Cheng-Yu Li, Di Cao, Chong-Yang Song, Chun-Miao Xu, Yu-Yan Ma, Zhi-Ling Zhang, Dai-Wen Pang and Hongwu Tang
Sensitive non-amplification detection of biomolecules is a major concern in analytical science. Here, we report a single-microsphere based imaging assay method by integrating up-converting luminescence with optical tweezers (OT) for detecting microRNAs. By taking advantages of the anti-Stokes luminescence and a minimal three-dimensional excitation region formed by OT, there exist a very low background signal around a trapped sandwich structure complex microsphere enriched with targets (miRNA-21). This effect is further enhanced by combining it with a sensitive imaging detector (EMCCD) and thus achieves a competitive detection limit of 12 fM with quite sound selectivity and no complicated signal amplification designs. As a proof-of-concept study, this analytical methodology can also be employed to quantify the amount of miRNA-21 sequences from as low as 100 cancer cells, making it a promising new means for biomedical applications.