Six open questions about the migration of engineered nano-objects from polymer-based food-contact materials: a review

Figures & data

Table 1. Silver migration studies from silver-based food-contact materials.

Polymer matrix^a	Commercial availability	Initial Ag concentration in the polymer	Migration conditions: time/temperature	Food simulant/food^b	Analytical techniques	Maximum total Ag migration	Evidence for migration of AgNPs	Size of the migrated AgNPs (used technique)	Reference
LDPE	Yes	100 µg g^–1	15 days/25–50°C	Water AA 4% E 95% Hexane	SEM-EDX AAS (Atomic absorption spectrometry)	4.2 µg dm^–^2	Yes	300 nm (SEM)	Huang et al. (2011)
LDPE	No	5000–50,000 µg g^–1	10 days/60, 70°C; 2 h/60, 70°C; microwave	Water AA 3%	SEM ICP-AES	217 µg dm^–^2	Yes	215–945 nm (SEM)	Hannon et al. (2015b)
LDPE PP	Yes	3300 µg g^–1	10 days/40°C; 2 h/70°C	E 50% AA 3%	SEM-EDX sp-ICP-MS (semi-quantitative)	3.15 µg dm^–^2	Yes	10–200 nm (SEM)	Echegoyen and Nerín (2013)
PC PP	Yes	28–62 µg g^–1	10 days/20–40°C; 2 h/70°C	Water AA 3% E 10% ×E 95%	SEM-EDX sp-ICP-MS	1.9 µg dm^–^2	Yes	18–30 nm (sp-ICP-MS)	Ramos et al. (2016)
PE PP	Yes	9–37 µg g^–1	10 days/20°C	Water AA 3% E 10% ×Olive oil	TEM-EDX sp-ICP-MS	0.95 µg dm^–^2	Yes	20–100 nm (SEM); 100–350 nm (sp-ICP-MS)	von Goetz et al. (2013)
PE HDPE	Yes	1–31 µg g^–1	10 days/40°C	Water AA 3% E 10%	TEM-EDX sp-ICP-MS	0.31 µg dm^–^2	Yes	23–89 nm (sp-ICP-MS)	Mackevica et al. (2016)
PP HDPE	Yes	28 µg g^–1	10 days/20–40°C; 2 h/70°C	Water AA 3% ×E 10% ×E 95%	AF^4-ICP-MS SEM ICP-MS	0.014 µg dm^–^2	Yes	40–60 nm (AF^4-ICP-MS)	Artiaga et al. (2015)
LDPE PP PES	Yes	7–36 µg g^–1	4 h/100°C	Water AA 3%	TEM ICP-MS	0.64 µg dm^–^2	No	n.a.	Ntim et al. (2015)
LDPE	No	50–250 µg g^–1	10 days/60°C; 24 h/40°C	AA 3% E 10% ×E 95% ×Isooctane	ICP-MS	1.01 µg dm^–^2	Not studied	n.a.	Bott et al. (2014b)
PE	No	5000 µg g^–1	1, 3 days/8, 21°C	Chicken breast	ICP-MS	5.0 µg dm^–^2	Not studied	n.a.	Cushen et al. (2014)
PE	Yes	234 µg g^–1	9 h/20, 40, 70°C	AA 3% E 95%	ICP-MS	13.10 µg g^–1	Not studied	n.a.	Song et al. (2011)
PLA-clay	No	340–3400 µg g^–1	8 days/RT	0.03% HNO3	Voltammetry	6.0 µg g^–1	Not studied	n.a.	Busolo et al. (2010)
PE	Yes	29–34 µg g^–1	6 days/5, 12°C; 35 days/–18°C	Chicken meatballs	ICP-MS	No migration	not studied	n.a.	Gallocchio et al. (2016)
LDPE	No	1–22 µg g^–1	30 days/4, 40°C	Water AA 3% E 10% Apple juice	AAS	117 µg dm^–^2	Not studied	n.a.	Jokar and Abdul Rahman (2014)
PVC	No	5000–50,000 µg g-1^–1	4 days/5, 20°C	Chicken breast	ICP-MS	670 µg dm^–^2	Not studied	n.a.	Cushen et al. (2013)

Notes: ^aHDPE, high-density polyethylene; LDPE, low-density polyethylene; PP, polypropylene; PES, polyether sulfone; PE, polyethylene; PC, polycarbonate; PLA, polylactic acid.

^bFood simulant with the maximum observed migration underlined; no migration is indicated by ‘×’.

^cOnly analytical LOD presented. AAS: Atomic absorption spectrometry.

Table 2. Comparison of the analytical techniques used for studying migration of ENOs from FCMs. The presented detection limits are indicative values, as they strongly depend on the chemical composition of the ENOs and the used instrumentation.

Analytical technique	Limit of detection – mass/mass concentration	Limit of detection – size	Information
ICP-MS*	pg l^–1–ng l^–1	–	Total element concentration
sp-ICP-MS*	pg l^–1–ng l^–1	≥ 10 nm	Mass and number concentration of the ENO Ratio (mass concentration) between ionic and nano-form Size distribution of the ENO (geometric size, typically spherical shape assumed)
TEM/SEM	µg l^–1–mg l^–1	1–10 nm (TEM/SEM)	Size distribution of the ENO (geometric size from two dimensional projection) Shape of the ENO
AF^4-ICP-MS*	µg l^–1–mg l^–1	1 nm	Mass concentration of the ENO Size distribution of the ENO (hydrodynamic size)

*Applicable to metal-containing ENOs only.

Figure 1. Overview of the six open questions identified in this review paper.

Figure 2. Risk of potential human exposure to ENOs from FCMs.

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