One-Step, On-Site Chemical Printing of a 3D Plasmon-Coupled Silver Nanocoral Substrate toward SERS-Based POCT

Abstract

Surface-enhanced Raman scattering (SERS) with the advantages of high sensitivity, nondestructive analysis, and a unique fingerprint effect shows great potential in point-of-care testing (POCT). However, SERS faces challenges in rapidly constructing a substrate with high repeatability, homogeneity, and sensitivity, which are the key factors that restrict its practical applications. In this study, we propose a one-step chemical printing strategy for synthesizing a three-dimensional (3D) plasmon-coupled silver nanocoral (AgNC) substrate (only need about 5 min) without any pretreatments and complex instruments. The galvanic replacement between AgNO3 and Cu sheets will provide both Ag0 for the formation of silver nanostructures and Cu2+ for the polymerization of fish sperm DNA (FSDNA). The protection of AgNCs is facilitated by the crosslinked FSDNA, which can improve the stability of the substrate and promote the control of its coral-like morphology. The obtained substrate displays excellent capacity of signal enhancement due to the 3D plasmon coupling both between nanocoral tentacles and between nanocorals and Cu sheets as well. Therefore, the AgNC substrates display high activity (enhancement factor = 1.96 × 108) and uniformity (RSD < 6%). Food colorants have been widely used in various foods to improve their color, but the inevitable toxicity of colorants seriously threatens food safety. Therefore, the proposed AgNC substrates were used to directly quantify three kinds of weak-affinity food colorant molecules including Brilliant Blue, Allura Red, and Sunset Yellow assisted by the capture by cysteamine hydrochloride (CA), showing the detection limits (S/N = 3) of 0.053, 0.087, and 0.089 ppm, respectively. The SERS method has been further applied in the detection of the three kinds of food colorants in both complex food samples and urine with recoveries of 91–119%. The satisfactory detection results suggest that the facile preparation strategy of AgNC substrates will be widely used in SERS-based POCT to promote the development of food safety and on-site healthcare.

Positively Charged Silver and Gold Nanoparticles with Controllable Size Distribution for SERS Detection of Negatively Charged Molecules

“…According to the concentration-dependent SERS spectra (Figure S8), the lowest detectable concentration of each molecule is listed in Table [the “PPITA-Ag NPs (+)” column], which varied from 1 to 100 μg/L. For a better comparison, Table also lists the lowest detectable concentrations of some molecules reported [the “Other methods” column]. ,,– …”

“…Compared with the strategy of using thiourea as the linker on the Ag NPs (−) (Table , the “Ag-Cit NPs + Thiourea” column), the detection of negatively charged molecules by Ag NPs (+) improved the SERS sensitivity significantly, such as up to 3 orders of magnitude for the case of eosin Y. Further, the sensitivity toward acid orange, sunset yellow, and lemon yellow was either at the same level or 1–2 orders of magnitude higher, in comparison with that by other Au NPs (+) or Ag NPs (+) nanostructures (nanodumbbells, nanoflower, nanocoral, or nanoshells) (Table , the “Other methods” column). The sensitivity for sunset yellow by Ag NPs (+) is about 1 order of magnitude lower than that by cysteamine-modified Au bipyramids .…”

SERS-based microdevices for use as in vitro diagnostic biosensors

“…198–230 3D bottom-up self-assembly nanostructures are described owing to facile preparation and cost-effectiveness. 231–251 Combinatory detection is used for synergetic enhancements. 252–266…”

Portable SERS-Based POCT Kit for Ultrafast and Sensitive Determining Paraquat in Human Gastric Juice and Urine

“…The rising popularity of point-of-care diagnostic testing platforms in clinical settings can be attributed to their ability to deliver rapid results, user-friendly interfaces, and cost-effectiveness . Leveraging the advantages of high sensitivity and the distinctive fingerprint effect, the SERS technique holds significant promise in the realm of point-of-care testing (POCT) . The adoption of a portable Raman spectrometer approach may thus represent a novel alternative for POCT applications, markedly enhancing detection efficiency and furnishing crucial information for the treatment of PQ poisoning.…”

“…21 Leveraging the advantages of high sensitivity and the distinctive fingerprint effect, the SERS technique holds significant promise in the realm of point-of-care testing (POCT). 22 The adoption of a portable Raman spectrometer approach may thus represent a novel alternative for POCT applications, markedly enhancing detection efficiency and furnishing crucial information for the treatment of PQ poisoning. This study introduces a portable SERS-based POCT kit for rapidly and sensitively determining the PQ in human gastric juice and urine.…”