Portable ceria nanoparticle-based assay for rapid detection of foodantioxidants (NanoCerac)

Abstract

With increased awareness of nutrition and the advocacy for healthier food choices, there exists a great demand for a simple, easy-to-use test that can reliably measure the antioxidant capacity of dietary products. We report development and characterization of a portable nanoparticle based-assay, similar to a small sensor patch, for rapid and sensitive detection of food antioxidants. The assay is based on the use of immobilized ceria nanoparticles, which change color after interaction with antioxidants by means of redox and surface chemistry reactions. Monitoring corresponding optical changes enables sensitive detection of antioxidants in which the nanoceria provides an optical ‘signature’ of antioxidant power, while the antioxidants act as reducing agents. The sensor has been tested for the detection of common antioxidant compounds including ascorbic acid, gallic acid, vanilic acid, quercetin, caffeic acid, and epigallocatechin gallate and its function has been successfully applied for the assessment of antioxidant activity in real samples (teas and medicinal mushrooms). The colorimetric response was concentration dependent, with detection limits ranging from 20–400 μM depending on the antioxidant involved. Steady-state color intensity was achieved within seconds upon addition of antioxidants. The results are presented in terms of Gallic Acid Equivalents (GAE). The sensor performed favorably when compared with commonly used antioxidant detection methods. This assay is particularly appealing for remote sensing applications, where specialized equipment is not available, and also for high throughput analysis of a large number of samples. Potential applications for antioxidant detection in remote locations are envisioned.

Broadly Available Imaging Devices Enable High-Quality Low-Cost Photometry

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] Ozcan and co-workers and Henry and co-workers have recently reviewed the literature in the field. [17][18][19] Test strips, however, typically only provide semi-quantitative results; for full quantitation, test kits for liquid samples remain the gold standard.…”

Nanomaterial-functionalized Cellulose: Design, Characterization and Analytical Applications

“…The authors tested the assay with nitrated ceruloplasmin with a detection limit of 8 ng/mL in undiluted plasma and 0.4 ng/mL for spiked plasma which demonstrates a greater sensitivity compared to gold immunoassays. 68 Technical aspects and challenges in the development of microfluidic paper-based analytical devices with colorimetric detection have recently been reviewed by Carrilho et al 69 In addition to Au and AgNPs, CeO2NPs that contain dual oxidation state at their surface (Ce 4+ /Ce 3+ ) 27 have been used as sensing particles. These NPs have rich surface hydroxyl functionalities when placed in an aqueous environment which allow for facile modification and complex formation.…”

“…25,26 CeO2 can serve as a colorimetric agent independently, 70 a mechanism that has been demonstrated for detection of H2O2, phenolic antioxidants and enzyme activity. 27,71 Enzymes such as glucose oxidase and horseradish peroxidase can be utilized in addition to CeO2NPs to impart selectivity and expand the range of analytes that can be detected.…”

“…47 Evans et al 48 modified μPADs with SiO2NPs to improve color intensity and uniformity of a colorimetric device applied to three different enzymatic reactions with clinical relevance (lactate, glucose, and glutamate). Sharpe et al developed novel chemical sensing arrays based on redox active metal oxide NPs as a portable and inexpensive paper-based colorimetric method for polyphenol detection 49 and field characterization of antioxidant containing samples 27 ( Fig. 5).…”

“…24b In addition, CeO2 NPs are able to react selectively with catechol-containing molecules 26 which makes them interesting sensing materials for detection of polyphenol antioxidants on paper, in the absence of exogenous materials or soluble redox dyes. 27 Another popular oxide for biosensing is MnO2 which has found many applications in the development of optical sensors for antioxidant detection in serum, 28 and of enzymatic sensors for detection of glucose (using glucoseoxidase) and acetylcholinesterase inhibitors 29 using redox dyes like 3,3′,5,5′-tetramethylbenzidine (TMB). In a recent example, MnO2 nanosheets have been used as an oxidase-mimetic material that can oxidize TMB in the absence of horseradish peroxidase and H2O2 to develop a paper-based strip for detection of acetylcholinesterase (AChE) activity.…”