Biotin determination in food supplements by an electrochemical magneto biosensor

An electrochemical magneto biosensor for the rapid determination of biotin in food samples is reported. The affinity reaction was performed on streptavidin-modified magnetic microbeads as a solid support in a direct competitive format. The biotinylated horseradish peroxidase enzyme (biotin-HRP) competes with free biotin in the sample for the binding sites of streptavidin on the magnetic microbeads. The modified magnetic beads were then easily captured by a magneto graphite–epoxy composite electrode and the electrochemical signal was based on the enzymatic activity of the HRP enzyme under the addition of H2O2 as the substrate and o-phenilendiamine as cosubstrate. The response was electrochemically detected by square wave voltammetry. The limit of detection was 8.4×10−8molL−−1 of biotin (20μgL−−1) with a dynamic range from 0.94 to 2.4×10−7molL−−1. Biotin-fortified commercial dietary supplement and infant formula samples were evaluated obtaining good performances in the results. Total time of analysis was 40min per 20 assays. ► Horseradish peroxidase activity was related to biotin amount. ► The response was obtained by square wave voltammetry. ► Magnetic beads modified with streptavidin were used and captured by a magneto electrode. ► Biotin-fortified real samples were analyzed by electrochemical magneto sensor.