 articles

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13 pages, 5134 KiB  
Article
Effects of Mode of Preparation of Titanium Dioxide Nanotube Arrays on Their Photocatalytic Properties: Application to p-Nitroaniline Degradation
by Nisreen Alshibeh Alwattar, Florence Vacandio, Laurent Vassalo, Thierry Djenizian, Bruno Coulomb and Jean-Luc Boudenne
Micro 2023, 3(1), 369-381; https://doi.org/10.3390/micro3010025 - 22 Mar 2023
Viewed by 1890
Abstract
The aim of this study was to investigate the photoactivity of dioxide titanium (TiO2) nanotube films depending on different structure factors including pore size, tube length, tube wall thickness and crystallinity. Aqueous p-nitroaniline was used as a probe to assess [...] Read more.
The aim of this study was to investigate the photoactivity of dioxide titanium (TiO2) nanotube films depending on different structure factors including pore size, tube length, tube wall thickness and crystallinity. Aqueous p-nitroaniline was used as a probe to assess the photocatalytic activity of titanium dioxide nanotube layers under UV irradiations. Self-organized titanium dioxide nanotube thin films were prepared by electrochemical anodization of titanium (Ti) foils and Ti thin films sputtered onto silicon (Si). The amorphous as-formed titanium nanotube layers were then annealed at different temperatures ranging from 450 to 900 °C in order to form crystalline phases. The structure and the morphology of the films were characterized by surface analysis techniques and scanning electron microscopy, respectively. The photocatalytic activity of the resulting TiO2 thin films was evaluated by monitoring the UV degradation of p-nitroaniline by UV spectrophotometry and by determining nitrification yields of by ion chromatography. The highest photocatalytic activity was exhibited for titanium nanotubes annealed at 450 °C. The presence of rutile -obtained for an annealing temperature of 900 °C—appeared to reduce the photodegradation yield of p-nitroaniline. Finally, the TiO2 nanotubes obtained from Ti foils revealed the most efficient photocatalytic properties. Full article
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16 pages, 5554 KiB  
Article
The Influence of Fibre Cross Section Shape and Fibre Surface Roughness on Composite Micromechanics
by James Thomason
Micro 2023, 3(1), 353-368; https://doi.org/10.3390/micro3010024 - 20 Mar 2023
Cited by 2 | Viewed by 2293
Abstract
Many of the carbon and natural fibres used in composite reinforcement have a non-circular cross section. Recently non-circular, or flat, cross section glass fibre products have become commercially available. This paper explores the potential effects that such non-circular fibre cross section shapes may [...] Read more.
Many of the carbon and natural fibres used in composite reinforcement have a non-circular cross section. Recently non-circular, or flat, cross section glass fibre products have become commercially available. This paper explores the potential effects that such non-circular fibre cross section shapes may have on the micromechanics of stress transfer at the composite fibre–matrix interface and the resulting changes in composite strength performance. Analytical modelling is used to show how the critical fibre length in composites with non-circular fibres is always less when compared to circular fibres with an equal cross-sectional area. This can result in significant changes to the strength performance of discontinuous fibre reinforced composites. Additionally, it is shown that the surface roughness found on natural and carbon fibres, many of which are also non-circular in cross section, can decrease the critical fibre length still further. These effects have important consequences for the use of single fibre micromechanical tests used for the characterisation of interfacial strength. Full article
(This article belongs to the Section Microscale Materials Science)
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15 pages, 2417 KiB  
Article
Advanced Technologies in the Fabrication of a Micro-Optical Light Splitter
by Giovanna Stella, Lorena Saitta, Alfredo Edoardo Ongaro, Gianluca Cicala, Maïwenn Kersaudy-Kerhoas and Maide Bucolo
Micro 2023, 3(1), 338-352; https://doi.org/10.3390/micro3010023 - 10 Mar 2023
Cited by 4 | Viewed by 1594
Abstract
In microfluidics, it is important to confine and transport light as close as possible to the sample by guiding it into a small volume of the microfluidic channel, acquiring the emitted/transmitted radiation. A challenge in this context is the miniaturization of the optical [...] Read more.
In microfluidics, it is important to confine and transport light as close as possible to the sample by guiding it into a small volume of the microfluidic channel, acquiring the emitted/transmitted radiation. A challenge in this context is the miniaturization of the optical components and their integration into the microfluidic device. Among all of the optical components, a particular role is played by the beam splitter, an important optical device capable of splitting light into several paths. In this paper, a micro-splitter is designed and realized by exploiting low-cost technologies. The micro-splitter consists of a micro-mirror in-between two micro-waveguides. This component was fabricated in different materials: poly-dimethyl-siloxane (PDMS), poly(methyl methacrylate) (PMMA), and VeroClear RGD810. A 3D printing master–slave fabrication protocol was used with PDMS, a direct 3D printing approach with VeroClear, and a laser cutting procedure with PMMA. The experimental results obtained show the high potential of the proposed fabrication protocols, based on low-cost technologies, for the realization of micro-optical components, which could also be easily integrated with microfluidics systems. Full article
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18 pages, 1791 KiB  
Review
The Importance of Biofilms on Microplastic Particles in Their Sinking Behavior and the Transfer of Invasive Organisms between Ecosystems
by Christine C. Gaylarde, Marcelo P. de Almeida, Charles V. Neves, José Antônio Baptista Neto and Estefan M. da Fonseca
Micro 2023, 3(1), 320-337; https://doi.org/10.3390/micro3010022 - 2 Mar 2023
Cited by 9 | Viewed by 3164
Abstract
Although plastic is ubiquitous in marine systems, our current knowledge of its transport is limited. Recent studies suggest size-selective removal of small plastic particles (<5 mm) from the ocean surface as a result of the formation of a biofilm (the “plastisphere”) on the [...] Read more.
