Label-free and highly sensitive immunosensor based on L-cysteine capped vanadium disulfide quantum dots for amoxicillin detection

[Display omitted] •The VS2QDs used were synthesised by our group using hydrothermal method.•L-CYS played dual role of capping agent and sulphur source during synthesis.•This immunosensor shows improved sensitivity and a faster response compared to other biosensors reported in literature.•Spiked fish samples study proved the applicability in real sample applications. Excess and unmonitored use of antibiotics across globe is rapidly leading to antibiotics resistance. Thus, early-stage detection of antibiotics resistance has become necessary to monitor and control their use to reduce the side effects. Amoxicillin (Amoxi) is a type of beta-lactam antibiotic that is often used to treat bacterial infections. Herein, L-cysteine capped vanadium disulphide quantum dots (L-CYST-VS2QDs) were synthesized via hydrothermal method and used to construct an electrochemical immunosensor for Amoxi detection. To prepare Ab-Amoxi/L-CYST-VS2QDs/ indium tin oxide coated glass (ITO) immunoelectrode, monoclonal antibodies against Amoxi were immobilized on the L-CYST-VS2QDs/ITO followed by blocking uncovered sites with BSA. This BSA/Ab-Amoxi/L-CYST-VS2/ITO bioelectrode was revealed selective and specific interaction towards Amoxi among various other antibiotics. The immunoelectrode showed linearity within 1 pM to 100 µM range, with sensitivity of 4.827 µA nM−1 cm2, and detection limit of 0.5 pM, with better results than chitosan–TGA-VS2QDs based immunosensor. The applicability in real sample testing was proved by monitoring the response in spiked fish samples, which yielded positive outcomes.