Electrostatic Self-Assembly Mono-Layered Composite Films For Glucose Biosensors

Supramolecular electrostatic self-assembly technique for constructingpolyelectrolyte multiplayer (PEM) nanocomposite films has gained wide applicationsdue to its technical simplicity, good stability, low requirement on matrix materials andthe controllability of the composition, thickness and surface polarity of the PEM on ananoscale level. In biosensor research, supramolecular electrostatic self-assemblytechnique has still its unique advantages as an enzyme immobilization method. Forinstance, it is viable to select specific materials such as biocompatible and functionalmaterials; by varying the number of the layers, we can control the immobilizedenzyme amount thus improve the sensitivity of the glucose biosensors; it is alsofeasible to improve the specificity and selectivity in molecule permeation by changingthe structure of the PEM. It is observed that current glucose biosensors have poor biocompatibility,stability and selectivity. Our research intends to improve this unsatisfactory situation.By selecting specific materials and employing supramolecular electrostaticself-assembly technique, we fabricate new glucose biosensors with goodbiocompatibility, conductivity and molecule selectivity. (Cs/GOx)n modified glucose biosensors were developed using supramolecularelectrostatic self-assembly technique and biocompatible material Chitosan (CS) asmatrix material. It is shown in the Cyclic Voltammograms (CV) and Amperometric(IT) curves that GOx has been successfully immobilized in the enzyme electrodemaintaining its biological activity. Moreover, by increasing the number of layers, theamount of GOx in the enzyme electrode can be increased to some extent. As a result,the lowered minimum responsive concentration ensures better sensitivity and stability. It should be noted that the number of layers can not increase infinitely because ofthe limitation on experiment conditions. Therefore, by graft polymerization onchitosan, we also examined the introduction of conductive polyaniline into the PEM.(CS-PAN/GOx)n modified glucose biosensor is thereby deviced by electrostaticself-assembly. It is demonstrated that this new biosensor not only has goodbiocompatibility but also enhanced electron transfer capability. IT curves of this newsensor suggest higher response current, steeper slope and bigger correlationcoefficient compared to the (CS/GOx)n modified biosensor. The resulted slope and II摘 要correlation coefficient are 0.0668μA mM-1and 0.995(n＝13)respectively. According to the size exclusion effect, the PEMs have selectivity over H2O2 inthe presence of ascorbic acid and uric acid. In our study, PEMs were prepared byelectrostatic self-assembly between polyelectrolytes PAA and PVS. Furthermore,sol-gel technique was applied in preparing (PAA/PVS)3/Sol-Gel-GOx modifiedglucose biosensor by using TMOS as the precursor. It is clearly shown in the ITcurves that this new biosensor has good specific response on glucose, ascorbic acidand uric acid. Additionally, the problem of gel and matrix electrodes separation aswell as the problem of gel cracking has been solved.