Novel food packaging films based on biopolymers combined with antimicrobial inorganic nanostructures (NSs) have been developed to replace traditional plastics. However, little is known about their possible toxicity and oral bioaccessibility if accidentally ingested.
In this contribution, we studied the zinc bioaccessibility of ZnO NSs-modified alginate films, setting up a dedicated flow system utilizing sequential injection analysis (SIA) for its automatic evaluation over time through a dynamic approach mimicking human digestion by gastric fluid (GF).
Crosslinked ZnO NSs/alginate films were thus fabricated. NSs were prepared using an electrochemical–thermal method and added directly to the alginate solution. Films were formed by dry casting and crosslinked with Ca2+ solution. ICP-OES characterization was carried out to verify the real zinc content in the films before testing, as compared to the nominal mass content. An SIA system was designed to profile the temporal release of zinc ions from nanocomposites. The analysis started by pumping synthetic GF onto film pieces in a flow-through container under fluidized-bed conditions, and then, at fixed times, part of this fluid was automatically retrieved and mixed on-line with borate buffer and Zincon for in-line spectrophotometric detection. A sudden release occurred within the first 3 minutes of extraction followed by a more gradual release.
The proposed approach based on a dynamic extraction method using an automatic SIA system is deemed an interesting solution for the high-throughput assessment of metal ion bioaccessibility in antimicrobial-containing packages without using in vivo or in vitro cell tests. Moreover, it could be applied to other targets (e.g., plasticizers, antioxidant compounds) just by modifying the analytical method.
AVM acknowledges funding from the European Union—NEXTGENERATIONEU—NRRP MISSION 4, COMPONENT 1. MO and MM acknowledge financial support from the Spanish Ministry of Science and Innovation (MCIN), and the Spanish State Research Agency (AEI/10.13039/501100011033) through the project PID2020-117686RB-C33 (MCIN/AEI).
