Preliminary Observation of Nanoplastic-Associated Optical Interaction Morphology in Unprocessed Human Urine Samples Using the EcoExposure™ Platform

Abstract Most laboratory methods for nanoplastic analysis in biological matrices rely on extensive preprocessing, including digestion, filtration, extraction, or hyperspiking. In contrast, the EcoExposure™ platform evaluates microplastic- and nanoparticle-associated optical interaction behavior directly in minimally processed liquid matrices using large-volume optical analysis.

This technical note documents preliminary observations suggesting that recognizable nanoparticle-associated optical interaction morphology remains observable in aged decentralized human urine samples despite expected matrix complexity and biochemical changes. These aged samples represent an extreme stress test, as the assay is intended to be performed in real-time (within minutes to hours of collection) under normal use conditions. The nanoparticle patterns appear qualitatively consistent with prior experiments in filtered water and saltwater systems, supporting the possibility of transferable interaction-state dynamics across multiple matrices.

This article can also be found at:

https://doi.org/10.5281/zenodo.20150538  

Background

Microplastics and nanoplastics have been identified in a growing number of biological matrices, including urine, blood, and various organ systems. Scalable decentralized monitoring remains limited by concerns regarding matrix variability, contamination, storage conditions, and operational robustness.

Urine offers a particularly attractive non-invasive matrix for assessing systemic environmental exposure. However, urine analysis presents notable challenges due to substantial donor-to-donor differences in baseline color and biochemical composition, as well as post-collection changes such as oxidation of urobilinogen to urobilin, mild bacterial metabolism with ammonia generation, and progressive baseline darkening. These effects are often amplified in decentralized shipping and delayed-processing workflows.

Despite these challenges, the EcoExposure™ optical interaction assay evaluates concentration-associated organizational behavior directly within minimally processed urine under real-world decentralized conditions.

Experimental ConditionsMultiple decentralized human urine samples (~7+ days aged, returned in sealed steel containers) were evaluated using the standardized EcoExposure urine workflow. Nanoparticle interaction behavior was assessed across a range of concentrations relevant to real-world exposure levels. Images were captured at standard intervals; representative 30-minute photographs are shown below.

Preliminary ObservationsConcentration-associated optical interaction progression remained visually recognizable across the nanoparticle ladder.

Compared with microplastic-dominant systems, nanoparticle-associated interaction morphology appeared: • more diffuse • more speckled • less radially scaffolded • and more uniformly distributed across the interaction field

Higher nanoparticle concentrations demonstrated progressively greater organizational behavior relative to control conditions.

Importantly, the nanoparticle-associated morphology remained qualitatively consistent with prior filtered-water and saltwater experiments despite the biologically complex urine matrix. Typical aged-urine components and expected biochemical drift (urobilin formation, ammonia generation, pH changes, and baseline color variability) did not appear to abolish recognizable nanoparticle-associated optical interaction behavior within the evaluated assay window.

Figure 1. Representative nanoparticle-associated optical interaction morphology in aged decentralized human urine samples at 30 minutes. Top-down images demonstrating concentration-associated optical interaction progression across control and increasing nanoparticle concentration conditions following approximately 7+ days of decentralized storage and transport prior to assay processing. Despite expected urine matrix complexity and aging-associated biochemical changes, recognizable nanoparticle-associated interaction morphology remained observable.

Conceptual InterpretationThe preliminary findings suggest that nanoparticle-dominant interaction systems may exhibit characteristic distributed fine-scattering organizational states that are distinct from the more scaffold-associated morphology observed in microplastic-dominant systems.

The persistence of recognizable nanoparticle-associated morphology across filtered water, saltwater, and minimally processed aged urine supports the possibility that the EcoExposure™ interaction framework may capture transferable interaction-state dynamics across multiple liquid matrices rather than purely matrix-specific artifacts.

LimitationsThis technical note represents preliminary exploratory observations and not formal analytical validation. Limitations include small sample number, decentralized uncontrolled storage conditions, qualitative morphology interpretation, and exploratory interaction-state analysis. Additional controlled studies remain necessary.

Conclusion

Preliminary observations in aged decentralized human urine samples demonstrate recognizable nanoparticle-associated optical interaction morphology despite substantial biological and operational variability.

It is important to note that these aged samples represent an extreme stress test of matrix stability. In the intended product workflow and planned decentralized observational studies, the assay is performed on fresh urine in real-time (within minutes to hours of collection). Under these normal use conditions, aging-related changes such as urobilinogen oxidation, ammonia generation, and baseline darkening are minimal or absent.

These findings support continued development of the EcoExposure™ platform for scalable, decentralized environmental exposure monitoring of microplastics and nanoplastics.