A Paper-Based Device Printed With DNA Superstructures For Escherichia Coli Detection

With the growing problem of food-borne pathogens,the detection of pathogens in water or food has attracted more and more attention.According to the World Health Organization,diarrheal pathogens are one of the most common and highly pathogenic bacteria.Among them,Escherichia coli is the most common and main diarrheal pathogen.Escherichia coli not only has a wide variety of pathogenicity,but can also cause diarrhea,gastroenteritis,inflamemation and malnutrition,and even worse,it can cause severe symptoms such as sepsis and hemolytic uremic.Since E.coli can be pathogenic at low doses,the development of a rapid and sensitive method for identifying E.coli has become more essential.First,this thesis constructed a paper chip based on bacterial lysate to extract bacterial protein.Under different conditions,the BCA protein detection kit was used to test the ability of the chip to extract bacterial protein.Whatman 3MM CHR chromatographic paper is determined as the best paper-based model for retaining bacterial protein.The reaction time is3 minutes,the bacterial protein extracted on paper has reached saturation,and the minimum limit of bacterial protein extraction is 10~3 CFU.Later,the study found that the E.coli protein extracted from the paper could activate the corresponding DNAzyme to catalyze the reaction,proving that the bacterial protein extracted from the paper chip did not lose activity.On this basis,this paper has developed an integrated paper chip,which connects bacteria on paper,protein extraction,molecular recognition of target response,and signal amplificati-on of rolling circle amplification in series to detect bacteria.The chip used different origami methods to carry out the diffusion and flow of reagents to achieve the rapid detection.Moreover,the results showed that the detection range of this device was 10~3-10~7 CFU/m L.During 35 minutes,the limit of detection was able to reach 10~3 CFU/m L.Furthermore,the chip has a wide range of application value in E.coli diagnosis and field detection due to its advantages of high speed,sensitivity and versatility.Therefore,this fully integrated paper chip has great potential for the real-time detection of pathogenic bacteria in resource-limited environments.