Microfluidic Chip-based Immunosensor

Microfluidic devices are becoming powerful tools in chemical or biological assays,due to the advantages of high performance,miniaturization,increased speed and reliability at reduced sample consumption.Microfluidic chips have been used in biochemistry,medical test,medicine screening and environmental monitoring,etc. Polymer materials are now widely used as the fabrication substrates because of the lower cost,better flexibility and feasibility,compared to traditional glass or silicon substrates.But there are some disadvantages of the polymer materials,such as nonspecific adsorption,etc.In this work,we synthesized a copolymer to modify the inner surfaces of mcirochannel,and realized the protein immobilization within microfluidic chips.This new strategy was applied in immunoassay and then followed by the end-column electrochemical detection.The results showed that the chip-based immunoassay was fast and efficient.The detailed points of the thesis are expanded as follows:1.Introduction of microfluidics and its application in bioanalysisA review on microfluidics and its application in bioanalysis is presented.This part includes:(1) brief introduction of the recent research progress in microfluidics(2) introduction of microfuidic technologies,including various chip materials, fabrication techniques,and microfluidic detection techniques:(3) trend of microfluidics in bioanalysis application,(4) purpose and significance of this thesis.2.Microfluidic immunosensor based on stable antibody-patterned surface in PMMA microchipThe preface section reviewed application of microfluidic chip,also summarized the new progress and important achievements on the fields of microfluidic chip.We chose the PMMA substrate for the chip fabrication,and used a new protocol to modify the substrate,then successfully immobilized the proteins in the matrix of alumina sol-gel for immunoassay.The details points of this thesis are expanded as follows:(1) Through the method of hot-embossing,PMMA microchip was fabricated for the following research.Chemical modification of poly(methyl methacrylate) microchannel surface has been explored to functionalize microfluidic chip.A craft copolymer(BMA)_x-(MAOPTAS)_y was designed and synthesized to introduce the silicane functional groups bridge which was formed by tethering to these functional groups,and a stable patterning network of gel matrix could be achieved.Thus, anchorage of proteins could be realized onto the hydrophobic PMMA microchannels with bioactivity preserved as far as possible.(2) By the immobilization method above-mentioned,the antibodies(anti-IgG) were encapsulated within the alumina sol-gel network patterning on PMMA microchip after the(BMA)_x-(MAOPTMS)_y copolymer modification.The alumina gel-derived microchannel surface can preserve the bioactivity of the antibodies and resist nonspecific adsorption.After the immunoreaction of the antibodies(anti-IgG), antigen(IgG),and alkaline phosphatase-labeled antibodies(ALP-anti-IgG),a substrate solution containing 4-aminophenyl phosphate(p-APP) was introduced to the microchannel for end-column electrochemical detection.Therefore,the microchip immunosensor showed a low detection limit(1 pg/ml),and broad linear response range(1-500 pg/ml).The results indicate that microfluidic immunosensor with high sensitivity and fast response has great potential for clinical and environmental analysis.3.Chitosan/Hyaluronic acid(CS/HA) nanoparticle-assembled interface and its application towards sensitive biosensingA biocompatible surface has been constructed on the electrode surface via layer-by-layer assembly of chitosan/hyaluronic acid(CS/HA) nanoparticles and polydiallyldimethylammonium(PDDA) for the adsorption of enzymes(tyrosinase) toward sensitive biosensing of phenol.The tyrosinese biosensor showed a high sensitivity,very low detection limit(10^-7M),broad linear response range from 10^-4M to 10^-7M,and high operational stability.The assembly-controlled CS/HA nanoparticle film could provide a biocompatible functional surface for the interaction study between enzymes and target molecules.