Although plastic is ubiquitous in marine systems, our current knowledge of its transport is limited. Recent studies suggest size-selective removal of small plastic particles (<5 mm) from the ocean surface as a result of the formation of a biofilm (the “plastisphere”) on the microplastic particle (MP) surface. This localized microenvironment can isolate the microcosm from the adjacent aqueous medium, and thus protect component alien species from the surrounding physico-chemical conditions. Apart from resulting in specific conditions for the transfer of alien species through the environment, the plastisphere can impact MP hydrodynamics and cause MPs to move through the water column, initially sinking. The importance of this phenomenon has not been previously considered for these particles. The size-dependent vertical movement of MPs through the water column determines their distribution, which will vary with time of exposure and colonization. Some plastisphere organisms have plastic-degrading activities, which could be harnessed in marine depollution strategies. This article seeks to increase our understanding of the role of biofilms in the biological dynamics and diffusion of plastic microparticles. Full article
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12 pages, 2460 KiB  
Article
Effect of CdSTe QDs’ Crystal Size on Viability and Cytochrome P450 Activity of CHO-K1 and HEP-G2 Cells
by Luis Alamo-Nole, Adriana Ponton-Almodovar and Ivan Ortiz-Laboy
Micro 2023, 3(1), 308-319; https://doi.org/10.3390/micro3010021 - 2 Mar 2023
Viewed by 1567
Abstract
In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study [...] Read more.
In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study was on an evaluation of how crystal sizes of CdSTe QDs affect the viability and response of the cytochrome P450 system in CHO-K1 and HEP-G2 cells. CdSTe QDs were synthesized using a microwave-assisted system at different reaction temperatures (60, 120, 150, and 180 °C) to obtain different crystal sizes. The optical and structural characterization confirmed four crystal sizes from 3 to 8 nm. Fluorescence microscopy confirmed that CdSTe QDs are incorporated into both cell lines. Viability studies suggested that CHO-K1 cells are more sensitive than HEP-G2 cells to CdSTe QDs and Cd+2 ions. The responsible mechanisms for the toxicity of QDs and Cd+2 are apoptosis followed by necrosis. The activity of CYP 1A1, 1A2, and 3A4 isoenzymes suggests that the smallest CdSTe crystals are recognized in a manner similar to that of Cd+2. Furthermore, the largest CdSTe crystals can have different metabolic routes than Cd+2. Full article
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34 pages, 18268 KiB  
Article
The New Italian Standard on the Life Assessment of Martensitic Steels—First Results of the Experimental Validation Activity of XRD by Testing P91 and P92 Samples from Interrupted Uniaxial Creep Tests
by Andrea Tonti and Pietro De Blasi
Micro 2023, 3(1), 274-307; https://doi.org/10.3390/micro3010020 - 2 Mar 2023
Viewed by 1765
Abstract
The Italian Thermotechnical Committee is drafting a new standard for the life assessment of creep-operated pressure equipment, including modern steam boilers. For the evaluation of the spent life ratio several methods are available, even if each of them is not exhaustive. It should [...] Read more.
The Italian Thermotechnical Committee is drafting a new standard for the life assessment of creep-operated pressure equipment, including modern steam boilers. For the evaluation of the spent life ratio several methods are available, even if each of them is not exhaustive. It should be noted that the methods described must be considered in combination with NDTs and other kinds of tests, e.g., hardness tests. X-ray diffraction (XRD) is one of the methods that could be used to assess material evolution under creep conditions. The method allows for the study of phase transitions involving structural variations. It is possible to operate on both massive samples and powders. In this paper, work done with XRD, in the frame of a wider project regarding the study of the high-temperature behavior of welded martensitic steels, is presented. The results of the XRD analysis were compared with the results of the extraction replicas. This work concerns the controls of eight failed crept specimens submitted to XRD examinations. Eight XRD diagrams were produced and subsequently compared with 12 replicas for each specimen; that is, 96 extraction replicas were produced for this work. Then, around 5000 precipitates were analyzed for each specimen; therefore, for this work, around 40,000 precipitates were characterized with their chemical compositions. The average size of the precipitates was around 97 nm. Full article
(This article belongs to the Special Issue State-of-the-Art Microscale and Nanoscale Researches in Italy)
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10 pages, 945 KiB  
Article
Hydrofluoric Acid-Free Digestion of Organosilicon Nanoparticles for Bioanalysis by ICP-OES
by Nooshin Yousefpour, Olof Björnberg, Ingrid Yao Mattisson and Oskar Axelsson
Micro 2023, 3(1), 264-273; https://doi.org/10.3390/micro3010019 - 2 Mar 2023
Cited by 1 | Viewed by 2094
Abstract
A novel ICP-OES method has been developed for the determination of Si concentration, originating from polyorganophosphosilanes, in biological specimens that also contain metal ions. The method is free of hazardous hydrofluoric acid (HF) and involves digestion with HNO3/H2O2 [...] Read more.
