Analysis of Correlation Between Contrast and Component of Polylatic Acid Composite for Fused Deposition Modeling 3D Printing.

Additive manufacturing or three-dimensional (3D) printing is considered a disruptive technology for producing components with topologically optimized complex geometries as well as functionalities that are not achievable by traditional methods. 3D printing is expected to revolutionize the manufacturing of components. While several 3D printing systems are available, printing based on fused-deposition modeling (FDM) using thermoplastics is particularly widespread because of the simplicity and potential applicability of the method. In this study, we report the analysis of correlation between contrast and component of polylactic acid (PLA) based composite for FDM 3D printing. The pre-fabricated white composite and black composite were mixed in the fraction of 100:0, 90:10, 75:25, 50:50, 25:75, and 0:100% (v/v) and the obtained mixture was extruded using HX-35 3D filament extrusion line. The samples in different contrast were printed in disk like shape, and the gray scale filaments and 3D printed samples were measured the morphology and components using a field emission scanning electron microscope and energy dispersive X-ray spectroscopy. The CIE-lab values of the samples were measured using a colorimeter and the correlation between CIE-lab values and the components were analyzed. Although the component of Ti was linearly increased, the CIE-lab values show a clear exponential increase by increasing the white composite.

Fabrication of periodic nano-porous surface structure for highly sensitive gravimetric quartz crystal applications.

A periodic nano-porous surface on quartz crystal electrodes was carefully fabricated for increasing the mass-sensitive areas. Detailed porous structures were prepared by analyzing Au electrochemical reduction process of PS layer coated quartz crystals. The sensitivity measurement of the porous quartz crystals was performed with several traditional methods, and an optimized reduction time for higher sensitivity was determined. The frequency shift of the nano-porous quartz crystals showed 10 times bigger change with the same concentration of target solutions in self-assembly procedures. In the procedures, the freshly increased surface portion did not produce additional molecular slip-effects on the measured resonant resistance values, thus, the periodic porous chips showed another side merit for the mass sensor applications. We propose a possible use of the current porous surface as a platform for developing other high-performance sensors and analyses.

Detection of Amyloid ß Using a Poly-L-Lysine Mediated Nanobiosensor.

Amyloid ß (Aß) peptide is secreted from the outside of neural cell by a neural signal pathway and it accumulated each other results in the highly toxicity amyloid plaque which is a critical causative factor in the pathogenesis of Alzheimer's Disease (AD). The peptide is considered to be a potential biomarker to diagnose AD. Here we introduce a novel poly-L-lysine (PLL) mediated nanobiosensor to detect Aß in vitro. The PLL molecules were utilized as a signal amplifier of Aß detection. The indirect enzyme-linked immunosorbent assay (ELISA) method and the sandwich ELISA method have tried to the detection of Aß. A commercially available ELISA plate was modified by PLL using a chemical agent and the amplified amino groups were activated by a functional group for the binding of Aß. The bound Aß was further modified with a primary antibody and fluorescence molecules conjugated secondary antibody by the traditional immunochemistry. In the result, the fluorescence intensity was increased by the increasing concentration of Aß, and the best Aß detection results were obtained in the PLL mediated indirect ELISA nanobiosensor. We expected that the present method would be optimized and applied for the detection of Aß in human fluid.

Development of Chemically Signal Amplified Nano-Biosensor Mediated by Poly-L-Lysine.

Amyloid ß (Aß) is considered to be one of a potential biomarker to monitor Alzheimer's Disease (AD) not only for diagnostic purposes but for early detection. Here we describe a novel nano-biosensor for Aß mediated by poly-L-lysine (PLL) which was used for the amplification of detection signal for Aß. The indirect enzyme-linked immunosorbent assay (ELISA) method was modified using PLL for the amplification of the Aß detection signal. A commercially available ELISA plate was modified by PLL using chemical agent and the amplified amino groups were activated by a chemical agent for the detection of Aß. The detection was carried out by the traditional immunochemistry using primary antibody and fluorescence molecules conjugated secondary antibody. In the result, the fluorescence intensity was increased by the increasing treated Aß amount, and the sensitivity was approximately 2 times higher in the concentration of 2 ng/mL Aß treatment, and approximately 4 times higher in the concentration of 200 ng/mL Aß treatment compare with that of indirect ELISA detection method. We suggest our novel signal amplification method for the Aß early detection.

