Short Peptide Amphiphile Cage Facilitate Engineering of Gold Nanoparticles Under the Laser Field

Abstract

Engineering of nanomaterials for nanotechnological applications is always in high demand. In this work, we have designed four special classes of short peptide amphiphiles (sPA) consisting hydrophobic palmitoyl tail which is conjugated with ditryptophan unit followed by a nonaromatic acid(s). We observed that variation in head group of sPA according to the hydrophobicity scale provide variation in their self assembly too, therefore used for the engineering of the especial class of metal-organic nanohybrids. The sPA containing highly hydrophobic head exhibit vesicular morphology in organic and aqueous organic solvents and exposure of sunlight to the solution of sPA with Au(III) ions leads to the formation of multi-shaped AuNPs followed by encapsulation by sPA envelope. The purified gold colliod was further irradiated by continuous wave (CW) laser of 532 nm wavelength which leads to the conversion of multi-shaped AuNPs into uniform shape and size as confirmed by spectroscopic and microscopic investigations. Prolonged irradiation by laser, leads to the plasmonic welding of AuNPs which is mainly guided by sPA envelope produced, nanorods of submicron length. Such template guided laser induced engineering of AuNRs can show the potential applications in the field of nano-medicine, bio-nanotechnology and theranostics.

Self‐assembly of a Sequence‐shuffled Short Peptide Amphiphile Triggered by Metal Ions into Terraced Nanodome‐like Structures

“…A short peptide amphiphile (sPA) was designed (Scheme ) which consists of three important segments; hydrophobic lipid chain (tail) and an aromatic dipeptide in the middle followed by a small non‐aromatic amino acid of varied hydrophilic nature (head). It is obvious that, upon suspending the sPA in a polar solvent, the lipid chains are attracted towards each other and away from polar solvent while the polar part (head) stabilizes by moving towards polar solvent and the aromatic section helps into self organisation followed by stabilization of sPA nanostructres through π–π interaction . Therefore, the shape of this self‐assembly primarily dependent on the nature of the hydrophilic head and used aromatic dipeptide(s) …”

“…To control the proper agreement between hydrophilic and hydrophobic interactions during self assembly process, we sequentially synthesized various sPAs which consist a slight modifications. In our first set of study, initially, we fixed hydrophobic chain with Trp‐Trp aromatic dipeptide and employed variation only in hydrophilic head (Palmitoyl‐Trp‐Trp‐X, X=Gly/Ala/β‐Ala/Val) . The variation in hydrophilicity of the head group was following the order from Val<Ala<β‐Ala<Gly, in which Gly and β‐Ala resulted the fabrication of fibreous morphology which can be used to synthesize fascinating nanostructures such as; AuNPs encapsulated peptide hybrid structures and AgNPs embedded peptide nanowreath formation .…”

“…The variation in hydrophilicity of the head group was following the order from Val<Ala<β‐Ala<Gly, in which Gly and β‐Ala resulted the fabrication of fibreous morphology which can be used to synthesize fascinating nanostructures such as; AuNPs encapsulated peptide hybrid structures and AgNPs embedded peptide nanowreath formation . On the other hand, less polar head groups; l ‐Val and l ‐Ala produced robust spherical structures which is used to synthesize AuNRs of submicron length . Interestingly, a strategic change in the middle aromatic region by dipeptide Tyr‐Tyr with fixed hydrophilic epitope, β‐Ala, produced β‐sheet like fibres with metal chelating properties .…”

“…A noteworthy feature is that by sequential change of amino acids in the basic skeleton of sPA unquestionably resulted entirely different morphology of potential applications . Hence fine tuning and inclusion of appropriate number of key residues in the tunable region would be a tactful strategy to obtain potent and fascinating nanostructures.…”

“…Aggregated fibrous assembly was seen in the presence of Co II and distorted disc like morphologies were seen in the presence of Ni II , Cu II and Zn II ions. For another control experiments Pal‐Trp‐Trp‐β‐Ala and Pal‐Tyr‐Tyr‐β‐Ala were also used and it is observed that these sPA failed to show such assembly in the presence of these metal ions …”