A novel ICP-OES method has been developed for the determination of Si concentration, originating from polyorganophosphosilanes, in biological specimens that also contain metal ions. The method is free of hazardous hydrofluoric acid (HF) and involves digestion with HNO3/H2O2 prior to the analysis by ICP-OES. High and reproducible spike recovery was obtained from the controls. Full article
(This article belongs to the Section Analysis Methods and Instruments)
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8 pages, 1434 KiB  
Article
Structural Consequences of Post-Synthetic Modification of Cu2P3I2
by Gregory R. Schwenk, John T. Walters and Hai-Feng Ji
Micro 2023, 3(1), 256-263; https://doi.org/10.3390/micro3010018 - 1 Mar 2023
Viewed by 1532
Abstract
In an attempt to widen the family of Phosphorus Metal Halides (MxPyXz) and enable new applications, post-synthetic modifications to the MxPyXz, Cu2P3I2 have been reported. While such [...] Read more.
In an attempt to widen the family of Phosphorus Metal Halides (MxPyXz) and enable new applications, post-synthetic modifications to the MxPyXz, Cu2P3I2 have been reported. While such a technique suggests access to an entirely new family of MxPyXz-based materials, we report, in this work, that the ion-exchange process seemingly influences important properties such as the crystallographic pattern and vibrational modes. Full article
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17 pages, 80791 KiB  
Article
Influence of the Chromium Content on the Characteristics of the Matrix, the Tantalum Carbides Population, and the Hardness of Cast Co(Cr)-0.4C-6Ta Alloys
by Patrice Berthod, Merzouk Bouaraba and Junfu Cai
Micro 2023, 3(1), 239-255; https://doi.org/10.3390/micro3010017 - 16 Feb 2023
Cited by 1 | Viewed by 1440
Abstract
The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences [...] Read more.
The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences on the melting temperature, microstructure, and mechanical properties at high temperatures and at room temperature. Seemingly, the effect of chromium content on the microstructure and properties of cast equi-axed Co-Cr-Ta-C superalloys containing TaC as single reinforcing carbide and in high-enough quantities to achieve a high level of creep resistance has not been the subject of previous investigations. The present work is devoted to the exploration of this influence of Cr content on the as-cast microstructure of a model alloy in this category, as well as on its microstructure transformations at high temperatures. The work aims to help rate the Cr content to achieve the best characteristics in machinability and high-temperature properties. This is of great importance for fabricability (production cost) and sustainability in service (long enough lifetime performance). A series of six alloys derived from a rather well-known alloy and presenting various Cr contents were thus elaborated by casting. Their microstructures were investigated in their as-cast state as well as in an aged state resulting from a 4-day stage at 1400 K. Vickers indentation was also carried out to study how hardness may evolve with Cr content. It was seen that the higher the Cr content, the lower the solidus temperature, the coarser the TaC population, the harder the alloy, and the higher the risk of brittleness. In order to reach the best compromise, the preferred Cr weight content range, as identified by this work, is 20–30%; indeed, for such Cr contents: (1) the matrix is austenitic, then dense, and then hard and not brittle, and thus is mechanically resistant and tough; (2) the TaC carbides are script-shaped and resistant against morphology changes at high temperatures, and thus efficiently preserve interdendritic cohesion for a long time, and, consequently, (3) the alloys are machinable, have expected good toughness, and can be resistant against creep deformation as well as oxidation and corrosion at high temperatures thanks to the Cr content, allowing for chromium-forming behavior. Full article
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15 pages, 5648 KiB  
Article
Fluorescence Sensing of Some Important Nitroaromatic Compounds by Using Polyaniline Ag Composite
by Satish Ashok Ture, Shruthy D. Pattathil, Bertrand Zing Zing and Venkataraman Abbaraju
Micro 2023, 3(1), 224-238; https://doi.org/10.3390/micro3010016 - 9 Feb 2023
Cited by 5 | Viewed by 2073
Abstract
Conducting polymers (CPs) have contributed significantly to the field of sensing. The sensing of nitroaromatic compounds by fluorescence has recently gained more attention due to its sensitivity and selectivity. In this study, polyaniline (PANI) was functionalized by forming a polyaniline-Ag (PANI-Ag) composite and [...] Read more.
