The urgency behind this work stems from what is already known about these particles. Nanoplastics — generally defined as plastic particles below 1000 nanometres — are generated ceaselessly as ever-larger amounts of plastic debris fragment in the environment, and because particle numbers rise steeply as size falls, their abundance in soil may well exceed that of microplastics in the 1-to-5000-micrometre range. Their minute dimensions make them far more available for uptake by living organisms, including into individual cells, and their colloidal behaviour governs how they travel through soil and water. Laboratory studies have linked nanoplastic exposure to molecular toxicity in soil nematodes, transcriptomic disruption in soybean, and intestinal disruption in earthworms, while wheat seedling roots have been shown to accumulate them. Yet despite these warnings, scientists know remarkably little about how many nanoplastics soils actually contain, which polymers they are made of, or what shapes they take — because detecting them in a matrix as complex as soil is extraordinarily difficult.

Every existing analytical tool falls short somewhere. Micro-Fourier-transform infrared spectroscopy, a workhorse of microplastic research, cannot reliably detect particles below roughly 10 micrometres, and micro-Raman spectroscopy bottoms out near 300 nanometres — leaving the smallest, most biologically relevant particles invisible to routine screening. Pyrolysis gas chromatography–mass spectrometry, or Py-GC-MS, can identify polymer chemistry and quantify mass, and it has already detected nanoplastics in soil, water, plants, and animal tissues, but it incinerates the sample, sacrificing all information about particle size and shape, and it demands large starting volumes because nanoplastic mass concentrations are expected to be vanishingly low. Advanced imaging techniques such as scanning electron microscopy, atomic force microscopy–infrared spectroscopy, and scanning transmission X-ray microscopy can resolve individual nanoparticles, but they cannot reliably distinguish plastic from mineral grains or organic debris unless the sample is exceptionally pure. The German-led team set out to build a single extraction workflow that preserved particle integrity, stayed compatible with both microscopy and mass-based analysis, and came with honest, quantified recovery data — something no previous soil method had offered.

The key to measuring losses that would normally go undetected was a clever piece of chemical engineering. Instead of relying on ordinary plastic particles, the researchers used palladium-doped nanoplastics: spheres with a polyacrylonitrile core loaded with palladium and wrapped in a polystyrene shell, synthesised using a method co-developed by study co-author Denise Mitrano of ETH Zurich. Because the embedded metal can be quantified with exquisite sensitivity by inductively coupled plasma mass spectrometry, the palladium serves as a faithful proxy for the plastic itself. The team spiked 50-gram samples of an agricultural soil from Wageningen in the Netherlands with roughly 150-nanometre doped particles at a concentration of 188 milligrams per kilogram of soil, then tested each stage of the purification chain in isolation before chaining the steps together. For the imaging experiments, they used fluorescent polystyrene spheres of 100 and 250 nanometres, whose smooth, uniform shape makes them easy to spot and measure under an electron microscope.

The first hurdle — simply liberating particles from soil aggregates — proved to be the deepest. The soil was mixed with a litre of 2.5 millimolar tetrasodium pyrophosphate, a dispersing agent, shaken for 30 minutes, ultrasonicated for two minutes at 35 kilohertz, and left undisturbed for 18 hours so that large mineral grains would sink. The top centimetre of the suspension was then collected on the assumption that nanoplastics behave like colloids and remain evenly distributed in the liquid. Recovery was just 38 percent, with a standard deviation of 7 percent, making this initial extraction the single largest bottleneck of the entire protocol. The approach was adapted from a method that had recovered 84 percent of silver nanoparticles from soil, but nanoplastics differ from metallic nanoparticles in surface charge, density, hydrophobicity, and chemical reactivity, and they likely bind to different soil components with different strengths. The authors note that more powerful ultrasonic probes and denser soil-to-liquid ratios could push this number higher in future iterations.

Purification began with density separation, deliberately adapted for accessibility: instead of an ultracentrifuge, the team layered samples over a sucrose cushion of 1.22 grams per cubic centimetre and spun them in an ordinary benchtop centrifuge at 4696 times gravity for eight hours. This step recovered 74 percent of the particles, with a standard deviation of 18 percent that reflects how sensitive the procedure is to collecting the supernatant just five millimetres into the sucrose layer. Only 7 percent of particles landed in the pellet and a negligible 0.1 percent clung to the pipette; the rest stuck to the tube walls or stayed behind in the sucrose. Electron microscopy confirmed the spinning did not clump particles together. The sucrose approach involves a trade-off: its density accommodates common polymers such as polyethylene, polypropylene, polystyrene, polyamide, and polycarbonate, but excludes denser PVC and PET. Filtration proved equally revealing — conventional PTFE membrane filters clogged and trapped sub-micron particles, recovering only 25 percent, whereas single-layer stainless steel mesh filters with evenly spaced one-micrometre pores reached 92 percent recovery when rinsed with ethanol afterwards.

