Abstract
A degradable and antibacterial sodium alginate film containing functional Au-TiO2 nanocomposites for food packaging was successfully developed. The Au-TiO2 nanocomposites are synthesized hydrothermally and mixed with the alginate solution to form the film by a casting method. The Au-TiO2 nanocomposites enable the film with excellent visible light absorption and transfer ability with the light absorption rang covering UV–visible wavelength (300–800 nm) and induce the increase of the film water contact angle from 40° to 74°, which contributes to the film shape stability. Furthermore, compared to the TiO2 nanoparticle-incorporated film, the antibacterial ability of Au-TiO2/sodium alginate composite film is improved approximately by 60% and 50% against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively, in light conditions. The antibacterial property of the film arises from the increased production of reactive oxygen species (ROS) induced by the surface plasmonic resonance of Au nanoparticles. The degradable and antibacterial properties render the composite film of great application potential in food packaging industry.
Highlights
Active food packaging offers new opportunities for food preservation and films derived from biopolymers have been widely used in food packaging due to their edible, renewable, and biodegradable characteristics [1,2,3,4,5]
Sodium alginate derived from brown algae is a green candidate to fabricate food packaging films because of advantages such as the long polymeric chain, easy accessibility, and nontoxicity [6]; it has widespread applications in the pharmaceutical, cosmetics, and biomedical fields [7,8,9,10]
Light absorption by TiO2 NPs occurs mainly in the UV region below 380 nm, whereas that by the Au NPs is in the visible range (400–600 nm) with a peak at 512 nm
Summary
Active food packaging offers new opportunities for food preservation and films derived from biopolymers have been widely used in food packaging due to their edible, renewable, and biodegradable characteristics [1,2,3,4,5]. To extend the functionality of active food packaging, nanoparticles such as metal nanoparticles (silver, gold, zinc), ZnO, TiO2 and CeO2 have been used to prepare composite functional films [11,12,13]. The antibacterial activity of TiO2 NPs mainly stems from the production of reactive oxygen species (ROS) such as hydroxyl radicals (OH) and superoxide radical (O2−) upon illumination with UV light with a wavelength of 380 nm or lower [17,18]. The wide bandgap of TiO2 NPs (3.0–3.2 eV) limits the light response in the UV range and so they cannot absorb and transfer visible light efficiently [19]
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