Conducting polymers (CPs) have contributed significantly to the field of sensing. The sensing of nitroaromatic compounds by fluorescence has recently gained more attention due to its sensitivity and selectivity. In this study, polyaniline (PANI) was functionalized by forming a polyaniline-Ag (PANI-Ag) composite and used as a fluorophore for sensing. The nitro groups present in nitroaromatic compounds (NACs) such as 2,4,6-trinitrophenol (picric acid-TNP) and Dinitrobenzene (DNB) act as electron-accepting molecules and quench the fluorescence of polymer chains by showing an amplified quenching effect in which trace amounts of electron-accepting NACs quench emissions of several fluorophore units. The PANI-Ag composite synthesized by interfacial polymerization was analyzed using UV-vis spectroscopy and Fourier-transform infrared (FTIR) spectroscopy for determination of molecular structure; X-ray powder diffraction (XRD) and scanning electron microscopy (SEM/EDAX) for its morphology, which is cubic crystalline silver; and thermogravimetric analysis (TGA) for the thermal stability. The fluorescence quenching mechanism was deduced from the Stern–Volmer plot. The quenching constant value (Ksv) obtained from the Stern–Volmer (S–V) plot was found to be Ksv = 0.1037 × 106 M−1 (TNP) and Ksv = 0.161 × 104 M−1 (DNB). The plot shows a single mechanism with formation of an exciplex complex for TNP with a photoinduced electron transfer (PET) mechanism. The limit of detection (LOD) is found to be TNP = 5.58 × 10−7 M, whereas DNB = 23.30 × 10−6 M shows that the PANI-Ag composite is a potential fluorophore for sensing of nitroaromatic compounds in trace levels. Full article
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16 pages, 2052 KiB  
Article
Microplastics in Freshwater River in Rio de Janeiro and Its Role as a Source of Microplastic Pollution in Guanabara Bay, SE Brazil
by Thiago L. Drabinski, Diego G. de Carvalho, Christine C. Gaylarde, Marcos F. P. Lourenço, Wilson T. V. Machado, Estefan M. da Fonseca, André Luiz Carvalho da Silva and José Antônio Baptista Neto
Micro 2023, 3(1), 208-223; https://doi.org/10.3390/micro3010015 - 6 Feb 2023
Cited by 9 | Viewed by 2993
Abstract
In the present research, the occurrence of contamination by microplastics in the water column was investigated in 15 sample sites along the rivers Guapimirim, Macacu and Maracanã—important rivers that flow into Guanabara Bay, a very polluted estuarine environment in Brazil. The correctidentified polymers [...] Read more.
In the present research, the occurrence of contamination by microplastics in the water column was investigated in 15 sample sites along the rivers Guapimirim, Macacu and Maracanã—important rivers that flow into Guanabara Bay, a very polluted estuarine environment in Brazil. The correctidentified polymers were manually counted and classified as to their morphology and color using a binocular stereomicroscope and were characterized by ATR-FTIR spectroscopy. The total mean abundance of particles was 3651.5 items m−3, ranging from 3.6 to 51,166.5 items m−3. Plastic debris was identified in all samples, with a predominance of fibers (67.3%). Polyethylene, polyester fiber and high-density polyethylene (50%) were the major polymers, and the main colors were transparent followed by black and blue in all the water bodies studied. The highest quantities of microplastics were found in the Maracanã River. The figures show that microplastic concentrations are correlated to the level of urbanization. Full article
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16 pages, 11185 KiB  
Article
Barrier Performance of Spray Coated Cellulose Nanofibre Film
by Kirubanandan Shanmugam, Narendhar Chandrasekar and Ramachandran Balaji
Micro 2023, 3(1), 192-207; https://doi.org/10.3390/micro3010014 - 3 Feb 2023
Cited by 1 | Viewed by 2099
Abstract
Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication [...] Read more.
Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication method influences their barrier properties of the film. A spray-coating CNF on a stainless-steel plate was developed to form a compact film with two unique surfaces, namely a smooth layer on the base side and rough layer on the free side. It improves both the ease of preparation of the film and reduces the water vapour permeability via tailoring the basis weight and thickness of the film through simple adjusting CNF content in the suspension. The air permanence of the film from 1.0 wt.% to 2.0 wt.% CNF suspension is less than 0.003 µm/Pa·S confirming that is an impermeable film and proves a good packaging material. SEM, optical profilometry, and AFM revealed that the spray-coated surface was smooth and glossy. For sprayed CNF films with basis weight between 86.26 ± 13.61 and 155.85 ± 18.01 g/m2, WVP were ranged from 6.99 ± 1.17 × 10−11 to 4.19 ± 1.45 × 10−11 g/m·Pa·S. In comparison, the WVP of 100 g/m2 vacuum filtered CNF film was 5.50 ± 0.84 × 10−11 g/m·Pa·S, spray-coated film (of 96.6 g/m2) also show similar permeability at around 5.34 ± 0.603 × 10−11 g/m·Pa·S. The best performance was achieved with spraying of 2.0 wt.% CNF and a water vapour permeability of 3.91 × 10−11 g/m·s·Pa. Spray coated CNF film is impermeable against air and water vapour and a potential alternative to synthetic plastics. Full article
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20 pages, 6490 KiB  
Article
Polyaniline Hybrids with Biological Tissue, and Biological Polymers as Physiological—Electroactive Materials
by Mai Ichikawa, Masashi Otaki and Hiromasa Goto
Micro 2023, 3(1), 172-191; https://doi.org/10.3390/micro3010013 - 1 Feb 2023
Cited by 1 | Viewed by 1528
Abstract
A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. [...] Read more.
