# Presentation: 196871

## Safety of Nanomaterials in food packaging

- Raymond M. David, Ph.D., DABT
- Manager, Toxicology
- BASF Corporation

## Overview  

- Do ingested particles have the same concerns as inhaled particles?
- What are the hazards? Can we evaluate hazards the same way?
- What is the exposure?
- How do we evaluate risk? How do we communicate it?

## Uses of nanotechnology in food packaging

- Breathable membranes
- Enhanced barrier properties
- Improvements in mechanical and heat-resistance properties
- Flex-crack resistance
- Active antimicrobial and antifungal surfaces
- Intelligent packaging: sensing and signalling microbiological and/or biochemical change.

## Uses of nanomaterials

- Silver used in food containers and bags
- ZnO and MnO used in food wrap.
- Silicon dioxide in nanocomposites
- Nanoclay used in beverage packaging.
- Selenium used in Nanotea® delivery system

## Inhalation concerns

- Nanoparticles have unusual effects or properties.
- Smaller size and the surface chemistry have an impact on biological response for some nanomaterials.
- Smaller size means greater surface area per gram leading to greater potential for interaction.
- Smaller size means greater chance for movement within the body to other locations following inhalation exposure.
- Ambient ultrafine particles have been associated with:
- Respiratory disease
- Cardiovascular disease
- Allergic responses

## Deposition and translocation

**NP can migrate from respiratory tract. Traditional barriers no longer adequate.**
- Elemental Ag (17.1 nm) found in liver, kidneys, heart, posterior nasal cavity, **brain** (olfactory and other areas), and blood of rats 24 hours after inhalation (Takenaka *et al*., 2001).
- Solid lipid nanoparticles (200 nm) found in liver, kidneys, spleen, intestine, urine, and **testes** of rats 4 hrs after inhalation (Videira *et al*., 2002).

## Summary of findings following respiratory exposure

- Inflammation of the lungs.
- Potential of systemic immune responses; granuloma formation in the lungs associated with some nanomaterials.
- Wide-spread tissue distribution via the bloodstream and translocation via other mechanisms.

## Toxicity of ingested nanoparticles

**Mori *****et al*****., (2006) treated rats with 2000 mg/kg fullerenes in CMC using Tween 80 with no mortality.**
**Chen *****et al.,***** (2006) determined that LD****50**** value of Cu (23.5 nm) in mice to be 413 mg/kg compared with 17 ****μ****m Cu which had an LD****50**** of >5000 mg/kg. **
- Histopathology demonstrated effects on the kidneys (degeneration of tubules and glomerulitis), liver (steatosis), and spleen (atrophy) in nano-exposed animals not seen in micron-exposed groups.
- Serum chemistry changes reflected these pathologic changes (BUN, creatinine, bile acids, alkaline phosphatase).

## Is it particle number?

- From Meng *et al*., 2007

**Is it particle number?**

## Or particle reactivity?

- Nano-copper but not micro-copper converted to ionic form
- causing toxicosis.

- From Meng *et al*., 2007

**Or particle reactivity?**

## Effects of Repeated Exposure

- Zha *et al*., (2007) studied the effects of nanosized chromium (40-50 nm) dietary supplements on rats treated for 6 weeks.
- Relative testicular weights were lower in all treated groups, but the liver, heart, and kidney weights were unaffected. (body weight was higher in all treated groups)
- Cr localized in the liver and kidneys.
- Growth hormone levels were unchanged by treatment with nanoCr.
- Insulin levels were lower but not in a dose-related manner; cortisol levels were increased with dose.

## Serum chemistry following exposure to nanoCr

|  | Control | 75 ppb | 150 ppb | 300 ppb | 450 ppb | 600 ppb | 1200 ppb |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Insulin
μIU/mL | 47 | 38 | 28 | 26 | 28 | 45 | 34 |
| Cortisol
ng/mL | 3.86 | 3.91 | 4.35 | 4.27 | 5.07 | 5.08 | 8.75 |

- From Zha *et al*., 2007

## Effects of Repeated Exposure

- Kim *et al*., (2008) treated rats with up to 1000 mg/kg silver (60 nm) in 0.5% CMC daily for 4 weeks (gavage).
- Dose-related increases in alkaline phosphatase and cholesterol were seen. This was accompanied by an increase in the incidence of bile-duct hyperplasia.
- Dose-related increases in red blood cell count, hemoglobin concentration, and hematocrit were seen only in female rats. There was a decrease in thromoplastin time for high-dose females only.
- There was greater accumulation of silver in the kidneys of female rats compared with male rats.
- NOEL = 100 mg/kg/d

- N.B. Same authors treated animals by inhalation without any systemic effect.
- Dose ~ 10 μg/kg.

