Enzymatic and catalytic behaviour of low-dimensional gold nanomaterials in modular nano-composite hydrogels

Abstract

Inorganic nanoparticles have long been applied as catalysts and nanozymes with exceptional rate constants arising from their large surface areas. While it is understood that high surface area-to-volume ratios and low average atomic coordination are responsible for their exceptional catalytic properties, these facets remain under exploited in the design of gold nanoparticle catalysts and nanozymes. Here we have developed 3D, 2D, and quasi-1D gold nanoparticles for use as catalysts in reducing 4-nitrophenol by sodium borohydride. Each morphology was characterised with transmission electron microscopy and UV-Vis absorption spectroscopy, while the highest catalytic activity was achieved when the perimeter-to-surface area, or amount of ‘edge’, was maximised. The particles were then applied as nanozymes in modular nano-composite hydrogels. Independent hydrogel tiles containing either the substrate or catalyst were bonded in stacks, which allowed reagent transport across their interface for the colourimetric detection of hydrogen peroxide. This work presents novel insight into the catalytic activity of low-dimension nanoparticles and their potential application in nanozyme-based diagnostic devices.

Gold Nanotapes and Nanopinecones in a Quantitative Lateral Flow Assay for the Cancer Biomarker Carcinoembryonic Antigen

“…We recently reported that by increasing the MO concentration used in AuNS synthesis, AuNPCs can be obtained . SEM (Figure c) and TEM (Figure d) of AuNPCs show size monodisperse particles with rough hierarchical structure.…”

“…We recently reported that by increasing the MO concentration used in AuNS synthesis, AuNPCs can be obtained. 34 SEM (Figure 1c) and TEM (Figure 1d) of AuNPCs show size monodisperse particles with rough hierarchical structure. The ImageJ analysis of widefield TEM images of AuNPCs (Figure S1) gives a mean diameter of 89.6 ± 21 nm (N = 303).…”

“…Although the above literature 29−31 indicates that the rough AuNPC morphology would be desirable for LFA labels, the low dimensionality of AuNSs and AuNTs is also of interest. 34 The signal of LFAs has been enhanced by using AuNP bound to the TL to catalyze the reaction between H 2 O 2 and 3,3′,5,5′-tetramethylbenzidine (TMB) 35 or 3,3′-diaminobenzidine (DAB) 36 to yield colored products at the test line. Low dimensional nanoparticles were recently shown to display improved catalytic activity over higher dimensionality counterparts; 34 this could be desirable for substrate amplification in LFAs following particle binding at the TL or CL.…”

“…34 The signal of LFAs has been enhanced by using AuNP bound to the TL to catalyze the reaction between H 2 O 2 and 3,3′,5,5′-tetramethylbenzidine (TMB) 35 or 3,3′-diaminobenzidine (DAB) 36 to yield colored products at the test line. Low dimensional nanoparticles were recently shown to display improved catalytic activity over higher dimensionality counterparts; 34 this could be desirable for substrate amplification in LFAs following particle binding at the TL or CL. 35 Further, methods of producing many of the different gold particle morphologies described in the literature require multistep seeded synthesis procedures for the generation of hierarchical 29−31 and wire-like 37 structures.…”

“…AuNPCs (90 nm in diameter) display a hierarchical surface topology composed of clusters of the subnanometer 2D AuNS material, whereas AuNTs (∼35 nm in length) have a quasi-1D structure with a 3D “head” and 2D “tape” region. Although the above literature − indicates that the rough AuNPC morphology would be desirable for LFA labels, the low dimensionality of AuNSs and AuNTs is also of interest …”