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Three-dimensional (3D) bioprinting has attracted considerable attention for producing 3D engineered cellular microenvironments that replicate complex and sophisticated native extracellular matrices (ECM) as well as the spatiotemporal gradients of numerous physicochemical and biological cues. Although various hydrogel-based bioinks have been reported, the development of advanced bioink materials that can reproduce the complexity of ECM accurately and mimic the intrinsic property of laden cells is still a challenge. This paper reports 3D printable bioinks composed of phenol-rich gelatin (GHPA) and graphene oxide (GO) as a component for a myogenesis-inducing material, which can form a hydrogel network in situ by a dual enzyme-mediated cross-linking reaction. The in situ curable GO/GHPA hydrogel can be utilized successfully as 3D-printable bioinks to provide suitable cellular microenvironments with facilitated myogenic differentiation of C2C12 skeletal myoblasts. Overall, we suggest that functional bioinks may be useful in muscle tissue engineering and regenerative medicine.

As a model quasi-2D network intercalation electrodes, niobium pentoxide (Nb2O5) has gained numerous attention in electrochemical materials because of its structural stability and high safety. Nevertheless, Nb2O5 exhibits the inherent low conductivity of transition metal oxides, which limits the rate of ionic diffusion and charge transfer. To overcome the drawbacks, the nanoscale Nb2O5 can be synthesized to improve electrochemical performance. Here, we prepared the flower-like orthorhombic Nb2O5 (i.e., T-Nb2O5) nanostructures to evaluate the effect of Nb2O5 nanoparticle morphology associated with crystallinity for lithium-ion batteries (LIBs) anode. T-Nb2O5-2 displays superior crystallinity, pore structure, capacity, reversibility, and cycling stability. Specifically, T-Nb2O5-2 exhibits the initial charge/discharge capacity of 289 and 525 mAh g−1 at 0.1 C, and after 100 cycles, the capacity is 178.2 mAh g−1 at 1 C when the solvothermal time is 16 h. This study shows that Nb2O5 with good crystallinity can slow down the volume expansion and structural deformation generated during the intercalation–deintercalation of Li-ions. We believe that the specified Nb2O5 presented in this work has great potential as a promising candidate for high-performance LIB anodes.

Nb2O5 has attracted much attention in various research filed such as hybrid capacitors, photo/electrocatalysis, and especially Li-ion batteries (LIBs) due to stable structure and high safety. Nevertheless, its low electronic conductivity (~ 3×10−6 S cm−1) degrades Li-storage performance that limits the practical use in LIBs. Here, we present a facile method for synthesis of T-Nb2O5 nanospheres/reduced graphene oxide composites by using niobium oxalate and bituminous coal as raw materials via a solvothermal method and subsequent calcination to enhance the conductivity of Nb2O5. In this work, the prepared Nb2O5 particles have excellent crystallinity that can be uniformly distributed onto the surface of the rGO layer to form Nb2O5/rGO composites. The electrochemical properties indicate that Nb2O5/rGO electrodes exhibit outstanding capacity, excellent reversibility, and superior cycle stability compared to other transition metal oxide-based electrodes. Notably, the initial capacities of the Nb2O5/rGO electrode at 0.02 A g−1 are 603 and 1104 mAh g−1, and the capacity still maintained 332 mAh g−1 after 100 cycles at 0.2 A g−1. Our synthetic approach provides a viable route to produce anode materials in a composite form facilitating nanostructured Nb2O5 with rGO exfoliated from bituminous coal for excellent performance in LIBs.

Cells respond directly to the chemical and topographical cues of the engineered substrate. To date, recent extensive studies have been witnessed on the wide development of biomimetic substrates that can regulate the cellular behaviors by establishing the specific cues of the substrate. It is well known that the topographical features with nanoscale and microscale strongly modulate the behaviors of cells, including adhesion, migration, proliferation, and differentiation. Herein, we present a simple and robust strategy to generate the patterned arrays of reduced graphene oxide (rGO) on a substrate to be used for the cellular interfaces. The rGO patterned arrays were prepared by an evaporative self-assembly process, which is a highly efficient technique for the controlled deposition of rGO sheets on a flat substrate. Such periodic patterned arrays of rGO could be utilized as a micron topographic substratum for living cell culture to observe the growth and alignment behaviors of C2C12 skeletal and vascular smooth muscle cells (VSMCs). The exquisite evaluations showed that both cells were regularly grown along the rGO patterned arrays leading to the well-defined contact guidance, but the only C2C12 myoblasts exhibited slightly higher level in the morphological alignment features to the rGO patterned arrays, compared to the VSMCs. Our findings suggest that the nanotextured thin films and patterned arrays of rGO can serve as promising biomimetic substrates for skeletal muscle cells and provide subtle effects on cellular morphology discriminating in their responses.

Graphical Abstract The topographical interface of the extracellular environment has been appreciated as a principal biophysical regulator for modulating cell functions, such as adhesion, migration, proliferation, and differentiation. Despite the existed approaches that use two-dimensional nanomaterials to provide beneficial effects, opportunities evaluating their impact on stem cells remain open to elicit unprecedented cellular responses. Herein, we report an ultrathin cell-culture platform with potential-responsive nanoscale biointerfaces for monitoring mesenchymal stem cells (MSCs). We designed an intriguing nanostructured array through self-assembly of graphene oxide sheets and subsequent lithographical patterning method to produce chemophysically defined regions. MSCs cultured on anisotropic micro/nanoscale patterned substrate were spontaneously organized in a highly ordered configuration mainly due to the cell-repellent interactions. Moreover, the spatially aligned MSCs were spontaneously differentiated into smooth muscle cells upon the specific crosstalk between cells. This work provides a robust strategy for directing stem cells and differentiation, which can be utilized as a potential cell culture platform to understand cell–substrate or cell–cell interactions, further developing tissue repair and stem cell-based therapies. Supplementary Information The online version contains supplementary material available at 10.1186/s12951-021-01225-4.

