Source：School of Environmental Science and Technology

By Li Xiang, Liu Meng

Protein biomarkers often exist as degradation fragments in biological samples, and affinity agents derived using a purified protein may not recognize them, limiting their value for clinical diagnosis. Recently, Prof. Liu Meng from School of Environmental Science and Technology and his research team present a method to overcome this issue, by selecting aptamers against a degraded form of the toxin B protein, which is a marker for diagnosing toxigenic Clostridium difficile infections. This in vitro selection (also known as SELEX) approach has led to isolation of a DNA aptamer that recognizes degraded toxin B, fresh toxin B, and toxin B in human stool samples. In addition, this aptamer showed high selectivity against toxin A and glutamate dehydrogenase. Further studies suggested that the molecular weight of the targeted toxin B degradation fragment was about 50 kDa.

Figure 1.SELEX strategy

Using this new aptamer, they produced a simple paper-based analytical device for colorimetric detection of toxin B in stool samples, and the NAP1 strain ofClostridium difficile. This device can achieve higher sensitivity in a shorter time compared with commercial detection kits. It was able to detect 10⁴NAP1 strains in 30 minutes. The strategies demonstrated by this work can expand the practical utilities of DNA aptamers in clinical diagnosis.

Figure 2.Colorimetric detection of NAP1 strain usingpaper-based analytical device.

This work was collaborated with Prof. John D. Brennan and Prof. Li Yingfu from McMaster University, Canada.

Editor: Li Xiang