α-Alkyl cysteine-coated gold nanoparticles: effect of Cα-tetrasubstitution on colloidal stability

Significance Statement

Prof. Díaz Díaz and his co-workers have found a new way to enhance the aqueous stability of gold-nanoparticles capped with with L-cysteine-based ligands. The approach consists in using modified amino acids bearing a methyl group at the alpha-position. Such subtle structural modification allows the preparation of coated Au-nanoparticles with excellent dispersibility in aqueous solutions in a wide range of pH and ionic concentrations, from which they can be repeatedly isolated and redispersed. Atomistic molecular dynamics revealed that such prevention of coalescence is associated to the conformation restrictions imposed by the alpha-methyl group, which affect the organization of the amino acids with respect to both the gold surface and their spontaneous assembly with neighboring molecules. This work establishes a new scenario for the rational design of other aggregation-free metal and functionalized amino acid-coated metal nanoparticles.

 

 

α-Alkyl cysteine-coated gold nanoparticles: effect of Cα-tetrasubstitution on colloidal stability- Advances in Engineering

 

 

 

 

 

 

 

 

 

Journal Reference

Journal of Nanoparticle Research, 2014, 16:2224.

Iñaki Osante (1), Ester Polo (2), Guillermo Revilla-López (3), Jesús M. de la Fuente (2), Carlos Alemán (3,4), Carlos Cativiela (1), David Díaz Díaz (1,5,6).

[expand title=”Show Affiliations”]

1. Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, C/Pedro Cerbuna s/n, 50009, Zaragoza, Spain.

2. Instituto de Nanociencia de Aragón, Universidad de Zaragoza, Campus Río Ebro, Edif I+D, C/Mariano Esquillor s/n, Zaragoza, Spain.

3. Departament d’Enginyeria Química, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028, Barcelona, Spain.

4. Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C’, C/Pasqual i Vila s/n, 08028, Barcelona, Spain.

5. IQAC-CSIC, Jordi Girona 18-26, 08034, Barcelona, Spain.

6. Institut für Organische Chemie, Fakultät für Chemie und Pharmazie, Universität Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany.

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ABSTRACT

In this work, we report the synthesis of new α-methyl l-cysteine-coated gold nanoparticles (average core diameter ca. 3 nm) and the remarkable enhancement of their aqueous stability against aggregation in comparison with the nanoparticles capped with unmodified l-cysteine under the same experimental conditions. Atomistic molecular dynamics simulations of model gold surfaces capped with l-cysteine or α-methyl l-cysteine revealed important differences in both the organization of the amino acids with respect to the surface and their spontaneous assembly with neighboring molecules. These differences, which are originated by the introduction of the α-methyl group in the amino acid, could be associated with the observed increase in stability and dispersibility of the composites in aqueous solutions at different pH values and ionic concentrations.

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