During the last decade, graphene-family nanomaterials have been widely utilized, forming a composite with various polymers for potential applications in tissue engineering and regeneration due to their excellent physicochemical characteristics and biocompatibility. Above all, these graphene-family nanomaterials allow polymers to have novel biofunctional properties, while maintaining their intrinsic character. By virtue of this bioactivity of nanocomposites, they are able to modulate cellular behaviours such as cell attachment, proliferation and differentiation. In this study, the nanofibre composite matrices of poly(L-lactide-co-e-caprolactone) (PLCL) and laminin (Lam) functionalized with graphene oxide (GO) (PLCL/Lam/GO) were prepared via electrospinning to explore whether they have the potential to enhance the differentiation of hippocampal neuronal cells. The PLCL/Lam/GO nanofibre matrices could support the adhesion and proliferation of hippocampal neuronal cells by providing the extracellular matrix-like structure. Furthermore, these PLCL/Lam/GO composite matrices were found to promote neurite outgrowth and alignment from hippocampal neuronal cells through providing optimal microenvironments for neuronal differentiation. The underlying mechanism of this phenomenon was proposed according to the scenario in which neurite outgrowth was guided by biofunctional cues, such as Lam and GO, with nanofibre-mediated topographical cues, which upregulated the expression of some specific genes (i.e., DCX, MAP2 and Nestin) closely related to cytoskeletal interactions. In conclusion, it is suggested that these nanofibre composite matrices can be exploited to craft a range of strategies for the development of novel scaffolds to accelerate neural regeneration.

Background The excellent physicochemical properties of graphene-based materials, including graphene oxide (GO) and reduced GO (rGO), offer significant technological potential as multifunctional nanomaterials in biomedical fields. Lutein is a type of carotenoid that forms human macular pigments in the retina, where it inhibits harmful blue light and contributes to the strengthening of the antioxidant defense of retinal pigment epithelium cells. Methods Synthesis of the Lutein-rGO (Lu–rGO) complex was carried out for the optimized concentration. Then characterization of material was analyzed through ultraviolet-visible spectrophotometer (UV-Vis spectra), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). Antioxidant activity of Lu–rGO complex was measured by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2.2-diphenyl-1-picrylhydrazyl (DPPH), glutathione (GSH) oxidation assay. Then, oxidative stress induction by blue light and analyzed intracellular reactive oxygen species (ROS). Results and Conclusion Based on the FT-IR measurement, the reduction efficiency defined by area was found to be 87.3%, the ID/IG ratio of 0.98 demonstrated by the Lu–rGO complex in the Raman spectrum was slightly higher than that of the original GO. The exhibited significant decrease in the peak intensities of the oxygen functional groups of the XPS spectra of the Lu–rGO complex was observed compared with the GO. In the TEM image for the Lu–rGO complex, folded and wrinkled nanostructures over the lutein-covered rGO surface were evidenced by tight molecular binding. The Lu–rGO complex provided superior DPPH and ABTS radical scavenging activity than GO and lutein alone, and the oxidation of GSH was suppressed. It was confirmed that the content of intracellular ROS and lysosomes, increased by blue light, was reduced after treatment with the Lu–rGO complex on ARPE-19 cells. In summary, graphene-based nanocarriers could function as preventative antioxidants during photochemical ROS generation based on the mechanism of antioxidant action., Graphical Abstract

Recently, black phosphorus (BP) has garnered great attention as one of newly emerging two-dimensional nanomaterials. Especially, the degraded platelets of BP in the physiological environment were shown to be nontoxic phosphate anions, which are a component of bone tissue and can be used for mineralization. Here, our study presents the potential of BP as biofunctional and biocompatible nanomaterials for the application to bone tissue engineering and regeneration. An ultrathin layer of BP nanodots (BPNDs) was created on a glass substrate by using a flow-enabled self-assembly process, which yielded a highly uniform deposition of BPNDs in a unique confined geometry. The BPND-coated substrates represented unprecedented favorable topographical microenvironments and supportive matrices suitable for the growth and survival of MC3T3-E1 preosteoblasts. The prepared substrates promoted the spontaneous osteodifferentiation of preosteoblasts, which had been confirmed by determining alkaline phosphatase activity and extracellular calcium deposition as early- and late-stage markers of osteogenic differentiation, respectively. Furthermore, the BPND-coated substrates upregulated the expression of some specific genes (i.e., RUNX2, OCN, OPN, and Vinculin) and proteins, which are closely related to osteogenesis. Conclusively, our BPND-coating strategy suggests that a biologically inert surface can be readily activated as a cell-favorable nanoplatform enabled with excellent biocompatibility and osteogenic ability.

Surface imprinting used for template recognition in nanocavities can be controlled and improved by surface morphological changes. Generally, the lithographic technique is used for surface patterning concerning sensing signal amplification in molecularly imprinted polymer (MIP) thin films. In this paper, we describe the effects of silanized silica molds on sensing the properties of MIP films. Porous imprinted poly(MAA–co–EGDMA) films were lithographically fabricated using silanized or non-treated normal silica replica molds to detect 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide as the standard template. The silanized mold MIP film (st-MIP) (Δf = −1021 Hz) exhibited a better sensing response than the non-treated normal MIP (n-MIP) (Δf = −978 Hz) because the imprinting effects, which occurred via functional groups on the silica surface, could be reduced through silane modification. Particularly, two non-imprinted (NIP) films (st-NIP and n-NIP) exhibited significantly different sensing responses. The st-NIP (Δfst-NIP = −332 Hz) films exhibited lower Δf values than the n-NIP film (Δfn-NIP = −610 Hz) owing to the remarkably reduced functionality against nonspecific adsorption. This phenomenon led to different imprinting factor (IF) values for the two MIP films (IFst-MIP = 3.38 and IFn-MIP = 1.86), which was calculated from the adsorbed 2,4-D mass per poly(MAA–co–EGDMA) unit weight (i.e., QMIP/QNIP). Moreover, it was found that the st-MIP film had better selectivity than the n-MIP film based on the sensing response of analogous herbicide solutions. As a result, it was revealed that the patterned molds’ chemical surface modification, which controls the surface functionality of imprinted films during photopolymerization, plays a role in fabricating enhanced sensing properties in patterned MIP films.