A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. Optical microscopy observation revealed that polyaniline was deposited into the micro-tissue of the sprout to form the conductive polymer bio-composite. Micro-optical fiber functions for the composite were visually confirmed. Furthermore, the sprout/polyaniline based organic diode exhibited an avalanche breakdown phenomenon. Next, a fucoidan/polyaniline composite as a physiological active material/conducting polymer composite was prepared. This composite showed good film-forming ability, electrochromism, and a micro-porous surface. This paper reports the preparation of conducting polymer composites with a combination of bio-tissue and bio-substance for the creation of bio-based electrically active organized architecture. Full article
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16 pages, 5023 KiB  
Article
In-Vitro Cell Response to Strontium/Magnesium-Doped Calcium Phosphate Nanoparticles
by Kathrin Kostka, Shabnam Hosseini and Matthias Epple
Micro 2023, 3(1), 156-171; https://doi.org/10.3390/micro3010012 - 1 Feb 2023
Cited by 3 | Viewed by 1638
Abstract
Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based [...] Read more.
Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based biomaterials. Strontium-doped calcium phosphate nanoparticles and magnesium-doped calcium phosphate nanoparticles with degrees of cation substitution of 5, 10, 15, and 20 mol% with respect to calcium were prepared by precipitation, followed by surface functionalization with polyethyleneimine (PEI, cationic) or carboxymethylcellulose (CMC, anionic). The nanoparticles were characterized by dynamic light scattering (DLS), zeta potential measurement, scanning electron microscopy (SEM), atomic absorption spectrometry (AAS), energy dispersive X-ray analysis (EDX), and X-ray powder diffraction (XRD). The particles were approximately spherical (diameter 40–70 nm). The addition of magnesium and strontium considerably decreased the internal crystallinity, i.e., the doped particles were almost X-ray amorphous. The cell-biological effects were assessed on three different cell lines, i.e., HeLa cells, MG63 cells, and MC3T3 cells. Cell viability tests (MTT) showed a low cytotoxicity, the alkaline phosphatase (ALP) activity was strongly increased, and the nanoparticles were taken up well by the three cell lines. Full article
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13 pages, 10358 KiB  
Article
Graphene Formation through Spontaneous Exfoliation of Graphite by Chlorosulfonic Acid: A DFT Study
by Alfredo Bol-Arreba, Isabel G. Ayala and Nicolás A. Cordero
Micro 2023, 3(1), 143-155; https://doi.org/10.3390/micro3010011 - 31 Jan 2023
Cited by 1 | Viewed by 1440
Abstract
Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield [...] Read more.
Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield for the liquid phase single-surfactant spontaneous exfoliation of graphite, i.e., without sonication, has been obtained using chlorosulfonic acid. The ability of this acid to disperse graphite is studied within the framework of Density Functional Theory (DFT). Equilibrium configurations, electron transfers, binding energies, and densities of states are presented for two acid concentrations and for two situations: adsorption (on monolayer and bilayer graphene) and intercalation (in between simple hexagonal and Bernal-stacked bilayer graphene). Experimental exfoliation power and dispersion stability are explained in terms of charge transfer—the largest found among several studied exfoliating and surfactant agents—facilitated by the good geometrical matching of chlorosulfonic acid molecules to constituent carbon rings of graphene. This matching is in the origin of the tendency toward adsorption of chlorosulfonic acid molecules on graphene monolayers when they separate, originating the charging of the monolayers that precludes their reaggregation. Full article
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25 pages, 4773 KiB  
Article
Chitosan/Hydroxyapatite Scaffolds with P28 as a Promising Osteoinductive Scaffold for Bone Healing Applications
by Farah Alwani Azaman, Florence Daubiné, Amélie Lebatard, Margaret E. Brennan Fournet and Declan M. Devine
Micro 2023, 3(1), 118-142; https://doi.org/10.3390/micro3010010 - 31 Jan 2023
Cited by 4 | Viewed by 1890
Abstract
Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although [...] Read more.
Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although covalently binding the growth factors was reported as a great alternative to the conventionally physical adsorption and encapsulation methods, this method presents the risk of altering the molecular activity and interaction of the growth factors. Therefore, alkaline phosphatase (ALP) activity and alizarin red staining (ARS) with a quantitative cetylpyridinium chloride (CPC) assay were conducted to validate that our photo-crosslinking fabrication method did not interfere with the functionality of the growth factors. The ALP activity of C2C12 with 100 µg/mL P28 was found to be comparable to 0.5 µg/mL BMP-2 after two weeks, where 0.001 U/mL was recorded for both treatments. The C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds also showed an increased ALP activity compared to the negative control. ARS-CPC assay presented the highest optical density in 0.3 µg/mL BMP-2 and 50 µg/mL P28, while the highest intensity of ARS was observed in C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds compared to the negative controls. The osteoconductive capability of this delivery system was then investigated through a rat femoral condyle defect model, where the new bone mineral density and the bone volume increased for all CS/HAp scaffolds compared to the collagen sponge control treatment. The histological assessment showed a favourable bone regeneration efficacy of the CS/HAp/P28 compared to the CS/HAp/BMP-2 treatment, thus showing the use of CS/HAp scaffolds with P28 as a promising osteoinductive scaffold for bone healing applications. Full article
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11 pages, 3765 KiB  
Article
Intramolecular OHO Hydrogen Bonding in Dibenzoylmethane Enol: Raman Spectroscopic and Quantum Chemical Study
by Boris A. Kolesov, Elena A. Pritchina and Aleksey Ya. Tikhonov
Micro 2023, 3(1), 107-117; https://doi.org/10.3390/micro3010009 - 30 Jan 2023
Viewed by 1511
Abstract
In the present work, the intramolecular O-H···O hydrogen bonding in 3-hydroxy-1,3-diphenylprop-2-en-1-one (keto-enol form of dibenzoylmethane, DBM) was investigated. For this purpose, the Raman spectra of polycrystalline samples of ordinary (H-DBM) and deuterated (D-DBM) 3-hydroxy-1,3-diphenylprop-2-en-1-one in the temperature range of 5–300 K were measured. [...] Read more.
