Fountain Pen-Inspired 3D Colloidal Assembly, Consisting of Metallic Nanoparticles on a Femtoliter Scale.

The 3D colloidal assemblies composed of nanoparticles (NPs) are closely associated with optical properties such as photonic crystals, localized surface plasmon resonance, and surface-enhanced Raman scattering. However, research on their fabrication remains insufficient. Here, the femtoliter volume of a 3D colloidal assembly is shown, using the evaporation of a fine fountain pen. A nano-fountain pen (NPF) with a micrometer-level tip inner diameter was adopted for the fine evaporation control of the ink solvent. The picoliters of the evaporation occurring at the NFP tip and femtoliter volume of the 3D colloidal assembly were analyzed using a diffusion equation. The shape of the 3D colloidal assembly was dependent on the evaporation regarding the accumulation time and tip size, and they exhibited random close packing. Using gold-, silver-, and platinum-NPs and mixing ratios of them, diverse 3D colloidal assemblies were formed. The spectra regarding a localized surface plasmon resonance of them were changed according to composition and mixing ratio. We expect that this could be widely applied as a simple fabrication tool in order to explore complex metamaterials constructed of nanoparticles, as this method is highly flexible in varying the shape as well as composition ratio of self-assembled structures.

Quantitative comparison of EGFR expression levels of optically trapped individual cells using a capacitance biosensor.

Cellular endocytosis is an essential phenomenon which induces cellular reactions, such as waste removal, nutrient absorption, and drug delivery, in the process of cell growth, division, and proliferation. To observe capacitance responses upon endocytosis on a single-cell scale, this study combined an optical tweezer that can optically place a single cell on a desired location with a capacitance sensor and a cell incubation chamber. Single HeLa cancer cell was captured and moved to a desired location through optical trapping, and the single-cell capacitance change generated during the epidermal growth factor (EGF) molecule endocytosis was measured in real time. It was found that single HeLa cells showed a larger increase in capacitance values compared to that of the single NIH3T3 cells when exposed to varying EGF concentrations. In addition, the capacitance change was in proportion to the cell's EGF receptor (EGFR) level when cells of different levels of EGFR expression were tested. An equation derived from these results was able to estimate the EGFR expression level of a blind-tested cell. The biosensor developed in this research can not only quickly move a single cell to a desired location in a non-invasive manner but also distinguish specific responses between cancer and normal cells by continuous measurement of real-time interactions of a single cell in culture to the external ligands.

Chemically Tuned Intracellular Gene Delivery by Core-Shell Nanoparticles: Effects of Proton Buffering, Acid Degradability, and Membrane Disruption.

Nanoparticles consisting of a condensed nucleic acid core surrounded by protective layers which aid to overcome extracellular and intracellular hurdles to gene delivery (i. e., core-shell nanoparticles, CSNPs) synthetically mimic viruses. The outer shells shield the core and are particularly designed to enable facilitated release of the gene payload into the cytoplasm, the major limiting step in intracellular gene delivery. The hypothetical proton sponge effect and degradability in response to a stimulus (i. e., mildly acidic pH in the endosome) are two prevailing, although contested, principles in designing effective carriers for intracellular gene delivery via endosomal escape. Utilizing the highly flexible chemical-tuning of the polymeric shell via surface-initiated photo-polymerization of the various monomers at different molecular ratios, the effects of proton buffering capacity, acid-degradability, and endosomal membrane-lysis property on intracellular delivery of plasmid DNA by CSNPs were investigated. This study demonstrated the equivalently critical roles of proton buffering and acid-degradability in achieving efficient intracellular gene delivery, independent of cellular uptake. Extended proton buffering resulted in further improved transfection as long as the core structure was not compromised. The results of the study present a promising synthetic strategy to the development of an efficient, chemically-tunable gene delivery carrier.

A Review of Advanced Impedance Biosensors with Microfluidic Chips for Single-Cell Analysis.

Electrical impedance biosensors combined with microfluidic devices can be used to analyze fundamental biological processes for high-throughput analysis at the single-cell scale. These specialized analytical tools can determine the effectiveness and toxicity of drugs with high sensitivity and demonstrate biological functions on a single-cell scale. Because the various parameters of the cells can be measured depending on methods of single-cell trapping, technological development ultimately determine the efficiency and performance of the sensors. Identifying the latest trends in single-cell trapping technologies afford opportunities such as new structural design and combination with other technologies. This will lead to more advanced applications towards improving measurement sensitivity to the desired target. In this review, we examined the basic principles of impedance sensors and their applications in various biological fields. In the next step, we introduced the latest trend of microfluidic chip technology for trapping single cells and summarized the important findings on the characteristics of single cells in impedance biosensor systems that successfully trapped single cells. This is expected to be used as a leading technology in cell biology, pathology, and pharmacological fields, promoting the further understanding of complex functions and mechanisms within individual cells with numerous data sampling and accurate analysis capabilities.

