Development Of Biosensors For Food Safety Based On Nucleic Acids And Nanomaterials

Functional nucleic acids(FNA),are oligonucleotides,provide special structural and functional properties,such as target-specific recognization,catalytic properties(DNAzymes),metal-specific catalytic cleavage,energy storage,or the formation of G-quadruplexes,base-metal ion complexes,supramolecular,and i-motifs.The FNA,which not limit to traditional base pairing but with abundant structural and biological function,is becoming a mainstay in the field of analysis.The functional nucleic acids,are alternative of protein enzymes or antibody,have a wide range of applications in optical or electronic biosensors.In our study,the methodologies for the detection and recognition of risk factors within the food substrates have been developed based on the functional nucleic acids and nanomaterials.The main contents and conclusions of our study are summarized and listed below:1.We have introduced HRP-mimicking DNAzymes into LAMP system to develop a facile DNAzyme mediated LAMP(dLAMP)optical sensor for colorimetric detection of Salmonella.We established a four-step principle to tailor DNAzymes into LAMP system,first step,acquisition of zero background signal by selecting the complementary sequence of DNAzyme as the signal precursor;second step,modifying the forwward inner primers with signal precursors to adapt to the amplification characteristics of LAMP;third step,optimizing DNAzyme sequence release format to enhance the enzymatic activity;fourth step,enhancing the catalytic activity of the G-quadruplex/hemin DNAzyme for colorimetric detection of target DNA by determination of the appropriate K+concentration to stabilize the G4 topology structures and to provide a favorable microenvironment for the catalytic reaction.Then,we validated the analysis performance of the developed dLAMP in contaminative prok samples.Finally,a dLAMP strategy integrates the ultrasensitivity and high specificity of LAMP and the visuality of DNAzymes have been established,and it facilitates an ultrasensitive colorimetric assay for even less 0.5 pg target DNA.2.We develop a novel label-free colorimetric system based on the different absorption properties of unmodified GNPs between ssDNA sticky-end modified hairpins and dsDNA concatemers.We designed an aptamer-inserted fuel Hairpin 1(H1)and a Functional Hairpin to remould the DNA assembly,generating a target-induced switchable DNA concatemers,for both response sequence-specific DNA and small molecule simultaneously.We designed a Functional Hairpins(FH)by optimization of the blocking direction and length.We designed an aptamer-inserted fuel H1 to introduce multi-binding sites of small molecule target in dsDNA concatemers via reversing the aptamer sequence and deleting the flank sequence.The developed switchable DNA concatemer-mediated two-way sensing system provides insight for the disease-related integrated diagnose.The detection limits of both targets were below nanomole.3.Integrating DNA superstructure into cylindrical alumina nanochannels establishes a sequence-specific nanofluidic diode to understand and imitate the superior performance characteristics of living systems in ion transport and biomolecule sensing.Herein,we asymmetrically assembled a hybridization chain reaction(HCR)motored biological nanofluidic diode that exhibits both high ON-OFF ratios and ion current rectification performance within one nanochannel.The fabricated nanofluidic diode displays pH-tunable or charge polarity responsive rectifying characteristics and is response to specific sequence stimuli at single base level.Further,a theoretical model based on coarse-grained models&Poisson-Nernst-Planck(PNP)equations is established to numerical simulate the ion transport behavior in DNA superstructures asymmetrically modified nanochannels,and shed light on the underlying mechanism and its potential application.4.A smart response gating system for Cu2+was developed based on the Cu2+-dependent DNA-cleaving DNAzyme(cDNAzyme)and nanoporous alumina membranes.First,we transfer the target copper(?)ion into transition sequence X by Cu2+-dependent DNA-cleaving DNAzyme,then we enriched the sequence X into sequence Y based on the Exponential amplification reaction(EXPAR);Finally,we used the sequence Y as the intiator sequence to develop the smart response gating system.The gating system displayed a high selectivity and anti-interference for Cu2+and is applicable to monitoring Cu2+in picomole.The established functional nucleic acids analysis platform for various food risk factors and biomarkers based on DNAzyme,cDNAzyme,aptamer,gold nanoparticles and nanochannels in our study will not only provide the technique support for integrated diagnosis and uniform platform monitoring,but also provide the new thought and methods for the related researches.