Mycobacterium tuberculosis [MTB] is the causative agent of tubercle bacillus [TB], accounting for approximately two million deaths annually, mainly in developing countries , and remains one of the leading causes of respiratory infections and has posed critical threats to public health . Currently, the global number of TB cases is rising at a rate of 2% per year . Hence, the key to the control of this infectious disease is to provide the short course therapy and the post-exposure vaccine. Moreover, the rapid detection method with high sensitivity and specificity is essential to aid the diagnosis, assess the prognosis, and monitor the disease recurrence .
Until now, many analytical methods have been applied to the routine detection of MTB, which include the staining of acid-fast bacilli [AFB], cultivation and numerous serological and biochemical tests such as polymerase chain reaction [PCR] and enzyme immunoassay [EIA] for identification [5–8]. AFB has been evaluated on sputum samples, giving simple operation but relatively poor sensitivity . Although cultivation usually provides reliable and accurate results, it requires several weeks to obtain a result due to the slow-growing nature of these mycobacteria . PCR-based methods are useful techniques for amplification of small amounts of genetic material but require complicated sample prepurification before analysis. EIA employing multiple antibody probes for bacteria detection leads to both the complexity and the cost of the method. Hence, there are still needs to develop better technologies that can reduce detection complexity and perform faster diagnosis while maintaining high sensitivity and specificity. The uses of nanoparticles and electrochemical and optical methods for nucleic acid detection have been explored extensively [1, 11, 12]. Other strategies based on antibody-antigen recognition with fluorescence and microgravimetric techniques for analyses of MTB were reported recently . In contrast to the detection of antigen, the bioassay based on antibody detection is an alternative approach for latent TB. Detection of expressed TB polyclonal antibodies is more useful than detection of the monoclonal antibodies since such an antibody may not be expressed in TB-infected individuals, resulting in the poor performance of the TB detection . A multiantigen print immunoassay has been recently employed for profiling multiple antibodies to tuberculosis . Nonetheless, this immunoassay requires longer incubation time to carry out the antibody-antigen interaction compared with other biosensors.
Surface plasmon resonance [SPR] has attracted much attention because of several important properties. The main advantage of an SPR-based assay is that it is an extremely sensitive optical sensor, capable of detecting subnanogram levels in real time without any specific label . Moreover, a SPR biosensor can detect trace amounts of specific analytes from complex fluids without sample preparation . Due to these advantages, SPR has emerged as a powerful optical tool that can greatly provide valuable information on biomedical and chemical analyses [16–20]. In addition, several groups have developed multispot SPR for studying the biomolecular interaction with an array format [21–23]. This technique provides a possible means of quick and simultaneous detection for observing many interaction events and is thus considered as a promising technique for proteome profiling methods. However, to our knowledge, no attempt has been reported to use the SPR-based biosensor for clinical antibody detection of TB diseases in a parallel manner.
In the present study, we developed a new SPR-based biosensor for clinical antibody detection of TB diseases in a parallel manner for the first time. The sensitivity, specificity, and reproducibility of the array-based SPR results were evaluated and finally compared to those of enzyme-linked immunosorbent assay [ELISA], a conventional immunological method.