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Micro, Volume 1, Issue 2 (December 2021) – 7 articles

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17 pages, 3174 KiB  
Article
Preparation, Characterization, and Acetylcholinesterase Inhibitory Ability of the Inclusion Complex of β-Cyclodextrin–Cedar (Juniperus phoenicea) Essential Oil
by Eleni Kavetsou, Ioanna Pitterou, Annita Katopodi, Georgia Petridou, Abdelaziz Adjali, Spyros Grigorakis and Anastasia Detsi
Micro 2021, 1(2), 250-266; https://doi.org/10.3390/micro1020019 - 8 Dec 2021
Cited by 6 | Viewed by 2419
Abstract
The aim of the present study was the encapsulation of cedar (Juniperus phoenicea) essential oil (CEO) of Greek origin in β-cyclodextrin (β-CD) through the formation of inclusion complexes (ICs) using the co-precipitation method with different β-CD-to-CEO weight ratios (90:10, 85:15, 80:20, [...] Read more.
The aim of the present study was the encapsulation of cedar (Juniperus phoenicea) essential oil (CEO) of Greek origin in β-cyclodextrin (β-CD) through the formation of inclusion complexes (ICs) using the co-precipitation method with different β-CD-to-CEO weight ratios (90:10, 85:15, 80:20, 70:30 (w/w)). The encapsulation of CEO in β-CD through host–guest interactions was confirmed by Nuclear Magnetic Resonance (NMR) spectroscopy, FT-IR spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The obtained ICs exhibited nanoscale size (315.9 nm to 769.6 nm),Polydispersity Index from 0.326 to 0.604 and satisfactory stability in suspension (−37.0 mV to −17.0 mV). The process yield was satisfactory, ranging between 65% and 78%, while the inclusion efficiency ranged from 10% to 27%. The in vitro release study conducted for the IC with the optimal characteristics (β-CD:CEO 80:20 (w/w)) exhibited a sustained release profile, with an initial burst effect in the first 5 h. The release profile could be well expressed by the Higuchi equation: Q = 18.893 t1/2 + 9.5919, R2 = 0.8491. The cedar EO presented significant acetylcholinesterase inhibition (IC50 37 μg/mL), which was prolonged by its encapsulation into the β-CD cavity. Full article
(This article belongs to the Section Microscale Materials Science)
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8 pages, 1815 KiB  
Communication
Single Cell Micro-Pillar-Based Characterization of Endothelial and Fibroblast Cell Mechanics
by Julia Eckert, Yasmine Abouleila, Thomas Schmidt and Alireza Mashaghi
Micro 2021, 1(2), 242-249; https://doi.org/10.3390/micro1020018 - 25 Nov 2021
Viewed by 2696
Abstract
Mechanotransduction, the ability of cells to sense and respond to the mechanical cues from their microenvironment, plays an important role in numerous cellular processes, ranging from cell migration to differentiation. Several techniques have been developed to investigate the underlying mechanisms of mechanotransduction, in [...] Read more.
Mechanotransduction, the ability of cells to sense and respond to the mechanical cues from their microenvironment, plays an important role in numerous cellular processes, ranging from cell migration to differentiation. Several techniques have been developed to investigate the underlying mechanisms of mechanotransduction, in particular, force measurement-based techniques. However, we still lack basic single cell quantitative comparison on the mechanical properties of commonly used cell types, such as endothelial and fibroblast cells. Such information is critical to provide a precedent for studying complex tissues and organs that consist of various cell types. In this short communication, we report on the mechanical characterization of the commonly used endothelial and fibroblast cells at the single cell level. Using a micropillar-based assay, we measured the traction force profiles of these cells. Our study showcases differences between the two cell types in their traction force distribution and morphology. The results reported can be used as a reference and to lay the groundwork for future analysis of numerous disease models involving these cells. Full article
(This article belongs to the Section Microscale Biology and Medicines)
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14 pages, 13700 KiB  
Article
Silicon Nitride Interface Engineering for Fermi Level Depinning and Realization of Dopant-Free MOSFETs
by Benjamin Richstein, Lena Hellmich and Joachim Knoch
Micro 2021, 1(2), 228-241; https://doi.org/10.3390/micro1020017 - 21 Nov 2021
Cited by 7 | Viewed by 5627
Abstract
Problems with doping in nanoscale devices or low temperature applications are widely known. Our approach to replace the degenerate doping in source/drain (S/D)-contacts is silicon nitride interface engineering. We measured Schottky diodes and MOSFETs with very thin silicon nitride layers in between silicon [...] Read more.
