Robust Long-Nanowire Fabrication by Clean-Phase-Assisted Micro Chemical Pen for Enhanced Bioassay Sensitivity.

Long nanowires offer an increased surface area for biomolecule immobilization, facilitating enhanced binding capacity and sensitivity in the detection of target analytes. However, robust long-nanowire fabrication remains a significant challenge. In this paper, we developed a novel construction of a micro chemical pen (MCP), called a clean-assisted micro chemical pen (CAMCP), for robust long-nanowire fabrication.

Development of a C-reactive protein quantification method based on flow rate measurement of an ink solution pushed out by oxygen gas generated by catalase reaction.

A novel determination method for protein biomarkers based on on-chip flow rate measurement was developed using a microchip with organic photodiodes (OPDs). This quantitative method is based on the flow rate measurement of an ink solution pushed out by oxygen gas generated through catalase reaction. The amount of oxygen gas generated in the sample reservoir is dependent on the concentration of the analyte; therefore, the flow rate of the ink solution is also dependent on the concentration of the analyte.

Development of small-sized fluorescence detector for pipette tip-based biosensor for on-site diagnosis.

A small-sized fluorescence detector (referred to as a pipette tip [PT]-reader) was developed for a pipette tip-based biosensor. The PT-reader allows us to measure the fluorescence intensity of a solution in a truncated cone-shaped pipette tip with only the tip inserted into the PT-reader. A pipette holder made from a mixture of polydimethylsiloxane (PDMS) and carbon black was capable of the rigorous position arrangement of a truncated cone shaped-pipette tip and the prevention of stray light.

Hydrophilic interaction chromatography-type sorbent prepared by the modification of methacrylate-base resin with polyethyleneimine for solid-phase extraction of polar compounds.

Hydrophilic interaction chromatography (HILIC)-type sorbents were newly developed for the solid-phase extraction (SPE) of polar compounds. Two methacrylate-base resins with different cross-linking monomers and pore properties were synthesized, and three polyethyleneimines (PEIs) with different molecular weights were modified onto each base resin. In both cases, PEIs with a molecular weight of 10,000 (PEI-10,000) exhibited the highest adsorption properties for polar compounds (uracil, uridine, adenosine, cytidine, and guanosine).

Microsphere amplified fluorescence and its application in sensing.

The far-field fluorescence amplification, the intense fluorescence emission addresses the great potential in sensitive detection to large biomolecules, was seriously ignored for the failure in amplifying the weak fluorescence excepting the electromagnetic field (EM) induced fluorescence amplification on the metallic surfaces. Here, a microsphere in hundreds of micrometers was adopted to proceed with the fluorescence amplification via building up a local dielectric surrounding for fluorophore. The wide range of contribution-angle fluorescence could be efficiently restricted within the microsphere by facilitating the energy of reflection restraining and declining the energy of refraction decaying and the intense fluorescence emission confined within the microsphere could be directly observed.

Localized hydrodynamic flow confinement assisted nanowire sensor for ultrasensitive protein detection.

Affordable methods for ultra-sensitive biomarkers detection may improve the standard of living in resource-constrained countries. Nanowire biosensor is preponderant in ultra-sensitive protein detection. However, current strategies for nanowire sensor (NWS) fabrication often require sophisticated instruments, being inaccessible in less-resourced laboratories.

Regioselective fabrication of gold nanowires using open-space laminar flow for attomolar protein detection.

Gold nanowires are expected to be applied to biosensing due to their advantages, such as high stability and biocompatibility. However, it is still inconvenient to fabricate a single gold nanowire at a precise position, and without a special demanding environment. In this study, we present an open-space laminar flow approach for fabricating a single gold nanowire at a precise position under normal conditions.

Development of a surface plasmon resonance sensor using an optical fiber prepared by electroless displacement gold plating and its application to immunoassay.

A simple and low-cost method of fabricating an optical fiber for a surface plasmon resonance (SPR) sensor was proposed. The method is based on the electroless nickel plating and subsequent displacement gold plating of the core of the optical fiber. The thickness of the nickel and gold thin films deposited on the core of the optical fiber could be controlled by measuring the reflected light intensity from the tip of the optical fiber during the plating processes.

Development of a fluorescence microplate reader using an organic photodiode array with a large light receiving area.

