Electrochemical Detection of Four Prominent Tuberculosis Biomarkers Using Functionalized Titania Nanotubular Array Sensing Platform

Current available state-of-art tuberculosis (TB) detection techniques face four challenges: cost, time of detection, equipment portability, and performance. For rapid, point-of-care (POC) detection, sensing of volatile organic compounds (VOCs) from the breath is important for early diagnosis of several pulmonary diseases such as TB. VOCs such as methyl nicotinate, methyl p-anisate, methyl phenylacetate, and o-phenylanisole have been identified as prominent TB breath biomarkers. Sensing of VOCs using solid-state TiO₂ nanotube array sensors is a robust method to detect VOC vapors.

Highly ordered titania nanotubular arrays (TNA) were synthesized through electrochemical anodization and functionalized with cobalt. Passing nitrogen gas through an ethanol biomarker solution was used to deliver the vapor of the individual biomarkers to the sensor. Detection of biomarkers was carried out in amperometric mode at optimized bias potentials determined from cyclic voltammetry studies. The sensor response towards the biomarkers was calculated by subtracting the base current (only N₂/ethanol) from the peak current obtained (N₂/ethanol + biomarker). Varying the concentration of the biomarker in solution was used to determine the sensitivity of the sensors. Further, the sensitivity was also examined through electrochemical sensing of all the four biomarkers mixed in solution. The selectivity of the sensor was investigated by operating the sensor at different potentials when exposed to the mixture of biomarker vapors.

The results illustrate that titania nanotubular morphology and cobalt are necessary for volatile organic biomarker (VOB) detection. Also, the sensor exhibits good sensitivity and selectivity towards the four prominent TB biomarkers. Further, mechanisms have been proposed to describe the attachment of the biomarkers to Co-TNA and are supported by XPS characterization and band theory.