Background Titanium (Ti) has been utilized as hard tissue replacement owing to its superior mechanical and bioinert property, however, lack in tissue compatibility and biofunctionality has limited its clinical use. Reduced graphene oxide (rGO) is one of the graphene derivatives that possess extraordinary biofunctionality and are known to induce osseointegration in vitro and in vivo. In this study, rGO was uniformly coated by meniscus-dragging deposition (MDD) technique to fabricate rGO-Ti substrate for orthopedic and dental implant application. Methods The physicochemical characteristics of rGO-coated Ti (rGO-Ti) substrates were evaluated by atomic force microscopy, water contact angle, and Raman spectroscopy. Furthermore, human mesenchymal stem cells (hMSCs) were cultured on the rGO-Ti substrate, and then their cellular behaviors such as growth and osteogenic differentiation were determined by a cell counting kit-8 assay, alkaline phosphatase (ALP) activity assay, and alizarin red S staining. Results rGO was coated uniformly on Ti substrates by MDD process, which allowed a decrease in the surface roughness and contact angle of Ti substrates. While rGO-Ti substrates significantly increased cell proliferation after 7 days of incubation, they significantly promoted ALP activity and matrix mineralization, which are early and late differentiation markers, respectively. Conclusion It is suggested that rGO-Ti substrates can be effectively utilized as dental and orthopedic bone substitutes since these graphene derivatives have potent effects on stimulating the osteogenic differentiation of hMSCs and showed superior bioactivity and osteogenic potential.

A dataset in this report is regarding an article “Ultrathin Effective TiN Protective Films Prepared by Plasma-Enhanced Atomic Layer Deposition for High Performance Metallic Bipolar Plates of Polymer Electrolyte Membrane Fuel Cells” [1] . TiN (Titanium Nitride) thin films were deposited by Plasma-Enhanced Atomic Layer Deposition (PEALD) method using well known two types of precursor: using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4), and plasma. Summarized reports, growth characteristics (growth rate as a function of each precursor pulse time, plasma power, precursor and plasma purge time, thickness depending on the number of PEALD cycles), each precursor structural information and the atomic force micrographs (AFM) data are herein demonstrated. For TDMAT-TiN, N2 plasma was used as a reactant whereas, H2+N2 plasma was used as TiCl4-TiN reactant. To apply the bipolar plate substrate, two types of TiN thin films were introduced into Stainless steel (SUS) 316L.

Graphene, a two-dimensional (2D) carbon nanomaterial, has received great attention owing to its advantageous characteristics, including superior electrical, chemical and physical properties. In particular, exfoliation of graphite with strong oxidants has been explored to prepare a suspension of individual 2D graphene oxide (GO) nanosheets dispersed in various types of solvents. This colloidal suspension can readily be employed in a wide range of promising potential applications. However, one major challenge is to assemble such individual nanosheets on defined areas of surfaces forming specific structures. Here, we developed a simple and robust one-step strategy to create highly regular ordered nanostructures composed of chemically reduced graphene oxide (rGO) nanosheet building blocks on SiO2/Si or glass substrates over large areas. An aqueous suspension of rGO nanosheets dispersed in a volatile solvent was subjected to a confined geometry to induce a spontaneous formation of rGO patterned arrays with unprecedented regularity by utilizing both a controlled coffee ring effect and consecutive stick-slip motions of rGO solutions during the drying process. As a result, the generation of ultrathin nanotextured films in the form of micropatterns (i.e., concentric gradient rGO coffee rings) was effectively tailored. As a biological approach, to fully utilize patterned rGO associated with the nanoscale surface topography, we used these patterned rGO arrays as a biomimetic in vitro architecture to study interfacial interactions of living cells such as fibroblasts, myoblasts, and neuronal cells. The observed results show that the patterned rGO arrays can be used as manipulated cellular responsive templates to form living cell assemblies and related patterns that are useful for regenerative tissue engineering.

In this study, formaldehyde (HCHO)-imprinted hemispherical pore-patterned thin films, consisting of poly(2-(trifluoromethyl)acrylic acid–co–ethylene glycol dimethacrylate–co–styrene) (poly(TFMAA–co–EGDMA–co–ST)), were fabricated using the design of molecularly imprinted polymers (MIPs) and a subsequent lithographic micro/nanoimprinting method to amplify HCHO sensing signals in quartz crystal microbalance (QCM) sensors. Its molecular imprinting condition was optimized by controlling the added amount of a ST monomer in a MIP precursor solution. From the resonant frequency change with respect to HCHO adsorption, the imprinting factor of the porous MIP film was calculated to have a value of 2.38 and the sensitivity (0.132 mg g−1 ppm−1) of the porous MIP film exhibited markedly improved characteristics with respect to the porous non-imprinted polymer (NIP) film (0.05 mg g−1 ppm−1). The selectivity of the MIP-QCM sensors for the detection of HCHO was examined in the presence of other analogous toxic gases such as hydrogen chloride and hydrogen fluoride. The HCHO-absorbed porous MIP film had higher selective features with selectivity coefficients (k* ≈ 3.83 (HCl) and 4.46 (HF)) than porous NIP films (k* ≈ 1.53 (HCl) and 2.20 (HF)). Moreover, the relative selectivity of the porous MIP film appeared to be 2.03–2.5, which was higher than those of the planar MIP film (1.70–1.73).

