In-plane anisotropic two-dimensional materials for twistronics.

In-plane anisotropic two-dimensional (2D) materials exhibit in-plane orientation-dependent properties. The anisotropic unit cell causes these materials to show lower symmetry but more diverse physical properties than in-plane isotropic 2D materials. In addition, the artificial stacking of in-plane anisotropic 2D materials can generate new phenomena that cannot be achieved in in-plane isotropic 2D materials. In this perspective we provide an overview of representative in-plane anisotropic 2D materials and their properties, such as black phosphorus, group IV monochalcogenides, group VI transition metal dichalcogenides with 1T' and Tdphases, and rhenium dichalcogenides. In addition, we discuss recent theoretical and experimental investigations of twistronics using in-plane anisotropic 2D materials. Both in-plane anisotropic 2D materials and their twistronics hold considerable potential for advancing the field of 2D materials, particularly in the context of orientation-dependent optoelectronic devices.

A literature review of bioactive substances for the treatment of periodontitis: In vitro, in vivo and clinical studies.

Periodontitis is a common chronic inflammatory disease of the supporting tissues of the tooth that involves a complex interaction of microorganisms and various cell lines around the infected site. To prevent and treat this disease, several options are available, such as scaling, root planning, antibiotic treatment, and dental surgeries, depending on the stage of the disease. However, these treatments can have various side effects, including additional inflammatory responses, chronic wounds, and the need for secondary surgery. Consequently, numerous studies have focused on developing new therapeutic agents for more effective periodontitis treatment. This review explores the latest trends in bioactive substances with therapeutic effects for periodontitis using various search engines. Therefore, this study aimed to suggest effective directions for therapeutic approaches. Additionally, we provide a summary of the current applications and underlying mechanisms of bioactive substances, which can serve as a reference for the development of periodontitis treatments.

Ishophloroglucin A-based multifunctional oxidized alginate/gelatin hydrogel for accelerating wound healing.

This study investigated the potential applicability of wound dressing hydrogels for tissue engineering, focusing on their ability to deliver pharmacological agents and absorb exudates. Specifically, we explored the use of polyphenols, as they have shown promise as bioactive and cross-linking agents in hydrogel fabrication. Ishophloroglucin A (IPA), a polyphenol not previously utilized in tissue engineering, was incorporated as both a drug and cross-linking agent within the hydrogel. We integrated the extracted IPA, obtained through the utilization of separation and purification techniques such as high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) into oxidized alginate (OA) and gelatin (GEL) hydrogels. Our findings revealed that the mechanical properties, thermal stability, swelling, and degradation of the multifunctional hydrogel can be modulated via intermolecular interactions between the natural polymer and IPA. Moreover, the controlled release of IPA endows the hydrogel with antioxidant and antimicrobial characteristics. Overall, the wound healing efficacy, based on intermolecular interactions and drug potency, has been substantiated through accelerated wound closure and collagen deposition in an ICR mouse full-thickness wound model. These results suggest that incorporating IPA into natural polymers as both a drug and cross-linking agent has significant implications for tissue engineering applications.

Recent trends in covalent functionalization of 2D materials.

Covalent functionalization of the surface is more crucial in 2D materials than in conventional bulk materials because of their atomic thinness, large surface-to-volume ratio, and uniform surface chemical potential. Because 2D materials are composed of two surfaces with no dangling bond, covalent functionalization enables us to improve or precisely modify the electrical, mechanical, and chemical properties. In this review, we summarize the covalent functionalization methods and related changes in properties. First, we discuss possible sites for functionalization. Consequently, functionalization techniques are introduced, followed by the direct synthesis of functionalized 2D materials and characterization methods of functionalized 2D materials. Finally, we suggest how the issues may be solved to enlarge the research area and understanding of the chemistry of 2D materials. This review will help in understanding the functionalization of 2D materials.

Antibiotic susceptibility of Bacillus velezensis.

We evaluated the antibiotic minimum inhibitory concentrations (MICs) of 123 Bacillus velezensis strains predominantly isolated from fermented soybean foods from Korea. When the 2018 European Food Safety Authority breakpoint values for Bacillus spp. were applied, all the strains were sensitive to chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, tetracycline and vancomycin, and eight strains (6.5%) were resistant to streptomycin. The population distribution in MIC tests with streptomycin was continuous and the profile was clearly different from that expected for acquired antibiotic resistance. As of 25 October 2021, there were 181 complete published genomes of B. velezensis strains; 175 (96.7%) and 136 (75.2%) of these strains, respectively, possess potential tetracycline and streptomycin resistance genes tetL and ant(6) in the chromosome. In Bacillus licheniformis, SpeG confers resistance to clindamycin and there is an 'speG' gene annotated in the genomes of 180 B. velezensis strains; however, the gene products exhibit ≤26.6% amino acid identity with that from B. licheniformis DSM 13T. All the potential antibiotic resistance genes in the 181 B. velezensis strains were intrinsic, and traits of lateral gene transfer were not found. In this context, B. velezensis may not present a high risk in terms of antibiotic resistance in food fermentation or human use.

