Aptamer Sensor Based On Hybridization Chain Reaction For Saxitoxin Detection

In recent years,the deterioration of the marine environment has accelerated the breeding of red tide algae.Although the filtering and feeding of marine organisms on red tide algae has no impact on itself,the accumulated marine biotoxins in the body further threaten the quality and safety of marine products.Frequent poisoning incidents due to marine products.According to the different symptoms after poisoning,marine biotoxins can be divided into paralytic,diarrhoeal,and other shellfish toxins.Saxitoxin（STX）is one of the strongest paralytic shellfish toxins and one of the most toxic marine toxins.It is extremely harmful because of its frequent poisoning events.Therefore,effective detection of STX is of great significance to human life and health.In view of some shortcomings in the current STX detection methods,combined with the many advantages of signal amplification technology and aptamer,we developed two simple sensors to realize the sensitive detection of STX.First of all,an aptamer sensor based on hybridization chain reaction and the CRISPR-Cas9system was developed for application to the detection of STX.The synthetic aptamer biosensing probe enabled to release the aptamer chain in the presence of STX.Simultaneously,the aptamer complementary chain was released into solution equally as a promoter to trigger a hybridization chain reaction to produce discontinuous ds DNA and realize signal amplification.The CRISPR-Cas9system was introduced to achieve accurate recognition of the formed products and to exert the cleavage activity to achieve fluorescence recovery.The limit of detection for the STX was 1.2 f M,with a recovery rate of 102.4%-104.1%,all of which suggested that the sensor has good detection performance.Secondly,an aptamer sensor based on hybridization chain reaction and DNAzyme was developed for the detection of STX.As a new functional nucleic acid,DNAzyme has strong cleavage activity on DNA with the help of metal ions.The sequence of the DNAzyme was designed into hairpin DNA.When STX was absent from the system,the hairpin DNA was in a steady state.When STX was present,the hairpin DNA was successively opened when triggered by the STX aptamer complementary chain,and the exposed DNAzyme captured the substrate hairpin DNA and exerted cutting activity under the regulation of Zn²⁺to achieve fluorescence recovery.The limit of detection for the STX was 0.22 p M,and the recovery rate was 98.1%-101.3%,all of which suggested that the sensor has good detection performance.