A coffee-ring effect-based paper sensor chip for the determination of beta-lactoglobulin in foods via a smartphone

To determine allergen beta-lactoglobulin (beta-LG) in foods, a method by a coffee-ring effect (CRE)-based paper sensor chip combined with a smartphone has been developed. The strategy was based on the principle of fluorescence quenching by the quantum dot-aptamer-graphene oxide (QD-Apt-GO) and where the degree of quenching was inversely proportional to the concentration of beta-LG. First, the prepared beta-LG solution was added to the QD-Apt fluorescent probe solution followed by an appropriate amount of GO. After the reaction, a certain amount of the mixture was dispensed onto the detection zone of the sensor chip, resulting in the spread of the analyte solution by evaporation-driven flow. The QD-Apt and the QD-Apt-beta-LG in the mixed solution formed a visible fluorescent coffee-ring. For signal quantitation, an image of the coffee-ring was taken by a smartphone and imported into self-programmed software for analysis. The quantitative results for beta-LG were acquired rapidly based on the magnitude of the generated fluorescent coffee-ring. The limit of detection (LOD) for beta-LG was 0.048 mg L-1 and the linear range for the optimized assay was 0.39-1000 mg L-1. The method was validated for analysis of real food samples and the results were consistent with those of a commercial ELISA assay kit. The smartphonebased assay provides a simple, economic, compact, and visual detection platform for the determination of beta-LG in foods.

Automated summary

A method using a coffee-ring effect (CRE)-based paper sensor chip combined with a smartphone has been developed for the determination of allergen beta-lactoglobulin (beta-LG) in foods. The method utilizes fluorescence quenching and image analysis software to rapidly and quantitatively detect beta-LG. It has been validated for analysis of real food samples.