Synthesis of Monofunctionalized Gold Nanoparticles by Fmoc Solid-Phase Reactions

Abstract

In this communication, solid-phase reactions for the synthesis of Lys-monofunctionalized gold nanoparticles are described. A controlled and selective fabrication of linear nanoparticle arrays can be achieved through peptide linkage systems, and therefore it is essential to prepare Fmoc amino acid nanoparticle building blocks susceptible to Fmoc solid-phase peptide synthesis. Gold nanoparticles containing carboxylic acids (2) in the organic shell were covalently ligated to Lys on solid supports through amide bond coupling reactions. We employed Fmoc-Lys-substituted polymer resins such as Fmoc-Lys-Wang or Fmoc-Lys-HMPA-PEGA. The low density of Lys on the matrix enabled 2 nm-sized gold nanoparticles to react with Lys in a 1:1 ratio. Subsequent cleavage reactions using 60% TFA reagent resulted in Lys transfer from the solid matrix to gold nanoparticles, and the Fmoc-Lys-monofunctionalized gold nanoparticles (5) were obtained with 3-15% yield. Synthesis using HMPA-PEGA resin increased productivity due to the superior swelling properties of PEGA resin in DMF. Monofunctionalization of nanoparticles was microscopically characterized using TEM for the ethylenediamine-bridged nanoparticle dimers (6). By counting the number of 6, we found that at least 60% of cleaved nanoparticles were monofunctionalized by Lys. This method is highly selective and efficient for the preparation of monofunctionalized nanoparticles.

Directed Assembly of Discrete Gold Nanoparticle Groupings Using Branched DNA Scaffolds

“…27 Controlled conjugation is of primary importance in the formation of discrete DNA-based nanoparticle arrays. Several means to controlled conjugation have been investigated, including electrophoresis, 28 solid-phase methods, 29 and solution-phase extraction based on product solubility. 30 In the electrophoretic protocol used here, conjugation initially results in a statistical mixture of non-, mono-, and poly-conjugated Au particles based on the DNA:Au ratio used.…”

A systems approach towards the stoichiometry-controlled hetero-assembly of nanoparticles

“…The key challenge is to develop general methodologies to assemble colloidal nano-objects with precise stoichiometry. Previously, homo-aggregates such as dimers and trimers were prepared by exploiting either random aggregation [6][7][8] , steric effects [9][10][11][12] or specific control over surface ligands (for example, divalent NPs) [13][14][15][16] . Compared with these 'homo-coupling' nanoreactions, controlling stoichiometry in the 'cross-coupling' of NPs presents different and arguably greater challenges.…”

Plasmonic Nanoparticles and Their Conjugates: Preparation, Optical Properties and Antimicrobial Activity

“…After cleaving off from the solid support, nanoparticles with a single carboxylic group were obtained as the major product. Jacobson et al published an almost identical approach toward the synthesis of gold nanoparticles with a single amino acid moiety [49] . These nanoparticles with a single functional group attached can be treated as giant "molecules" and linked together into very sophisticated structures through traditional chemical reactions, just like the total synthesis of complicated natural product from small molecular units.…”