Label-free Pb2+ detection on the layer-by-layer platform using real-time dual polarization interferometry

Contamination of Lead ion (Pb2+) poses a serious threat to human health and the environment. Developing sensitive and reliable Pb2+ biosensor is essential and significant for prevention and control of the water pollution. In this work, we utilized the direct conformational signal changes in specific interaction process between Pb2+ and guanine-rich (G-rich) oligonucleotides to establish a sensing system. The binding of Pb2+ and G-rich oligonucleotides results in conformational transition from single strand to G-quadruplex, which was recorded real-time by dual polarization interferometry (DPI). The sensing platform was established via layer-by-layer assembly strategy that employing polyethyleneimine and ploythymine as media layers to link the G-rich DNA on the DPI chip, which is simple, facile and without need of synthesizing sophisticated nanomaterial. On the basis of above sensing platform and quantifiable conformational changes, a simple, sensitive, specific and label-free Pb2+ biosensor was established. This research provides us a simple and sensitive method for detection of ions, also encourages us to combine surface technique to biosensing application and explore the relationship between structures and functions.