There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13

In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28

Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37



Figure 1

Physical properties of AuNPs and schematic illustration of an AuNP-based detection system.



In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

/pdf/gold-nanoparticles-in-chemical-and-biological-sensing-5e2qojkdzn.pdf

Gold nanoparticles in chemical and biological sensing.

基礎講座 電気泳動(Electrophoresis)

This protocol provides an introduction to soft lithography--a collection of techniques based on printing, molding and embossing with an elastomeric stamp. Soft lithography provides access to three-dimensional and curved structures, tolerates a wide variety of materials, generates well-defined and controllable surface chemistries, and is generally compatible with biological applications. It is also low in cost, experimentally convenient and has emerged as a technology useful for a number of applications that include cell biology, microfluidics, lab-on-a-chip, microelectromechanical systems and flexible electronics/photonics. As examples, here we focus on three of the commonly used soft lithographic techniques: (i) microcontact printing of alkanethiols and proteins on gold-coated and glass substrates; (ii) replica molding for fabrication of microfluidic devices in poly(dimethyl siloxane), and of nanostructures in polyurethane or epoxy; and (iii) solvent-assisted micromolding of nanostructures in poly(methyl methacrylate).

/pdf/soft-lithography-for-micro-and-nanoscale-patterning-21e1ngmrqv.pdf

Soft lithography for micro- and nanoscale patterning

A review of the substrates used in microbial fuel cells (MFCs) for sustainable energy production.

Rapid and accurate diagnosis of C-reactive protein (CRP) is crucial for preventing cardiovascular diseases because it is a well-known biomarker for evaluating risks of cardiovascular diseases. Our previous work has shown that a microfluidic system equipped with a field-effect-transistor (FET)-based biosensor could detect CRP in 0.1X PBS and provided a limit of detection (LOD) of 26 pM CRP without gate bias. To improve the LOD, a new microfluidic device with a new methodology for measuring FET-based biosensors is presented in this study. Not only can the proposed system work in a solution with a physiological salt concentration but it also detects CRP with ultra-high sensitivity in an automatic fashion. This is the first time that a FET-based biosensor can effectively and automatically detect CRP in a physiological salt concentration without decreasing the sensitivity. The LOD of CRP using aptamer-immobilized AlGaN/GaN high-electron-mobility transistors (HEMTs) was experimentally found to be 1fM, demonstrating the superior performance of this new technique. It may be used as a point-of-care device for CRP detection in the near future.

An integrated microfluidic system with field-effect-transistor-based biosensors for automatic highly-sensitive C-reactive protein measurement

Integrated microfluidic system for rapid selection of CRP aptamers utilizing systematic evolution of ligands by exponentail enrichment

This study reports an approach to dynamically separate cultured human B-lymphoma (Raji) cells from normal human red blood cells (RBCs), mixed in an isotonic solution, by utilizing a hydrogenated amorphous silicon-based optically-induced electrokinetics chip. A theoretical calculation of the polarization model for the two different types of cells is first presented. The differential velocity between the cell types, generated as a result of the optically-induced dielectrophoresis (ODEP) force is obtained using a finite element method. The theoretical results indicate that the two types of cells could be separated by using the ODEP force. Experimental results verified that the two types of cells can be separated by using two optically projected lines of different widths, with one projected line moving and the other line stationary, as the virtual electrodes for generating the ODEP force. Separation is achieved with these virtual electrodes using a bias potential of 20 Vpp at a driving frequency of 50 kHz. To the best of our knowledge, this work is the first experimental validation of rapid separation of Raji cells from RBCs using optically-induced electrokinetics.

Dynamic separation of b-lymphoma cells from red blood cells using optically-induced electrokinetics

A microfluidic chip is provided, including: a plurality of first storage tanks and a plurality of second storage tanks that respectively store different solutions for a preprocess and hybridization process of the fluorescence in situ hybridization; a transmission unit adjacent to the first storage tanks; a reaction unit adjacent to the second storage tanks for a biological target to be placed thereon; a plurality of first valves disposed between the first storage tanks and the transmission unit; and a plurality of second valves disposed between the second storage tanks and the reaction unit, wherein the first valves and the second valves are opened in a predetermined sequence so as to transmit the solutions of the first storage tanks and the second storage tanks to the reaction unit, such that the solutions perform the preprocess and hybridization process of the fluorescence in situ hybridization to the biological target in sequence.

Microfluidic chip, operating system and operating method of the microfluidic chip for fluorescence in situ hybridization

Toward the development of micropumps that operate under low external air pressures, a new polydimethylsiloxane (PDMS), pneumatic micropump using amplified deformation of resilient PDMS membranes through oil hydraulics was presented in this study. The new micropump employed oil-hydraulic chambers with pre-filled mineral oil to amplify the deformation of flexible PDMS membranes; it therefore delivered a higher pumping rate and withstood a greater back pressure while requiring a significantly lower external air pressure for actuation. The optimized pumping rate and back pressure of the oil-hydraulic micropump compared favorably to previous pneumatic micropumps. Characterization of the micropump revealed that the oil hydraulics amplified the deformation of PDMS membranes by approximately threefold and improved the pumping rate and the back pressure by 77 and 21 %, respectively. With high pumping performances and the capability to be driven with only a low air pressure, this new micropump may therefore become a key component in future microfluidic devices and lab-on-a-chip systems.

Gwo-Bin Lee

Papers

An integrated microfluidic system with field-effect-transistor-based biosensors for automatic highly-sensitive C-reactive protein measurement

Integrated microfluidic system for rapid selection of CRP aptamers utilizing systematic evolution of ligands by exponentail enrichment

Dynamic separation of b-lymphoma cells from red blood cells using optically-induced electrokinetics

Microfluidic chip, operating system and operating method of the microfluidic chip for fluorescence in situ hybridization

A micropump using amplified deformation of resilient membranes through oil hydraulics