Castillo-León / Svendsen Micro and Nanofabrication Using Self-Assembled Biological Nanostructures

1. Auflage 2014
ISBN: 978-0-323-29652-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 126 Seiten

Reihe: Micro and Nano Technologies

Self-assembled nanostructures based on peptides and proteins have been investigated and presented as biomaterials with an impressive potential for a broad range of applications such as microfabrication, biosensing platforms, drug delivery systems, bioelectronics and tissue reparation. Through self-assembly peptides can give rise to a range of well-defined nanostructures such as nanotubes, nanofibers, nanoparticles, nanotapes, gels and nanorods. However, there are challenges when trying to integrate these biological nanostructures in the development of sensing devices or drug-delivery systems - challenges such as controlling the size during synthesis, the stability in liquid environments and manipulation. In 'Micro and Nanofabrication Using Self-assembled Biological Nanostructures' the options and challenges when using self-assembled peptide nanostructures in micro and nanofabrication are discussed. The publication covers different ways to manipulate, deposit and immobilize on specific locations these biological nanostructures in order to use them in the fabrication of new structures or as part of biosensing platforms. Examples where researchers used biological nanostructures for those types of applications are provided. Finally, future applications are discussed as well as parameters to accelerate and expand the use of these biological building blocks in nano- and micro-fabrication processes by taking advantage of their impressive properties such as low-cost and short synthesis time.

Autoren/Hrsg.