Problems with doping in nanoscale devices or low temperature applications are widely known. Our approach to replace the degenerate doping in source/drain (S/D)-contacts is silicon nitride interface engineering. We measured Schottky diodes and MOSFETs with very thin silicon nitride layers in between silicon and metal. Al/SiN/p-Si diodes show Fermi level depinning with increasing SiN thickness. The diode fabricated with rapid thermal nitridation at 900 C reaches the theoretical value of the Schottky barrier to the conduction band ΦSB,n=0.2 eV. As a result, the contact resistivity decreases and the ambipolar behavior can be suppressed. Schottky barrier MOSFETs with depinned S/D-contacts consisting of a thin silicon nitride layer and contact metals with different work functions are fabricated to demonstrate unipolar behavior. We presented n-type behavior with Al and p-type behavior with Co on samples which only distinguish by the contact metal. Thus, the thermally grown SiN layers are a useful method suppress Fermi level pinning and enable reconfigurable contacts by choosing an appropriate metal. Full article
(This article belongs to the Special Issue Innovative Methods for Semiconductor Doping)
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13 pages, 3612 KiB  
Article
Soft-Microstructured Transparent Electrodes for Photonic-Enhanced Flexible Solar Cells
by Jenny L. N. Boane, Pedro Centeno, Ana Mouquinho, Miguel Alexandre, Tomás Calmeiro, Elvira Fortunato, Rodrigo Martins, Manuel J. Mendes and Hugo Águas
Micro 2021, 1(2), 215-227; https://doi.org/10.3390/micro1020016 - 11 Oct 2021
Cited by 5 | Viewed by 2990
Abstract
Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and [...] Read more.
Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and (2) the reduced sheet resistance of the front illuminated contact. This work developed a method for the fabrication and optimization of wavelength-sized indium zinc oxide (IZO) microstructures, which were soft-patterned on flexible indium tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) substrates via a simple, low-cost, versatile, and highly scalable colloidal lithography process. Using this method, the ITO-coated PET substrates patterned with IZO micro-meshes provided improved transparent electrodes endowed with strong light interaction effects—namely, a pronounced light scattering performance (diffuse transmittance up to ~50%). In addition, the photonic-structured IZO mesh allowed a higher volume of TCO material in the electrode while maintaining the desired transparency, which led to a sheet resistance reduction (by ~30%), thereby providing further electrical benefits due to the improvement of the contact conductance. The results reported herein pave the way for a new class of photonic transparent electrodes endowed with mechanical flexibility that offer strong potential not only as advanced front contacts for thin-film bendable solar cells but also for a much broader range of optoelectronic applications. Full article
(This article belongs to the Section Microscale Materials Science)
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21 pages, 4106 KiB  
Article
Comparison of the Therapeutic Effects of Native and Anionic Nanofibrillar Cellulose Hydrogels for Full-Thickness Skin Wound Healing
by Raili Koivuniemi, Qian Xu, Jasmi Snirvi, Irene Lara-Sáez, Arto Merivaara, Kari Luukko, Markus Nuopponen, Wenxin Wang and Marjo Yliperttula
Micro 2021, 1(2), 194-214; https://doi.org/10.3390/micro1020015 - 11 Oct 2021
Cited by 7 | Viewed by 4582
Abstract
Nanofibrillar cellulose (NFC)-derived dressings such as films, hydrogels, and aerogels are one of the favorable materials for wound healing due to their proper mechanical properties and water holding ability. However, the therapeutic differences between native and anionic NFC materials are rarely studied. In [...] Read more.
