A hybrid catalyst-triggered cascade reaction for cholesterol detection using a smartphone-based miniature fluorescent apparatus.

[Display omitted] • Innovative cholesterol detection using smartphone-based miniature fluorescent apparatus. • A new hybrid functional catalyst comprising ChOx and Fe 3 O 4 nanoparticles is highlighted. • Smartphone camera captures fluorescence signal and simultaneously analyzed by application. • The quantification of cholesterol in milk samples can be efficiently performed. • This approach delivers on-site detection with low cost and energy consumption. A new hybrid biological-chemical catalyst, magnetic nanoparticles functionalized with cholesterol oxidase (Fe 3 O 4 /APTES/ChOx), was developed for cholesterol detection. In the presence of cholesterol, the enzyme produced H 2 O 2 , which facilitated the generation of fluorescent molecules from the fluorogenic substrate with the assistance of Fe 3 O 4 nanoparticles. A smartphone camera with a miniature fluorescent apparatus was used to assess fluorescence emission. Then, a smartphone application was employed to translate the fluorescence intensity to the red, green, and blue (RGB) domain. The developed approach achieved excellent selectivity and acceptable performances while supporting an onsite analysis approach. The practical operational range spanned from 5 to 100 nM, with a detection limit of 0.85 nM. Fe 3 O 4 /APTES/ChOx was applied for up to four replicates of reuse and demonstrated stability for at least 30 days. The applicability of the method was evaluated in milk samples, and the results were in accordance with the reference method. [ABSTRACT FROM AUTHOR]