Ultrasensitive, recyclable and portable microfluidic surface-enhanced raman scattering (SERS) biosensor for uranyl ions detection

Sensitive, fast and reliable detection of UO22+ ions is of great significance in nuclear industry and environment protection, due to the serious threats of UO22+ ions to human health. However, such suitable sensor is still rare. Herein, an ultrasensitive and recyclable SERS-microfluidic biosensor with specific UO22+ response has been developed. Aptamer-modified ZnO-Ag hybrids arrays was firstly designed and utilized as highly functional sensor by colloidal crystals templating method. The relationship between aptamers (different types, length and reaction time) and UO22+ ions was fully screened to improve the detection efficiency. In the absence of UO22+, Rhodamine B (RhB)-labeled double-stranded DNA formed a rigid structure, and weak Raman signals were detected. After pumping the UO22+ solution into microdevice, DNAzyme-cleavage reaction was triggered. And RhB-modified 5'-single DNA strand (cleavage production) dropped down to the surface of SERS substrates, leading to strong Raman signals. After signal amplification, the detection limit of UO22+ achieved as low as 7.2 x 10(-13) M, which is nearly five orders below the EPA-defined maximum contaminant level. More importantly, the specially designed microfluidic device could be reused and refreshed by supplementation of substrate strands DNA for three times. A further application to determine UO22+ ions in natural real systems such as tap water and river water was also complied with good recoveries and RSDs. This SERS-based microfluidic sensor shows great potential for in-the-field sensing platforms, due to its ultra-sensitivity, high efficiency, and portability.