Nanostructures from Single Amino Acid-Based Molecules: Stability, Fibrillation, Encapsulation, and Fabrication of Silver Nanoparticles

The small-sized molecules that have been developed from single hydrophobic amino acids (Phe, Trp, Tyr and Leu) by suitably protecting the -NH2 and -CO2 H groups generate diverse nanoscopic structures - such as nanorods, nanofibrils, nanotubes, and nanovesicles - depending upon the protection parameters and solvent polarity. The vesicular structures get disrupted in the presence of various salts, such as KCl, CaCl2, (NH4)(2)SO4 and N(n-Bu)(4) Br. Insertion of unnatural (o/m/p)-aminobenzoic acids as a protecting group and the lack of conventional peptide bonds in the molecules give the nanostructures proteolytic stability. The nanostructures also show significant thermal stability along with a morphological transformation upon heat treatment. Our in vitro studies reveal that the addition of micromolar concentration curcumin significantly reduces the formation of amyloid-like fibrils. These diverse nanostructures are used as a template for fabricating silver nanoparticles on their outer surfaces as well as in the inner part, followed by calcination in air which helps to obtain a 1D silver nanostructure. Furthermore, the nanovesicles are observed to encapsulate a potent drug (curcumin) and other biologically important molecules, which could be released through salt-triggered disruption of vesicles.