Investigation of the Extracellular Matrix Effect for the QCM/CCD Cell Activity Monitoring System.

A real-time quartz crystal microbalance (QCM) cell activity monitoring system coupled with micro CCD cameras was developed to investigate the cultured cell activity, which could measure the viscoelastic characteristics of the cell with the QCM and observe the cell morphology changes with CCD camera simultaneously. Both the viscoelastic characteristics and the shape of the cultured cell are important factors to estimate the cell activity and the cell adhesion. The extracellular matrix (ECM) on the surface of the QCM is essential to culture the cell stably in the QCM monitoring system. To find the ECM optimization condition, the adhesive strength of cultured cells on the ECM modified glass surface was measured by using rotating water stream and CCD camera. After culturing HepG2 cells for 24 hours on the ECM modified glass plates, the glass plates were dipped in the PBS solution and rotated with 1,000, 1,300, and 1,500 rpm for 30 seconds. The adhesiveness of ECMs was investigated by calculating the remained cells after rotating. Four types of ECM, such as amino group, carboxyl group, collagen monomer, and collagen polymer, were used and tested. The current paper improves the sensing system of previous report so that measurements of four ECMs can be simultaneously conducted under the same conditions in order to enhance reliability. A collagen polymer exposed ECM was the most stable on an adhesiveness point of view, but not suitable for the QCM cell activity monitoring due to the decrease of the QCM sensitivity. The sensitivity of the QCM cell activity monitoring system using collagen monomer as ECM is about 2.6 times better than that using collagen polymer. A collagen monomer exposed ECM was more stable than amino group and carboxyl group exposed ECMs based on an adhesiveness point of view. Therefore, a collagen monomer exposed ECM was the most stable and suitable for the QCM cell activity monitoring system among the four ECMs. The changes of the resonance frequency and the resonance resistance of the ECM film with the cultured cells were investigated and compared the results of CCD camera images. From these results, we showed the QCM cell activity monitoring system coupled with the micro CCD camera could be applied to the evaluation of the cell activities.

Morphology analysis of sodium chloride crystallization on the mica substrate using atomic force microscope.

The morphology of the specific face growth of sodium chloride (NaCI) crystal on the mica surface was analyzed using atomic force microscope (AFM). The supersaturation of the NaCI was induced to lead to the crystal nucleation and growth by the addition of methylalcohol. The effects of methylalcohol concentration and mica surface functionality on the NaCI crystal growth morphology were investigated. The crystalline nucleus was formed scaterringly on the mica surface at 10% methylalcohol. It was grown laterally at 20% methylalcohol and agglomerated at 30% methylalcohol before lateral growth. The difference in the crystallization efficiency originated from the surface conditions is discussed by comparison of the crystallizations on surfaces of the bare mica and mica treated with Mg2+, 3-aminopropyltriethoxysilane, and ethyltriethoxysilane. The lateral growth of sodium chloride crystal was restricted by the different treatment of the mica surface. From these results, it was known that sodium chloride crystal growth morphology could be controlled by using additional solvent and substrate surface treatment. These results imply that the morphology analysis as well as reaction kinetics should be conducted in the crystallization analysis.

Electrochemical characteristics of zinc oxide-polyethyleneglycol complex films using EQCM.

ZnO-PEG-ZnO complex film was fabricated by forming ZnO thin film on the Polyethyleneglycol (PEG) thin film. ZnO thin films were formed by an electrostatic method and ZnO-PEG complex films were fabricated by adsorbing PEG on the ZnO thin films surface with hydrogen bond. The electrochemical characteristic of the ZnO-PEG-ZnO film was analyzed by EQCM techniques. The resonance frequency, resistance and current changes were measured simultaneously with scan rate 100 mV/s, sweep range -1.4-1.2 V in 5 mM ZnCl2 aqueous solution. The electrochemical characteristic of the ZnO-PEG-ZnO complex film was compared with that of the ZnO thin film, and the possible electrode applications of ZnO-PEG-ZnO complex films were examined.

Single-cell manipulation and DNA delivery technology using atomic force microscopy and nanoneedle.

