Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

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.

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Gold nanoparticles in chemical and biological sensing.

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.

/pdf/nanoparticles-proteins-and-nucleic-acids-biotechnology-meets-4nzdmnwi4l.pdf

Nanoparticles, Proteins, and Nucleic Acids: Biotechnology Meets Materials Science

9.2. Protein-Based Hg(II) Detectors 3467 9.3. Oligonucleotide-Based Hg(II) Detector 3467 9.4. DNAzyme-Based Hg(II) Detectors 3469 9.5. Antibody-Based Hg(II) Detector 3469 10. Mercury Detectors Based on Materials 3469 10.1. Soluble and Fluorescent Polymers 3469 10.2. Membranes, Films, and Fibers 3471 10.3. Micelles 3473 10.4. Nanoparticles 3473 11. Perspectives 3474 12. Addendum 3475 12.1. Small Molecules 3475 12.2. Biomolecules 3477 12.3. Materials 3477 13. List of Abbreviations 3477 14. Acknowledgments 3478 15. References 3478

Tools and tactics for the optical detection of mercuric ion.

The Flavonoid Baicalein Inhibits Fibrillation of α-Synuclein and Disaggregates Existing Fibrils

The aggregation of alpha-synuclein is believed to be a key step in the etiology of Parkinson's disease. Alpha-synuclein is found in the cytosol and is associated with membranes in the presynaptic region of neurons and has recently been reported to be associated with lipid rafts and caveolae. We examined the interactions between several brain sphingolipids and alpha-synuclein and found that alpha-synuclein specifically binds to ganglioside GM1-containing small unilamellar vesicles (SUVs). This results in the induction of substantial alpha-helical structure and inhibition or elimination of alpha-synuclein fibril formation, depending on the amount of GM1 present. SUVs containing total brain gangliosides, gangliosides GM2 or GM3, or asialo-GM1 had weak inhibitory effects on alpha-synuclein fibrillation and induced some alpha-helical structure, while all other sphingolipids studied showed negligible interaction with alpha-synuclein. alpha-Synuclein binding to GM1-containing SUVs was accompanied by formation of oligomers of alpha-synuclein. The familial mutant A53T alpha-synuclein interacted with GM1-containing SUVs in an analogous manner to wild type, whereas the A30P mutant showed minimal interaction. This is the first detailed report showing a direct association between GM1 and alpha-synuclein, which is attributed to specific interaction between helical alpha-synuclein and both the sialic acid and carbohydrate moieties of GM1. The recruitment of alpha-synuclein by GM1 to caveolae and lipid raft regions in membranes could explain alpha-synuclein's localization to presynaptic membranes and raises the possibility that perturbation of GM1/raft association could induce changes in alpha-synuclein that contribute to the pathogenesis of PD.

GM1 specifically interacts with alpha-synuclein and inhibits fibrillation.

http://www.jbc.org/content/282/8/5862.full.pdf

Effect of 4-Hydroxy-2-nonenal Modification on α-Synuclein Aggregation

Elucidating the details of the assembly of amyloid fibrils is a key step to understanding the mechanism of amyloid deposition diseases including Parkinson's disease. Although several models have been proposed, based on analyses of polypeptides and short peptides, a detailed understanding of the structure and mechanism of α-synuclein fibrillation remains elusive. In this study, we used trypsin and endoproteinase GluC to digest intact α-synuclein fibrils and to analyze the detailed morphology of the resultant fibrils/remnants. We also created three mutants of α-synuclein, in which the N-terminal and C-terminal regions were removed, both individually and in combination, and investigated the detailed morphology of the fibrils from these mutants. Our results indicate that the assembly of mature α-synuclein fibrils is hierarchical:  protofilaments → protofibrils → mature fibrils. There is a core region of ∼70 amino acids, from residues ∼32 to 102, which comprises the β-rich core of the protofilaments and fibril...

Role of Different Regions of α-Synuclein in the Assembly of Fibrils†

http://faculty.uncfsu.edu/shan/research/2001 hg bb.pdf

Shubo Han

Papers

The Flavonoid Baicalein Inhibits Fibrillation of α-Synuclein and Disaggregates Existing Fibrils

GM1 specifically interacts with alpha-synuclein and inhibits fibrillation.

Effect of 4-Hydroxy-2-nonenal Modification on α-Synuclein Aggregation

Role of Different Regions of α-Synuclein in the Assembly of Fibrils†

A methylene blue-mediated enzyme electrode for the determination of trace mercury(II), mercury(I), methylmercury, and mercury-glutathione complex