Protein–inorganic nano hybrid sheets of Pd embedded BSA as a robust catalyst in water for oxidase mimic activity and C–C coupling reactions, and as a sustainable material for micromolar sensing of dopamine

Abstract

Protein–inorganic hybrids with tunable morphology offer excellent applications in several fields due to their versatile characteristics. Herein, we report a new hybrid material prepared using commercially available protein bovine serum albumin (BSA) and a palladium salt. Employing a green process, distinctive colonies of Pd-nanoparticles (Pd_NPs) (2–5 nm) embedded in BSA hybrid sheets (Pd_NP@BSA_sheet) were synthesized and characterized using different microscopy techniques. While naked Pd_NPs show larger particles of ∼52 nm in size, the size of the Pd_NPs embedded in BSA sheets is as small as ∼4 nm and they form well separated colonies by providing a much greater number of distinct reaction centers. Further characterization was performed using thermal, spectral and diffraction techniques. Pd_NP@BSA_sheet shows excellent oxidase enzyme mimic activity as demonstrated using 3,3′,5,5′-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) as substrates. The selective detection of the neurotransmitter dopamine by the in situ generated oxidized species of TMB has been demonstrated in buffer, human serum and urine samples to a micromolar detection limit. The hybrid Pd_NP@BSA_sheet was also shown to have superior catalytic activity in Suzuki coupling reactions performed in water as compared to several other literature reported Pd-based catalysts and its reusability has been demonstrated. Thus, the hybrid Pd_NP@BSA_sheet material is promising and sustainable as an oxidase enzyme mimic, as a biosensor for sensing crucial neurotransmitter dopamine and as a catalyst for C–C coupling in aqueous medium.