Novel strategy for screening aptamers of Staphylococcus aureus enterotoxin A based on active fragments and fusion design

Background

Staphylococcus aureus enterotoxin A (SEA) is the major toxin responsible for food poisoning caused by Staphylococcus aureus infection. Aptamers are an ideal solution for visual detection of SEA. However, screening for aptamers is generally expensive and time-consuming. Therefore, a new method for efficient screening of high-affinity SEA aptamers needs to be established and supplemented with smartphone image recognition to enable visual and rapid detection of SEA.

Results

A new aptamer for sensitive detection of SEA was screened using active fragments and fusion design. The novel high-affinity aptamer (BX1) was derived by intercepting active nucleotide fragments of several aptamers and fusing them; it was verified to have high affinity, with a K_d value of 4.16 ± 0.22 nM. Molecular dynamic simulation illustrated that BX1 formed a stable complex conformation with SEA, which maintained its stability for 200 ns. This novel aptamer can be used for visual inspection of SEA. A smartphone-assisted aptasensor was designed to sensitively detect SEA in milk with a wide linear range (1-250 ng/mL), low detection limit (0.42 ng/mL), and satisfactory spiked recovery.

Significance

A new method for screening SEA aptamers based on active fragments and fusion design was developed, which can rapidly screen high-affinity aptamers in a short duration and at a low expenditure. In addition, a new strategy for the rapid detection of SEA using a smartphone-assisted colorimetric aptamer sensor was successfully applied. This research method may provide a reference for the highly sensitive detection of other biotoxins.