Preparation Of Magnetic Fluorescent Silica Microspheres And Application In DNA Storage

With the advancement of modern scientific technology and the popularization of information technology,the existing storage devices obviously can not meet the needs of long-term storage of huge data in the future.Deoxyribonucleic acid(DNA)is a natural information storage medium,which has the advantages of high storage density and long longevity.However,DNA will be degraded because it is easily affected by the external environment,so long-term storage and reading of DNA requires manual protection.The magnetic fluorescent microspheres,as multi-functional nanomaterials,not only have excellent magnetic properties,which can achieve rapid enrichment and separation of samples to be tested,but also have good fluorescent properties,so they have great application potential in the field of DNA storage.This article aims at the problems existing in the preparation of magnetic fluorescent silica microspheres,such as tedious steps,easy aggregation of microspheres,weak magnetic response of microspheres after the introduction of composite materials,and fluorescence quenching caused by magnetic nanomaterials,focuses on the limitations of the current DNA storage scheme,such as not being able to read the DNA information repeatedly,mainly for one-time use,non-recovery,high preparation cost,tedious operation and so on.Based on the preparation of silica microspheres,fluorescent silica microspheres and magnetic fluorescent silica microspheres,a switchable DNA storage structure complex was successfully constructed,which can release DNA under temperature control and magnetic separation manipulation,and can realize repeated reading and long-term storage of DNA information,providing a new medium and technology for DNA storage.First of all,by adjusting the parameters of the amount of ammonia,TEOS,water and rotational speed,temperature,reaction time and other influencing factors,a series of silica microspheres from 100 nm to 600 nm with uniform particle size,good monodispersion and good sphericity were successfully prepared by St(?)ber method using the principle that TEOS can hydrolyze and condensate in aqueous ethanol solution to form silica particles.Then Cy5 fluorescent molecules were successfully embedded in silica microspheres by silane coupling agent APTES,and fluorescent silica microspheres with uniform particle size,good monodispersion,excellent photobleaching resistance and low dye leakage were prepared.And the effects of the amount of TEOS,ammonia,reaction time,fluorescent molecular connection mode and Cy5 dosage on the morphology and properties of fluorescent microspheres were studied systematically.The fluorescent silica microspheres can emit bright red fluorescence after being excited with excitation light under the fluorescence confocal microscope.The fluorescence intensity decreased by only 3% after being irradiated by a xenon lamp for 1 hour,and there was no significant decrease of the fluorescence intensity after being preserved for one year.Next,based on the prepared fluorescent silica microspheres,positively charged PEI and negatively charged Fe3O4 magnetic nanoparticles were modified on the surface of fluorescent microspheres by electrostatic force using layer-by-layer method,and the magnetic fluorescent silica microspheres adsorbed Fe3O4 magnetic nanoparticles with the outermost layer amino modified were prepared.A series of characterization methods such as SEM-EDS,FTIR,TGA and VSM characterization showed that the magnetic fluorescent microspheres had strong fluorescence intensity,Fe3O4 magnetic nanoparticles were successfully modified on the surface of the fluorescent microspheres,and the prepared magnetic fluorescent silica microspheres had superparamagnetism and good magnetic responsiveness.Finally,on the basis of about 70 nm silica microspheres and about 500 nm magnetic fluorescent silica microspheres,SA coated magnetic fluorescent silica microspheres,carboxylated silica microspheres and carboxylated magnetic fluorescent silica microspheres were prepared,and then the DNA single strands for recording information and complementary DNA single strands were modified on the surfaces of magnetic fluorescent microspheres and silica microspheres by covalent bond.They can be self-assembled by DNA hybridization to form a switchable DNA storage structure complex with magnetic fluorescent silica microspheres as core and silica microspheres as shell.When in use,the composite can open double-stranded DNA by thermal denaturation,and re-obtain the carboxylated magnetic fluorescent silica microspheres and silica microspheres coupled with DNA by magnetic separation.The carboxylated magnetic fluorescent silica microspheres coupled with the recording information DNA were quantitatively PCR and sequenced,and the sequencing results were more than 90% similar to the known sequences.It is stated that the prepared switchable DNA storage structure complex can successfully read DNA information,and has the advantages of simple controllable and recyclable operation.