Immunodipstick based gold nanosensor for vitamin B_(12) in fruit and energy drinks

摘要

The aim of the work is to develop a gold nanoparticle-based immunodipstick for the rapid detection of vitamin B_(12) in food samples. The membrane was coated with capturing reagents, that is, Bovine serum albumin-vitamin B_(12) conjugate and was dipped in different concentrations of vitamin B_(12) solution containing vitamin B_(12) IgY antibodies labeled with gold nanoparticles (GNPs). The intensity of color development was inversely proportional to the vitamin B_(12) concentration with maximum intensity at zero vitamin B_(12) concentration. The visible detection limit of vitamin B_(12) was determined to be 1 ng ml-1. GNPs of definite size were synthesized and conjugation efficiency of the GNP-protein conjugates was confirmed qualitatively and quantitatively through gel electrophoresis, flocculation assay, UV-visible, fluorescence spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy. The detection limit of this method is higher than the conventional method, enzyme-linked immunosorbent assay. The results of fruit drinks spiked with 1, 10 and 100 ng ml~(-1) of vitamin B_(12) and labeled drinks were in good agreement with those obtained by ELISA. The reproducibility and stability were checked. The simple and non-instrumental dipstick method may further be extended to the screening of other forms of vitamin B_(12) in food.