Immobilisation of bovine serum albumin on graphene oxide through covalent and noncovalent interactions

Developing robust, user-friendly platforms for protein and enzyme immobilisation is a key challenge in biomedical and industrial fields. Graphene oxide (GO) has emerged as a promising support for immobilising various biomolecules. This study explores both covalent and noncovalent immobilisation of bovine serum albumin (BSA) onto GO under varying conditions. Noncovalent immobilisation at different pH levels relies on electrostatic and hydrophobic interactions, hydrogen bonding, and van der Waals forces to form the GO-BSA complex. Covalent immobilisation involves activating GO's carboxyl groups with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. hydrochloride (EDC) and stabilising with N-hydroxysuccinimide (NHS) to produce functionalised GO (FGO), which reacts with BSA's amine groups to form FGO-BSA conjugates. X-ray photoelectron spectroscopy (XPS) confirmed covalent binding through the detection of amide bonds and aromatic nitrogen. Interestingly, XPS also revealed higher BSA loading in GO-BSA (noncovalent) compared to FGO-BSA (covalent) under acidic conditions. Bradford assays further showed that GO can adsorb up to 80 % of introduced BSA via both immobilisation methods.