In recent years, much research has been suggested and examined for the development of tissue engineering scaffolds to promote cellular behaviors. In our study, RGD peptide and graphene oxide (GO) co-functionalized poly(lactide-co-glycolide, PLGA) (RGD-GO-PLGA) nanofiber mats were fabricated via electrospinning, and their physicochemical and thermal properties were characterized to explore their potential as biofunctional scaffolds for vascular tissue engineering. Scanning electron microscopy images revealed that the RGD-GO-PLGA nanofiber mats were readily fabricated and composed of random-oriented electrospun nanofibers with average diameter of 558 nm. The successful co-functionalization of RGD peptide and GO into the PLGA nanofibers was confirmed by Fourier-transform infrared spectroscopic analysis. Moreover, the surface hydrophilicity of the nanofiber mats was markedly increased by co-functionalizing with RGD peptide and GO. It was found that the mats were thermally stable under the cell culture condition. Furthermore, the initial attachment and proliferation of primarily cultured vascular smooth muscle cells (VSMCs) on the RGD-GO-PLGA nanofiber mats were evaluated. It was revealed that the RGD-GO-PLGA nanofiber mats can effectively promote the growth of VSMCs. In conclusion, our findings suggest that the RGD-GO-PLGA nanofiber mats can be promising candidates for tissue engineering scaffolds effective for the regeneration of vascular smooth muscle.

In this article, we describe a facile method to fabricate MIP patterns in specifically designed microfluidic channels. With this design, homogenous and stable MIP films were spatially immobilized inside the patterned PDMS channels. In this system, the fluorescent response was identified by detection of the fluorescence-labeled bovine serum albumin (BSA) template. In comparison, non-imprinted polymer (NIP) was also prepared. From the results of fluorescent response, significant binding behaviors of BSA molecules into the cavities of MIP patterns was observed due to the increased residence time in each ancillary hexagonal channel caused by the turbulent flow. However, the NIP patterns did not show the fluorescent response. Thus, the use of this system provides effective MIP-based microfluidic channels for the application of biosensors.

We developed amorphous porous carbon (i.e. humic acid resin-based amorphous porous carbon, HARC800) with the controlled porosity in the ordered structure as anode material for sodium-ion batteries (SIBs) through the optimized annealing process supported by functional lignite and sodium alginate precursors. HARC800 has well-developed interconnected mesoporous and micropores, accounting for 85.7% and 14.3%, respectively. The porous characteristic of amorphous carbon materials can curtail the diffusion path of Na+, and promote the penetration of electrolyte in the material, which is very instrumental in intensify the dynamic property of the material, thereby promoting the storage of Na+. When it is applied to the anode for SIBs, the HARC800 provides an initial reversible capacity of 260 mA h g−1 at 30 mA g−1. Even at 2000 mA g−1, it appears 99 mA h g−1, indicating that it has excellent rate performance. It could be yielded 133 mA h g−1 after 200 cycles at 500 mA g−1, and maintain 119 mA h g−1 after 1000 cycles at 1000 mA g−1, suggesting its outstanding long-life cycle performance. This research proposes that reasonable control of the ratio of mesoporous and micropores can promote the Na+ storage performance of amorphous porous carbon materials.

Guided bone regeneration (GBR) is a technique where a barrier membrane is placed over the bone defect to prevent cell growth from the connective tissue and epithelium. Titanium (Ti) has excellent mechanical properties and is one of the most frequently used materials in implant dentistry. This study examined how graphene oxide (GO)-coated Ti (GO-Ti) membranes can enhance the osteogenesis of MC3T3-E1 preosteoblasts and promote new bone formation for potential applications to GBR. The physicochemical properties of GO-Ti membranes were characterized by atomic force microscopy, Raman spectroscopy, X-ray diffraction, and contact angle measurements. The cellular behaviors of MC3T3-E1 preosteoblasts on GO-Ti membranes were examined by cell counting kit-8 and alkaline phosphatase (ALP) activity assays. The effects of GO-Ti membranes on bone regeneration were evaluated by implanting them into rat calvarial defects. GO was coated uniformly on Ti substrates, which allowed a decrease in surface roughness and c...

Recently, numerous studies have focused on the development of scaffolds for skeletal tissue engineering and regeneration with various structures. Among various structures, in situ forming hydrogels have attracted considerable attention because they can provide 3D microenvironments for cells, and their stiffness and elasticity can be easily controlled by physical or chemical means. Over the last decade, graphene oxide (GO) has been widely explored as a potential candidate for biomaterials because of its excellent physicochemical properties and outstanding biocompatibility. In this study, horseradish peroxide-reactive gelatin polymer (GH) hydrogels incorporated with GO were prepared and their physicochemical and biomechanical properties were characterized by scanning electron microscopy, Raman and Fourier transform-infrared spectroscopy, ther-mogravimetric analysis, and rheological study. The cellular behaviors of the C2C12 myoblasts within the GO-incorporated GH (GH/GO) hydrogels were examined by a...

Bisphenol A (BPA), which is extensively used in the plastic industry, is a known endocrine disrupting chemical whose release into the environment from industrial products is detrimental to human health. In this study, to characterize BPA-detectable imprinted films on quartz crystals (QCs), sensitive molecularly imprinted quartz crystal microbalance (MIP-QCM) sensors were fabricated. The MIP films were synthesized on 2D porous SiO2 and Au pinholes that were generally observed from replica structures prepared using a polystyrene colloidal monolayer as an insulating mold. For MIP film formation, surface-initiated atom transfer radical polymerization was precisely controlled to adjust the MIP film growth on initiator-modified porous structures. Note that three BPA-imprinted poly(4-VP-co-EGDMA) films, i.e., MIP(8-h), MIP(16-h), and MIP(24-h), under reaction time control were successfully prepared. Furthermore, all imprinted patterned surfaces were characterized via atomic force microscopy (AFM) and scanning electron microscopy (SEM). The MIP(24-h) film demonstrated the highest imprinting factor (i.e., IF ≈ 2.4) and sensitivity (i.e., 1.219 ± 0.079 Hz nM−1), although the maximum binding capacity (Qmax) and binding capacity (Qe) at 1-h rebinding equilibrium was relatively lesser than those of the MIP(8-h) and MIP(16-h) owing to the differentiation of the deposited MIP mass. Using the Freundlich isotherm model, the binding affinity of the BPA imprinted MIP films measured in an aqueous solution of BPA whose concentration ranged between 45 and 225 nM was evaluated. Finally, the selectivity of the MIP-QCM sensors for BPA detection was investigated in aqueous solutions in the presence of other analogous chemicals such as bisphenol F (BPF), bisphenol AP (BPAP), and bisphenol B (BPB). The MIP(8-h) film showed extremely high recovery percentage (≈ 94.54 %) owing to the relatively thinner film formation, which was significantly comparable with that of other MIP films, i.e., 68.37 % for MIP(16-h) and 61.99 % for MIP(24-h). However, the MIP(24-h) film appeared to have higher selective features with selectivity coefficients and relative selectivity (k* and k’ ≈ 2.5, respectively) despite measurement in a limited period (i.e., 1-h rebinding process).

