Fabrication And Property Of ZnO-Ethylcellulose/gelatin Composite Nanofibers

The antibacterial packaging demand increases year by year,since microbial spoilage is responsible for shortened shelf life and degraded food quality.Safety,stability and bacteriostasis are the main features of bacteriostatic food packaging.Gelatin(G),as FDA approved biopolymer,has excellent non-immunogenicity,biocompatibility and biodegradability,ensuring the safety of raw materials.Ethylcellulose(EC),with good mechanical properties and hydrophobicity,guarantees a stable structure.Due to the desired mechanical performance,high specific surface area,minimum impact on human cells,and extensive antimicrobial activity,zinic oxide(ZnO)nanoparticles are promising antibacterial agents in food packaging.In this study,employing EC and G as materials,the effects of electrospinning and solvent casting process on the properties of films and their formation mechanism were compared.The fibers properties at different polymer ratios were investigated to select high-quality fibers for ZnO loading.The properties and antibacterial ability of the composite fibers were analyzed.The main contents are as follows:Firstly,the ethylcellulose/gelatin composite films were fabricated by solvent casting and electrospinning,respectively.The characterizations including morphology,chemical structure and surface hydrophicity of the casted and electrospun films were performed by scanning electron microscopy(SEM),thermal analysis,X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectrometer(XPS)and water contact angle measurements(WCA).Results showed that blending EC with G improved the spinninability of the composite film with higher thermal stability.Compared with solvent casting,electrospinning provided a more compact network structure.Interestingly,the electrospun composite film had a hydrophobic surface with a water contact angle of 113.8°,while the casted composite film showed a hydrophilic surface at 67.5°.The solvent immesion results suggested that the electrospun composite film were more water resistance,while the the casted composite film were more stable to ethanol solution.Secondly,the EC/G blends at various weight ratios in acetic acid/ethanol/water solution were electrospun to fabricate nanofibers with tunable physical properties.The solution compatibility was predicted based on Hansen solubility parameters and evaluated by rheological measurements.The physical properties were characterized by SEM,porosity,thermal analysis,FTIR,and WCA.Results showed that the entangled structures among EC and G chains through hydrogen bonds gave rise to a fine morphology of the composite fibers with improved thermal stability.The fibers with higher G ratio(75%),possessed hydrophilic surface(WCA of 53.5°),and adequate water uptake ability(1234.14%),while the fibers with higher EC proportion(75%),tended to be highly water stable with a hydrophobic surface(WCA of 129.7°).Additionally,the composite fibers with equal composition proportion were most uniform with the highest solution compatibility and porosity(92.46%),possessing wonderful surface hydropobicity and water stability.This work suggested that the composite EC/G nanofibers with tunable physical properties have potentials as materials for bioactive encapsulation,food packaging,and filtration applications.Lastly,the EC/G solutions at weight ratio of 1:1 containing various concentrations of zinc oxide(ZnO)nanoparticles were electrospun.Results indicated that ZnO nanoparticles acting as fillers interacted with polymers,resulting in the enhanced surface hydrophobicity and water stability of nanofibers.The antibacterial assay showed a concentration-dependent effect of ZnO on the viabilities of Escherichia coli and Staphylococcus aureus.Notably,the antimicrobial efficiency of the 1.5 wt%ZnO-containing fibers against S.aureus was 43.7%,but increased to 62.5%after UV irradiation at 364 nm,possibly due to the significantly increased amounts of intracellular reactive oxygen species.These results suggested that the ZnO-containing nanofibers with excellent surface hydrophobicity,water stability and antimicrobial activity exhibited potential uses in food packaging.