Dual Enlargement of Gold Nanoparticles: From Mechanism to Scanometric Detection of Pathogenic Bacteria

Abstract

A mechanism of dual enlargement of gold nanoparticles (AuNPs) comprising two steps is described. In the first step, the AuNPs are enlarged by depositing Au atoms on their crystalline faces. In this process, the particles are not only enlarged but they are also observed to multiply: new Au nuclei are formed by the budding and division of the enlarged particles. In the second step, a silver enhancement is subsequently performed by the deposition of silver atoms on the enlarged and newly formed AuNPs to generate bimetallic Au@Ag core-shell structures. The dual nanocatalysis greatly enhances the electron density of the nanostructures, leading to a stronger intensity for colorimetric discrimination as well as better sensitivity for quantitative measurement. Based on this, a simple scanometric assay for the on-slide detection of the food-born pathogen Campylobacter jejuni is developed. After capturing the target bacteria, gold-tagged immunoprobes are added to create a signal on a solid substrate. The signal is then amplified by the dual enlargement process, resulting in a strong color intensity that can easily be recognized by the unaided eye, or measured by an inexpensive flatbed scanner. In this paper, dual nanocatalysis is reported for the first time. It provides a valuable mechanistic insight into the development of a simple and cost-effective detection format.

Biomedical imaging and sensing using flatbed scanners

“…Dual enlarged silver enhanced gold nanoparticles have also been used in conjunction with a scanner to perform the detection of Campylobacter jejuni . 76 …”

Development of nanoparticle-based optical sensors for pathogenic bacterial detection

“…Bimetallic silver–gold clusters were obtained through synthesis of gold nanoparticle (AuNP) seeds that catalyzed the reduction of gold salts, enhancing the nanoparticles and supplying more gold nuclei with the subsequent addition of silver atoms on AuNPs [60]. The synergistic enhancement effects of a dual catalyst include improved optical intensity that enhances color perception and sensitivity (Fig.…”

Targeted Enlargement of Aptamer Functionalized Gold Nanoparticles for Quantitative Protein Analysis

“…Compared to conventionally-used fluorescent or luminescent labels, AuNPs offer high light-scattering intensities, quenching and photo-bleaching resistance, and colorimetric signal read-out that enables robust detection of target molecules [4,5]. These advantages have spurred the development of diverse AuNP-based assays for the detection of nucleic acids [6,7,8], proteins [9,10,11,12,13], pathogens [14], and cancer cells [15]. However, surfaces of AuNPs are known to cause strong nonspecific binding via electrostatic and hydrophobic interactions [16,17].…”

“…Catalytic deposition of metal onto AuNPs, e.g., silver enhancement or gold enhancement, has been widely used as signal amplification strategies in scanometric assays and other colorimetric immunoassays [6,9,10,11,12,13,14]. It has been demonstrated that the light-scattering intensity can be amplified over 5 orders of magnitude by enlarging AuNP labels with silver or gold enhancement [19].…”