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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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.

Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. A variety of materials including cyclodextrins, metal complexes, porphyrins, polymers, dendrimers and biomolecules have been extensively explored to mimic the structures and functions of naturally occurring enzymes. Recently, some nanomaterials have been found to exhibit unexpected enzyme-like activities, and great advances have been made in this area due to the tremendous progress in nano-research and the unique characteristics of nanomaterials. To highlight the progress in the field of nanomaterial-based artificial enzymes (nanozymes), this review discusses various nanomaterials that have been explored to mimic different kinds of enzymes. We cover their kinetics, mechanisms and applications in numerous fields, from biosensing and immunoassays, to stem cell growth and pollutant removal. We also summarize several approaches to tune the activities of nanozymes. Finally, we make comparisons between nanozymes and other catalytic materials (other artificial enzymes, natural enzymes, organic catalysts and nanomaterial-based catalysts) and address the current challenges and future directions (302 references).

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes

[Ru(bpy)3]2+-doped silica (RuSi) nanoparticles were synthesized by using a water/oil microemulsion method. Stable electrochemiluminescence (ECL) was obtained when the RuSi nanoparticles were immobilized on a glassy carbon electrode by using tripropylamine (TPA) as a coreactant. Furthermore, the ECL of the RuSi nanoparticles with layer-by-layer biomolecular coatings was investigated. Squential self-assembly of the polyelectrolytes and biomolecules on the RuSi nanoparticles gave nanocomposite suspensions, the ECL of which decreased on increasing the number of bilayers. Moreover, factors that affected the assembly and ECL signals were investigated. The decrease in ECL could be assigned to steric hindrance and limited diffusion of the coreactant molecules in the silica matrix after they were attached to the biomolecules. Since surface modification of the RuSi nanoparticles can improve their biocompatibility and prevent leaking of the [Ru(bpy)3]2+ ions, the RuSi nanoparticles can be readily used as efficient and stable ECL tag materials in immunoassay and DNA detection.

/pdf/ru-bpy-3-2-doped-silica-nanoparticles-within-layer-by-layer-1hnri9otbi.pdf

[Ru(bpy)3]2+‐Doped Silica Nanoparticles within Layer‐by‐Layer Biomolecular Coatings and Their Application as a Biocompatible Electrochemiluminescent Tag Material

Selective glucose detection based on the concept of electrochemical depletion of electroactive species in diffusion layer

Department of Biomedical Engineering, College of Engineering and Applied Sciences, Nanjing National Laboratory of Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Jiangsu 210093, China; State Key Laboratory of Analytical Chemistry for Life Science and State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Jiangsu 210023, China

Design of high performance nanozymes: a single-atom strategy

Using light as an external stimulus plays a key role not only in modulating activities of nanozymes, but also in constructing efficient biosensing systems. This mini-review highlights recent advances in light-responsive nanozyme-based biosensing systems. First, we introduce the light stimulation for regulating nanozymes' activities. Then, several strategies are presented to construct efficient photo-responsive nanozyme-based detection systems by using metal-based nanozymes, carbon-based nanozymes, and MOF-based nanozymes, respectively. Moreover, the detection mechanisms of current biosensors are discussed. Finally, we discuss the current challenges and future perspectives of this research area.

Light-responsive nanozymes for biosensing

Two-dimensional (2D) nanomaterials (such as 2D MnO2 nanosheets) have received increasing attention due to their unique photophysical properties, rich redox chemistry, excellent colloidal stability, good biocompatibility, etc. Recently, numerous sensing platforms have been reported by exploring the 2D MnO2 nanosheet mediated fluorescence quenching towards fluorophores and/or redox reactions between MnO2 and reductive targets. Though various fluorophores have been used in 2D MnO2 nanosheet based turn-on sensing systems, ultrasmall metal nanoclusters have not been exploited yet. Furthermore, the quenching mechanisms of MnO2 nanosheets towards various fluorophores have remained elusive. To address these issues, we studied the quenching of Au nanocluster fluorescence by 2D MnO2 nanosheets. First, we demonstrated that 2D MnO2 nanosheets were effective quenchers towards the fluorescence of metal nanoclusters (e.g., AuNC@BSA, the bovine serum albumin stabilized Au nanocluster). We further revealed that both dynamic and static quenching effects played critical roles in the quenching process while fluorescence resonance energy transfer (FRET) and inner filter effect (IFE) only played very minor roles in the quenching process. Finally, we developed a turn-on sensing strategy for detection of glutathione (GSH), an important antioxidant with good sensitivity and selectivity. This work provides useful insights in understanding the mechanisms of nanomaterial-induced fluorescence quenching. It also paves a way to design turn-on fluorescent sensors for important reductive targets.

Hui Wei

Papers

[Ru(bpy)3]2+‐Doped Silica Nanoparticles within Layer‐by‐Layer Biomolecular Coatings and Their Application as a Biocompatible Electrochemiluminescent Tag Material

Selective glucose detection based on the concept of electrochemical depletion of electroactive species in diffusion layer

Design of high performance nanozymes: a single-atom strategy

Light-responsive nanozymes for biosensing

Deciphering the quenching mechanism of 2D MnO2 nanosheets towards Au nanocluster fluorescence to design effective glutathione biosensors