Conjugated polymers, with π electron systems and highly delocalized conjugated structures, exhibit excellent luminescence properties. The polymer chains can work as molecular wire, which will lead to the amplification of optical signals and thus improve the detecting sensitivity. Aptamer has advantages in specificity, affinity with targets and signal transmission, hence, nucleic acid biosensors based on conjugated polymers have witnessed a rapid development in bio-detection. The applications of nucleic acid biosensors based on conjugated polymers in recent years are summarized. Finally, an outlook of the developing trend for these sensors is given.

Contents
1 Introduction
2 The sensing mechanism of fluorescent sensor
3 FRET
3.1 Detection of complementary DNA
3.2 Real-time monitoring of DNA hybridization
3.3 Real-time monitoring of DNA structure
3.4 Detection of protein and the activity of enzyme
3.5 Detection of specific gene
4 Aggregation and conformation change
4.1 Detection of complementary DNA
4.2 Real-time monitoring of DNA hybridization
4.3 Real-time monitoring of DNA structure
4.4 Detection of enzyme
4.5 Detection of specific DNA sequence
4.6 Detection of metal ion
5 Superquenching
6 Conclusion