Magnetic beads-based electrochemical immunosensing of HIF-1α, a biomarker of tumoral hypoxia

Abstract Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor involved in tumor growth and metastasis by regulating genes involved in response to hypoxia. This work reports the first magnetic beads (MBs)-based electrochemical immunoassay for the determination of HIF-1α. The design involves a sandwich immunoassay using MBs and amperometric detection at disposable screen-printed carbon electrodes (SPCEs). Magnetic immunoconjugates of carboxylic acid-microsized magnetic particles (HOOC-MBs) modified with a specific antibody were used to selectively capture the target protein which was sandwiched with a biotinylated secondary antibody further conjugated with a streptavidin peroxidase conjugate (Strep-HRP). The great analytical performance of the immunoassay in terms of selectivity and low limit of detection (76 pg mL−1) for HIF-1α allows the determination of the endogenous amount of this biomarker in 0.5 μg raw cancer cells lysates cultured in normoxia or induced-hypoxia with CoCl2. In addition, the developed immunosensing approach was employed to analyze HIF-1α in saliva samples with results that agree with those provided by an ELISA kit involving the same immunoreagents.