We developed a small fluorescence microplate reader with an organic photodiode (OPD) array. The OPD array has nine OPDs that have a large light receiving area (9.62 mm per one OPD).

Single-Cell Stimulation and Real-Time Electrochemical Detection of Lactate Response Using a Microfluidic Probe.

Metabolism of a single cell, even within the same organization, differs from other cells by orders of magnitude. Single-cell analysis provides key information for early diagnosis of cancer as well as drug screening. Any slight change in the microenvironment may affect the state of a single cell.

A Fluidic Isolation-Assisted Homogeneous-Flow-Pressure Chip-Solid Phase Extraction-Mass Spectrometry System for Online Dynamic Monitoring of 25-Hydroxyvitamin D Biotransformation in Cells.

It is well known that cell can response to various chemical and mechanical stimuli. Therefore, flow pressure variation induced by sample loading and elution should be small enough to ignore the physical impact on cells when we use a Chip-SPE-MS system for cells. However, most existent Chip-SPE-MS systems ignored the pressure alternation because it is extremely difficult to develop a homogeneous-flow-pressure hyphenated module.

Film-Thickness-Controllable System for Preparing Silver Nanofilms through Absorbance Monitoring of the Thickness during a Silver-Mirror Reaction.

An innovative technique is proposed for forming silver thin films of nanometer-order thickness via a silver-mirror reaction. This approach is made possible by the real-time monitoring of the thickness of a silver thin film formed on the edge surface of a fiber core during the silver-mirror reaction using a homemade absorbance measurement system. The monitored absorbance value increases as silver plating progresses, and the relationship between the absorbance values and the thickness of the silver thin film is linear in the thickness range from approximately 30 to 60 nm.

Development of an on-chip sample injection system with a 6-port valve incorporated in a microchip.

Micro-flow-injection analysis (μFIA) is amenable to high-throughput systems with lower consumption of sample and reagent volumes. On-chip sample injection methods are important to prevent reduced analytical performance associated with dead volumes and diffusion of sample solutions. In this study, we have developed an on-chip sample injection system with a small-sized 6-port valve incorporated on a microchip.

Droplet Sensitized Fluorescence Detection for Enzyme-Linked Immune Sorbent Assays on Microwell Plate.

The microwell plate/microtiter plate is among the most widely used tools in immune assays. In this paper, we report on a sensitive method for enhancing fluorescence emission detection by simply adding several droplets of an immiscible organic compound into the microwells before detection. To prove the concept, human IgA was determined on a microwell plate using this droplet enhanced fluorescence (DEF) detection method.

Reversibly Switching Molecular Spectra.

Manipulation of light transmission/absorbance and reflection/emission has a great significance in smart windows and displaying media like liquid crystal. Here, we report the usage of an external electric field to reversibly switch the molecular spectra of a model molecule on the basis of its interaction with an electroresponsible polymer brush. Both the UV-vis absorbance spectrum and the fluorescence emission spectrum of the model molecule were confirmed to be electroswitchable.

Inkjet Printing Based Droplet Generation for Integrated Online Digital Polymerase Chain Reaction.

We report on the development of a novel and flexible online digital polymerase chain reaction (dPCR) system. The system was composed of three parts: an inkjet for generating the droplets, a coiled fused-silica capillary for thermal cycling, and a laser-induced fluorescence detector (LIFD) for positive droplet counting. Upon inkjet printing, monodisperse droplets were continuously generated in the oil phase and then introduced into the capillary in the form of a stable dispersion.

Elaborately programmed nanowires fabricated using a tapered push-pull nozzle system.

Elaborately programmed silver nanowire arrays can be prepared using a tapered push-pull nozzle system (TPPNS), which is used to directly write micro-nano wires on a substrate via a two-reagent reaction in the diffusion mixing region. The wires could be precisely positioned on the substrate and their width could be freely controlled from the micro to the nano scale, indicating an advance in the methodologies of controlling and fabricating nanowires. The as-prepared silver three-electrode device can serve as a three-electrode sensor.

Inkjet Printing Based Separation of Mammalian Cells by Capillary Electrophoresis.

