A Smartphone-Based Chemosensor to Evaluate Antioxidants in Agri-Food Matrices by In Situ AuNP Formation

Abstract

In recent years, there has been a continuously growing interest in antioxidants by both customers and food industry. The beneficial health effects of antioxidants led to their widespread use in fortified functional foods, as dietary supplements and as preservatives. A variety of analytical methods are available to evaluate the total antioxidant capacity (TAC) of food extracts and beverages. However, most of them are expensive, time-consuming, and require laboratory instrumentation. Therefore, simple, cheap, and fast portable sensors for point-of-need measurement of antioxidants in food samples are needed. Here, we describe a smartphone-based chemosensor for on-site assessment of TAC of aqueous matrices, relying on the antioxidant-induced formation of gold nanoparticles. The reaction takes place in ready-to-use analytical cartridges containing an hydrogel reaction medium preloaded with Au(III) and is monitored by using the smartphone’s CMOS camera. An analytical device including an LED-based lighting system was developed to ensure uniform and reproducible illumination of the analytical cartridge. The chemosensor permitted rapid TAC measurements of aqueous samples, including teas, herbal infusions, beverages, and extra virgin olive oil extracts, providing results that correlated with those of the reference methods for TAC assessment, e.g., oxygen radical absorbance capacity (ORAC).

Content of polyphenolic compounds, flavonoids, antioxidant activity and antibacterial activity of Jatropha dioica hydroalcoholic extracts against Streptococcus mutans

“…Gallic acid is most commonly used as a standard for total phenols evaluation. Thus, TP is reported as micrograms of gallic acid equivalent per litre (Singleton et al ., 1999; Calabria et al ., 2021). The dry root extract evaluated here had a higher TP (46.06 mg GAE g −1 of extract) than reported before (43 μg GAE mL −1 ) (Ramírez‐Moreno et al ., 2016).…”

3D Printing Technologies in Biosensors Production: Recent Developments

“…The system is readily adaptable for the detection of other pathogens by changing the antibodies composition on the surface of the nanocatalyst; this flexibility brings new promising insights for the screening of pathogenic bacteria, representing a powerful tool for avoiding food poisoning [48]. Additional applications for agri-food matrices has been provided by Calabria et al [49]: in this study, the authors developed a smartphone-based chemosensor for evaluating the total antioxidant capacity (TAC) of food extracts and beverages. TAC can be evaluated by spectrophotometric measurements of electronic transfer between the antioxidant species and free radicals; otherwise, fluorescence and chemiluminescence can be employed.…”

“…The presented method exploited the nucleation of gold nanoparticles (AuNPs) directed by the reducing power of an antioxidant in the presence of Au(III). The 3D-printed components of the chemosensor were fabricated by stereolithography using black-colored resins; this choice was made to avoid unwanted reflection from the light source, and the printed device was equipped with an LED-based light system to ensure optimal illumination conditions [49]. The increased concentration of Au NPs (related to the reduction driven by the antioxidant) led to a color change in the cartridge-from colorless to red.…”

Smartphone-Based Chemiluminescent Origami µPAD for the Rapid Assessment of Glucose Blood Levels

“…However, at short distances, it is not possible to image large areas, or, at best, the perspective distortion of the images could affect the measurement. As previously described [23], we used two flat angled mirrors to fold the path of the CL emission and thus increase the distance between the smartphone's CMOS camera and the detection zone without compromising the compactness of the device. The use of mirrors also made it possible to image the CL signal generated in the lowest level of the biosensor from below.…”