The recent single-cell manipulation technology using atomic force microscopy (AFM) not only allows high-resolution visualization and probing of biomolecules and cells but also provides spatial and temporal access to the interior of living cells via the nanoneedle technology. Here we review the development and application of single-cell manipulations and the DNA delivery technology using a nanoneedle. We briefly describe various DNA delivery methods and discuss their advantages and disadvantages. Fabrication of the nanoneedle, visualization of nanoneedle insertion into living cells, DNA modification on the nanoneedle surface, and the invasiveness of nanoneedle insertion into living cells are described. Different methods of DNA delivery into a living cell, such as lipofection, microinjection, and nanoneedles, are then compared. Finally, single-cell diagnostics using the nanoneedle and the perspectives of the nanoneedle technology are outlined. The nanoneedle-based DNA delivery technology provides new opportunities for efficient and specific introduction of DNA and other biomolecules into precious living cells with a high spatial resolution within a desired time frame. This technology has the potential to be applied for many basic cellular studies and for clinical studies such as single-cell diagnostics.

Synthesis and electroluminescent properties of a novel electroluminescence material of bis-2-(4-(diphenylphosphino)phenyl)benzo[d]oxazole (DPB).

A new light-emissive material, bis-2-(4-(diphenylphosphino)phenyl)benzo[d]oxazole (DPB), has been synthesized and characterized by FT-NMR, FT-IR, UV-Vis and elemental analysis. DPB has the band gap of 4.3 eV between HOMO and LUMO levels. The photoluminescence (PL) of DPB was measured at 410 nm from the chloroform solution. The electroluminescent (EL) devices with structures of ITO/NPB/DPB/LiF/Al and ITO/NPB/DPB/Alq3/LiF/Al were constructed and showed maximum emission at 540 nm. The device using DPB as emitting material showed the luminance of 1000 cd/m2 at 11 V. The CIE chromaticity of the device showed near the region of white color emission.

Copolymerization of electroactive poly(benzyl ether) dendrimer and terthiophene monomer.

In this study, we report the copolymerization, film properties, and HOMO/LUMO levels of the first generation (G1) poly(benzyl ether) dendrimer functionalized on its periphery with terthiophene and terthiophene monomers. Pure G1 dendrimer (DN1), 1:1 and 1:18 molar ratios of the G1 dendrimer and the monomer (e.g., DNTT11 and DNTT118, respectively) are used to compare film formation and HOMO/LUMO levels. The conjugated polymer network (CPN) film obtained from the highest molar ratio of terthiophene monomers shows smooth film formation. Addition of the terthiophene monomer for electrochemical cross-linking controls the surface morphology and the tunability of energy levels of the CPN films. Furthermore, in situ electrochemical quartz crystal microbalance (EQCM) measurements are performed to characterize frequency change (corresponding to mass change) per sweep cycle and relative viscoelastic properties through resonant resistance-resonant frequency (R-F) diagram during the formation of each CPN film. The DN1 film has relatively higher eleastic film and mass loading on the QCM surface than the copolymeried DNTT11 and DNTT118 films. Furthermore, the addition of terthiophene monomers increases the viscosity of the film due to the effect of introducing linear species on the CNP film formation in solution. Thus, the copolymerization of eletroactive dendrimers with the same electroactive monomers enables control on surface morphological features and energy bandgap for future optoelectronic device applications and physical properties (i.e., viscoelasticity) of the films.

Increase the reliability and applicability of quartz crystal resonator coupled with other instruments.

The principle and applications of quartz-crystal resonator systems and the methods to increase their reliability and applicability coupled with other instruments were reported. The principle of quartz-crystal resonator system was documented with based on the three basic concepts for mass, viscosity, and viscoelastic changes. In the preliminary discussion, the realization of a resonant frequency-resonant resistance diagram was described in detail. As the examples of quartz-crystal resonator applications with introducing the resonant resistance concept and the resonant frequency, the fabrication of a carbon-coated quartz crystal sensor and monitoring changes in the viscoelastic properties of thin polymer films were carefully discussed. Examples for increasing their reliability and applicability of quartz crystal resonator systems combined with UV-visible spectroscopy, Atomic Force Microscope (AFM), Surface Plasmon Resonance (SPR), or Charge Coupled Device (CdCD) camera were described.

