Clinical immunosensing of tuberculosis CFP-10 in patient urine by surface plasmon resonance spectroscopy

The antigen (Ag) CFP-10, found in tissue fluids of tuberculosis (TB) patients, is an excellent candidate for use as a sensitive TB marker for early and simplified diagnosis of TB when combined with an effective sensing method. In this study, chemical and optical optimizations were carried out using novel immuno-materials to establish a self-assembled surface plasmon resonance (SPR) optical immunosensing system for the detection of CFP-10 Ag in clinical urine samples from TB patients, which is the first clinical trial as far as we know to monitor Ag in urine. To create a simple sensing interface, a monoclonal antibody (anti-CFP-10) was immobilized directly on a gold surface, followed by blocking with cystamine. The orientation and accessibility of anti-CFP-10 were assessed by the selective binding of CFP-10. The results reveal a linear relationship between the SPR angle shift and the acid-fast bacilli stain stage (0–4) of TB patients. Significant differences were seen between urine samples from TB patients and controls. This method, using urine samples and SPR spectroscopy, is promising and can be rapidly developed into a reliable diagnostic method to monitor TB.