Linkage Mechanism Between Glucose Oxidase And Paper Fibers And The Micro-control To Enhance The Biostability Of Paper Chips

Paper-based microfluidic chips(PMCs),also known as " microlabs on paper",have many advantages as an emerging research field.Compared with traditional microfluidic chips,such as silicon wafers,quartz,glass and other materials,microfluidic paper chips have unique advantages,mainly due to virtues of abundant raw materials,low production cost,large specific surface area,good biocompatibility and simple subsequent processing.So,the application of PMCs in biomedicine,environmental testing,food quality and safety control have attracted more and more research interests.The processing and manufacturing technology of PMCs based on filter paper is increasingly mature.To maintain the storage stability and detection stability of the PMCs,the current method is freezing-dry the marker and load it on the surface of the paper.Few studies focus on the influence of the surface properties and structure of the substrates on the stability of biomarkers.In order to improve the biostability of PMCs,this thesis focused on paper substrates and explored several micro-control methods to increase the adsorption of biological enzymes.The specific content is as follows:Firstly,three kinds of chemical pulps(hardwood pulp,softwood pulp,cotton pulp)and a thermo-mechanical pulp(Birch pulp)were selected as the raw materials of the paper substrates to eliminate the impacts of pulp types on results.The micro-control methods includes:1)improving the hydrophobic properties of the fiber surface by adding lignin;2)increasing the beating degree of plant fibers within a certain range to increase the accessible hydroxyl groups on the fiber surface,resulting in enhancement of the van der Waals and hydrogen bonding interactions between fibers;3)introducing hydroxyl and carboxyl groups on the fiber surface to increase the affinity between fibers and enzymes;4)introducing positively charged amino groups on the fiber surface to change their electrical property.The above-mentioned modified paper-based fibers were characterizated as well.Secondly,the influence of the micro-controls on the amount of enzyme adsorption on paper was investigated using filter paper and the original pulps as control groups.The glucose oxidase was more likely to be loaded on the surface of plant fibers.The fluorescence spectra results showed that the concentration of the enzyme showed a highly linear correlation with its fluorescence intensity(R=0.9617).After several micro-control treatments,the amount of enzyme adsorption increased significantly,especially for the papers grafted with amino groups.Comparing with the unmodified paper,its fluorescence intensity increases by 94.9%?308.2%.The micro-control methods are effective for both chemical pulp and thermo-mechanical pulp.Thirdly,the physical properties of the paper before and after micro-control were studied and compared through surface contact angle,Zeta potential,capillary water absorption properties and tensile strength.The results showed that after the paper with addition of 1 weight%lignin,the contact angle is 1.8-2.4 times for that of unmodified paper substrate at 0.04 s.Zeta potential tests showed that polyethyleneimine to the plant fibers made its Zeta potential move to the positive direction.The Klemm water absorption height measurements showed that except for improving the degree of fiber beating,other micro-control methods improved the capillary water-absorption height of the paper by 0.1%?13.9%.Comparing with the unmodified paper,the capillary water absorption height of paper with 50 oSR decreases by 26.7%?37.5%.The mechanical property tests indicated that the tensile strength of the modified paper was rapidly increased by 431.7%?757.8%when the beating degree was improved.Addition of HEC,CMC to the papers made their tensile strength increase by 15.1%?70.8%.In contrast,after adding lignin to the papers,their tensile strength decreased slightly by 6.3%?18.8%.Finally,a combination of dissolved oxygen analyzer and(Ru(bpy)3Cl2)·3H2O fluorescent indicator was used to examine the activity of adsorbed enzymes before and after micro-control.The results show that compared with the unmodified paper-base and qualitative filter paper,the enzyme activity is enhanced after the micro-control,especially introduced with the amino group has the best effect.After the micro-control,overall dissolved oxygen consumption was 6.3%?12.5%,but they improved fluorescence intensity by 108.7%?204.3%.We explored the relationship between ?DO and ?FI,the results showed a high linear correlation(Rhardwood=0.9986,Rfilter=0.9998).