Effect of Nanoparticle Incorporation on Functional Properties and Migration of Ag/polyhydroxyalkanoate Nanocomposites

Abstract

Silver-nanocomposites offer great potential as active packaging material due to their antimicrobial properties. However, limited understanding of silver nanoparticle (Ag NP) release mechanisms, especially from biodegradable nanocomposites, poses challenges in terms of human health and environmental risks, resulting in restrictive regulatory measures. This study aims to understand how the incorporation of Ag NPs affects dispersity, functional properties and Ag°/Ag+ migration from Ag/poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx) nanocomposite films. Commercial spherical polyvinylpyrrolidone-coated Ag NPs of 40 nm were incorporated in PHBHHx (0.2-2 wt.%) via melt extrusion (Dry-mix method). Alternatively, a Masterblend method was applied by pre-dispersing the NPs via solvent casting, before extrusion. Nanocomposite films were obtained via subsequent hot-pressing for further characterization. Specific migration was assessed by full immersion tests, using Milli-Q water and food simulants A and B at 40 °C (EU Regulation 10/2011). The leachate was analysed over 10 days via Single Particle Inductively Coupled Plasma Mass Spectrometry to monitor NP size, particle number concentration and dissolved concentrations. The Dry-mix approach seems optimal in terms of time efficiency and NP dispersity. The latter is evidenced by colour, opacity, UV-VIS transmittance and scanning electron microscopy analyses. Interestingly, using both methods, the tensile properties, crystallinity and thermal stability do not change significantly when varying NP loading up to 2 wt.%. In addition, a 30 % reduction in oxygen permeability is achieved for the highest NP loading. Although increasing NP loading did result in an incremental release of Ag°/Ag+, the migration remained under the specific migration limit of 50 µg Ag/kg food for all food simulants, with the highest migration in the acidic food simulant B. So far, we conclude that the fabricated Ag/PHBHHx films show potential as safe, non-transparent active food packaging material with improved oxygen barrier properties.