Calcium Alginate Gel Beads Containing Gold Nanobipyramids for Surface-Enhanced Raman Scattering Detection in Aqueous Samples

Abstract

The application of surface-enhanced Raman scattering (SERS) in aqueous sample detection is normally limited by the low affinity between analytes and SERS-active nanoparticles. Furthermore, a tendency of uncontrollable aggregation of solute (nanoparticles or analytes) can cause poor reproducibility of the detected SERS signal. Herein, a ready-to-use plasmonic gel bead was developed for rapid and effective detection of aqueous samples with high sensitivity and reproducibility. The SERS gel bead is made of calcium alginate gel beads (CAGBs) that contain gold nanobipyramids (Au NBPs) and an aqueous sample, which can be prepared and detected within only 1 min. Au NBPs/CAGBs can generate an in-depth three-dimensional SERS-active gel network for trapping analytes and offering a uniform hotspot region, which produces a reproducible and uniform signal. Using rhodamine 6G as a model target, the proposed method exhibits excellent reproducibility with a relative standard deviation of 6.57% and a detection limit of 0.4 nM. Then, Au NBPs/CAGBs were applied to quantitatively detect serum uric acid in the range of 10−1000 μM and a limit of detection of 0.18 μM, and the results were strongly consistent with those of the commercial ELISA method. This work offers a low-cost and easy route for the fabrication of a versatile SERS substrate for monitoring disease-related biomarkers and point-of-care testing.

A simple and efficient alginate hydrogel combined with surface-enhanced Raman spectroscopy for quantitative analysis of sodium nitrite in meat products

“…The AuNPs-alginate hydrogel substrates were prepared using a straightforward ion cross-linking method. 22,25 Briefly, sodium alginate was dissolved in the synthesized AuNP solution and configured into different concentrations (0.5%, 1%, 1.5%, 2%, w/v) of the hydrogel precursor solution. Once the precursor solution was free of bubbles, it was carefully transferred to a separatory funnel.…”

Hydrogel‐based surface‐enhanced Raman spectroscopy for food contaminant detection: A review on classification, strategies, and applications

“…Alginate hydrogel is usually formed by the ionic cross‐linking process, whereby calcium ions are added to the alginate aqueous solution, resulting in the formation of a cross‐linked three‐dimensional network (Hernandez‐Gonzalez et al., 2020; Zhang & Zhao, 2020). Since alginate can be cross‐linked rapidly within seconds, hydrogel particles with SERS‐activity can be formed instantaneously by dropping target molecules with gold nanobipyramids and alginate solution into the calcium solution with a disposable dropper (Figure 2b) (Chen et al., 2021). The detection can be performed without any evaporation process, thus avoiding the coffee ring effect and having the better reproducibility of detection by this method.…”

Regulated synthesis of an Au NB-DT@Ag bimetallic core-molecule–shell nanostructure for reliable SERS detection

“…[38][39][40] For example, Hong et al encapsulated Au NBs with calcium alginate gel beads and achieved the sensitive SERS detection of uric acid with a limit of detection (LOD) down to 0.18 mM. 41 In this work, we have synthesized a novel bimetallic CMS nanostructure (Au NB-DT@Ag NRs) with Au NBs as the inner core. Specically, we synthesized ve Au NBs of different sizes by increasing the volume of added seeds and compared their SERS performance.…”

“…38–40 For example, Hong et al encapsulated Au NBs with calcium alginate gel beads and achieved the sensitive SERS detection of uric acid with a limit of detection (LOD) down to 0.18 μM. 41…”