Size controllable, pH triggered reduction of bovine serum albumin and its adsorption behavior with SnO/SnS quantum dots for biosensing application.

The pH dependent size control of Bovine Serum Albumin (BSA) and its biosensing potential with Tin Oxide and Tin Sulfide Quantum Dots (SnO/SnS QDs) is reported. The role of disulfide bond cleavage in BSA at acidic and circumneutral pH conditions (3 and 7.2) with sodium borohydride as reducing agent, makes changes in its stability, prone to aggregation and microcapsule formation respectively. Here, the structural reduction in BSA (r-BSA2) at pH 7.2 probed more -OH groups eventually creating adhesive surfaces for SnO/SnS QDs due to electrostatic and hydrophobic forces, thus avoids the aggregation of SnO/SnS QDs in composite formation. The accumulation of more active sites in SnO/SnS QDs decorated r-BSA2 (SnO/SnS@r-BSA2) nanobiocomposite favored suitable orientation for Melatonin (Mel) detection. The designed SnO/SnS@r-BSA2 nanobiocomposite over the screen printing electrode exhibited electrochemical detection capabilities for the selective and sensitive recognition of Mel in the linear range of 0.2-1000 μM with a lower detection limit of 16 nM. Additionally, the fabricated biosensor was successfully validated for the determination of Mel in real samples.