The Application Of Functionalized Magnetic Nanoparticles In Microfluidic Chip

Nanotechnology is the dominant technology in today’s society, the core is nanomaterials,magnetic nanomaterials representing an important part of the nanomaterials. Magneticnanomaterials with micro/nanometer size, the large surface areas, low toxicity,biocompatibility and unique magnetic responsivity, which can make them easily manipulatedand fast separated the sample from solution. Consequently, such magnetic nanomaterials havebeen widely used in the applications of biological chemistry and biomedical research, such asenhanced medical imaging, targeted drug delivery, immunoassay detection and so on.Microfluidic chip technology has developed rapidly in recent decades, it is also one ofthe fastest growing separation techniques in recent years. Compared with conventionalseparation technique, microchip electrophoresis has several advantages including simplicity,short analysis time, low sample and reagent consumption, and ease of integration, and hasbeen widely used for the separation and detection of many compounds such as smallmolecules, nucleic acid and protein. Polydimethylsiloxane (PDMS) has become a popularmaterial for fabricating multifunctional microfluidic devices due to its nontoxicity, goodoptical transparency and easy sealing with other materials. However, the hydrophobicity anduncontrolled EOF of native PDMS is a major obstacle for the application in microfluidicdevices. It may lead to non-specific adsorption of hydrophobic analytes, peak tailing and pooranalyze results.In this work, we employed functionalized magnetic nanoparticles for surfacemodification of native PDMS to improve the stability of EOF, the surface wettability forfacilitating liquid delivery and decreasing non-specific adsorption of hydrophobic analytes,which were as follows.1. A new strategy for facile construction of graphene oxide magnetic nanocomposites(GO/Fe3O4MNCs)-based on-chip enzymatic microreactor and ultrasensitive pesticidedetection has been proposed. GO/Fe3O4MNCs were first prepared through an in situ chemicaldeposition strategy. Then, acetylcholinesterase (AChE) was adsorbed onto the GO/Fe3O4surface to form GO/Fe3O4/AChE MNCs which was locally packed into PDMS microchannelsimply with the help of external magnetic field to form an on-chip enzymatic microreactor.The constructed GO/Fe3O4/AChE MNCs-based enzymatic microreactor not only have themagnetism of Fe3O4NPs that make them conveniently manipulated by an external magnetic field, but also have the larger surface and excellent biocompatibility of graphene which canincorporate much more AChE molecules and well maintain their biological activity. On thebasis of the AChE inhibition principle, a novel on-chip enzymatic microreactor wasconstructed for analyzing dimethoate which is usually used as a model of organophosphoruspesticides. Under optimal conditions, a linear relationship between the inhibition rates ofAChE and the concentration of dimethoate from1to20μg·L-1with a detection limit of0.18μg·L-1(S/N=3) was obtained. The developed electrophoretic and magnetic-based chipexhibited excellent reproducibility and stability, which provided a new and promising tool forthe analysis of enzyme inhibitors with low cost and excellent performance.2. In this work, molecularly imprinted polymers were one-step prepared employing Fe3O4NPs as the supporting substrate and dopamine as the functional monomer. By simply mixingFe3O4NPs with template molecules in a weak alkaline solution of dopamine, a thin adherentpolydopamine (PDA) film imprinted with template molecules was formed by theself-polymerization of dopamine on the surface of Fe3O4NPs. After extracting the embeddedtemplate molecules, the produced imprinted Fe3O4@PDA NPs are of three dimensional shapeof template molecules favoring high binding capacity and magnetism property for easymanipulation. The imprinted Fe3O4@PDA NPs prepared with L-tyrosine, Gly-L-Phe, orS-ofloxacin as template molecules were packed in the PDMS microchannel via magnetic fieldas novel stationary phase to successfully enantioseparation of corresponding target analysts(D/L-tyrosine, Gly-D/L-Phe and racemic ofloxacin).