Enhancing Electrical Outputs of Piezoelectric Nanogenerators by Controlling the Dielectric Constant of ZnO/PDMS Composite.

Structural optimizations of the piezoelectric layer in nanogenerators have been predicted to enhance the output performance in terms of the figure of merit. Here, we report the effect of dielectric constant on electrical outputs of piezoelectric nanogenerator using ZnO/PDMS composites with varied ZnO coverages. The dielectric constant of piezoelectric layers was adjusted from 3.37 to 6.75. The electrical output voltage of 9 mV was achieved in the nanogenerator containing the ZnO/PDMS composite with the dielectric constant of 3.46, which is an 11.3-fold enhancement compared to the value of the nanogenerator featuring the composite with high dielectric constants. Significantly, lowering the dielectric constant of the piezoelectric layer improves the electrical output performance of piezoelectric nanogenerators.

WO3-ZnO and CuO-ZnO nanocomposites as highly efficient photoanodes under visible light illumination.

We prepared ZnO nanocomposites with WO3 or CuO nanostructures to improve the photocatalytic performance of ZnO nanostructures. Characterization of the nanocomposites using scanning electron microscopy, x-ray diffraction, UV-vis spectrometry and photoluminescence revealed the morphologies and wide light absorption range of the materials. The highest current densities of WO3/ZnO and CuO/ZnO nanocomposites were 1.28 mA cm-2 and 2.49 mA cm-2 at 1.23 V (versus a reversible hydrogen electrode) under AM 1.5 100 mW cm-2, which are ~1.2- and 3.5-fold greater than those of bare ZnO nanostructures, respectively. The easy fabrication process suggests that nanocomposites with narrow bandgap materials, such as WO3 and CuO, will improve the performance of electrochemical and optoelectrical devices such as dye-sensitized solar cells and biosensors.

PMMA Thin Film with Embedded Carbon Quantum Dots for Post-Fabrication Improvement of Light Harvesting in Perovskite Solar Cells.

Perovskite solar cells (PSCs) with a standard sandwich structure suffer from optical transmission losses due to the substrate and its active layers. Developing strategies for compensating for the losses in light harvesting is of significant importance to achieving a further enhancement in device efficiencies. In this work, the down-conversion effect of carbon quantum dots (CQDs) was employed to convert the UV fraction of the incident light into visible light. For this, thin films of poly(methyl methacrylate) with embedded carbon quantum dots (CQD@PMMA) were deposited on the illumination side of PSCs. Analysis of the device performances before and after application of CQD@PMMA photoactive functional film on PSCs revealed that the devices with the coating showed an improved photocurrent and fill factor, resulting in higher device efficiency.

Recent Advances in Organic Piezoelectric Biomaterials for Energy and Biomedical Applications.

The past decade has witnessed significant advances in medically implantable and wearable devices technologies as a promising personal healthcare platform. Organic piezoelectric biomaterials have attracted widespread attention as the functional materials in the biomedical devices due to their advantages of excellent biocompatibility and environmental friendliness. Biomedical devices featuring the biocompatible piezoelectric materials involve energy harvesting devices, sensors, and scaffolds for cell and tissue engineering. This paper offers a comprehensive review of the principles, properties, and applications of organic piezoelectric biomaterials. How to tackle issues relating to the better integration of the organic piezoelectric biomaterials into the biomedical devices is discussed. Further developments in biocompatible piezoelectric materials can spark a new age in the field of biomedical technologies.

Increased EGFR expression induced by a novel oncogene, CUG2, confers resistance to doxorubicin through Stat1-HDAC4 signaling.

