Functionalized Nucleic Acids Modified Magnetic Nanomaterials And Its Application In The Diagnosis Of Tumor Markers

Cancer is one of the serious diseases that endanger human health and threaten human life.Early diagnosis is of great significance for reducing patient mortality and improving treatment efficiency.In recent years,the rapid development of DNA nanotechnology has provided adaptable platforms to explore new types of biological diagnostic methods.Among various biosensors,the nucleic acid-functionalized magnetic nanoprobes have attracted wide attention due to its easy-to-enrich,excellent biomolecule recognition ability and biocompatibility,thus been widely used in biodiagnosis,cell imaging,drug delivery and other fields.Fluorescent probes based on magnetic materials can collect the fluorescent signal easily under magnetic fields.This property is highly helpful to develop biosensors with high sensitivity and selectivity.This work constructed nano-fluorescent probes based on the functional nucleic acidmodified magnetic nanoparticles,which achieved sensitive detection of tumor markers in serum samples and living cells.The specific research content is as follows:1.Based on DNA functionalized magnetic beads and Circular Strand Displacement Amplification(CSDA),we report the design of a nucleic acid circuit for gastric cancerrelated micro RNA-27a(mi RNA-27a)detection.Magnetic beads(Magnetic Beads,MB)have high specific surface area and good separation ability,which can enrich probe molecules rapidly.In the presence of mi RNA-27 a,CSDA is initiated and target mi RNA-27 a is released to participate the cyclic reaction.Therefore,a greatly enhanced fluorescence signal is produced.The efficient magnetic separation makes the sensitive detection of mi RNA-27 a be accomplished within 45 min.With the efficient CSDA,the detection limit of the system(0.8 p M)is ?100 folds lower than that of the system based on strand displacement without CSDA(79.3 p M).This study provides a novel platform and approach for the rapid quantitative determination of mi RNA,which has great potential in clinical diagnosis and disease treatment.2.We develop an enzymatic "DNA walker" based on magnetic field activation,which was applied to the highly sensitive detection and imaging of the mi RNA-21 in living cells.The method can image RNA with high-temporal-resolution,which transmits the driving instructions to the DNA walker in a remote and non-invasive magnetic activation mode.In the absence of magnetic activation,the DNA walker remains the "unawakened" state,showing a low fluorescent background signal in cells.The presence of endogenous mi RNA-21 can trigger the efficient walking of the DNAzyme-mediated "DNA walker",which can effectively achieve the amplification detection of target tumor markers under magnetic field-triggered magnetic bead accumulation.This strategy can distinguish the difference in the expression levels of endogenous mi RNA-21 in normal cells and cancer cells,and can successfully achieve time-sensing imaging of target tumor markers through remote magnetic control.This strategy provides a new analysis method for the controllable imaging of endogenous RNA,and has broad application prospects in the field of biological diagnosis.