Sensitive detection of telomerase activity in cancer cells using portable pH meter as readout

This study developed a portable and sensitive biosensor for the detection of telomerase activity extracted from HeLa cells by monitoring urease regulated pH change. In the presence of telomerase, the telomerase substrate (TS) primer was elongated by adding telomeric repeats (TTAGGG)n firstly. The TS primer was then immobilized onto streptavidin magnesphere paramagnetic particles (PMPs). The elongated repeat unit can hybridize with biotinylated complementary DNA (cDNA) to specifically capture biotinylated urease onto PMPs. After magnetic separation, the PMPs complex was mixed with urea solution. As urease can catalyze the hydrolysis of urea into ammonia and induce pH increasing of the solution, the activity of telomerase can be detected by pH-sensitive dyes or by a portable pH meter easily. The changed pH has a linear relationship with the logarithm of the number of HeLa cells from 50 to 10,000 and with a detection limit of ~20 HeLa cells, which indicated the proposed method have potential application in telomerase-related cancer diagnosis.