Safety and Technological Characterization of Staphylococcus xylosus and Staphylococcus pseudoxylosus Isolates from Fermented Soybean Foods of Korea.

We evaluated the antibiotic susceptibilities, hemolytic activities, and technological properties of 36 Staphylococcus xylosus strains and 49 S. pseudoxylosus strains predominantly isolated from fermented soybean foods from Korea. Most of the strains were sensitive to chloramphenicol, erythromycin, gentamycin, kanamycin, lincomycin, oxacillin, tetracycline, and trimethoprim. However, 23 strains exhibited potential phenotypic acquired resistance to erythromycin, lincomycin, and tetracycline. Based on breakpoint values for staphylococci from the Clinical and Laboratory Standards Institute, >30% of the isolates were resistant to ampicillin and penicillin G, but the population distributions in minimum inhibitory concentration tests were clearly different from those expected for acquired resistance. None of the strains exhibited clear α- or ß-hemolytic activity. S. xylosus and S. pseudoxylosus exhibited salt tolerance on agar medium containing 20% and 22% (w/v) NaCl, respectively. S. xylosus and S. pseudoxylosus strains possessed protease and lipase activities, which were affected by the NaCl concentration. Protease activity of S. pseudoxylosus was strain-specific, but lipase activity might be a characteristic of both species. This study confirms the potential of both species for use in high-salt soybean fermentation, but the safety and technological properties of strains must be determined to select suitable starter candidates.

Fabrication and characterization of the 3D-printed polycaprolactone/fish bone extract scaffolds for bone tissue regeneration.

Fish bone extract (FBE) containing a trioligopeptide (FBP-KSA, Lys-Ser-Ala) isolated from Johnius belengerii could induce osteogenic activities on MC3T3-E1 pre-osteoblasts in our previous study. Regarding the osteogenic effect of FBE, in the present study, we fabricated the three-dimensional (3D) interconnected polycaprolactone (PCL)/FBE scaffolds for bone tissue regeneration. After fabrication of PCL scaffolds using 3D printing, FBE was coated on the surface of PCL scaffolds by self-assembly process. In the physical characteristic and mechanical property tests, the results demonstrated that the fabricated scaffolds have the strut diameter (between 340 and 345 µm), pore size (between 470 and 480 µm), porosity (between 50% and 55%), and tensile properties (Young's modulus: 9.18-9.42 MPa; max tensile strengths 82.3-87.4 MPa) were similar to those of PCL scaffold. In the cell proliferation and osteogenic assay, the results showed that PCL/FBE scaffolds could significantly induce cell proliferation, calcium deposition, and the expression of osteogenic phenotype markers such as alkaline phosphatase, osteopontin, osteocalcin, and bone morphogenetic protein-2 in the osteoblasts. These results suggest that FBE-coated PCL scaffolds are promising materials for use in biomedical application to promote bone tissue regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1937-1944, 2019.

Droplet Impinging Behavior on Surfaces with Wettability Contrasts.

Heterogeneous substrates with moderate and extreme wettability contrasts were fabricated by comprising of superhydrophobic/hydrophilic and superhydrophobic/extremely hydrophilic surfaces, respectively. The interactions of water droplets impinging on the surfaces with sharp wettability contrasts were investigated experimentally. The impinging droplets that slightly touch the hydrophilic or extremely hydrophilic areas on each substrate exhibit a directional rebounding towards the more wetting surfaces, i.e., hydrophilic or extremely hydrophilic surface. The trajectory and landing distance of the rebounded droplets were tailored by controlling the releasing height of the droplet, wetting contrast across the border, and portion of the droplet touching the more wetting surface of the substrates with wettability contrasts. The landing distance of the droplet increases with the increased releasing height and higher wettability contrast across the border. Increasing the portion of the impinging droplet touching the more wetting surface of the heterogeneous substrates leads to the shorter landing distance of rebounded droplets.

Hydrothermal Growth of ZnO Nanowires on UV-Nanoimprinted Polymer Structures.

Integration of zinc oxide (ZnO) nanowires on miniaturized polymer structures can broaden its application in multi-functional polymer devices by taking advantages of unique physical properties of ZnO nanowires and recent development of polymer microstructures in analytical systems. In this paper, we demonstrate the hydrothermal growth of ZnO nanowires on polymer microstructures fabricated by UV nanoimprinting lithography (NIL) using a polyurethane acrylate (PUA). Since PUA is a siloxane-urethane-acrylate compound containing the alpha-hydroxyl ketone, UV-cured PUA include carboxyl groups, which inhibit and suppress the nucleation and growth of ZnO nanowires on polymer structures. The presence of carboxyl groups in UV-cured PUA was substantiated by Fourier transform infrared spectroscopy (FTIR), and a Ag thin film was deposited on the nanoimprinted polymer structures to limit their inhibitive influence on the growth of ZnO nanowires. Furthermore, the naturally oxidized Ag layer (Ag2O) reduced crystalline lattice mismatches at the interface between ZnO-Ag during the seed annealing process. The ZnO nanowires grown on the Ag-deposited PUA microstructures were found to have comparable morphological characteristics with ZnO nanowires grown on a Si wafer.

