Copper release from nano‑copper/polypropylene composite films to food and the forms of copper in food simulants

Copper-based nanoparticles against microbial infections

Drug-resistant bacteria and highly infectious viruses are among the major global threats affecting the human health. There is an immediate need for novel strategies to tackle this challenge. Copper-based nanoparticles (CBNPs) have exhibited a broad antimicrobial capacity and are receiving increasing attention in this context. In this review, we describe the functionalization of CBNPs, elucidate their antibacterial and antiviral activity as well as applications, and briefly review their toxicity, biodistribution, and persistence. The limitations of the current study and potential solutions are also shortly discussed. The review will guide the rational design of functional nanomaterials for antimicrobial application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Capability of Copper Hydroxy Nitrate (Cu2(OH)3NO3) as an Additive to Develop Antibacterial Polymer Contact Surfaces: Potential for Food Packaging Applications

The globalization of the market, as well as the increasing world population, which require a higher demand for food products, pose a great challenge to ensure food safety and prevent food loss and waste. In this sense, active materials with antibacterial properties are an important alternative in the prolongation of shelf life and ensuring food safety. In this work, the ability of copper(II) hydroxy nitrate (CuHS) to obtain antibacterial films based on low density polyethylene (LDPE) and polylactic acid (PLA), was evaluated. The thermal properties of the composites, evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), showed that the concentrations of added CuHS do not particularly change these characteristics with respect to the neat polymer matrix films. The mechanical properties, determined using dynamic mechanical analysis (DMTA), indicate a small increase in the brittleness of the material in PLA-based composites. The antibacterial properties against Listeria monocytogenes and Salmonella enterica were evaluated using a surface contact test, and a bacterial reduction of at least 8 to 9 logarithmic units for the composites with 0.3% CuHS, both in LDPE and PLA and against both bacteria, were achieved. The reusability of the composite films after their first use demonstrated a higher stability against Listeria monocytogenes. The migration and cytotoxicity of the composites loaded with 0.3% CuHS was evaluated, demonstrating the safety of these materials, which reinforces their potential use in food packaging applications.

Advances in two-dimensional engineered nanomaterials applications for the agro- and food-industries

Two-dimensional nanomaterials, such as graphene, transition metal dichalcogenides, MXenes, and other layered compounds, are the subject of intense theoretical and experimental research for applications in a wide range of advanced technological solutions, given their outstanding physical, chemical, and mechanical properties. In the context of food science and technology, their contributions are starting to appear, based on the advantages that two-dimensional nanostructures offer to agricultural- and food-related key topics, such as sustainable water use, nano-agrochemicals, novel nanosensing devices, and smart packaging technologies. These application categories facilitate the grasping of the current and potential uses of such advanced nanomaterials in the field, backed by their advantageous physical, chemical, and structural properties. Developments for water cleaning and reuse, efficient nanofertilizers and pesticides, ultrasensitive sensors for food contamination, and intelligent nanoelectronic disposable food packages are among the most promising application examples reviewed here and demonstrate the tremendous impact that further developments would have in the area as the fundamental and applied research of two-dimensional nanostructures continues. We expect this work will contribute to a better understanding of the promising characteristics of two-dimensional nanomaterials that could be used for the design of novel and feasible solutions in the agriculture and food areas. © 2023 Society of Chemical Industry.

Surface defects and particle size determine transport of CdSe quantum dots out of plastics and into the environment

Polymers incorporating quantum dots (QDs) have attracted interest as components of next-generation consumer products, but there is uncertainty about how these potentially hazardous materials may impact human health and the environment. We investigated how the transport (migration) of QDs out of polymers and into the environment is linked to their size and surface characteristics. Cadmium selenide (CdSe) QDs with diameters ranging from 2.15 to 4.63 nm were incorporated into low-density polyethylene (LDPE). Photoluminescence was used as an indicator of QD surface defect density. Normalized migration of QDs into 3% acetic acid over 15 days ranged from 13.1 ± 0.6-452.5 ± 31.9 ng per cm² of polymer surface area. Migrated QD mass was negatively correlated to QD diameter and was also higher when QDs had photoluminescence consistent with larger surface defect densities. The results imply that migration is driven by oxidative degradation of QDs originating at surface defect sites and transport of oxidation products along concentration gradients. A semi-empirical framework was developed to model the migration data. The model supports this mechanism and suggests that QD surface reactivity also drives the relationship between QD size and migration, with specific surface area playing a less important role.

Sulfides mediate the migration of nanoparticle mass out of nanocomposite plastics and into aqueous environments

We show that inorganic sulfides strongly influence transfer (migration) of nanoparticle mass out of polymer nanocomposites (PNCs) and into aqueous environments. We first manufactured two families of PNCs: one incorporating silver nanoparticles (AgNPs) and one incorporating CdSe quantum dots (QDs). Then, we assessed migration out of these PNCs and into aqueous media containing Na₂S at concentrations ranging from 0 to 10^-4 M. Results show that Na₂S strongly suppressed migration of Ag from AgNP-based PNCs: the migration into water spiked with 10^-6 M Na₂S was 79% less than migration into water without Na₂S, and no migration was detected (LOD ≈ 0.01 ng/cm²) in water spiked with Na₂S at 10^-5 M or 10^-4 M. With CdSe QD-based PNCs, Na₂S suppressed Cd migration but enhanced Se migration, resulting in only a small net effect on the total QD migration but a large shift of the leachate composition (from favoring Cd by an average of 5.8 to 1 in pure water to favoring Se 9.4 to 1 when Na₂S was present at 10^-4 M). These results show that common inorganic substances like sulfides may play a strong role in determining the environmental fate of polymer-dispersed nanoparticles and imply that migration tests conducted in purified water may not always accurately reflect migration into real environments.