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.

An aptamer-based sandwich assay for detection of alpha-defensin human neutrophil protein 1 on a microfluidic platform

There is a critical need for early detection of pathogens in Phalaenopsis orchid due to its high economic value in agriculture. In our previous work [1], an integrated microfluidic system capable of detecting these pathogens through pathogen-specific ribonucleic acid (RNA) purification and RNA amplification by using reverse transcription loop-mediated-isothermal-amplification (RT-LAMP) was presented. In this study, a buried optical fiber-based detection module was integrated with the microfluidic chip to monitor the RT-LAMP reaction directly on-chip such that in-line optical detection can be realized. Successful RT-LAMP reaction, which amplifies the nucleic acids that yield the precipitate, magnesium pyrophosphate, and therefore increased the turbidity in the LAMP products could be detected optically. Furthermore, a fluorescent dye, calcein, could be also used in our system to detect the fluorescent signals, if necessary. Thus sensitive and fast diagnosis of the pathogens in Phalaenopsis orchids could be successfully achieved by using the integrated microfluidic system.

An integrated microfluidic system using buried optical fibers for detection of phalaenopsis orchid pathogens

In this study, a new screening process called "bacterial SELEX" was reported to screen favorable aptamers targeting four common nosocomial and antibiotics-resistant bacteria, including Acinetobacter baumannii, vancomycin-resistant Enterococci (VRE), Escherichia coli, and multidrug-resistant Staphylococcus aureus (MRSA). The new bacterial SELEX system performed three critical selecting stages for screening of bacteria-specific aptamers. A paper-based microfluidic system was further developed by using the selected specific aptamers and a biotin-streptavidin color reaction for rapid detection of these four bacteria. The proposed paper-based microfluidic chip has several advantages, such as compactness in size, ease to handle, high specificity and capability to detect multiple pathogens simultaneously. It may be promising for point-of-care applications in the near future.

Using bacterial selex to select highly-specific aptamers and their applications in paper-based microfluidic chips for rapid diagnosis of multiple bacteria

This study reported a portable microfluidic system which can be used to automatically perform antibiotic screening with single antibiotic, double antibiotic combinations and even triple antibiotic combinations on clinically isolated bacteria strains. With the incorporation of the integrated pneumatically-driven microfluidic chip, a pneumatic control module, a temperature control module, and an optical detection module, the developed system was capable of achieving significant improvement of operation flexibility as well as cost reduction for determination of antimicrobial susceptibility test and the efficacy of drug combinations via colorimetric results within 4 hours. Personalized antibiotic screening may be realized by using the developed microfluidic system for rapid clinical decision-making.

A Portable, Automatic Microfluidic System for Rapid Personalized Antibiotic Screening

Optimization of drug cocktails has been an important issue for a number of therapies of complicated diseases; however, it is an extremely task using traditional methods. Here we demonstrate a new microfluidic platform capable of automatically dispensing, mixing a small amount of drug combinations, and adding them to the cell cultures such that a precise and fine-tuned drug cocktails may be formed for the subsequent cell-level testing. Our proposed system could decrease manual bias and enhance the throughput of drug cocktail formulation on an automated and minituriazed microfluidic system.

Gwo-Bin Lee

Papers

An aptamer-based sandwich assay for detection of alpha-defensin human neutrophil protein 1 on a microfluidic platform

An integrated microfluidic system using buried optical fibers for detection of phalaenopsis orchid pathogens

Using bacterial selex to select highly-specific aptamers and their applications in paper-based microfluidic chips for rapid diagnosis of multiple bacteria

A Portable, Automatic Microfluidic System for Rapid Personalized Antibiotic Screening

Optimization of drug cocktail on an integrated microfluidic system