In the present work, the intramolecular O-H···O hydrogen bonding in 3-hydroxy-1,3-diphenylprop-2-en-1-one (keto-enol form of dibenzoylmethane, DBM) was investigated. For this purpose, the Raman spectra of polycrystalline samples of ordinary (H-DBM) and deuterated (D-DBM) 3-hydroxy-1,3-diphenylprop-2-en-1-one in the temperature range of 5–300 K were measured. It was found that low-temperature hydrogen bonding is extremely strong, the proton and deuteron are located in the midpoint of the O···O segment, and their ground and first excited vibrational states are located above the barrier U0 between the local minima. The vibrational frequencies, in this case, are 1543 and 1709 cm−1 for the proton and 1045 and 1087 cm−1 for the deuteron. As the temperature rises and the barrier height increases in H-DBM, the zero-point vibrational state of the proton begins to move into one of the local minima at T > 50 K, while the excited state remains in the broad single-well potential. The same is observed in D-DBM, but with a significant temperature delay. Compounds with donor (−OCH3) and acceptor (−NO2) substituents in the phenyl ring were also synthesized and their spectra were obtained. Both results confirm existing ideas about the nature of the extremely strong hydrogen bond. The quantum-chemical calculation of the vibrational spectrum of H-DBM and D-DBM is consistent with the experimental results. Full article
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23 pages, 6689 KiB  
Article
Transferrin-Grafted Albumin Nanoparticles for the Targeted Delivery of Apocynin and Neuroprotection in an In Vitro Model of the BBB
by Venkatesan Perumal, Arun Reddy Ravula, Agnieszka Agas, Manisha Kannan, Xiangshan Liu, Shanmuga Sundari I, Sivakumar Vijayaraghavalu, James Haorah, Yuanwei Zhang and Namas Chandra
Micro 2023, 3(1), 84-106; https://doi.org/10.3390/micro3010008 - 23 Jan 2023
Cited by 1 | Viewed by 2694
Abstract
Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide, affecting over 10 million people annually, with an estimated cost of $76.5 billion. Although apocynin freely transverses the blood–brain barrier (BBB), its application is limited due to its rapid elimination, [...] Read more.
Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide, affecting over 10 million people annually, with an estimated cost of $76.5 billion. Although apocynin freely transverses the blood–brain barrier (BBB), its application is limited due to its rapid elimination, low terminal half-life (t1/2 = 6.7 min), narrow dose–response relationship, and cytotoxicity, thereby requiring repeated dosages. With this study, we aimed to develop transferrin-functionalized nanoparticles encapsulating apocynin to treat neuroinflammation for targeted drug delivery to sites of brain injury. As a preliminary approach, we endeavored to optimize the formulation parameters of apocynin-loaded albumin nanoparticles prepared through the desolvation method. The nanoparticles were characterized for their size, polydispersity, surface charge, drug loading and in vitro drug release. In this study, we also investigated the anti-inflammatory and neuroprotective effects of free apocynin and nanoparticle-loaded apocynin in neuronal cells. We show that the developed formulation displayed monodispersed, nanosized particles with higher entrapment efficiency, loading, stability, and sustained release profiles. The permeability of the nanoparticles across HBMECs reached the maximum at 67%. The in vivo evaluation revealed the enhanced uptake of transferrin-anchored nanoparticles in the brain tissues when compared with unmodified nanoparticles after I.V. administration. In vivo nanoparticle localization studies using a blast TBI (bTBI) model and confocal fluorescence microscopy have shown that tf-apoANPs are successful in delivering relatively high amounts of nanoparticles to the brain parenchyma and glial cells compared to non-targeted nanoparticles. We also establish that targeted nanoparticles accumulate in the brain. In conclusion, tf-apoANPs are efficacious carriers for targeted delivery across the blood–brain barrier to potentially treat neuroinflammation in brain injury and other diseases. Full article
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22 pages, 7798 KiB  
Article
Integrated Characterization of Mudstones in the Andes of Colombia: Understanding Its Complexities for Risk Mitigation
by German Alfonso Reyes-Mendoza, José Antonio Henao-Martínez and Eduardo Castro Marín
Micro 2023, 3(1), 62-83; https://doi.org/10.3390/micro3010007 - 23 Jan 2023
Viewed by 2060
Abstract
This article presents a comprehensive vision of particularities and constraints of the Paja Formation in the Northern Andes of Colombia, supported by personal, institutional, and academic experiences, including a doctoral thesis in completion (geomorphology and risks research line). Such fine-grained marine rocks cause [...] Read more.
