Study Of Surface Plasma Resonance Technology Based On DNA Tetrahedron And Gold Nanoparticles

Surface plasmon resonance（SPR）sensor technology has the characteristics of high sensitivity,small damage,no labeling,convenience and real-time monitoring,which has been widely used in the fields of environmental monitoring,drug screening,food analysis and clinical diagnosis.In this paper,the exosomes of human hepatoma cell line（SMMC-7721）and gliotoxin were used as model targets,and a series of SPR sensor technologies suitable for target detection in complex systems were developed by using gold nanoparticles（Au NPs）and DNA tetrahedral probes（DTPs）.The details are as follows:1.A SPR sensor based on aptamer and polydopamine-functionalized gold nanoparticles as signal amplification for specific detection of cancerous exosomesBy using SMMC-7721 exosomes as model targets,an SPR sensor was proposed based on dual aptamer recognition and polydopamine functionalized gold nanoparticles（Au@PDA NPs）assisted signal amplification.First,SMMC-7721exosomes were specifically captured using DTPs containing aptamer ZY-sls immobilized on the surface of Au film,and then aptamer CD63 functionalized Au@PDA NPs recognition target forms sandwich structure to enhance SPR signal.Next,Au@PDA NPs were used to reduce HAu Cl₄to small Au NPs in situ to further enhance SPR signal,so that SMMC-7721 exosomes as low as 5.6×10⁵particles/m L could be detected.This method could not only distinguish SMMC-7721 exosomes from other exosomes,but also directly detected SMMC-7721 exosomes in human serum.This work is expected to provide a new idea for the detection of cancer exosomes in liquid biopsy.2.A colorimetry based on DNA tetrahedral and gold nanoparticles for the detection of gliotoxinBy using gliotoxin as model targets,a modification-free of the colorimetric method based on DNA tetrahedron and Au NPs was constructed.Due to the steric effect of its phosphate backbone and a large number of negative charges on its surface,aptamer functionalized DTPs（DTPs-Apt）could effectively prevent the aggregation of Au NPs in high salt solution,and the solution was red.In presence of gliotoxin,aptamer combines with gliotoxin,which made DTPs-Apt to compete on the surface of Au NPs,resulting in Au NPs aggregate and the color of solution changes（red to blue）.By optimizing the size of DTPs,it was found that the colorimetric method based on26 bases of DTPs（26-DTPs-Apt）and Au NPs could detect as low as 8 n M of gliotoxin,and could also quantify the gliotoxin in human serum and urine.However,the linear range of this method was narrow（30-500 n M）,and the detection time was relatively long（45 min）.This work is expected to improve the sensitivity of colorimetry and expand its application.3.A colorimetry based on multivalent DNA tetrahedral and gold nanoparticles for the detection of gliotoxinA quantitative colorimetric method based on multivalent DNA tetrahedron and Au NPs was constructed.The multivalent DNA tetrahedron（26-DTPs-Apt（IV））was obtained by modifying one aptamer at each top of 26-DTPs.The colorimetric method constructed by 26-DTPs-Apt（IV）and Au NPs could not only rapidly detect as low as18 n M of gliotoxin in 15 min,but also broaden the linear range of detection of gliotoxin（0.05-1.5μM）.Meanwhile,the method could also be used for the quantitative determination of gliotoxin in human serum and urine samples,which is expected to provide a new idea for point-of-care testing.