Nanofibrillar cellulose (NFC)-derived dressings such as films, hydrogels, and aerogels are one of the favorable materials for wound healing due to their proper mechanical properties and water holding ability. However, the therapeutic differences between native and anionic NFC materials are rarely studied. In this report, we compared the differences and addressed the regenerative potential of native and anionic wood-derived NFC hydrogels for wound treatment. In vitro characteristics of the hydrogels were detected using scanning electron microscopy, rheological measurements, and swelling and hemolytic activity assays. Skin regeneration at an early stage after hydrogel treatment was analyzed using an in vivo splinted excisional full-thickness skin wound model in C57BL/6 mice. Both native NFC and anionic NFC (ANFC) hydrogel with differing mechanical and surface properties were shown to be biocompatible. Surprisingly, wounds treated with NFC and ANFC hydrogel did not show any statistical difference compared with control wounds and progressed through normal wound closure, inflammatory response, re-epithelialization, vascularization, and tissue maturation with no signs of fibrosis. The data show here for the first time the therapeutic performance of native and anionic NFC hydrogel in a wound mimicking human wound healing mechanisms. The mechanical properties of native and anionic NFC hydrogels such as the capability to modify material stiffness may also prove to be valuable in the management of wounds in the future. Full article
(This article belongs to the Section Microscale Biology and Medicines)
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13 pages, 3768 KiB  
Article
Moderate Hypothermia Has the Potential to Reveal the Dominant/Submissive Relationship in a Co-Culture System Consisting of Osteoblasts and Endothelial Cells
by Kouki Inomata and Michiyo Honda
Micro 2021, 1(2), 181-193; https://doi.org/10.3390/micro1020014 - 27 Sep 2021
Viewed by 2697
Abstract
Microvessels in bone are indispensable for maintaining bone homeostasis based on a dynamic remodeling system. In cell-based tissue engineering, vascularization into the regenerative bone is a key strategy to avoid hypoxia and necrosis around re-implanted tissues. Previous studies have shown that direct contact [...] Read more.
Microvessels in bone are indispensable for maintaining bone homeostasis based on a dynamic remodeling system. In cell-based tissue engineering, vascularization into the regenerative bone is a key strategy to avoid hypoxia and necrosis around re-implanted tissues. Previous studies have shown that direct contact between osteoblasts and endothelial cells stimulates differentiation of both cell types. However, no studies have revealed the dominant/submissive relationship. In the present study, we examined the effect of hypothermia on monoculture and co-culture to assess which cells tightly coordinated osteogenesis and angiogenesis in the co-culture system. As for osteoblasts, exposure to hypothermia suppressed cellular proliferation, migration, and differentiation. Evaluation of the behavior of endothelial cells showed that hypothermia should not affect basic functions such as proliferation and migration. Under co-culture conditions, both osteogenic differentiation and the formation of vessel-like angiogenic structures were suppressed by hypothermia, but the spatial organization of alkaline phosphatase-positive cell clusters, which tend to localize around microvascular lumens, was not altered. These data suggest that hypothermia attenuates heterotypic intercellular crosstalk which robustly depends on osteoblasts to inhibit both osteogenesis and angiogenesis in the co-culture system. Taken together, this approach will provide new insights into the relationship between osteoblasts and endothelial cells in tissue engineering. Full article
(This article belongs to the Section Microscale Biology and Medicines)
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17 pages, 5089 KiB  
Article
Micro 3D Printing by Two-Photon Polymerization: Configurations and Parameters for the Nanoscribe System
by Ada-Ioana Bunea, Nuria del Castillo Iniesta, Ariadni Droumpali, Alexandre Emmanuel Wetzel, Einstom Engay and Rafael Taboryski
Micro 2021, 1(2), 164-180; https://doi.org/10.3390/micro1020013 - 25 Sep 2021
Cited by 44 | Viewed by 14211
Abstract
3D printing by two-photon polymerization enables the fabrication of microstructures with complex shapes and critical dimensions of a few hundreds of nanometers. On state-of-the art commercial two-photon polymerization systems, an immense 3D design freedom can be put into practice by direct laser writing [...] Read more.
3D printing by two-photon polymerization enables the fabrication of microstructures with complex shapes and critical dimensions of a few hundreds of nanometers. On state-of-the art commercial two-photon polymerization systems, an immense 3D design freedom can be put into practice by direct laser writing using a precise fabrication technology, which makes this approach highly attractive for different applications on the microscale, such as microrobotics, micro-optics, or biosensing. However, navigating the different possible configurations and selecting the optimal parameters for the fabrication process often requires intensive testing and optimization. In addition to the more established acrylate-based resins, there is a growing interest in the use of soft materials. In this paper, we demonstrate the fabrication of various microscale structures by two-photon polymerization using a Nanoscribe Photonic Professional GT+ commercial system. Furthermore, we describe the different configurations of the system and parameter selection, as well as commercial resins and their chemical and mechanical properties. Finally, we provide a short guide aiming to serve as starting point for the two-photon polymerization-based fabrication of various microscale architectures with distinct characteristics. Full article
(This article belongs to the Section Microscale Engineering)
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