Single-particle Nanoprobe Constructed Based On Tetrahedral Structure DNA And Its Light-controlled Sensing Application

The localized surface plasmon resonance(LSPR)phenomenon of precious metal nanoparticles has wide application prospects in the fields of biochemical analysis,sensory detection,drug tracking,photothermal targeting therapy and catalysis due to its unique optical and physical properties.The LSPR properties of precious metal nanoparticles are closely related to their composition,morphology and size.Therefore,in the research process,researchers used different methods to prepare plasma biosensors with clever design and good performance with specific recognition capabilities,such as: modifying the surface of different types of metal nanoparticles,self-assembling between different types of metal nanoparticles and various synthetic methods of exploring metal nanoparticles,so as to achieve the purpose of single nanoparticles in a complex system can be detected quickly,real-time,high sensitivity.This paper mainly studies a single-particle nanobiosensor based on tetrahedral DNA,which can realize the light-controlled detection of mi RNA-21 by alternating irradiation of ultraviolet light and visible light.The details are as follows:1.Gold-silver core-shell nanocubic biosensor based on tetrahedral structure DNA.First,the seed growth method is used to prepare a gold ball with a controllable morphology and size,and then silver is coated on the gold surface by deposition to prepare gold-silver core-shell nanoparticles;then four DNA strands A,B,C,and D(where the D chain is embedded with azobenzene molecules)mixed in equal proportions,and assembled into tetrahedral DNA after annealing and cooling at high temperature.Finally,the tetrahedral DNA is modified on the surface of the gold-silver core-shell by silver-sulfur bonds.2.A gold-silver core-shell nanocubic biosensor constructed based on DNA with tetrahedral structure is used to detect mi RNA-21.Using the localized surface plasmon resonance phenomenon of gold-silver core-shell nanoparticles,the localized surface plasmon resonance scattering spectrum is collected by a dark field microscope to realize the detection and analysis of mi RNA-21.Mi RNA-21 and the azobenzene molecule embedded in the D chain are base-paired,which causes the local environment of the surface of the gold-silver core-shell nanoparticles to change,causing the localized surface plasmon resonance light scattering color of the gold-silver core-shell nanoparticles.Changes occurred,causing the red-shift of the localized surface plasmon resonance scattering spectrum of the particles,and the amount of red-shift of the spectrum is linearly related to the concentration of mi RNA-21.3.The ultraviolet-visible light cycle irradiation is used to realize the light control detection of mi RNA-21 by the gold-silver core-shell nanocubic biosensor.In the natural state,the azobenzene molecule embedded in the DNA chain has a trans structure.At room temperature,the tetrahedral DNA can interact with the target molecule mi RNA-21 by complementary pairing.After irradiated with ultraviolet light at 365 nm for a certain period of time,the azobenzene molecule undergoes photo-isomerization,changing from the trans structure to the cis structure,which causes mi RNA-21 to melt.Under visible light irradiation,the azobenzene molecule undergoes photoisomerization again,changing from the cis structure to the trans structure,and interacting with mi RNA-21 again.The goldsilver core-shell nanoparticles LSPR scattering peak signal and particle color changes are used to realize the light-controlled detection of mi RNA-21 by the gold-silver core-shell nanocubic biosensor.