BACKGROUND: Previously, it has been found that the cancer upregulated gene 2 (CUG2) and the epidermal growth factor receptor (EGFR) both contribute to drug resistance of cancer cells. Here, we explored whether CUG2 may exert its anticancer drug resistance by increasing the expression of EGFR. METHODS: EGFR expression was assessed using Western blotting, immunofluorescence and capacitance assays in A549 lung cancer and immortalized bronchial BEAS-2B cells, respectively, stably transfected with a CUG2 expression vector (A549-CUG2; BEAS-CUG2) or an empty control vector (A549-Vec; BEAS-Vec). After siRNA-mediated EGFR, Stat1 and HDAC4 silencing, antioxidant and multidrug resistance protein and mRNA levels were assessed using Western blotting and RT-PCR. In addition, the respective cells were treated with doxorubicin after which apoptosis and reactive oxygen species (ROS) levels were measured. Stat1 acetylation was assessed by immunoprecipitation. RESULTS: We found that exogenous CUG2 overexpression induced EGFR upregulation in A549 and BEAS-2B cells, whereas EGFR silencing sensitized these cells to doxorubicin-induced apoptosis. In addition, we found that exogenous CUG2 overexpression reduced the formation of ROS during doxorubicin treatment by enhancing the expression of antioxidant and multidrug resistant proteins such as MnSOD, Foxo1, Foxo4, MRP2 and BCRP, whereas EGFR silencing congruently increased the levels of ROS by decreasing the expression of these proteins. We also found that EGFR silencing and its concomitant Akt, ERK, JNK and p38 MAPK inhibition resulted in a decreased Stat1 phosphorylation and, thus, a decreased activation. Since also acetylation can affect Stat1 activation via a phospho-acetyl switch, HDAC inhibition may sensitize cells to doxorubicin-induced apoptosis. Interestingly, we found that exogenous CUG2 overexpression upregulated HDAC4, but not HDAC2 or HDAC3. Conversely, we found that HDAC4 silencing sensitized the cells to doxorubicin resistance by decreasing Stat1 phosphorylation and EGFR expression, thus indicating an interplay between HDAC4, Stat1 and EGFR. CONCLUSION: Taken together, we conclude that CUG2-induced EGFR upregulation confers doxorubicin resistance to lung (cancer) cells through Stat1-HDAC4 signaling.

Eu, Gd-Codoped Yttria Nanoprobes for Optical and T1-Weighted Magnetic Resonance Imaging.

Nanoprobes with multimodal functionality have attracted significant interest recently because of their potential applications in nanomedicine. This paper reports the successful development of lanthanide-doped Y2O3 nanoprobes for potential applications in optical and magnetic resonance (MR) imaging. The morphology, structural, and optical properties of these nanoprobes were characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and photoluminescence (PL). The cytotoxicity test showed that the prepared lanthanide-doped Y2O3 nanoprobes have good biocompatibility. The obvious contrast enhancement in the T1-weighted MR images suggested that these nanoprobes can be used as a positive contrast agent in MRI. In addition, the clear fluorescence images of the L-929 cells incubated with the nanoprobes highlight their potential for optical imaging. Overall, these results suggest that prepared lanthanide-doped Y2O3 nanoprobes can be used for simultaneous optical and MR imaging.

Highly Durable Ti-Mesh Based Triboelectric Nanogenerator for Self-Powered Device Applications.

We describe a highly durable Ti-mesh based triboelectric nanogenerator (Ti-TENG) with a sandwich structure that harvests electrical energy from contact electrification. The electrical output from the fabricated Ti-TENG by compressing and releasing strain was measured under different applied loads and frequencies. The Ti-TENG generated a peak voltage and current up to -1.1 V and -14 nA at an applied force of 30 N and frequency of 1.1 Hz. Obtained potentials were used to charge a capacitor and power a commercially available light emitting diode (LED). In particular, the Ti-TENG, which exhibited high electrical stability, can be used in applications requiring high levels of robustness and durability. For example, the Ti-TENG was applied as step counter while walking and running, demonstrating its capability to self-power devices. We believe that the device provides a highly promising, robust and durable platform for self-powered applications that effectively harnesses energy from mechanical movements.

Probing the interaction of caffeic acid with ZnO nanoparticles.

The binding of ZnO nanoparticles (NPs) and caffeic acid (CFA) was investigated using fluorescence quenching, UV/vis absorption spectrscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) at different temperatures. The study results indicated fluorescence quenching between ZnO NPs and CFA rationalized in terms of a static quenching mechanism or the formation of non-fluorescent CFA-ZnO. From fluorescence quenching spectral analysis, the binding constant (K(a)), number of binding sites (n) and thermodynamic properties were determined. Values of the quenching (K(SV)) and binding (K(a)) constants decrease with increasing temperature and the number of binding sites n = 2. The thermodynamic parameters determined using Van't Hoff equation indicated that binding occurs spontaneously involving the hydrogen bond, and van der Waal's forces played a major role in the reaction of ZnO NPs with CFA. The FTIR, TEM and DLS measurements also indicated differences in the structure, morphology and size of CFA, ZnO NPs and their corresponding CFA-ZnO.

Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching, UV/vis and FTIR spectroscopic techniques.

The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non-fluorescent CF-CFA and CF-CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (KSV), quenching rate constant (kq), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (KSV) between CF and CGA, CFA are 1.84 × 10(4) and 1.04 × 10(4) L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA.

Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal.

Well-aligned ZnO nanostructures have been intensively studied over the last decade for remarkable physical properties and enormous applications. Here, we describe a one-step fabrication technique to synthesis freestanding ZnO nanorod/graphene/ZnO nanorod double heterostructure. The preparation of the double heterostructure is performed by using thermal chemical vapor deposition (CVD) and preheating hydrothermal technique. In addition, the morphological properties were characterized by using the scanning electron microscopy (SEM). The utility of freestanding double heterostructure is demonstrated by fabricating the piezoelectric nanogenerator. The electrical output is improved up to 200% compared to that of a single heterostructure owing to the coupling effect of the piezoelectricity between the arrays of ZnO nanorods on the top and bottom of graphene. This unique double heterostructure have a tremendous potential for applications of electrical and optoelectrical devices where the high number density and specific surface area of nanorod are needed, such as pressure sensor, immuno-biosensor and dye-sensitized solar cells.

Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments.

The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV-vis electronic absorption spectra. From solvatochromic theory the ground and excited-state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations are quite similar. The ground and excited-state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO-LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent.

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer.

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.

Mesoporous silica with fibrous morphology: a multifunctional core-shell platform for biomedical applications.

Multifunctional mesoporous silica nanocomposites are attractive carriers for targeted drug delivery in nanomedicine. Although promising developments have been made in the fabrication of multifunctional mesoporous silica nanocomposites, the design and mass production of novel multifunctional carriers are still challenging. This paper reports the facile one-pot fabrication of a multifunctional inorganic composite composed of superparamagnetic Fe3O4 nanoparticles and coated dye-functionalized mesoporous silica with a high specific surface area. The resulting composite particles had a tunable particle size, special open pore channels with high specific surface area, which is quite favorable for drug loading and release properties, as well as luminescent and superparamagnetic properties suitable for targeted drug delivery and tracking. This composite exhibited low toxicity, suggesting potential biomedical applications.

Color-tunable properties of Eu3+- and Dy3+-codoped Y2O3 phosphor particles.

Rare-earth phosphors are commonly used in display panels, security printing, and fluorescent lamps, and have potential applications in lasers and bioimaging. In the present study, Eu3+- and Dy3+-codoped uniform-shaped Y2O3 submicron particles were prepared using the urea homogeneous precipitation method. The structure and morphology of the resulting particles were characterized by X-ray diffraction, field emission scanning electron microscope, and field emission transmission electron microscope, whereas their optical properties were monitored by photoluminescence spectroscopy. The room-temperature luminescence color emission of the synthesized particles can be tuned from red to yellow by switching the excitation wavelength from 254 to 350 nm. The luminescence intensities of red and yellow emissions could be altered by varying the dopant concentration. Strong quenching was observed at high Eu3+ and Dy3+ concentrations in the Y2O3 host lattice.

Synthesis and photoluminescence properties of Ho3+ doped LaAlO3 nanoparticles.

Nanosized particles with different Ho3+ concentrations were synthesized in LaAlO3 lattices using a simple Pechini-type sol-gel method. X-ray diffraction measurements were used to investigate the structural composition and the effects of holmium dopant concentration on LaAlO3:Ho3+ crystal formation. Field-emission scanning-electron microscopy images confirm the formation of approximately spherical particles with an average size about 100 nm. The photoluminescence results yielded optimal holmium ion concentration in LaAlO3 host matrices was about 3% in mol equivalent. The mechanism that are responsible for the photoluminescence emission processes discussed with the help of Ho3+-ion Dieke energy level diagram. Power dependent slope measurements were performed to identify up-conversion photoluminescence process involved in LaAlO3:Ho3+.

Advantages of using Ti-mesh type electrodes for flexible dye-sensitized solar cells.

We used Ti meshes for both the photoanodes and counter electrodes of dye-sensitized solar cells (DSSCs) to improve the flexibility and conductivity of the electrodes. These mesh type electrodes showed good transparency and high bendability when subjected to an external force. We demonstrated the advantages of cells using such electrodes compared to traditional transparent conducting oxide based electrodes and back side illuminated DSSCs, such as low sheet resistance, elevated photo-induced current and enhanced sunlight utilization. Nanotube layers of different thicknesses were investigated to determine their effect on the photovoltaic parameters of the cell. The overall efficiency of the best cells was approximately 5.3% under standard air mass 1.5 global (AM 1.5 G) solar conditions. Furthermore, the DSSCs showed an efficiency of approximately 3.15% due to the all Ti-mesh type electrodes even after illumination from the back side.