This article presents a comprehensive vision of particularities and constraints of the Paja Formation in the Northern Andes of Colombia, supported by personal, institutional, and academic experiences, including a doctoral thesis in completion (geomorphology and risks research line). Such fine-grained marine rocks cause severe damage in diverse zones, with little spread, and are very unfavorable, especially within the Eastern Cordillera (departments of Santander and Cundinamarca), whose socio-environmental problems motivated a popular legal action in the municipality of Vélez due to the cracking and collapse of houses, damage to roads and landslides in the urban area, as well as flows, subsidence, and high hydrogeochemical dynamism or rare earths, although they also presented spontaneous ignition at the rural area. Understanding how these problems originate and interrelate is the main objective of the work. At the beginning, we include some brief definitions, terms, and key approaches to understand the consolidated geomaterials, location, and background of the problem; then, the results of meso–macro–micro studies, obtained by combining the field techniques and conventional instrumental laboratory analyses (tests on the chemistry of water and soil, description of samples with magnifying glasses, petrography with a polarized light microscope, micromorphology of regoliths–colluvions) of nanoscientists (emphasizing RXD-RXF, SEM, IR-Raman spectroscopy, TOC-TS) are presented. These characterizations and new knowledge must be socially and institutionally appropriated and applied in land use planning and risk management for the sustainability of challenging environments with the stratiforms of Lower Cretaceous rocks and associated Quaternary deposits in populated mountainous areas and contrasting intertropical hydroclimatological regimes, geologically active, so unstable and insecure. Full article
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2 pages, 168 KiB  
Editorial
Acknowledgment to the Reviewers of Micro in 2022
by Micro Editorial Office
Micro 2023, 3(1), 60-61; https://doi.org/10.3390/micro3010006 - 20 Jan 2023
Viewed by 871
Abstract
High-quality academic publishing is built on rigorous peer review [...] Full article
9 pages, 1443 KiB  
Communication
Synthesis, Characterization, and Acute Cytotoxicity Evaluation of Chloroquine Encapsulating Liposomes
by Nathan D. Donahue, Ellen A. Vance, Vinit Sheth, Emmy R. Francek and Stefan Wilhelm
Micro 2023, 3(1), 51-59; https://doi.org/10.3390/micro3010005 - 13 Jan 2023
Cited by 1 | Viewed by 2174
Abstract
Liposomes encapsulating chloroquine were synthesized and characterized. Cryogenic transmission electron microscopy and dynamic light scattering confirmed a liposome size of ~100 nm and uniform shape. Two independent analytical methods were used to quantify chloroquine encapsulation: (i) HPLC, and (ii) UV-Vis spectrophotometry. Using RAW264.7 [...] Read more.
Liposomes encapsulating chloroquine were synthesized and characterized. Cryogenic transmission electron microscopy and dynamic light scattering confirmed a liposome size of ~100 nm and uniform shape. Two independent analytical methods were used to quantify chloroquine encapsulation: (i) HPLC, and (ii) UV-Vis spectrophotometry. Using RAW264.7 murine macrophages as model immune cells, cell culture experiments revealed an improved acute cytotoxicity profile of chloroquine encapsulating liposomes with >90% cell viability compared to free chloroquine (cell viability ~30%) at equivalent drug doses. These results may potentially be relevant for liposome-based chloroquine delivery for nanomedicine applications. Full article
(This article belongs to the Special Issue Microenvironment and Nanocarriers)
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16 pages, 4053 KiB  
Article
Capacitive-Type Pressure Sensor for Classification of the Activities of Daily Living
by Ji Su Park, Sang-Mo Koo and Choong Hyun Kim
Micro 2023, 3(1), 35-50; https://doi.org/10.3390/micro3010004 - 9 Jan 2023
Cited by 1 | Viewed by 1592
Abstract
In order to operate a gait rehabilitation device, it is necessary to accurately classify the states appearing in activities of daily living (ADLs). In the case of force sensing resistors (FSRs), which are often used as pressure sensors in gait analysis, it is [...] Read more.