The stainless steel (SS)-based bipolar plate with high conductivity and corrosion resistance is one of the key components in recent polymer electrolyte membrane fuel cells. Therefore, an excellent corrosion protection and good electrical conductivity in SS316L-based bipolar plates can be achieved through plasma-enhanced atomic layer deposition (PEALD) of ultrathin (25–67 nm) TiN thin films. To this end, two types of TiN protective coatings deposited by PEALD using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4) precursors were evaluated; the evaluations were conducted under conditions simulating the operating conditions of PEMFCs. Regardless of the precursor type, PEALD-TiN onto SS316L resulted in great improvements in electrical conductivity and corrosion resistance. Notably, the TiN thin films prepared using TDMAT exhibited excellent corrosion resistance (

Osteoprogenitor cells, known as preosteoblasts, that arise from mesenchymal stem cells in the bone marrow are types of cells that work in the growth or repair of bones. These cells possess the prominent potential to differentiate toward the osteogenic lineage, and therefore offer promising opportunities for bone tissue engineering and regenerative therapy. However, to fully exploit the application of osteoprogenitor cells in bone regeneration, it is critical to develop biochemical, physical or pharmaceutical factors that can precisely control their osteogenic differentiation. In this study, we hypothesized that reduced graphene oxide (rGO) and hydroxyapatite (HAp) composites could synergistically enhance the osteogenic differentiation of preosteoblasts. Without interference with the proliferation of MC3T3-E1 preosteoblasts, rGO/HAp composites synergistically enhanced the osteogenic differentiation of the preosteoblasts, which had been confirmed by determining alkaline phosphatase activity and mineralization of calcium and phosphate as early and late stage markers of osteogenic differentiation. This osteogenic activity mediated by rGO/HAp composites was further accelerated under osteogenic culture conditions. It is suggested that rGO/HAp hybrid composites can serve as biocompatible, transferable, and implantable scaffolds for bone regeneration because these graphene-based composite materials have the potential to promote spontaneous osteogenesis in the absence of any osteogenic factors.

In this paper, we examined a novel molecularly imprinted polymer (MIP) patterned matrix, consisting of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as functional and cross-linking monomers, respectively, for detection of trace atrazine in an aqueous solution. A solvent assisted soft lithography and UV-initiated polymerization were used to develop striped poly(MAA-EGDMA) patterns. In comparison to a planar MIP film (Δ f p-MIP = −158 Hz), the striped patterns showed faster sensing response (Δ f s-MIP = −269 Hz) for the 30 min detection period due to the relatively increased binding sites generated from the MIP stripes. Furthermore, the sensitivity of the MIP sensor was found to be −9.98 Hz (μM) −1 via gravimetric quartz crystal microbalance (QCM) measurements and the selectivity of the MIP stripes was evaluated through sensing characteristics of other herbicides. Thus, a control of binding sites via this lithographic technique could contribute to the development of efficient MIP sensing platforms.

We present broadband antireflective microstructures (AMSs) for high-performance imaging systems in mid- and far-infrared wavelength ranges. Diffraction efficiencies of AMSs on ZnS substrates were calculated using a rigorous coupled wave analysis method. The results show the effect of height, period, and shape of AMSs on the reflection characteristics. We also discuss the optimum geometry of AMSs by considering fabrication tolerances.

Hierarchically arranged stripes of photoswitchable liquid crystal polymers (LCPs) containing azobenzene moieties were conveniently crafted via a flow-enabled self-assembly (FESA). Interestingly, by subjecting a drop of LCP solution to dry in a restricted geometry comprising two nearly parallel plates with a stationary upper plate and a movable lower plate that programmably traveled in a "stop-and-move" manner during the FESA process, photoswitchable LCP stripes were yielded, displaying two modes of deposition, namely, periodic primary stripes of large dimensions and regularly spaced secondary stripes of small dimensions situated between adjacent primary stripes (i.e., forming hierarchical LCP stripes). Notably, these hierarchical azobenzene moieties-containing stripes demonstrated sequential photoinduced reversible phase transition (i.e., photoswitching) due to the thickness difference between primary and secondary stripes. A UV light-induced expansion effect was observed on the LCP stripes. Clearly, such rapid creation of hierarchical stripes by FESA represents a robust means of organizing polymers, nanoparticles, colloids, DNA, etc. into complex yet ordered patterns over a large area in a simple and controllable manner for potential use in surface relief grating, photoactuators, photoswitchable devices, antifake labels, etc.

