A signal-decreased electrochemical immunosensor for the sensitive detection of LAG-3 protein based on a hollow nanobox-MOFs/AuPt alloy.

In this work, hollow nanobox metal-organic framework (HNM) nanocomposites were synthesised and utilised for the first time in a signal decreased electrochemical immunosensor for the ultrasensitive quantitative determination of lymphocyte activation gene-3 (LAG-3) protein, which is a newly discovered biomarker. With the aid of signal materials, namely, SiO2-tagged anti-LAG-3 antibody (SiO2-Ab2) and the biotin-streptavidin system, the sensor can achieve signal amplification. Encapsulation of tin dioxide-functionalised reduced graphene oxide (rGO-SnO2) and gold and platinum alloys (AuPt alloys) onto the surface of hollow nanobox metal-organic frameworks (MOFs) was performed to prepare rGO-SnO2/hollow nanobox-MOFs/AuPt alloys (rGO-SnO2/HNMs/AuPt) as the matrix. SiO2-Ab2, which is used as the signal-decreased label, can be utilised to enhance the distinction of the electrochemical signal after the specific recognition between antibodies and antigens, owing to its large steric hindrance property. In this sensor, this proposed sandwich immunosensor can achieve a high sensitivity, especially in the presence of low concentrations of the LAG-3 protein. Under optimal conditions, this sandwich-designed immunosensor exhibited a sensitive detection of the LAG-3 protein from concentrations of 0.01 ng mL-1 to 1 μg mL-1, with a lower detection limit of 1.1 pg mL-1 (based on 3σ). We proposed that this ultrasensitive biosensor can be utilised for the detection of the LAG-3 protein in early clinical tumour diagnosis.