Gold-copper nanoshell dot-blot immunoassay for naked-eye sensitive detection of tuberculosis specific CFP-10 antigen.

Herein, a straightforward and highly specific dot-blot immunoassay was successfully developed for the detection of Mycobacterium tuberculosis antigen (10 kDa culture filtrate protein, CFP-10) via the formation of copper nanoshell on the gold nanoparticles (AuNPs) surface. The principle of dot-blot immunoassay was based on the reduction of Cu2+ ion on the GBP-CFP10G2-AuNPs conjugates, which has gold binding and antigen binding affinities, simultaneously, favouring to appear red dot that can be observed with naked-eye. The dot intensity is proportional to the concentration of tuberculosis antigen CFP-10, which offers a detection limit of 7.6 pg/mL. The analytical performance of GBP-CFP10G2-AuNPs-copper nanoshell dot-blot was superior than that of conventional silver nanoshell. This method was successfully applied to identify the CFP-10 antigen in the clinical urine sample with high sensitivity, specificity, and minimized sample preparation steps. This method exhibits great application potential in the field of nanomedical science for highly reliable point-of-care detection of CFP-10 antigen in real samples to early diagnosis of tuberculosis.