Fabrication of AuNS and o-ABA mediated electrochemical immunosensor for voltammetric detection of osteocalcin.

A novel electrochemical immunosensor was designed for the ultrasensitive and selective detection of osteocalcin (OCN) normally overexpressed by osteosarcoma cells. The immunosensing was performed using anti-osteocalcin antibody (anti-OCN) modified probe along with a bio-conjugate, where the probe was fabricated by the covalent assembly of anti-OCN with conducting polymer poly-o-aminobenzoic acid (poly-o-ABA) formed over a layer of gold nanostar (AuNS). Bio-conjugates comprised of hydrazine (Hyd) along with anti-OCN was covalently immobilized on citrate capped AuNPs, reveals the immunoreaction at the sensor probe, where Hyd in bioconjugate was used to reduce hydrogen peroxide for direct signal amplification. The osteocalcin was quantitively analyzed using cyclic voltammetry. This technique exhibited an excellent diagnosis tool for the sensitive and selective detection of OCN, and shows broad dynamic range 2 to 64 ng mL-1 with the detection limit of 0.19 ng mL-1. More importantly, it could distinguish osteocalcin from normal and other cancerous proteins, which indicated the promising applications in clinical diagnosis and treatment of osteosarcoma.