Comparative evaluation of interaction force between cofilin protein and peptide probe to actin protein.

In current study, we report the direct interaction force comparison for a synthesized peptide probe to actin and cofilin protein to actin using atomic force microscopy. The peptide probe was synthesized following the actin binding module of cofilin protein. Thus, the functionality of the peptide probe was similar with that of the cofilin protein. The difference between the peptide probe and cofilin protein was the molecular size. The small peptide probe enables highly dense surface modification, thus produces different interaction force curves compared with that of original cofilin protein to actin. The results showed the peptide probe was possible to measure many numbers of the interaction force though the measurement of single molecular order interaction force was a weak point. These imply that the peptide probe has a merit when that was applied surface related applications such as protein sensor and protein-protein interaction separation.

Observation of interaction force in large area between actin modified surface and actin antibody modified microsphere probe.

In order to observe the force interaction in large areas, a novel force detection probe was fabricated by two-photon absorbed photopolymerization (TPAP) techniques. The probe was based on a commercial cantilever, and a docking structure for adopting a microsphere immobilized with actin antibody was fabricated by the TPAP techniques. The commercial AFM tip was also modified with the antibody for comparison. Using force curve measurement, the interaction force was compared between the modified probes and the sample surface which was immobilized with actin using a spotting system. The adhesive force of 1.3 nN was measured applying the commercial cantilever. The value was comparable to the measured interaction force of 130 nN applying the microsphere modified cantilever. The measured adhesive force of the novel probe was 100-fold larger than that obtained by the sharp AFM cantilever tip. This strong adhesive force of the microsphere modified cantilever to actin is explainable by the large contact area between the microsphere and the sample surface.

Quartz crystal microbalance technique for analysis of cooling crystallization.

A quartz crystal microbalance (QCM) technique is developed for the in situ analysis of the cooling crystallization processes of crystal nucleation and growth. In contrast to conventional techniques based on property changes in the solid or solution phase, the proposed QCM technique simultaneously exploits property changes in both the solid and solution phases, such as the solid mass and liquid viscosity, to analyze the crystallization processes. When initially cooling the solution, an increase in the solution viscosity is reflected in the QCM responses for the resonant frequency and resonant resistance. With further cooling, the resonant frequency and resonant resistance sharply change at the induction point of crystal nucleation, as the viscous liquid film on the sensor suddenly shifts to an elastic solid phase. Thereafter, the QCM responses are mainly controlled by the suspension viscosity due to simultaneous crystal nucleation and growth with further cooling. As a result, the QCM responses allow accurate measurement of the induction point and metastable zone width during the cooling crystallization. Additional mechanistic information on the crystallization, including molecular cluster formation, crystal nucleation, and crystal growth, is also extracted from a resonant frequency-resistance plot (F-R plot) of the QCM responses when varying the cooling conditions.

Investigating chiral recognizability of diastereomeric crystallization of mandelic acid and L-phenylalanine.

The present study investigated the mechanism of the chiral recognition of the resolving agent (L-phenylalanine) to the chiral isomers (D/L-mandelic acid). According the NMR analysis, the distinctive chemical shifts of between two diastereomer crystals (L-mandelic acid-L-phenlyalanine and D-mandelic acid-L-phenylalanine) were observed even though there was no difference of the chemicals shift of the two diastereomer solutions. This result indicated that the chiral recognition of the resolving agent mainly occurred during the crystallization of the diastereomers in the solution. Then, the chiral recognition of the diastereomers was confirmed by using thermal analysis and AFM. The diastereomer crystal of L-mandelic acid-L-phenylalanine was much more thermally stable due to the higher lattice energy than the diastereomer crystals of D-mamdelic acid-L-phenylalanine. Also, the adhesive force measured with AFM exhibited a stronger molecular interaction between L-mandelic acid and 4-amino-L-phenylalanine than between D-mandelic acid and 4-amino-L-phenylalanine. Plus, the AFM results implied that the hydroxyl group abundance on the mandelic acid surface was a possible explanation for the different chiral selectivity of the L-phenylalanine.

Evaluation of interaction between histidine binding Cu2+ ion and histidine by atomic force microscopy.

