Gold nanoparticle-biotinylated liposome hybrids as analytical reagents for biotin determination using a competitive assay and resonance light scattering detection.

The preparation of hybrid nanostructures formed by gold nanoparticles (AuNPs) into biotinylated liposomes and their analytical application are presented. The surface of negatively charged AuNPs was modified with 1-dodecanethiol and the NPs were encapsulated into biotinylated liposomes using the rapid solvent evaporation method. Liposomes were resized by both mechanical shaking and ultrasound treatments and filled liposomes were separated from empty liposomes using sucrose density gradient centrifugation. The analytical usefulness of AuNP-liposome hybrids as amplification probes for biotin determination was checked using the competitive affinity reaction based on the avidin-biotin interaction and biotilynated phospholipids for the synthesis of the liposome hybrids. The method was automatized using a flow system and measuring the resonance light scattering signal. The dynamic range of the calibration graph was 0.001-20 μg mL(-1), (r(2)=0.9998, n=14), with a detection limit of 0.3 ng mL(-1). The precision, expressed as relative standard deviation (RSD%), was lower than 5% and the sampling frequency was 9 h(-1). The approach has been applied to the determination of biotin in food samples, with recovery values ranging between 88.2 and 105.2%.