Fish bone peptide promotes osteogenic differentiation of MC3T3-E1 pre-osteoblasts through upregulation of MAPKs and Smad pathways activated BMP-2 receptor.

Fish bone, a by-product of fishery processing, is composed of protein, calcium, and other minerals. The objective of this study was to investigate the effects of a bioactive peptide isolated from the bone of the marine fish, Johnius belengerii, on the osteoblastic differentiation of MC3T3-E1 pre-osteoblasts. Post consecutive purification by liquid chromatography, a potent osteogenic peptide, composed of 3 amino acids, Lys-Ser-Ala (KSA, MW: 304.17 Da), was identified. The purified peptide promoted cell proliferation, alkaline phosphatase activity, mineral deposition, and expression levels of phenotypic markers of osteoblastic differentiation in MC3T3-E1 pre-osteoblast. The purified peptide induced phosphorylation of mitogen-activated protein kinases, including p38 mitogen-activated protein kinase, extracellular regulated kinase, and c-Jun N-terminal kinase as well as Smads. As attested by molecular modelling study, the purified peptide interacted with the core interface residues in bone morphogenetic protein receptors with high affinity. Thus, the purified peptide could serve as a potential pharmacological substance for controlling bone metabolism.

3D nanomolding and fluid mixing in micromixers with micro-patterned microchannel walls.

Microfluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.Graphical abstractIn this paper we show that a micromixer with patterned walls can be fabricated using 3D nanomolding and solvent-assisted bonding to manipulate the flow patterns to improve mixing.

Surface modification of droplet polymeric microfluidic devices for the stable and continuous generation of aqueous droplets.

Droplet microfluidics performed in poly(methyl methacrylate) (PMMA) microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid-liquid segmented flow when using a hydrophobic carrier fluid such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with nonuniform sizes that were often trapped on the wall surfaces, leading to unstable and poorly controlled liquid-liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used to make microfluidic devices. The surface-modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution-phase reaction with heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane dissolved in fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful in reducing the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils.

Titer-plate formatted continuous flow thermal reactors: Design and performance of a nanoliter reactor.

Arrays of continuous flow thermal reactors were designed, configured, and fabricated in a 96-device (12 × 8) titer-plate format with overall dimensions of 120 mm × 96 mm, with each reactor confined to a 8 mm × 8 mm footprint. To demonstrate the potential, individual 20-cycle (740 nL) and 25-cycle (990 nL) reactors were used to perform the continuous flow polymerase chain reaction (CFPCR) for amplification of DNA fragments of different lengths. Since thermal isolation of the required temperature zones was essential for optimal biochemical reactions, three finite element models, executed with ANSYS (v. 11.0, Canonsburg, PA), were used to characterize the thermal performance and guide system design: (1) a single device to determine the dimensions of the thermal management structures; (2) a single CFPCR device within an 8 mm × 8 mm area to evaluate the integrity of the thermostatic zones; and (3) a single, straight microchannel representing a single loop of the spiral CFPCR device, accounting for all of the heat transfer modes, to determine whether the PCR cocktail was exposed to the proper temperature cycling. In prior work on larger footprint devices, simple grooves between temperature zones provided sufficient thermal resistance between zones. For the small footprint reactor array, 0.4 mm wide and 1.2 mm high fins were necessary within the groove to cool the PCR cocktail efficiently, with a temperature gradient of 15.8°C/mm, as it flowed from the denaturation zone to the renaturation zone. With temperature tolerance bands of ±2°C defined about the nominal temperatures, more than 72.5% of the microchannel length was located within the desired temperature bands. The residence time of the PCR cocktail in each temperature zone decreased and the transition times between zones increased at higher PCR cocktail flow velocities, leading to less time for the amplification reactions. Experiments demonstrated the performance of the CFPCR devices as a function of flow velocity, fragment length, and copy number. A 99 bp DNA fragment was successfully amplified at flow velocities from 1 mm/s to 3 mm/s, requiring from 8.16 minutes for 20 cycles (24.48 s/cycle) to 2.72 minutes for 20 cycles (8.16 s/cycle), respectively. Yield compared to the same amplification sequence performed using a bench top thermal cycler decreased nonlinearly from 73% (at 1 mm/s) to 13% (at 3 mm/s) with shorter residence time at the optimal temperatures for the reactions due to increased flow rate primarily responsible. Six different DNA fragments with lengths between 99 bp and 997 bp were successfully amplified at 1 mm/s. Repeatable, successful amplification of a 99 bp fragment was achieved with a minimum of 8000 copies of the DNA template. This is the first demonstration and characterization of continuous flow thermal reactors within the 8 mm × 8 mm footprint of a 96-well micro-titer plate and is the smallest continuous flow PCR to date.