Extracellular matrices (ECMs) are network structures that play an essential role in regulating cellular growth and differentiation. In this study, novel nanofibrous matrices were fabricated by electrospinning M13 bacteriophage and poly(lactic-co-glycolic acid) (PLGA) and were shown to be structurally and functionally similar to natural ECMs. A genetically-engineered M13 bacteriophage was constructed to display Arg-Gly-Asp (RGD) peptides on its surface. The physicochemical properties of RGD peptide-displaying M13 bacteriophage (RGD-M13 phage)/PLGA nanofibers were characterized by using scanning electron microscopy and Fourier-transform infrared spectroscopy. We used immunofluorescence staining to confirm that M13 bacteriophages were homogenously distributed in RGD-M13 phage/PLGA matrices. Furthermore, RGD-M13 phage/PLGA nanofibrous matrices, having excellent biocompatibility, can enhance the behaviors of vascular smooth muscle cells. This result suggests that RGD-M13 phage/PLGA nanofibrous matrices have potentials to serve as tissue engineering scaffolds.

In recent years, graphene and its derivatives have attracted much interest in various fields, including biomedical applications. In particular, increasing attention has been paid to the effects of reduced graphene oxide (rGO) on cellular behaviors. On the other hand, dicalcium phosphate (DCP) has been widely used in dental and pharmaceutical fields. In this study, DCP composites coated with rGO (DCP-rGO composites) were prepared at various concentration ratios (DCP to rGO concentration ratios of 5:2.5, 5:5, and 5:10 μg/mL, respectively), and their physicochemical properties were characterized. In addition, the effects of DCP-rGO hybrid composites on MC3T3-E1 preosteoblasts were investigated. It was found that the DCP-rGO composites had an irregular granule-like structure with a diameter in the range order of the micrometer, and were found to be partially covered and interconnected with a network of rGO. The zeta potential analysis showed that although both DCP microparticles and rGO sheets had negative surface charge, the DCP-rGO composites could be successfully formed by the unique structural properties of rGO. In addition, it was demonstrated that the DCP-rGO composites significantly increased alkaline phosphatase activity and extracellular calcium deposition, indicating that the DCP-rGO hybrid composites can accelerate the osteogenic differentiation by the synergistic effects of rGO and DCP. Therefore, in conclusion, it is suggested that the DCP-rGO hybrid composites can be potent factors in accelerating the bone tissue regeneration.

Shape-memory polymers (SMPs) are an intriguing class of smart materials possessing reversible shape change and recovery capabilities. Effective routes to shape-memory porous films (SMPFs) are few and limited in scope owing to the difficulty in manipulating the shape change of pores by conventional methods. Herein we report an unconventional strategy for crafting light-driven SMPFs by judiciously constructing highly ordered porous films via a facile "breath figure" approach, followed by sequential vapor crosslinking and nondestructive directional light manipulation. Micropores can thus be transformed into other shapes including rectangle, rhombus and size-reduced micropores at room temperature. The transformed micropores can be reverted to their original shapes by either thermal annealing or UV irradiation. As such, this strategy expands the rich diversity of SMPs accessible.

A zero-power, low-cost ultraviolet (UV)-C colorimetric sensor is demonstrated using a gallium oxide and reduced graphene oxide (rGO) hybrid via photoelectrochemical reactions. A wide bandgap semiconductor (WBS) such as gallium oxide with an energy bandgap of 4.9 eV generates electron-hole pairs (EHPs) when exposed under a mercury lamp emitting 254 nm. While the conventional UVC sensors employing WBS convert the generated EHPs into an electrical signal via a solid-state junction device (SSD), our newly proposed UVC sensory system works by converting EHPs into an electrochemical reaction. The electrochemical reaction causes the degradation of a cationic thiazine redox dye, methylene blue (MB) and thereby spontaneously changes its color. As more rGO was hybridized with the gallium oxide, MB degradation was effectively expedited. Thus, the level of MB degradation under UVC can be evaluated as a UVC indicator. Unlike conventional SSD-based UVC sensors, our responsive colorimetric sensor can be applied where needed inexpensively and zero power.

Recently, there have been tremendous efforts to develop the biofunctional scaffolds by incorporating various biochemical factors. In the present study, we fabricated poly(lactic-co-glycolic acid) (PLGA) nanofiber sheets decorated with graphene oxide (GO) and RGD peptide. The decoration of GO and RGD peptide was readily achieved by using RGD peptide-displaying M13 bacteriophage (RGD-M13 phage) and electrospinning. Furthermore, the aligned GO-decorated PLGA/RGD peptide (GO-PLGA/RGD) ternary nanofiber sheets were prepared by magnetic field-assisted electrospinning, and their potentials as bifunctional scaffolds for facilitating myogenesis were explored. We characterized the physicochemical and mechanical properties of the sheets by scanning electron microscopy, Raman spectroscopy, contact angle measurement, and tensile test. In addition, the C2C12 skeletal myoblasts were cultured on the aligned GO-PLGA/RGD nanofiber sheets, and their cellular behaviors, including initial attachment, proliferation and myogenic differentiation, were evaluated. Our results revealed that the GO-PLGA/RGD nanofiber sheets had suitable physicochemical and mechanical properties for supporting cell growth, and could significantly promote the spontaneous myogenic differentiation of C2C12 skeletal myoblasts. Moreover, it was revealed that the myogenic differentiation was further accelerated on the aligned GO-PLGA/RGD nanofiber sheets due to the synergistic effects of RGD peptide, GO and aligned nanofiber structure. Therefore, , it is suggested that the aligned GO-PLGA/RGD ternary nanofiber sheets are one of the most promising approaches for facilitating myogenesis and promoting skeletal tissue regeneration.

The development of three dimensional (3D) scaffolds for promoting and stimulating cell growth is one of the greatest concerns in biomedical and tissue engineering. In the present study, novel biomimetic 3D scaffolds composed of polyurethane (PU) foam and graphene oxide (GO) nanosheets were designed, and their potential as 3D scaffolds for skeletal tissue regeneration was explored. The GO-coated PU foams (GO-PU foams) were characterized by scanning electron microscopy and Raman spectroscopy. It was revealed that the 3D GO-PU foams consisted of an interconnected foam-like network structure with an approximate 300 μm pore size, and the GO was uniformly distributed in the PU foams. On the other hand, the myogenic stimulatory effects of GO on skeletal myoblasts were also investigated. Moreover, the cellular behaviors of the skeletal myoblasts within the 3D GO-PU foams were evaluated by immunofluorescence analysis. Our findings showed that GO can significantly promote spontaneous myogenic differentiation without any myogenic factors, and the 3D GO-PU foams can provide a suitable 3D microenvironment for cell growth. Furthermore, the 3D GO-PU foams stimulated spontaneous myogenic differentiation via the myogenic stimulatory effects of GO. Therefore, this study suggests that the 3D GO-PU foams are beneficial to myogenesis, and can be used as biomimetic 3D scaffolds for skeletal tissue engineering.

