DPPH radical scavenging assay: A tool for evaluating antioxidant activity in 3 % cobalt – Doped hydroxyapatite for orthopaedic implants

Abstract

In the present work, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was used to examine the antioxidant activity of hydroxyapatite (HAP) and of 3 % cobalt doped HAP (Co-HAP). The DPPH assay revealed that 3 % Co-HAP had significant DPPH radical scavenging activity. Co-HAP was synthesised using the sol-gel method, and its characteristics were assessed using energy-dispersive X-ray spectroscopy (EDS), Field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). As the ionic radius of Co is smaller than Ca ion, XRD study reveals that crystallite size reduces from 40.82 nm to 24.91 nm after incorporation of Co into HAP implying substitution of Ca by Co ions. Compared to ascorbic acid, Co-HAP showed exceptional antioxidant potential and, at some doses, even outperformed ascorbic acid in scavenging capability. Notably, the IC50 value for pure HAP was 35, whereas it was substantially lower for Co-HAP at 20.85, indicating that it has stronger antioxidant properties. According to these results, 3 % Co-HAP has much potential for biomedical uses, especially in tissue engineering biomaterials and antioxidant-based therapeutics. Its capacity to prevent diseases brought on by oxidative stress and encourage tissue regeneration makes it a promising option for additional biomedical research.