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Activation of Toll-like receptor 2 reveals microbial contamination beyond endotoxins on micro- and nanoplastics

Øyvind P Haugen1, Itziar Polanco-Garriz2, Victor Alcolea-Rodriguez3

  • 1National Institute of Occupational Health (STAMI), Oslo, Norway.

Toxicology in Vitro : an International Journal Published in Association with BIBRA
|December 15, 2025
PubMed

Insights

Micro- and nanoplastics (MNPs) research may be flawed due to microbial contamination. Toll-like receptor (TLR) reporter cells offer broader detection of microbial contaminants in MNP test materials than traditional assays.

Area of Science:

  • Environmental Science
  • Toxicology
  • Microbiology

Background:

  • Health hazard assessments of micro- and nanoplastics (MNPs) often overlook microbial contamination in test materials.
  • This oversight can lead to misinterpretation of MNP toxicity studies, assuming pristine material conditions.

Purpose of the Study:

  • To screen MNP test materials for microbial contaminants.
  • To compare the efficacy of Toll-like receptor (TLR) reporter cells (TLR2 and TLR4) with the Limulus amebocyte lysate (LAL) assay for detecting microbial ligands.

Main Methods:

  • Eight MNP test materials were screened for microbial contaminants.
  • Toll-like receptor (TLR) reporter cells for TLR2 and TLR4 were utilized.
  • The Limulus amebocyte lysate (LAL) assay was employed for comparison.

Main Results:

  • Five of eight MNP test materials contained microbial ligands activating TLR2 and/or TLR4.
  • MNPs negative for endotoxins via LAL and TLR4 assays could still activate TLR2.
  • TLR4-based screening detected endotoxin contamination more effectively than the LAL assay.

Conclusions:

  • Microbial ligands are prevalent in MNP test materials.
  • TLR reporter cell assays provide broader detection of microbial contaminants compared to the LAL assay.
  • Accurate MNP health hazard assessment requires accounting for microbial contamination.
Keywords:
EndotoxinsLAL assayMicrobial contaminationMicroplasticsNanoplasticsReporter cell assayToll-like receptors

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