Enzyme-free signal amplification for electrochemical detection of Mycobacterium lipoarabinomannan antibody on a disposable chip

A simple, rapid, and disposable immunosensor at screen printed carbon electrode (SPCE) was developed by using gold nanoparticles (AuNPs) labeled Staphylococcal protein A (Au-SPA) as the electrochemical tag for detection of lipoarabinomannan antibody (anti-LAM). The immunosensor as the disposable chip was prepared by immobilizing capture antigen on screen printed carbon working electrode by passive adsorption, and characterized with scanning electron microscopy. After binding with the anti-LAM for further capture of Au-SPA, AuNPs were introduced as an electrochemical tag by the eletrooxidation of AuNPs in 0.1 M HCl to produce strong electroactive substance for signal amplification. Comparied with the enzyme-based immunosensor, AuNPs as enzyme-free tag for signal amplification exhibited many advantages such as no requirement of deoxygenation, and high stability. Under optimal detection conditions and at a preoxidation potential of +1.3 V for 30 s, this method achieved the linear concentration of anti-LAM from 15.6 to 1000 ng mL−1 with a detection limit of 5.3 ng mL−1. The immunosensor showed a good performance with high selectivity, acceptable stability, and simple operation, providing a promising application as an adjunctive tool in early tuberculosis diagnosis.

► A simple, rapid, and disposable immunosensor is developed for detection of lipoarabinomannan antibody.
► The disposable chip is constructed by passive adsorption of antigen on the screen printed carbon working electrode.
► Gold nanoparticles produce the amplified electrochemical signal.
► Antigen and antibody are used without any further modification.
► The immunosensor shows high sensitivity, selectivity, and acceptable stability.