Photonic Crystals Enable Label-free And Ultra-Trace Detection Of Biotoxin In Food

Objective The contamination of biotoxins in food and the environment poses a great threat to human health,economic development and even social security.Among them,the abrin and Staphylococcal enterotoxin B（SEB）are listed as"potential biological warfare agents"because of their extremely low lethal dose.Therefore,the quantitative detection of these biotoxins is highly valued by international organizations and government regulatory agencies of various countries.At present,detection methods with high sensitivity and reliable results rely on expensive experimental equipment,and the operation process is relatively complicated,which can not satisfy the demands for rapid,simple and ultra-sensitive detection.Thus,two methods for the ultra-sensitive detection of abrin and SEB have been established based on stimuli-responsive photonic crystals.Methods The opal photonic crystals were stacked using SiO₂-AuNPs microspheres in a 24-well plate,and then modified with abrin polyclonal antibody（pAb）or SEB aptamer in order to perform the specific recognition of the abrin or SEB.The incubation conditions of the identification element and the photonic crystal were optimized by investigating the response performance of the sensing material to the target.TEM,SEM,and AFM were used to characterize the surface morphology of the microspheres and the PCs,and initially explore the response mechanism.Through specificity experiments and spike recovery experiments,the specificity and accuracy of the sensing materials were investigated.Results 1.Photonic crystal sensing materials were constructed using abrin polyclonal antibody（pAb）as a recognition element.Under optimal conditions,the intensity of the reflection peak of the sensing material decreased as the concentration of abrin increased,the linear range was 0.10 pg/mL to 10 ng/mL,the detection limit wass 0.011 pg/mL,and the recoveries ranged from 91.45±3.37%to 113.61±6.14%.2.Aptamer-PC sensing material for detecting SEB was established by immobilizing SEB aptamers on the SiO₂-AuNPs photonic crystals.Experimental optimization conditions included the aptamer incubation concentration and the pH of the reaction environment.Under optimal conditions,the reflection peak intensity of the sensing material would change with the increase of the SEB concentration,and the logarithm of the SEB concentration had a linear relationship with the decrease of the reflection peak intensity.The detection range was 1 fg/mL to 1 ng/mL,the detection limit was 0.103 fg/mL.Through the spiked recovery experiment of drinking water and milk samples,the recoveries ranged from 100.26±9.13%to 116.27±6.12%.Conclusion In this paper,a biocompatible SiO₂-AuNPs photonic crystal was prepared,and the organic combination of the photonic crystal and the identification element was realized by adding AuNPs.A photonic crystal sensing technology based on immunoassay was established.The combination of pAb and abrin could effectively destroy the periodic structure of the photonic crystal.The advantages of aptamers included fast synthesis,low cost,and great stability.Aptamer-PC sensor system was established through modification of specific groups.Compared with traditional methods,the detection range was wider and the limit was lower.In addition,the simple preparation process and excellent responsiveness made this sensing material expected to be one of the suitable technologies for rapid and ultra-sensitive detection which had wide application prospects in the fields of food safety detection,environmental monitoring and disease diagnosis.