Study On Modification And Separation Application Of PDMS Microchip Based On Magnetic Nanocomposites

In recent years,magnetic nanocomposites have received increasing attention due to their unique physical and chemical properties and their many potent ial applications in various fields such as drug delivery and cell separation.Magnetic nanocomposites combine the advantages of nanocomposites and magnetism,including large specific surface area,small size,good biocompatibility,low toxicity,and fast magnetic response.They are easy to operate and enable rapid separation.Consequently,magnetic nanocomposites have widely used in the applications of biological chemistry and biomedical research.Ultramicro analysis systems,also known as"on-chip laboratories,"dramatically change the way of biochemical analysis.Some laboratory procedures such as sample preparation,separation and detection are integrated on one microchip,and microchip electrophoresis is a new type of separation technology on the microchip.Compared with traditional separation analysis techniques,microchip electrophoresis technology has the advantages of rapid and efficient separation capability,low consumption,high automation,and small device size.However,the polydimethylsiloxane（PDMS）microchip,due to the inherent hydrophobicity of PDMS,lead to the electroosmotic flow instability and nonspecific adsorption of the sample,the separation efficiency is reduced.In this paper,magnetic nanocomposites were used to modify the PDMS microchip channels,not only effectively improve the hydrophilic properties of the microchip surface,reducing the nonspecific adsorption of analytes,but also improve the separation efficiency of chiral enantiomers and single nucleotide polymorphisms.The content is as follows:1.The introduction mainly summarizes the characteristics and applications of magnetic nanocomposites,the development of microfluidic chips and the principle of microchip capillary electrophoresis.The preparation of microchips of var ious materials and the methods of surface modification of PDMS microchips and detectors of microfluidic chips are described.At the same time briefly introduced of the main research work and significance of this paper are introduced.2.The mandelic acid enantiomers and histidine enantiomers were rapidly separated on microchip capillary electrochromatography using a magnetic molecularly imprinted polymer as stationary phase.On the surface of Fe₃O₄ NPs,R-mandelic acid or L-histidine were used as templates,norepinephrine was a functional monomer,and the molecular imprinting process under alkaline conditions.The template molecule was then eluted with an eluent to prepare an imprinted polymer（MIP-Fe₃O₄@PNE NPs）,which having a three-dimensional cavity that perfectly matches the template molecule.The MIP-Fe₃O₄@PNE NPs has the unique properties of both Fe₃O₄ NPs（strong magnetism and high surface to volume ratio）and PNE（multifunctional groups and good biocompatibility）,lead to the MIP-Fe₃O₄@PNE NPs can be easily fixed at any position of the separation channel by an external magnet,and template molecules have high binding capacity and good selectivity.The high molecular recognition ability of the mandelic acid enantiomers and histidine enantiomers was achieved on the MIP-Fe₃O₄@PNE NPs modified PDMS microchip.3.The separation and detection of SNPs on microchip capillary electrochromatography using GO@Fe₃O₄ nanocomposites（GO@Fe₃O₄）as a stationary phase.A methylene blue-labeled probe DNA completely complementary to miR-21 was designed.Duo to the GO@Fe₃O₄ good magnetic properties,it was immobilized in the PDMS microchannel under the action of an external magnetic field.The GO@Fe₃O₄ has strong adsorption of unstable P1 T1,results in different retention times of P1T1 and P1M1 on the GO@Fe₃O₄ modified microchip,thereby enabling identification of SNPs.Therefore,baseline separation of P1T1 and P1M1was achieved on the microchannel using GO@Fe₃O₄ as the stationary phase.