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

Repetitive chromatography of the methanol extract of the roots of Gentiana tibetica afforded two new secoiridoid glycosides and a novel antifungal anthranilic acid derivative, together with beta-sitosterol, daucosterol, oleanolic acid, loganic acid, gentiopicroside, sweroside, 2'-(2,3-dihydroxybenzoyl)sweroside, trifloroside, rindoside and macrophylloside A. The structures of the new products were determined mainly by spectroscopic methods as 8-hydroxy-10-hydrosweroside, isomacrophylloside and ethyl N-docosanoylanthranilate. Ethyl N-docosanoylanthranilate inhibited the growth of the human pathogenic fungi Candida albicans and Aspergillus flavus. The taxonomic significance of the constituent is discussed briefly.

Secoiridoid Glycosides and an Antifungal Anthranilate Derivative from Gentiana tibetica.

An approach was reported to synthesize silica hybridized ruthenium bipyridyl complex through amidation reaction by covalent attachment of bis(bipyridyl)-4,4′-dicarboxy-2,2′-bipyridyl-ruthenium to (3-aminopropyl)-triethoxy- silane. The hybrid complex then was gelatinized through acid catalytic hydrolysis method and a sol-gel modified indium tin oxide electrode was prepared via spin coating technique. As prepared indium tin oxide electrode possesses good stability therein with excellent electrochemiluminescence behavior.

Tris(2,2′‐bipyridyl) Ruthenium(II) Doped Silica Film Modified Indium Tin Oxide Electrode and Its Electrochemiluminescent Properties

Nanozymes are the functional nanomaterials with enzyme-like characteristics. After discussing the advantages of nanozymes compared with natural enzymes and conventional artificial enzymes in the introduction section, various nanozyme-based biosensing strategies for in vitro and in living systems were discussed. Four subsections were devoted to in vitro sensing with nanozymes. First, nanozymes with peroxidase-mimicking activities for colorimetric sensing of H 2 O 2 and other important targets were discussed. Second, nanozymes with oxidase-mimicking activities for colorimetric sensing of dopamine, acetylcholinesterase, etc., were discussed. Third, the colorimetric detection of oxidase substrates was achieved by combining natural oxidases and nanozymes with peroxidase-mimicking activities. For example, glucose, choline, d -alanine, uric acid, and xanthine have been successfully detected with this strategy. Fourth, other detection strategies based on fluorescence, chemiluminescence, and electrochemistry using nanozymes were discussed. Then, the recent progress in nanozymes for in vivo sensing of important biotargets was discussed. For instance, the monitoring glucose dynamic changes in living rats were achieved with newly fabricated integrative nanozymes. Finally, the remaining challenges and future directions in nanozymes research are speculated to inspire researchers for further studies.

Nanozymes for Biomedical Sensing Applications: From In Vitro to Living Systems

The promise of anti‐tumor immunotherapy is limited partially by low antigen exposure and the hypoxic tumor microenvironment. To address these two limitations simultaneously, herein, a multifunctional AuNR@BSA/MnO2 to enable photothermal therapy‐induced immunogenic cell death (ICD) and hypoxia relief‐benefited M1 polarization of macrophages for enhanced cancer immunotherapy, is designed. The ICD and M1 polarization are demonstrated both in vitro and in vivo by detecting the corresponding markers. Then, enhanced immunotherapeutic efficacy is achieved in a 4T1 tumor‐bearing mice model. Additionally, when combined with a checkpoint blockade therapy (PD‐1 inhibitor), the AuNR@BSA/MnO2 shows distant effects including anti‐distant tumor, anti‐metastasis, and even improved survival. Last, the AuNR@BSA/MnO2 has multi‐imaging functions, such as photoacoustic imaging and magnetic resonance imaging. This study provides a new strategy to design multifunctional nanomedicines for improving anti‐tumor immunotherapy and imaging guided therapy.

Combining Photothermal Therapy‐Induced Immunogenic Cell Death and Hypoxia Relief‐Benefited M1‐Phenotype Macrophage Polarization for Cancer Immunotherapy

Development of biosensors for the detection of oversulfated chondroitin sulfate (OSCS), the key contaminant in heparin (Hep), is a greatly demanding but challenging task. In this work, a FRET system for the detection of OSCS was successfully constructed by using supercharged green fluorescent protein (ScGFP) as the energy donor and dye labelled Hep (Hep-RF1) as the energy acceptor. With heparinase treatment, Hep-RF1 was hydrolyzed into small fragments, resulting in quenching of the FRET signal. On the other hand, since OSCS is an inhibitor for heparinase, the presence of OSCS would enable the effective FRET from ScGFP to Hep-RF1 even after heparinase treatment. With this ScGFP based FRET sensing platform, as low as 0.001% (w/w) OSCS in Hep has been successfully detected.

Hui Wei

Papers

Secoiridoid Glycosides and an Antifungal Anthranilate Derivative from Gentiana tibetica.

Tris(2,2′‐bipyridyl) Ruthenium(II) Doped Silica Film Modified Indium Tin Oxide Electrode and Its Electrochemiluminescent Properties

Nanozymes for Biomedical Sensing Applications: From In Vitro to Living Systems

Combining Photothermal Therapy‐Induced Immunogenic Cell Death and Hypoxia Relief‐Benefited M1‐Phenotype Macrophage Polarization for Cancer Immunotherapy

A supercharged fluorescent protein based FRET sensing platform for detection of heparin contamination