Using in vitro bioassays to guide the development of safer bio-based polymers for use in food packaging

Petroleum-based polymers traditionally used for plastic packaging production have been shown to leach dangerous chemicals such as bisphenol-A (BPA). Bio-based polymers are potentially safer alternatives, and many can be sustainably sourced from waste streams in the food industry. This study assesses bio-based polymers undergoing food packaging development for migration of endocrine disrupting leachates at the level of estrogen, androgen and progestagen nuclear receptor transcriptional activity. Reporter gene assays were coupled with migration testing, performed using standardised test conditions for storage and temperature. Test samples include nine biobased polymers and four inorganic waste additives mixed with a traditional petroleum-based polymer, polypropylene. Thermoplastic starch material, polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate (PBAT), two polylactic acid (PLA)/PBAT blends, polyhydroxybutyrate (PHB) and eggshell/polypropylene (10:90) presented no significant reduction in metabolic activity or hormonal activity under any test condition. Polypropylene (PP) presented no hormonal activity. Metabolic activity was reduced in the estrogen responsive cell line after 10 days migration testing of eggshell/polypropylene (0.1:99.9) in MeOH at 40 degrees C, and PP in MeOH and dH(2)0. Estrogenic agonist activity was observed after 10 days in poultry litter ash/polypropylene (10:90) in MeOH at 20 degrees C and 40 degrees C, poultry feather based polymer in MeOH and dH(2)O at 40 degrees C, and eggshell/polypropylene (40:60) and PLA in dH(2)O at 40 degrees C. Activity was within a range of 0.26-0.50 ng 17 ss-estradiol equivalents per ml, equating to an estrogenic potency of 3-similar to 2800 times less than the estrogenic leachate BPA. Poultry litter ash/ polypropylene (10:90) in MeOH for 10 days presented estrogenic activity at 20 degrees C and 40 degrees C within the above range and anti-androgenic activity at 40 degrees C. Progestagenic activity was not observed for any of the compounds under any test condition. Interestingly, lower concentrations of eggshell or PP may eliminate eggshell estrogenicity and PP toxicity. Alternatively eggshell may bind and eliminate the toxic elements of PP. Similarly, PLA estrogenic activity was removed in both PLA/PBAT blends. This study demonstrates the benefits of bioassay guidance in the development of safer and sustainable packaging alternatives to petroleum-based plastics. Manipulating the types of additives and their formulations alongside toxicological testing may further improve safety aspects.

Automated summary

This study assesses the migration of endocrine disrupting leachates from bio-based polymers used in food packaging development. The results show that most of the tested bio-based polymers and additives did not significantly reduce metabolic activity or hormonal activity. However, some combinations did exhibit estrogenic and anti-androgenic activity, although at much lower levels than traditional petroleum-based plastics. Manipulating additives and formulations alongside toxicological testing can further improve the safety of bio-based packaging alternatives.