Castillo-León, Jaime

Svendsen, Winnie

Leseproben

Chapter 1 Self-Assembled Biological Nanofibers for Biosensor Applications
Luigi Sasso1,2 Juliet A. Gerrard1,2
1    Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, New Zealand
2    MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand Abstract
Self-assembled biological nanofibers, such as protein amyloid fibrils or peptide nanotubes, have the potential of making an enormous impact in future biosensor technologies because of the many advantages associated with their biological and nano-properties, including their inexpensiveness, ease in production and high surface-to-volume ratios. There are, however, practical considerations when working with this type of material that have to be taken into account to ensure for stability, detection sensitivity, and efficiency in functionalization and nanomanipulation. This chapter discusses the major challenges of working with self-assembled biological nanofibers and several strategies and approaches that have been used for their handling and applications in biosensing. Keywords
Self-assembly bionanostructure biosensor functionalization amyloid fibril peptide nanotube electrochemical characterization nanomanipulation 1.1. Introduction
The use of nanomaterials in analytical systems has been gradually growing, due to the promise of increased precision and sensitivity offered by the nanoscale dimensions. When used as nanoscaffolds, the high surface-to-volume ratios provided by nanomaterials offer an increase in immobilization of functional sensing components, resulting in the ability to detect lower analyte concentrations [1]. Bionanomaterials, such as biological nanofibers, offer particular advantages over their inorganic counterparts: the laboratory conditions for their self-assembly and synthesis are mild when compared with harsh solvents and environments found in inorganic nanofabrication techniques; there are available primary sources for biological nanofibers originating from low-value coproducts of the pharmaceutical and biotech industry, offering cost-effectiveness and an environmentally friendly approach to the production of nanomaterials [2–5]; the biological nature of bionanofibers adds a biocompatibility element to their applications, as well as a versatility in functionalization due to the variety of chemical moieties provided by the amino-acid residues in their protein and peptide building blocks. Because of these benefits, biological nanofibers have been gathering considerable attention over the past decades by the scientific community, expanding the field by studying this bionanomaterial and showing its potential to be applied not only in biosensor systems, but also in a variety of bionanotechnological applications such as drug delivery systems, bioelectronics, and tissue reparation [6]. Although bionanofibers are a promising material and there are continuous advances in their integration with analytical detection systems, there are still major challenges that have to be overcome before being able to fully commercialize their use in biosensing. Even lab-bench approaches of their use result in issues and limitations – mostly a function of the same characteristics that make this material attractive. Their stability in extreme temperatures, solvents, and conditions, required for their commercial use, renders some types of bionanofibers unusable [7–13]. The variety in surface moieties available for functionalization, one of the most attractive features of bionanofibers, is on the other hand also a hurdle to commercialization, since a specific functionalization strategy is needed for different systems, depending both on the type of bionanofiber, the primary source, and the functional biosensing element [14–18]. The precise manipulation and characterization of bionanofibers is an additional challenge, and novel nanotechnological methods must be developed to achieve this [13,19–23]. Finally, the poor conductivity of bionanomaterials requires additional consideration, as charge-transfer is a major parameter in biosensing systems. 1.2. Types of self-assembled biological nanofibers
Via self-assembly, biological building blocks, such as peptides and proteins, can yield a variety of nanofibers, each with specific characteristics reflecting the source material and the self-assembly conditions. Natural proteins tend to form wire-like, flexible nanostructures with high internal structural order, resulting in stability in natural environments. Artificially designed biological building blocks, on the other hand, will self-assemble into a variety of well-defined nanofibers such as nanotubes, nanowires, or nanofibrils, each with specific properties and advantages. 1.2.1. Natural Protein Nanofibers
There are several protein sources that naturally self-assemble into fibrous nanostructures with mechanical and chemical properties that render them useful in biosensors applications. From collagen and actin to cellular microtubules, nature has provided us with a myriad of biological building blocks that, under the right conditions, can be made to self-assemble into bionanofibers in vitro [24]. Within this range of naturally occurring bionanofibers, silkworm and spider silk are of particular interest to the scientific community, due to their simple molecular design and the impressive mechanical strengths that these materials exhibit [25–27]. The primary proteins present in silk are fibroin and sericin, although there is a wide variation between silk-producing species, and therefore also in the structural conformation of the silk nanofibers produced [28]. Silk nanofibers have been extensively integrated into nano- and microtechnology, and micropatterned silk proteins have been used to develop biocompatible nanoscale biosensor platforms [29], utilizing a metallization method to create free-standing silk/metal composite nanofibers [30]. The photonic properties of silk nanofibers have also been exploited for the development of optical biosensor platforms [31,32], and the specific biocompatibility of this nanomaterial has moved the field toward implantable biosensor systems [33]. 1.2.2. Amyloid Fibrils
Amyloid fibrils are insoluble nanostructures resulting from the self-assembly of unfolded protein monomers. They hold a distinctive quaternary structure predominantly characterized by a rich, hydrogen-bonded, ß-sheet conformation [34,35], a configuration with a rigid internal order that provides nanostructures with high strength, stability, and high-morphological aspect ratios [12,36]. It is perhaps their stability and insolubility in aqueous media that renders amyloid fibrils favorable in biosensor applications [17,37–39] with advantages over other biological nanofibers such as peptide nanotubes [11]. Because of the versatility of protein monomers as molecular building blocks, the source proteins that have been shown to undergo fibrillation under controlled environmental conditions are abundant and span a wide range of biological materials. The list includes insulin [15,40–42], considered a historical standard amyloid fibril source for bionanotechnological applications, fungal hydrophobins [43], ovalbumin [2], and lysozyme [44]. Important additions to this list have been proteins that are considered industrial waste materials, such as whey proteins, [4,5,45–48] and eye lens crystallins [3,36,49]. 1.2.3. Peptide Nanotubes and Nanowires
Inspired by Nature’s great success in forming self-assembled fibrous materials, researchers have synthesized peptide monomers able to recreate protein-like interactions, by focusing on the same amino-acid repeat units that play a key role in the self-assembly of proteins [50,51]. One peptide in particular has attracted much attention from researchers in the field over the past decade: diphenylalanine. This aromatic dipeptide is known for being the core recognition motif of the Alzheimer’s disease ß-amyloid polypeptide, and its use in bionanotechnology has been encouraged by the mild environment (room temperature, aqueous conditions) needed for its self-assembly. An additional advantage of using peptides as molecular building blocks is their ability to form several different nanostructures depending on the environmental conditions used during the self-assembly [52], such as nanotubes [53,54] and nanowires [55–57]. Peptide nanotubes, hollow nanofiber structures formed by, among others, the diphenylalanine peptide, have been extensively considered for the application of self-assembled nanostructures in biosensor platforms. The amyloid-like aromatic stacking that allows the self-assembly of peptide nanotubes confers an unusual strength to this nanomaterial [58,59]. This property, along with an ease in functionalization offered by the chemistry available on their surface, has allowed for the creation of several biosensor platforms based on the use of peptide nanotubes [60–68]. Diphenylalanine nanowires, solid rod-like...