This paper presents a direct interaction force measurement between histidine molecules using AFM force-distance curve measurement. AFM force-distance curves between the histidine-modified cantilever and substrate in the different conditions with or without intercalating Cu2+ ion were measured and interpreted via Gaussian curve fitting analyses. The adhesion force between histidine molecules was shown to be 110 pN under the presence of Cu2+. The result was compareable to the measured adhesion force about 0 pN, which was measured by the removal of Cu2+ ion with the addition of EDTA. The result indicated the direct histidine-histidie interaction was difficult without the role of the bridigible ionic component. From the results, the possibility of direct measurement on chemical affinities between biomolecules was suggested by using AFM force-distance curve analyses. Especially, the current approach showed the possible affinity measurement techniques that elucidate the role of bridge ions.

Chiral recognition of mandelic acid by L-MA derivative-modified sensor in liquid environment.

This study demonstrates a new approach for the highly selective molecular recognition of chiral mandelic acid using an L-mandelic acid derivative with an optically active hydroxyl group as the selector. The proposed method is based on quartz crystal microbalance (QCM) detection combined with functional multilayer film techniques in a liquid environment. The present chiral recognition results suggest that the L-mandelic acid derivative is an excellent resolving agent for detecting chiral mandelic acid.

Construction of simultaneous SPR and QCM sensing platform.

To construct a novel simultaneous SPR and QCM sensing system, an AT-cut quartz crystal is fabricated by sputtering 250 nm of ITO on one side of the quartz plate over a 5-nm thick underlay of titanium, while a 50-nm thick layer of gold is sputter-deposited on the other side to induce a total light reflection of an incident laser beam on the thin gold layer. The signals of the sensing system are detected using a Handy-SPR and QCA922 when dropping 200 microL of Milli-Q water into the sensing cell. A decrease in the SPR reflected light intensity is clearly identified. In the same experiment, the changes in the resonant frequency and resistance are about 2 kHz and 200 Omega, respectively. Furthermore, the oscillation stabilities of the resonant frequency and resistance are about 50 Hz and 2 Omega, respectively, which are sufficient to detect a large mass change on the QCM/SPR chip.

Development of glucose sensor using two-photon adsorbed photopolymerization.

A novel glucose sensor was constructed, and its analytical potential examined. A chip-type three-electrode system for use in a flow-type electrochemical glucose sensor was fabricated using a UV lithography technique on a glass slide. An Ag/AgCl reference electrode was made by electroplating silver onto a Pt electrode and dipping in a saturated KCl solution for 30 min. In addition, a glucose-sensing electrode was fabricated using a two-photon adsorbed photopolymerization technique with a photo-reactive resin containing a glucose oxidase enzyme, ferrocene mediator, non-ionic surfactant, and carbon nanotubes. The cyclic voltammetry of the potassium ferrocyanide in the Pt sensor system showed a stable electrode condition. The response of the modified Pt sensor confirms the feasibility of using a two-photon adsorbed photopolymerization technique for the easy fabrication of functional biosensors.

Study of phase transformation of guanosine 5'-monophosphate in drowning-out crystallization.

The present study used a mechanistic approach to control the phase transformation of guanosine 5'-monophosphate (GMP) via the operating conditions of agitation and feed concentration during drowning-out crystallization. First, Fourier transform infrared and UV/vis spectrophotometry were successfully applied to monitor the mass fraction of GMP polymorphs (amorphous and hydrate crystalline GMPs) and GMP supersaturation, respectively, during the crystallization. The phase transformation of amorphous GMP into hydrate crystals was significantly influenced by the agitation, which promoted the mass transfer of GMP dissolution and growth. Therefore, the phase transformation was quickly finished when increasing the agitation speed. However, a high agitation caused breakage of the hydrate crystals, resulting in a reduced crystal size with a bimodal distribution. The phase transformation was also influenced by the GMP feed concentration, as the crystal growth was promoted and the crystal size increased when increasing the feed concentration up to 61 g/l. However, a further increase in the feed concentration caused secondary nucleation due to the induction of a high supersaturation level during the phase transformation, leading to a small crystal size with a bimodal distribution. In addition, the rectangular-shaped hydrate GMP crystals exhibited a higher growth rate in the b direction rather than the a direction. Therefore, the crystal morphology shifted from a long rectangle to a square when increasing the feed concentration.