This study describes a method to investigate the separation of cells by capillary electrophoresis (CE) coupled with inkjet printing system. The results validated the feasibility of inkjet printing for mammalian cells to achieve the drop-on-demand and convenient sampling into capillary then zone electrophoresis was applied to separate different cells according to their electrophoretic mobility, finally the peak signal were measured by UV detector. Linear relationship between the peak area and the droplet number was obtained within the range of 25-400 drops (R = 0.

Rapid ELISA Using a Film-Stack Reaction Field with Micropillar Arrays.

A film-stack reaction field with a micropillar array using a motor stirrer was developed for the high sensitivity and rapid enzyme-linked immunosorbent assay (ELISA) reaction. The effects of the incubation time of a protein (30 s, 5 min, and 10 min) on the fluorescence intensity in ELISAs were investigated using a reaction field with different micropillar array dimensions (5-µm, 10-µm and 50-µm gaps between the micropillars). The difference in fluorescence intensity between the well with the reaction field of 50-µm gap for the incubation time of 30 s and the well without the reaction field with for incubation time of 10 min was 6%.

Convection-Diffusion Layer in an "Open Space" for Local Surface Treatment and Microfabrication using a Four-Aperture Microchemical Pen.

A four-aperture microchemical pen was used to produce a stable convection-diffusion layer in an "open space" for microreactions and microfabrication. The process represents a new method for microreactions and microfabrication in a convection-diffusion layer. To prove the concept of a convection-diffusion layer in an "open space", bovine serum albumin was labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole to confirm that the small convection-diffusion layer was effective for local surface treatment.

The use of an inkjet injection technique in immunoassays by quantitative on-line electrophoretically mediated microanalysis.

The paper describes a new online quantitative electrophoretically mediated microanalysis (EMMA) for use in immunoassays based on the unique drop-by-drop introduction of a sample by means of an inkjet for capillary electrophoresis (CE). Plugs of a fluorescein-labeled antibody (Anti-humanIgG-DyL550) and human IgG were alternately injected into a capillary using the inkjet, followed by the merging of the plugs and the subsequent immune reaction. The antigen-antibody complex that was formed in the merged zone was then separated by CE.

Microchemical Pen: An Open Microreactor for Region-Selective Surface Modification.

Various micro surface-modification approaches including photolithography, dip-pen lithography and ink-jet systems have been developed and used to extend the functionalities of solid surfaces. While those approaches work in the "open space", push-pull systems which work in solutions have recently drawn considerable attention. However, the confining flows performed by push-pull systems have realized only the dispense process, while microscale, region-selective chemical reactions have remained unattainable.

Inkjet printing based assembly of thermoresponsive core-shell polymer microcapsules for controlled drug release.

A controlled drug delivery system (DDS) was designed by integrating the thermoresponsive copolymer poly(N-isopropylacrylamide-co-methacrylic acid) (poly(NIPAAm-co-MAA)) with core-shell 1,6-hexanediol diacrylate (HDDA) microparticles. The monodisperse HDDA particles with a hollow core and a nanoporous shell were fabricated in a continuous manner by an initially proposed inkjet printing process combined with UV polymerization. The thermoresponsive poly(NIPAAm-co-MAA) copolymer was grafted onto the surface of HDDA microcapsules by free radical initiated polymerization.

Development of a Portable Surface Plasmon Resonance Sensor with Multi-Sensing Points Based on the Linear CCD Sensor.

A portable-type surface plasmon resonance (SPR) sensor, composed from a new optical system for multi-sensing, has been developed to apply to environment analysis, clinical diagnosis etc., where many samples are desired to be analyzed at high throughput. The optical system of the sensor consists of a light-emitting diode, a pair of cylindrical lenses, a pair of collimator lenses, a correction lens, a prism, a polarizer and a linear CCD sensor with 2048 pixels.

Droplet Enhanced Fluorescence for Ultrasensitive Detection Using Inkjet.

A fluorescence enhanced phenomenon was found within a micrometer-sized liquid droplet, and it was adopted to construct droplet enhanced fluorescence (DEF) for ultrasensitive fluorescence detection. In this paper, an inkjet was utilized to eject perfect spherical droplets to construct a microspherical resonator and to develop a DEF system. It was utilized to implement ultrasensitive fluorescence detection in a liquid specimen with a volume of several microliters.