TiO2 nanoparticles reagent based nonenzymatic label-free optical sensor for the rapid detection of L-lactate in apple juice

Abstract

L-lactate is an essential organic chemical in food processing, clinical, chemical, and fermentation industries. Titanium oxide nanoparticles (TiO2 NPs) was synthesized by the green chemical method and structural, morphological, zeta potential characterization studies were performed for achieving lower limit of detection (LOD), stability, and sensor fabrication. First time reporting TiO2 NPs functionalized with 3-aminophenylboronic acid (3-APBA^TiO2 NPs) for L-lactate detection in apple puree (lab prepared) and commercial Tropicana (Indian local brand) apple juice samples. Nanocomposite in the aqueous phase (pH 7.4) shows a selective binding towards L-lactate that results in a blue shift of UV-VIS absorption wavelength from 300 nm to 288 nm as L-lactate binds to the boron atom of boronic acid and forms a tetragonal complex stabilized by the TiO2 NPs. The apple samples spiked with L-Lactate (1-10 mM) showed an absorption peak intensity increases as per lactate concentration with the LOD= 3.11 mM using the calibration graphs. The nanosensor data was validated with a commercial Megazyme kit and conventional High-performance liquid chromatography (HPLC) technique. L-lactate content in commercial Tropicana apple juice samples was detected as 6.1 mM with 93.5 % correlation. This method could be an alternative to conventional L-lactate detection techniques and can be interfaced with a smartphone for onsite detection device development.