Modified Zein Fibers Containing Gold Nanoparticles And Their Application In Biosensor

Due to their excellent biocompatibility and crude three-dimensional porous structure,electrospun natural nanofibers have been proved to use as a template to enzyme biosensor forhazardous substance determination in the water compared with conducting polymers whichpossess a complicated preparation process. However, natural nanofibers especially proteinnanofibers could hardly maintain their morphology in water, which severely restrict theirapplications in biological field. To solve the problems mentioned above in this paper, zeinnanofibers modified by blending with cellulose acetate (CA) and glyoxal chemicalcrosslinking using zein as raw material were fabricated by electrospinning. A seriescharacterizations for modified fibers were conducted, the results of FT-IR spectra indicatedthe success of fibers modification, the improvement of mechanical properties of fibers aftermodification accompanied with the favorable surface morphologies, and the hydrophilicdecreased for modified nanofibers with increasing water stability.Gold nanoparticles (Au NPs) have been used to improve the detection effect of enzymebiosensor, which is based on their good electrochemical performance, so Au NPs were coatedon the surface of modified nanofibers by one-step reduction method. Poly(ethyleneimine)(PEI) was used as the reducing and crosslinking agents in the process of experiment. Thestudy of reaction mechanism indicated that Au NPs were coated on the surface of glyoxalcrosslined zein ultrafine fibers by the combined effects of hydrogen bonding and covalentbonding between PEI and fibers, while Au NPs were merely attached to the surface ofZein/CA composite nanofibers. The results of FT-IR spectra indicated that PEI moleculesattached to the surface of glyoxal crosslined zein ultrafine fibers by interaction between thefunctional group of PEI and glyoxal. The uniform distribution of glyoxal crosslinked zeinultrafine fibers containing Au NPs were observed by scanning electron microscope (SEM)and transmission electron microscopy (TEM). The results obtained from energy dispersivex-ray analysis (EDAX), X–ray diffraction (XRD) and ultraviolet visible spectroscopy(UV–vis spectroscopy) for Au NPs–crosslinked zein ultrafine fibers confirmed the existenceof Au NPS coated on the surface of glyoxal crosslinked zein ultrafine fibers. The thermalproperties of composite nanofibers were studied by Differential Scanning Calorimetry (DSC)and thermal gravimetric analysis (TGA), the results from characterizations revealed that thethermal stability of composite nanofibers was improved with the addition of Au NPs.The laccase was immobilized on the surface of different modified Zein composites andelectrode surface via embedding, and then the biosensor based on laccase was fabricated. Bycomparing the electrochemical response of enzyme biosensor based on different materials,glyoxal crosslinked zein ultrafine fibers containing Au NPs were selected to be a substrate to fabricate enzyme biosensor for catechol determination. Furthermore, the comparison betweendifferent modified electrodes for analytical response confirmed that direct electron transferwhich is provided by Au NPs improved the process of electrochemical reaction, andinfluences of different pH and scan rate to laccase biosensor proved that the electrochemicalreaction of modified electrode was a reversible and complicated redox reaction. Square wavevoltammetry (SWV) were used to analyze the process of catechol determination by laccase,the results demonstrated that this biosensor possessed a high sensitive detection to catechol,the sensitivity is as high as1.626μA·μM-1. Meanwhile, the proposed biosensor exhibited goodstability, reproducibility and selectivity, and it could be used in real detection.