Distinct Optical Interaction Regimes in Low Concentration Mixed Microplastic–Nanoplastic Human Urine Samples Using the EcoExposure™ Platform (~30 minutes)
Abstract
Preliminary experiments demonstrate that the EcoExposure™ optical interaction assay can simultaneously detect and distinguish mixed microplastic (MP) and nanoplastic (NP) interaction signatures within the same minimally processed human urine sample.
Using 100 nm model nanoplastic particles, recognizable concentration-dependent optical morphologies were observed by the EcoExposure™ assay (~250 million particles per/L) at levels orders of magnitude lower than the ~20 billion particles/L (≥300 nm) reported in recent pyrolysis-based urine studies (Ji et al., 2025).
These signals remained clearly distinguishable from MP-only conditions at equivalent low MP concentrations and were obtained within approximately 30 minutes. Importantly, the concentrations tested in these experiments do not represent the lower limit of detection of the EcoExposure™ platform. These findings support the potential utility of decentralized optical interaction analysis for real-world environmental exposure monitoring where both micro- and nanoscale plastics coexist.
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Comparative Summary Table
Feature | Ji et al. (2025) Py-GC/MS Urine Study | EcoExposure™ Optical Interaction Assay |
Matrix | Human urine | Human urine |
Workflow Type | Destructive analytical chemistry by expert scientist | Non-destructive 3-step process to be performed by anyone (no training needed) |
Lower NP Size Reported | ≥300 nm | 100 nm model particles evaluated |
Sample size (mL) | 10 mL | 25 mL |
# of nanoplastics reported | ~20 billion | 250 million (tested in this experiment; not LOD) |
Sample Processing | Digestion, extraction, Py-GC/MS (hours–days) | Minimally processed + biodegradable reagent |
Instrumentation | Specialized laboratory instrumentation | Smartphone-compatible / digital camera optical workflow |
Mixed MP+NP Interaction Evaluation | Not reported or studied (to our knowledge) | Distinct mixed interaction morphology observed |
Approximate Time to Readout | Multi-step laboratory workflow (hours-days) | Observable interaction regimes within ~15–30 min |
Potential for Decentralized Use | Laboratory-based; difficult to scale | Designed for decentralized workflows and cohorts on the scale of thousands to millions |
Background
Recent laboratory studies have reported detection of micro- or nanoplastics (MNPs) in human urine using destructive analytical workflows involving digestion, filtration, extraction (hours-days), and high-complexity instrumentation in specialized labs.
For example, Ji et al. (2025) reported quantitative detection of MNPs ≥300 nm in human urine using double-shot pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) with internal standard calibration.
Unlike conventional workflows that distinguish microplastics from nanoplastics primarily through particle-size thresholds or filtration cutoffs, the EcoExposure™ optical interaction assay demonstrates distinct morphological and kinetic interaction regimes associated with MPs, NPs, and mixed MP+NP populations directly within minimally processed liquid matrices in ~30 minutes.
In the present exploratory experiments, 100 nm model nanoplastic particles were evaluated in filtered urine matrices from which particles ≥200 nm had been removed prior to experimentation. This allowed assessment of nanoplastic-associated optical interaction behavior below the ≥300 nm lower-size threshold reported in recent conventional urine studies.
Preliminary Observations
Low-concentration mixed MP+NP systems produced distinguishable optical interaction morphologies compared with MP-only conditions at equivalent MP concentrations.
Notably, conditions containing:
approximately 10 MP/L alone, versus
approximately 10 MP/L combined with ~250 million NP/L (100 nm model particles)
remained visually and morphologically distinguishable within the EcoExposure™ optical interaction framework.
Nanoplastic-associated interaction behavior appeared:
more diffuse,
more speckled,
less radially scaffolded,
and more uniformly distributed across the interaction field
compared with microplastic-dominant systems.
The nanoplastic-associated interaction morphology persisted even in mixed systems containing concurrent microplastic populations, suggesting that nanoplastic-associated optical behavior was not fully obscured by the presence of larger particles.
Additional exploratory mixed conditions included:
10 MP/L alone
10 MP/L + 250 million NP/L
50 MP/L + 2,500,000,000 NP/L
100 MP/L alone
Distinct optical interaction states were observed across these conditions despite minimal preprocessing and decentralized imaging conditions.
Note: It must be noted that 250 million NP/L is not the lower limit of detection of the EcoExposureTM assay. This is the concentration that was tested in this experiment. Previous experiments demonstrated orders of magnitude lower detection limit and will be repeated.
Limitations
These observations remain exploratory and qualitative. Limitations include:
small experimental sample size,
use of filtered urine matrices,
ongoing assay optimization,
absence of formal quantitative calibration,
and ongoing repeatability validation.
Further studies involving replicate measurements, expanded donor cohorts, additional nanoparticle size distributions, and formal quantitative analysis are ongoing.
Operational Significance
These preliminary findings are operationally notable because the assay:
Detections microplastics and nanoplastics including mixed MP-NP conditions
evaluates intact liquid interaction behavior without destructive preprocessing,
simple process that can be performed by anyone (no training needed)
does not require particle isolation workflows,
produces observable interaction regimes within approximately 15–30 minutes,
and may support future decentralized or at-home environmental exposure monitoring applications.
The results additionally support the broader EcoExposure™ interaction-state framework in which mixed particulate systems generate distinct emergent optical behaviors beyond simple bulk turbidity measurements alone.
Reference
Ji, S., et al. (2025). Quantitative Detection of Micro- and Nanoplastics (≥300 nm) in Human Urine Using Double-Shot Py-GC/MS with Internal Standard Calibration. Toxics, 13(6), 452.DOI: https://doi.org/10.3390/toxics13060452
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