Target-triggering multiple-cycle amplification strategy for ultrasensitive detection of adenosine based on surface plasma resonance techniques.

An ultrasensitive protocol for surface plasma resonance (SPR) detection of adenosine is designed with the aptamer-based target-triggering cascade multiple cycle amplification, and streptavidin-coated Au-NPs (Au NPs-SA) enhancement to enhance the SPR signals. The cascade amplification process consists of the aptamer-based target-triggering nicking enzyme signaling amplification (T-NESA), the nicking enzyme signaling amplification (NESA) and the hybridization chain reaction (HCR), the entire circle amplification process is triggered by the target recognition of adenosine. Upon recognition of the aptamer to target adenosine, DNA s1 is released from the aptamer and then hybridizes with hairpin DNA (HP1). The DNA s1 can be dissociated from HP1 under the reaction of nicking endonuclease to initiate the next hybridization and cleavage process. Moreover, the products of the upstream cycle (T-NESA) (DNA s2 and s3) could act as the "DNA trigger" of the downstream cycle (NESA and HCR) to generate further signal amplification, resulting in the immobilization of abundant Au NPs-SA on the gold substrate, and thus significant SPR enhancement is achieved due to the electronic coupling interaction between the localized surface plasma of Au NPs and the surface plasma wave. This detection method exhibits excellent specificity and sensitivity toward adenosine with a detection limit of 4 fM. The high sensitivity and specificity make this method a great potential for detecting biomolecules with trace amounts in bioanalysis and clinical biomedicine.