Clinical immunosensing of tuberculosis CFP-10 antigen in urine using interferometric optical fiber array

• A new clinical diagnostic platform has been developed that is based on interferometric immunoassays for tuberculosis diagnosis.
• The 3 different interferometric immunoassays were introduced with consideration of the antibody structure and bioconjugation route.
• The clinical urine samples were directly analyzed using optimized assay design.
• This method has the advantage of label-free, high-throughput analysis, and high compatibility with crude clinical samples.

The CFP-10 antigen (Ag), found in the tissue fluids of tuberculosis (TB) patients, is an excellent candidate marker for early and simplified diagnosis of TB when combined with an effective sensing method. In this study, clinical level immunosensing of CFP-10 in urine samples from TB patients was performed using a self-assembled interferometric optical fiber array system. To generate the immunosensing interface, two directions of assay designs were introduced: (I) the direct immobilization of anti-CFP-10 monoclonal antibody (mAb) on a fiber tip surface, (II) the indirect conjugation of anti-CFP-10 mAb with the assistance of primary capture layer. Then, the orientation and accessibility of the antibody were assessed by the selective binding of CFP-10 to this interface. The results revealed a linear relationship between the optical phase shift of the interferometric sensing system and the acid-fast bacilli (AFB) staining stage (0–3) of the TB patients. Significant differences were observed between urine samples from infected and non-infected patients. This method, which uses urine samples and an interferometric sensing system, allows fast and ultrasensitive clinical monitoring and can be rapidly developed into a reliable diagnostic method to monitor TB infection.