Self-Assembly

Self-assembly is another exciting area of research, especially in nanometer size and patterned biological structures. Self-assembly is now loosely defined as the autonomous organization of the molecule into an ordered structure without human intervention [236, 237]. The self-assembly of natural or synthetic molecules has been used to produce nanofiber materials with the potential as tissue engineering scaffolds [229].

A common method of self-assembly is the hydrophobic interaction of amphiphilic peptide sequences, because molecules are clustered together for the manufacture of 3D nanofiber structures in tissue engineering. The hydrophobic and hydrophilic domains within these peptides in aqueous solution interact together with the help of weak non covalent bonds, such as hydrogen bond, Van der Waals interactions, ionic bond and hydrophobic interaction, resulting in different rapid recovery of hydrogen [238]. Peptide self-assembling has been used to produce 3D cell culture systems and feature fibers diameters on the order of 10 nm with pore sizes between 200 and 500 nm [236]. The modification of the peptide ampholyte structure involves various self-assemblies including layered and lamellar structures, and its reversibility properties provide flexibility for the system [239]. Diblock polymer (AxBy) is another self-assembly method for the preparation of synthetic polymer nanofibers, which is not belong to the peptide. when the two blocks separate from each other in large quantities due to their incompatibility, the volume formation of A and B can be controlled to obtain B cylindrical domain with nanoscale diameter embedded into matrix A [165]. Hosseinkhani et al. [240] designed the hybrid scaffold consisting of two biomaterials, that is a hydrogel formed through self-assembly of peptide- amphiphile and a collagen sponge reinforced with PGA fiber. Zhou et al. [241] developed a versatile approach using layer-by-layer self-assembly to incorporate cell adhesion and spatial representation of neurotrophic factors into complex nanofibrous scaffolds. Therefore, self-assembly will be a good candidate for the formation of reinforced scaffolds both in the matrix and reinforcements.

Self-assembly has several advantages over the electrospinning. The fabricated nanofiber is much thinner [242] and have amino acid residues that can be chemically modified by adding bioactive moieties. The technique is carried out in aqueous salt solution or physiological media without the use of organic solvent, which reduces cytotoxicity [243]. Its main disadvantage is a complicated and elaborated process. In general, the self-assembly techniques show the potential to be used in the design of novel scaffolds for tissue engineering applications.

 
Source
< Prev   CONTENTS   Source   Next >