Nanoscale biosensor

Medintz, I.L., Clapp, A.R., Mattoussi, H., Goldman, E.R., Fisher, B., and Mauro, J.M. (2003) Self-assembled nanoscale biosensors based on quantum dot FRET donors. Nat. Mater. 2, 630-638. 

The lure of new physical phenomena and new patterns of chemical reactivity has driven a tremendous surge in the study of nanoscale materials. This activity spans many areas of chemistry. In the specific field of electrochemistry, much of the activity has focused on several areas (a) electrocatalysis with nanoparticles (NPs) of metals supported on various substrates, for example, fuel-cell catalysts comprising Pt or Ag NPs supported on carbon [1,2], (b) the fundamental electrochemical behavior of NPs of noble metals, for example, quantized double-layer charging of thiol-capped Au NPs [3-5], (c) the electrochemical and photoelectrochemical behavior of semiconductor NPs [4, 6-8], and (d) biosensor applications of nanoparticles [9, 10]. These topics have received much attention, and relatively recent reviews of these areas are cited. Considerably less has been reported on the fundamental electrochemical behavior of electroactive NPs that do not fall within these categories. In particular, work is only beginning in the area of the electrochemistry of discrete, electroactive NPs. That is the topic of this review, which discusses the synthesis, interfacial immobilization and electrochemical behavior of electroactive NPs. The review is not intended to be an exhaustive treatment of the area, but rather to give a flavor of the types of systems that have been examined and the types of phenomena that can influence the electrochemical behavior of electroactive NPs. 

Van Duyne RP, Haes AJ, Zou S, Schatz GC (2004) A Nanoscale Optical Biosensor The Long Range Distance Dependence of the Localized Surface Plasmon Resonance of Noble Metal Nanoparticles. J Phys Chem B 108 109-116... 

While the variety of NPs used in catalytic and sensor applications is extensive, this chapter will primarily focus on metallic and semiconductor NPs. The term functional nanoparticle will refer to a nanoparticle that interacts with a complementary molecule and facilitate an electrochemical process, integrating supramolecular and redox function. The chapter will first concentrate on the role of exo-active surfaces and core-based materials within sensor applications. Exo-active surfaces will be evaluated based upon their types of molecular receptors, ability to incorporate multiple chemical functionalities, selectivity toward distinct analytes, versatility as nanoscale receptors, and ability to modify electrodes via nanocomposite assemblies. Core-based materials will focus on electrochemical labeling and tagging methods for biosensor applications, as well as biological processes that generate an electrochemical response at their core. Finally, this chapter will shift its focus toward the catalytic nature of NPs, discussing electrochemical reactions and enhancement in electron transfer. 

In the above two independent studies, the feasibility of CPMV as a nanobuilding block for chemical conjugation with redox-active compounds was demonstrated. The resulting robust, and monodisperse particles could serve as a multielectron reservoir that might lead to the development of nanoscale electron transfer mediators in redox catalysis, molecular recognition, and amperometric biosensors and to nanoelectronic devices such as molecular batteries or capacitors. 

In this section, the potential application for amyloid fibrils and other selfassembling fibrous protein structures are outlined. These include potential uses in electronics and photonics presented in Section 4.1, uses as platforms for the immobilization of enzymes and biosensors presented in Section 4.2, and uses as biocompatible materials presented in Section 4.3. Each of these applications makes use of the ability of polypeptides to self-assemble and form nanostructured materials, a process that can occur under aqueous conditions. These applications also seek to exploit the favorable properties of fibrils such as strength and durability, the ability to arrange ligands on a nanoscale, and their potential biocompatibility arising from the natural materials used for assembly. 

Biosensors and devices may also include fiber components. Biosensors essentially contain two main components. These are the sensing element, which senses the molecule of interest, and the transducer, which generates a signal. Amyloid fibrils and other protein nanofibers could be used in biosensors in two ways. The first is as a scaffold to immobilize the sensing element on a nanoscale as described above. The second use is as a coating on the transducer where the presence of the protein fiber could enhance device performance. This enhancement could be carried out either with or without the aid of a further conductive coating (see Section 4.1 above). 

Haes AJ, van Duyne RP. A nanoscale optical biosensor Sensitivity and selectivity of an approach based on the localized surface plasmon resonance spectroscopy of triangular silver nanoparticles. J Am Chem Soc 2002 124 10596-604. 

Keywords Aptamer Biosensor Electrochemistry Nanoparticle Nanoscale... 

Haes, A.J. Zou, S. Schatz, G..C. Van Duyne, R.P. (2004) Nanoscale optical biosensor Short range distance dependence of the localized surface plasmon resonance of noble metal nanoparticles. Journal of Physical Chemistry B 108 6961-6968. 

In addition to its contribution described above, nanoscience can provide an alternative step forward to promoting biomolecular-fluorescence detection. Recent advances in nanoscience permits innovative assembly and fiibrication of nanomaterials for use as advanced biosensor substrates in fluorescence detection. Therefore, nanoscience may offer a much simpler and convenient route in promoting biomolecular fluorescence detection, even when using as-grown nanomaterials without any downstream modifications following their synthesis. In order to design such substrates comprised of nanonaaterials, four key characteristics of the candidate nanoscale materials should be carefiilly considered ... 

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