## Absorption from the GI tract

- Nanomaterials are sparingly absorbed from the GI tract
- Smaller size/more efficient absorption of 50 nm PS beads compared with 500 nm (Jani *et al*., 1990, 1996).
- 140 nm PS beads found mostly in feces after oral administration with small amount in liver (LeRay *et al*., 1994).
- Absorption of water-soluble fullerenes was limited (only trace amounts found in urine within 48 h) and distributed primarily to the liver (Yamago *et al*., 1995).

## Absorption from the GI tract

- As with dermal penetration, surface charge influences absorption
- 59 nm uncoated PS beads absorbed from GI tract but surfactant coated bead not absorbed (Florence *et al*., 1995).
- Carboxylate-coated PS beads not absorbed whereas non-ionic beads absorbed (Jani *et al*, 1989).

## Tissue distribution and translocation

- Localization primarily in the liver, spleen and GI tract following oral administration (Jani *et al*., 1989).
- Non-coated beads retained in more tissues than coated beads.
- Results consistent with studies of tissue distribution following tail-vein injection of TiO2 (Fabian *et al*., 2007) and quantum dots (Choi *et al*., 2007) in which particles observed only in liver, spleen, kidneys, and lung.

## From Jani et al., 1990

- From Jani *et al*., 1990

## Role of proteins in distribution

- Protein coating does occur and may influence tissue distribution and kinetics.
- Albumin coating enhances cellular uptake of gold nanorods (Hauck *et al*., 2008).
- Some proteins may preferentially bind to different nanomaterials (51 nm aluminum, 75 nm diamond, 50 nm nickel) once absorbed (Wasdo *et al*., 2008).

## From Wasdo et al., 2008.

- From Wasdo *et al*., 2008.

## Deposition and translocation

- Shape plays a role in dermal penetration (Ryman-Rasmussen *et al.*, 2006).
- Spherical quantum dots with neutral or carboxylate-coating remained in the epidermis, while amine-coated spheres penetrated to dermis.
- Elliptical quantum dots with neutral or amine-coating remained in the epidermis, while carboxylate-coated spheres did **not** even penetrate the stratum corneum.
- Some have suggested that shape is more important for other absorptive processes than is size. Certainly, absorption of particles > 20 nm does not occur through intact skin.

## Summary of health concerns following oral exposure

- When toxicity is observed, it can be correlated to deposition in the tissue. Effects observed following inhalation/intratracheal studies are not necessarily observed following oral administration.
- Absorption from the GI tract is size-dependent and could be shape-dependent. Absorption is generally a small fraction of oral dose.
- Particle coating (perhaps from serum proteins) may impact absorption and distribution.
- NP can translocate to any part of the body following inhalation exposure, not following oral exposure.
- Some differences may be due to medium used to expose animals – for oral administration, aqueous media are typically used. How does that influence the particle? Should the particle characteristics in the medium be tested?

## Exposure from food packaging can be controlled

- Migration from material can be controlled by the size of the particle.
- Sambhy *et al*. (2006) were able to control release of silver ions by varying the size of nanoparticle – smaller size, greater release.
- Impregnation versus coating surface may have longer-lasting antibacterial effect.
- Furno *et al*. (2004) showed long-lasting antimicrobial activity of impregnated silver even after washing.

## Evaluating nanomaterial hazards

- OECD validating the current study protocols. Nothing has been reported that might not be identified in a standard study. How the results are expressed may be important. Given the limited distribution, current protocols should be adequate.
- Techniques for following nanomaterials in the body are limited to fluorescence, elemental analysis, and microscopy (radioactivity in cases of carbon-derived nanomaterials), but BioRaman spectroscopy may be useful.
*In vitro* predictive tools not yet available.
- Current risk assessment methodologies should be adequate, but that is a topic of another meeting.

## Communicating the Risks and Hazards

- “Nano” has already been accepted, and ‘technology’ is usually good if there are clear benefits. ‘Particles’ carry no such caveat.
- Use of nanomaterials in food packaging seems acceptable based on a study by ETH Zurich. Nanomaterials in food was less acceptable.
- Good press and clear benefits may be the key to success. Pre-marketing communication is better than post-marketing explanations. The role of FDA may be important.

## Summary

- Safety of ingested nanoparticles can be determined using current methods. The limited absorption and distribution implies that the hazards are likely to be less than after inhalation exposure.
- Use of nanomaterials in food packaging can be controlled to reduce exposure.
- Communication of hazards and risk will be important to public perception.