Cylindrical silk fiber (SF) was coated with Graphene oxide (GO) for capacitive humidity sensor applications. Negatively charged GO in the solution was attracted to the positively charged SF surface via electrostatic force without any help from adhesive intermediates. The magnitude of the positively charged SF surface was controlled through the static electricity charges created on the SF surface. The GO coating ability on the SF improved as the SF’s positive charge increased. The GO-coated SFs at various conditions were characterized using an optical microscope, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and LCR meter. Unlike the intact SF, the GO-coated SF showed clear response-recovery behavior and well-behaved repeatability when it was exposed to 20% relative humidity (RH) and 90% RH alternatively in a capacitive mode. This approach allows humidity sensors to take advantage of GO’s excellent sensing properties and SF’s flexibility, expediting the production of flexible, low power consumption devices at relatively low costs.

In this study, vanadium pentoxide (V2O5) nanowires (NWs) with a diameter of 100–200 nm and a length of up to several micrometers as cathode for lithium ion batteries are synthesize using an electrospinning method. The reduced graphene oxide (rGO) and V2O5 NWs (GVO) composites are form by wet mixing the electrospun V2O5 NWs and rGO. Surface morphologies, microstructure and elemental mapping, and chemical bonding states of the composites are characterize. The initial and 60 cycles discharge capacities of GVO composite composed of 1 wt% rGO show up to 225 mAh g−1 and 125 mAh g−1, even higher than pure V2O5 NWs, when the lithium ion battery cycled between 2.0 and 4.0 V with a rate of 0.2 C, because of highly conductive rGO. The GVO composite could be promising as a high performance cathode for lithium ion batteries.

Surface imprinting is an effective and simple method to fabricate and retain imprinted templates and recognizable nanocavities after template extraction. The imprinted effects can be controlled depending on the surface morphological changes. In general, a planar film has a limited area compared to a structured film with relatively higher surface-to-volume (S/V) ratio (A/A0), leading to the conventional sensing response upon the functionality of monomers in a fixed chemical composition. To increase the limited sensing properties and develop simple fabrication of porous arrays on a large area, we herein demonstrate the 2,4-dichlorophenoxyacetic acid (2,4-D, herbicide)-imprinted porous thin film lithographically patterned using photopolymerization and silica colloidal array as a master mold, derived by a unidirectional rubbing method. The resonant frequency changes with respect to the adsorption of 2,4-D molecules on a template-extracted porous poly(MAA-co-EGDMA) (MIP) film in a 10&minus, 1 mM aqueous solution of 2,4-D for 1 h, and when compared to the planar MIP film, the higher sensing response (&Delta, f = &minus, 283 &plusmn, 7 Hz &asymp, 1543 &plusmn, 38 ng/cm2) appears on the porous MIP film due to the specific recognition toward the more accessible templated cavities of the structured porous array, indicating an imprinting effect (If) value of 3.5. In addition, a higher selectivity for 2,4-D was also displayed on the porous MIP film compared to other herbicides. From these results, it was revealed that these improved sensing properties can be determined from the effects of various parameters (template functionality, film structuring, hydroxyl groups of silica colloids, etc.).

Photolithography is a unique process that can effectively manufacture micro/nano-sized patterns on various substrates. On the other hand, the meniscus-dragging deposition (MDD) process can produce a uniform surface of the substrate. Graphene oxide (GO) is the oxidized form of graphene that has high hydrophilicity and protein absorption. It is widely used in biomedical fields such as drug delivery, regenerative medicine, and tissue engineering. Herein, we fabricated uniform GO micropatterns via MDD and photolithography. The physicochemical properties of the GO micropatterns were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. Furthermore, cell migration on the GO micropatterns was investigated, and the difference in cell migration on triangle and square GO micropatterns was examined for their effects on cell migration. Our results demonstrated that the GO micropatterns with a desired shape can be finely fabricated via MDD and photolithography. Moreover, it was revealed that the shape of GO micropatterns plays a crucial role in cell migration distance, speed, and directionality. Therefore, our findings suggest that the GO micropatterns can serve as a promising biofunctional platform and cell-guiding substrate for applications to bioelectric devices, cell-on-a-chip, and tissue engineering scaffolds.

Neurons are electrically excitable cells that transmit and process information in the nervous system. Recently, the differentiation of human neural stem cells to neurons has been shown to be enhanced on graphene substrates, and differentiated neurons have been shown to be able to still carry electrical signals when stimulated by graphene electrodes. Graphene films grown by using chemical vapor deposition were transferred onto glass coverslips by using the scooping method and were then coated with fetal bovine serum for a neuronal cell culture. The graphene substrates as biomimetic cues have been shown to enhance the neurite outgrowth of PC-12 cells. Our findings suggest that graphene has a unique surface property that can promote neuronal cells, which should open tremendous opportunities in neuroscience, neural engineering and regenerative medicine.