In order to operate a gait rehabilitation device, it is necessary to accurately classify the states appearing in activities of daily living (ADLs). In the case of force sensing resistors (FSRs), which are often used as pressure sensors in gait analysis, it is desirable to replace them with other sensors because of their low durability. In the present study, capacitive-type pressure sensors, as an alternative to FSRs, were developed, and their performance was evaluated. In addition, the timed up and go test was performed to measure the ground reaction force in healthy individuals, and a machine learning technique was applied to the calculated biosignal parameters for the classification of five types of ADLs. The performance evaluation results showed that a sensor with thermoplastic polyurethane (substrate and dielectric layer material) and multiwall carbon nanotubes (conductive layer) has sufficient sensitivity and durability for use as a gait analysis pressure sensor. Moreover, when an overlapping filter was applied to the four-layer long short-term memory (LSTM) or the five-layer LSTM model developed for motion classification, the precision was greater or equal to 95%, and unstable errors did not occur. Therefore, when the pressure sensor and ADLs classification algorithm developed in this study are applied, it is expected that motion classification can be completed within a time range that does not affect the control of the gait rehabilitation device. Full article
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13 pages, 3424 KiB  
Article
Role of Graphene Oxide in Inhibiting the Interactions between Nucleoside Diphosphate Kinases -B and -C
by Andrey Zaznaev and Isaac Macwan
Micro 2023, 3(1), 22-34; https://doi.org/10.3390/micro3010003 - 27 Dec 2022
Viewed by 1615
Abstract
Nucleoside diphosphate kinase (NDPK) enzyme in the sarcolemma membrane is crucial for the synthesis of cyclic adenosine monophosphate (cAMP) to maintain the calcium ion balance. Typically, NDPK-B residue His118, in the presence of NPDK-C, phosphorylates the stimulatory guanosine diphosphate, GDP(s). During a heart [...] Read more.
Nucleoside diphosphate kinase (NDPK) enzyme in the sarcolemma membrane is crucial for the synthesis of cyclic adenosine monophosphate (cAMP) to maintain the calcium ion balance. Typically, NDPK-B residue His118, in the presence of NPDK-C, phosphorylates the stimulatory guanosine diphosphate, GDP(s). During a heart failure, an increased quantity of NDPK-B also phosphorylates the inhibitory GDP(i), thereby inhibiting the cAMP synthesis. In this work, the interactions between NDPK-B and NDPK-C are quantified in the presence and absence of graphene oxide (GO) using molecular dynamics through stability analysis involving hydrogen bonds, center of mass (COM), RMSD, salt bridges, non-bonding energy analysis and interfacial water molecules. It is found that the adsorption of NDPK-B on GO triggers a conformational change in NDPK-B and its reduced interactions with NDPK-C, confirmed through a reduced COM distance between NDPK-B and GO (from 40 Å to 30 Å) and an increased COM distance between NDPK-B and NDPK-C (from 50 Å to 60 Å). This is also supported by fewer salt bridges between NDPK-B and NDPK-C, and an increased number of hydrogen bonds of the interfacial water molecules between NDPK-B and GO. This finding suggests that GO can suppress the interactions among NDPK-B/C complex required for phosphorylation of GDP(i). Full article
(This article belongs to the Section Microscale Biology and Medicines)
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13 pages, 1241 KiB  
Review
Characterization and Functionalization Approaches for the Study of Polymeric Nanoparticles: The State of the Art in Italian Research
by Biagio Todaro and Melissa Santi
Micro 2023, 3(1), 9-21; https://doi.org/10.3390/micro3010002 - 26 Dec 2022
Cited by 3 | Viewed by 3813
Abstract
Polymeric nanoparticles (PNPs) are a group of nanocarriers employed in a wide range of applications. Characterization is a fundamental step in PNPs formulation and many basic techniques are available to provide chemical-physical information such as dimensions, surface potential, stability and solubility. Recently, these [...] Read more.
Polymeric nanoparticles (PNPs) are a group of nanocarriers employed in a wide range of applications. Characterization is a fundamental step in PNPs formulation and many basic techniques are available to provide chemical-physical information such as dimensions, surface potential, stability and solubility. Recently, these techniques have been implemented with more innovative ones to obtain more precise knowledge of the nanomaterials. In this review we analyzed the state of the art in the field of polymeric nanoparticles produced by Italian laboratories. We described all methods available for PNPs characterization with their applications as drug delivery systems. We also reported the different types of molecules that were recently used for PNPs functionalization, a fundamental step in delivering drugs specifically to their targets and then resulting in reduced side effects in patients. Full article
(This article belongs to the Special Issue State-of-the-Art Microscale and Nanoscale Researches in Italy)
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8 pages, 1454 KiB  
Article
Maximum Power of Thin-Film Capacitive Electrostatic Micromotors Based on Nanogaps
by Igor L. Baginsky
Micro 2023, 3(1), 1-8; https://doi.org/10.3390/micro3010001 - 24 Dec 2022
Viewed by 1419
Abstract
This paper is devoted to the determination of the value of the maximum specific power of capacitive electrostatic micromotors based on nanometer working gaps. The motors under consideration were developed earlier. They have the following structure: a metal—thin crystalline ferroelectric layer with a [...] Read more.
This paper is devoted to the determination of the value of the maximum specific power of capacitive electrostatic micromotors based on nanometer working gaps. The motors under consideration were developed earlier. They have the following structure: a metal—thin crystalline ferroelectric layer with a high dielectric constant—a nanometer working gap—a movable electrode. The mechanism limiting the magnitude of the maximum field in the gap have also been determined in previous works. The mechanism is the stripping of atoms from the surface of the movable electrode under the action of electrostatic forces. It was shown that the maximum energy density in the working gap can be as high as 1.6 × 109 J/m3. In the presented paper, a maximum frequency of electromechanical energy conversion as high as 10 MHz is estimated for these motors, with a maximum specific power of 5 × 108 W/kg. The application of the proposed motors for micromachines is discussed. Full article
(This article belongs to the Section Analysis Methods and Instruments)
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