A SELEX Protocol to Identify ssDNA Biotemplates for Gold Nanoparticle Synthesis

TL;DR

This paper presents a modified ssDNA SELEX protocol to evolve sequences that facilitate gold nanoparticle formation, resulting in more uniform nanoparticles and identifying conserved motifs potentially acting as chelation sites.

Contribution

A novel SELEX protocol was developed to select ssDNA sequences that mediate gold nanoparticle synthesis, revealing conserved motifs involved in chelation and stabilization.

Findings

Evolved ssDNA sequences produce gold nanoparticles with narrower size distribution.

Distinct absorbance spectra indicate successful nanoparticle synthesis.

Shared conserved motifs suggest specific chelation sites for gold.

Abstract

A modified ssDNA SELEX protocol was developed in order to evolve a randomized library of imidazole modified ssDNA sequences towards sequences that mediate the formation of gold nanoparticles from Au3+ precursor ions in aqueous solution. Active sequences bound to nanoparticles were partitioned from inactive sequences based on density via ultracentrifugation through a discontinuous sucrose gradient. Colloidal gold solutions produced by the evolved pool had a distinct absorbance spectra and produced nanoparticles with a narrower distribution of sizes compared to colloidal gold solutions produced by the starting, randomized pool of imidazole modified ssDNA. Sequencing data from the evolved pool shows that conserved 5 and 6 nt motifs were shared amongst many of the isolates, which indicates that these motifs could serve as chelation sites for gold atoms or help stabilize colloidal gold solutions in a base specific manner.