This study concentrates upon investigating differential cellular responses to carbon nanoparticles (CNPs) such as pristine graphene flakes, single-walled carbon nanotubes (SWCNTs) and multiwalled CNTs (MWCNTs), in human dermal fibroblasts (HDFs) vs. the L-929 fibroblast cell line. Characterizing the surface morphology of each CNP by using scanning electron microscopy, we determined their cytotoxicity profiles by quantifying the mitochondrial activity. Graphene was found to have an irregular flake-like shape with various lengths within the ranges of 50 ∼ 1500 nm. The estimated sizes of the SWCNTs and the MWCNTs were about 400 nm and 1000 nm in diameter, respectively and several µm in length. All the CNPs tested here exerted adverse effects on the viability of HDFs even at 15.6 ppm, through intracellular uptake whereas except MWCNTs, they did not show any cytotoxicity against L-929 cells at 250 ppm. This result suggests that CNPs can have a differential influence on normal fibroblasts vs. immortalized ones.

A multi-performance MWCNT-reinforced chitosan nanocomposite was fabricated by two methods: a freeze-drying process associated with the sublimation and compression (SAC) method; and the casting-evaporation (CE) method. We obtained ordered and multilayered structures with limited porosity, and well-dispersed MWCNT structures of the chitosan nanocomposite, especially with the SAC method. In the case of the nanocomposite films prepared by the CE method, the mechanical strength and elongation were significantly increased by up to about 40% compared with the pure chitosan films. On the other hand, the ordered and porous multilayered pure chitosan films prepared by the SAC method showed significantly lower tensile strength and elongation compared to the pure solid chitosan films. However, the relative enhancement of the mechanical properties of multilayered MWCNT/chitosan nanocomposites with porosity was higher, especially in terms of the elongation, which showed a twofold improvement in strain. The relaxed bond, which could be a relatively strong hydrogen bond, between the functional groups in the chitosan chains and the functionalized surface of the MWCNTs might be stretched under stress, thereby improving the ductility of the multilayered nanocomposite films. In addition, the viscoplastic behavior of the films by the CE method could become more active with increasing strain rate. Interestingly, ordered and porous pure chitosan films did not reveal the viscoplastic behavior; it rather presented strain softening and viscoelastic characteristics. However, the interaction between the chitosan chains and the surface-modified MWCNTs could regenerate viscoplasticity of the chitosan films.

Electrospun polyacrylonitrile (PAN) nanofibers were subjected to surface modification by atmospheric pressure (AP) plasma treatment with reactive gases. There was no damage to the surfaces after this plasma treatment, and no significant changes were observed in the morphologies of the nanofibers. The surface energies of O2- and N2-plasma-treated PAN (abbreviated as OPP and NPP, respectively) nanofibers increased by almost 138.7% and 190.6%, respectively, in comparison with that of an untreated nanofiber (256.6 mJ/m2). The binding energies of both OPP and NPP samples increased through the formation of many hydrophilic bonds involving oxygen. The current–voltage (I–V) characteristics of the nanofibers were determined for the different reactive gases, and the plasma-treated nanofibers showed higher protein immobilization compared to the untreated ones. This result indicates that electrospun PAN nanofibers have the potential to be used in protein biosensor systems.

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors.

We report the first study of the controlled, evaporative self-organization of a polymer blend from a restricted geometry comprised of a spherical lens upon a Si substrate (i.e., a sphere-on-flat geometry). This geometry facilitated the control over the evaporation rate of solvent, thereby eliminating the temperature gradient and the possible convective instabilities. In this study, a drop of polystyrene (PS) and poly(methyl methacrylate) (PMMA) toluene solution evaporated in the sphere-on-flat geometry. The combination of controlled, consecutive pinning−depinning cycles (i.e., “stick−slip”) of the contact line at the edge of the geometry, spontaneous phase separation of incompatible polymers at the microscopic scale, and a dewetting process in the late stage of phase segregation led to the formation of gradient, hierarchically structured polymer blend rings composed of phase-separated PS and PMMA. The topographic distribution of PS and PMMA phases on the ring surface were revealed after removal of the PS ...

Hundreds of gradient concentric rings of linear conjugated polymer, (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4- phenylenevinyl-ene], i.e., MEH-PPV) with remarkable regularity over large areas were produced by controlled "stick-slip" motions of the contact line in a confined geometry consisting of a sphere on a flat substrate (i.e., sphere-on-flat geometry). Subsequently, MEH-PPV rings were exploited as a template to direct the formation of gradient concentric rings of multiwalled carbon nanotubes (MWNTs) with controlled density. This method is simple, cost effective, and robust, combining two consecutive self-assembly processes, namely, evaporation-induced self-assembly of polymers in a sphere-on-flat geometry, followed by subsequent directed self-assembly of MWNTs on the polymer-templated surfaces.

Recently, there has been considerable effort to develop suitable scaffolds for tissue engineering applications. Cell adhesion is a prerequisite for cells to survive. In nature, the extracellular matrix (ECM) plays this role. Therefore, an ideal scaffold should be structurally similar to the natural ECM and have biocompatibility and biodegradability. In addition, the scaffold should have biofunctionality, which provides the potent ability to enhance the cellular behaviors, such as adhesion, proliferation and differentiation. This study concentrates on fabricating cell-adhesive matrices composed of RGD peptide-displaying M13 bacteriophage (RGD-M13 phage) and poly(lactic-co-glycolic acid, PLGA) nanofibers. Long rod-shaped M13 bacteriophages are non-toxic and can express many desired proteins on their surface. A genetically engineered M13 phage was constructed to display RGD peptides on its surface. PLGA is a biodegradable polymer with excellent biocompatibility and suitable physicochemical property for adhesive matrices. In this study, RGD-M13 phage/PLGA hybrid nanofiber matrices were fabricated by electrospinning. The physicochemical properties of these matrices were characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and contact angle measurement. In addition, the cellular behaviors, such as the initial attachment, proliferation and differentiation, were analyzed by a CCK-8 assay and immunofluorescence staining to evaluate the potential application of these matrices to tissue engineering scaffolds. The RGD-M13 phage/PLGA nanofiber matrices could enhance the cellular behaviors and promote the differentiation of C2C12 myoblasts. These results suggest that the RGD-M13 phage/PLGA nanofiber matrices are beneficial to myoblast differentiation and can serve as effective tissue engineering scaffolds.