(337d) A Power-Free Colorimetric Biosensor for Detection of Mycobacterium Tuberculosis

Tuberculosis (TB) remains a significant health threat in the human society. Currently, about one-third of the human population is ill with TB worldwide due to the lack of appropriate technologies for treatment and prevention [1]. Mycobacterium tuberculosis is the etiological agent of tuberculosis. TB bacteria enter the body by inhalation of transmittable droplet nuclei. There are different clinical manifestations of tuberculosis such as weight loss, low-grade fever, and drenching night sweats [1].

Early diagnosis plays a major role in controlling the transmission of TB. Traditional microbial culture-based tests are the most common procedures currently used which involve cell culture, cell counts, and cell enrichment, however, this method is time consuming and difficult, particularly for the slow-growing bacteria like M. tuberculosis. The global public health problem of TB worldwide demands for the development of more rapid and sensitive detection methods. Currently, many methods and techniques have been developed for rapid detection of M. tuberculosis, such as polymerase chain reaction (PCR) [3], enzyme-linked immunosorbent assay (ELISA) [4], flow cytometry and the latest WHO-endorsed GeneXpert based test [5]. Nevertheless, they cannot provide the detection results in real-time and most of these methods are often difficult and complex to execute and centralized in large stationary laboratories because the difficulties of the operation would typically require professionals that are often expensive to retain [6]. As a result, the development of portable, real-time, sensitive, rapid, and accurate methods for M. tuberculosis detection is essential to effectively prevent TB infection.

Accordingly, the present study proposes a modified microchannel, a DNA nano-sensor and a portable detection system for rapid detection of mycobacterial tuberculosis enzyme activity. In the proposed detection method, a porous hydrogel was fabricated inside the microchannel via sol-gel chemistry. Polystyrene (PS) particles (45 µm) were self-assembled for 12 h under 30°C to form a closely-packed colloidal template. The poly(ethylene glycol) diacrylate solution was added dropwise on the PS template so that the solution filled the interstitial spaces within the self-assembled PS. The resulting hydrogel was cured for 30 min and then soaked in toluene for 24 h to form a porous hydrogel by removing the PS particles.

The DNA nano-sensor was prepared by conjugating a designed single DNA strand into carrier particles and AuNPs. The sensing mechanism was on the basis of cleaving hydrogen bonds between DNA strands with active MTopI and ligating the carrier particles and AuNPs. Samples containing active MTopI and DNA nano-sensor could flow along the modified microchannel driven by capillary force, at the middle of the microchannel a porous hydrogel with pore sizes smaller than the carrier particle diameter was embedded. When the MTopI was inactive, the carrier particles and AuNPs were not ligated. As a result, AuNPs were washed away from the microchannels. On the other hand, an active MTopI was capable of linking the carrier particles with AuNPs tended to aggregate in the front end of the porous hydrogel, resulting in a visible red color band in the microchannel. Readouts were performed using a smartphone-MATLAB algorithm interface. Overall, the proposed integrated platform presented in this study promotes point-of-care-testing and provides a compact and reliable tool for early diagnosis for TB patients in resource-limited areas.

• REFERENCE

1. WHO Global Tuberculosis Report, 2018.
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