A HCR based multivalent aptamer amplifier for ultrasensitive detection of Salmonella

Aptamer holds great promise as an alternative recognition element for foodborne pathogens detection because of its superior structural features. However, its application is still limited by the diminished affinity in food samples and the sophisticated signal amplifications. Herein, we fabricate a hybridization chain reaction (HCR) based multivalent aptamer (multi-Apt) as an effective signal amplifier for the sensitive detection of Salmonella. The aptamer was assembled on the HCR product to construct a DNA programmable multi-Apt, which displayed a 33-fold enhancement binding affinity and a much faster reaction kinetics than that of a monovalent aptamer (mono-Apt). Furthermore, the HCR scaffold was exploited as the signal carrier via the abundant DNA hairpins. Due to the synergism of the high affinity of multi-Apt and the scaffold-based signal amplification, the proposed HCR based multi-Apt amplifier could detect Salmonella as low as 7 cfu mL−1 with a broad detection range of 10 to 107 cfu mL−1. Besides, it also exhibited excellent specificity against target bacteria and performed well on the detection of spiked food samples, indicating the promise in practical detection of Salmonella.