Preparation of a visual protein chip for detection of IgG against Treponema pallidum.

A rapid, visual protein chip method for the detection of IgG against Treponema pallidum was developed using Staphylococcus protein A-modified gold nanoparticles. After recombinant T. pallidum antigen Tpp47 was arrayed on aldehyde-coated slides, qualitative and semiquantitative assay results were obtained from the hybridization signal and the subsequent gray stain values. The Tpp47-specific serum antibody was bound to immobilized Tpp47 antigen on the functionalized glass slides. The Staphylococcus protein A-modified gold nanoparticle probe exclusively recognized anti-Tpp47 IgG. The "sandwich" format hybridization signal was then amplified with silver staining, a high sensitivity visual detection technique. It took 3.5 h to prepare the detection protein chip, but only 20 min for real sample detection. The lowest titer of detectable antibody for this method was 1:128, which correlates to approx 1 ng/mL. Furthermore, the results can only be seen unaided, which drastically reduces the cost of detection, but can also be kept for a long time. The data also confirmed the proposed method's specificity, sensitivity, and convenience. As a result, the method could be applied as an alternative diagnostic tool in the clinical diagnosis of T. pallidum.