Molecular biomimetics self-assembly

Besides traditional 3-D scaffolds fabrication methods, electrospinning and molecular self-assembly are newly developed techniques to construct biomimetic polymer scaffolds. Scaffolds fabricated by those techniques are mainly used in four tissue engineering areas skin, cartilage, blood vessel, and nerve. 

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

Modern nanotechnology and nanofabrication processes are advancing towards manipulation of structure and functions on the molecular scale [19-23]. Many innovations and strategic areas of research which have appeared during the last 5-10 years corroborate the famous opinion of R. Feynman there is a plenty of space on the bottom [471]. Some prominent examples include self-assembly of small molecules and their ordering at interfaces [8,220,472,473 ], three-dimensional macromolecules with a defined shape, interior and surface structure [34-38], and templating of biomolecules [39-41,474]. Most of these concepts follow a biomimetic approach, where synthetic structures mimic organisation princi-... 

The successful synthesis of the biohybrid members of the family of amphiphiles, the giant amphiphiles, has also attracted the spotlight of fundamental sciences. The incorporation of biological molecules (proteins and enzymes) in to the amphiphilic structure mimics the self-assembly seen in Nature by amphiphilic proteins. Though enzymes and proteins have been extensively funtionalized in the past, the realization that they can express assembling properties similar to that of their molecular and polymeric counterparts offers new methods for the construction of functional biomimetic assemblages. The future for amphiphiles appears to be unlimited. 

The reviews that were not found to belong to a cluster tell us about areas within hybrid nanomaterials that may be either more peripheral or situated among stronger clusters. These include areas such as molecular imprinting, self-assembled mono-layers, or biomimetic materials. A larger analysis would be necessary to be able to have significant evidence of the relative position of these other areas in Figure 24.2. 

Interest in these studies arises from fundamental research where monolayers serve as models of biomimetic systems, as well as from important apphcations of such systems in molecular and bioelectronic devices, in sensors construchons, corrosion/inhibition phenomena, and synthesis of nanostructures ]93]. Although self-assembly processes of sulfur-containing compounds occur at the surfaces of many metals, especially the copper-group metals (Cu, Ag, Au), the most extensive studies have been... 

A. M. Kluwer, R. Kapre, F. Haiti, M. Lutz, A. L. Spek, A. M. Brouwer, R W. N. M. van Leeuwen, J. N. H. Reek, Self-assembled biomimetic [2Fe2S]-hydrogenase-based photocatalyst for molecular hydrogen evolution, Proc. Natl. Acad. Sci. USA, 2009, 106, 10460. 

An example from chemistry is the use of vesicles, liquids, and foams to direct biomimetic mineralization and polymerization. Such templates, that may only have a transitory existence were used to template the assembly of structurally complex, three-dimensional architectures. Subsequently, within supramolecular chemistry, the term "direeted self-assembly" has become more generally understood to include any templated process that brings together molecular components, even if the directing moiety is part of the final structure. " ... 

Figure 4.2 Self-assembling peptide amphiphiles (PA) used for biomimetic mineralization of HA/PA nanocomposite, (a) Chemical structure of the PA, comprising 5 regions (1) a hydrophobic alkyl tail (2) four cysteine residues that can form disulfide bonds to polymerize the self-assembled structure (3) a flexible linker region of three glycine residues (4) a single phosphorylated serine residue that was able to interact strongly with calcium ions and help direct mineralization of HA (5) the cell adhesion ligand ROD. (b) Molecular model of one single PA molecule, (c) Schematic showing the self-assembly of PA molecules into a cylindrical micelle.

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