Aluminum Foil vs. Gold Film: Cost-Effective Substrate in Sandwich SERS Immunoassays of Biomarkers Reveals Potential for Selectivity Improvement

Abstract

The first application of aluminum foil (Al F) as a low-cost/high-availability substrate for sandwich immunoassay using surface-enhanced Raman spectroscopy (SERS) is reported. Untreated and unmodified Al F and gold film are used as substrates for sandwich SERS immunoassay to detect tuberculosis biomarker MPT64 and human immunoglobulin (hIgG) in less than 24 h. The limits of detection (LODs) for tuberculosis (TB) biomarker MPT64 on Al foil, obtained with commercial antibodies, are about 1.8–1.9 ng/mL, which is comparable to the best LOD (2.1 ng/mL) reported in the literature for sandwich ELISA, made with fresh in-house antibodies. Not only is Al foil competitive with traditional SERS substrate gold for the sandwich SERS immunoassay in terms of LOD, which is in the range 18–30 pM or less than 1 pmol of human IgG, but it also has a large cost/availability advantage over gold film. Moreover, human IgG assays on Al foil and Si showed better selectivity (by about 30–70% on Al foil and at least eightfold on Si) and a nonspecific response to rat or rabbit IgG, in comparison to the selectivity in assays using gold film.

Wired for Success: Probing the Effect of Tissue-Engineered Neural Interface Substrates on Cell Viability

“…The properties of the substrate suggest that it could provide a highly conductive environment, potentially enhancing cellular processes that benefit from strong electrical cues. 28 The hydrogels GelMA (black line), GelMA-GO (pink line), and GelMA-GO-AuNRs (green line) on the gold mylar substrate (orange line) present the highest current response among the tested substrates, indicating superior conductivity but similar uptake of redox peaks as observed with platinum (Figure 1B, gray line). While there are no major differences among the current response of the hydrogels, a notable increase is observed when these hydrogels are interfaced with the gold mylar substrate (orange line).…”

“…Similar to the platinum substrate, a high conductivity of gold mylar substrate (orange line) is suggested by the high current response observed in the CV. The properties of the substrate suggest that it could provide a highly conductive environment, potentially enhancing cellular processes that benefit from strong electrical cues . The hydrogels GelMA (black line), GelMA-GO (pink line), and GelMA-GO-AuNRs (green line) on the gold mylar substrate (orange line) present the highest current response among the tested substrates, indicating superior conductivity but similar uptake of redox peaks as observed with platinum (Figure B, gray line).…”

Immunoassays: Analytical and Clinical Performance, Challenges, and Perspectives of SERS Detection in Comparison with Fluorescent Spectroscopic Detection

“…The performance of the assay on Al foil was compared with its performance on gold film. The assay on Al foil had better selectivity/lower non-specific binding and sometimes lower LODs than those obtained for the assay on gold film [32].…”

“…This hypothesis is supported by the SEM and AFM characterization of sandwich SERS immunoassays on gold, Al and Si, where the nanotag particle densities for blank (no-antigen) samples were substantially higher on gold substrate than on Al and Si substrates. For instance, 0.402 and 0.226 nanotags/µm 2 were calculated for blanks on gold and Al foil, respectively [32,137].…”

Advancing Mycotoxin Detection in Food and Feed: Novel Insights from Surface‐Enhanced Raman Spectroscopy (SERS)

“…Whilst Au SERS substrates are more expensive than those made of Al, a major advantage is that Au can strongly absorb mercaptans and other sulfur-containing compounds. [131] To detect OTA, Rojas et al exploited Au-coated glass slides as solid supports to dry sample extracts from wine and wheat mixed with colloidal AgNPs. During this procedure Au slides play a role in facilitating and enhancing SERS measurements.…”