Not every inherited step survived scrutiny. The protocol previously included oxidising organic matter with 5 percent hydrogen peroxide; the team tested a stronger 15 percent concentration and found it stripped neither the sucrose nor the dissolved organic carbon from the samples — non-purgeable organic carbon levels barely budged over three hours, and the solution’s temperature stayed flat, signalling no vigorous reaction. Notably, the peroxide did not damage the plastic particles themselves, with 100-nanometre polystyrene spheres unchanged in size even after two hours in 20 percent peroxide, but because the oxidation accomplished so little, it was dropped from the final workflow entirely. That made the last step, ultrafiltration through 10-kilodalton polyethersulfone membranes, doubly important for washing and concentrating the sample. Here the team discovered a subtle trap: stirring the device created a vortex that drove particles into the membrane, depressing recovery. Two gentle washes without stirring cut dissolved organic carbon from 136 milligrams per litre to 12 while retaining 74 percent of the particles.

Then came the moment of truth. When the optimised steps were chained end to end, the recovery predicted from the individual stages was about 19 percent. What the researchers actually measured was 1.4 percent, with a standard deviation of 0.4 percent. The gap points to losses that only emerge in a full soil-to-sample workflow: transfers through pipettes and intermediate vessels, membrane fouling by the real soil matrix, and the adsorption or agglomeration of particles onto residual soil surfaces. The team also cautions that its tests used freshly spiked, well-defined spheres, whereas nanoplastics that have weathered in the environment for years may carry eco-coronas of natural organic matter, sorb pollutants, and attach more stubbornly to soil — characteristics that could make them even harder to extract. This honest accounting, uncomfortable as the number is, is precisely what the researchers argue the field has been missing: without recovery data, no nanoplastic measurement from soil can be trusted or systematically improved.

The downstream feasibility tests produced a split verdict. For mass-based analysis, the team adapted a solvent-transfer protocol in which dried samples were dissolved at 150 degrees Celsius in a one-to-one mixture of 1,2,4-trichlorobenzene and p-xylene containing the antioxidant butylated hydroxytoluene — solvents chosen because they dissolve polyethylene, polypropylene, and polystyrene, the most common soil plastics. Aliquots dried in pyrolysis cups recovered 87 percent of the polymer, though with a wide standard deviation of 41 percent. The instrumental detection limits were competitive with the state of the art, but the method-scale arithmetic failed: because only 24 millilitres of the original one-litre extract can be processed, and the high-boiling solvent caps the injectable volume at 30 microlitres, the method’s detection limit sits near 3 micrograms of polymer per gram of soil even assuming perfect recovery — while measured polystyrene nanoplastic concentrations in real soils have been reported as low as 0.16 to 0.73 micrograms per gram. Quantitative Py-GC-MS of soil nanoplastics through this route is therefore not yet within reach.

Where mass quantification faltered, imaging triumphed. When soil spiked with the fluorescent polystyrene spheres was pushed through the full workflow, the extracted particles were deposited on silicon wafers, coated with a five-nanometre platinum-palladium film, and imaged by scanning electron microscopy. The 100- and 250-nanometre spheres appeared well separated, intact, and virtually free of contamination — the only interferences being thin, elongated organic filaments and a faint carbon- and oxygen-rich residue, likely sucrose, both easily distinguished from the smooth spherical targets. Blank samples showed negligible cross-contamination. The result establishes the protocol as the first recovery-tested, particle-preserving extraction method for soil nanoplastics that yields samples clean enough for advanced microscopy, opening the door to techniques such as STXM-NEXAFS and AFM-IR that can deliver size, shape, and polymer identity for individual particles. The team’s roadmap for improvement — more aggressive ultrasonic extraction, larger processed volumes, and validation across different soil types — now gives the field a quantified baseline. For the first time, scientists know not only where soil’s invisible plastic fraction is hiding, but exactly how much slips through the net each time anyone tries to catch it.

The backdrop to this research involves the growing concern over microplastics—small plastic fragments less than 5 millimeters—and even smaller nanoplastics, which are less than 100 nanometers in size. These particles have been detected in various environmental compartments including oceans, soil, and even the air. However, demonstrating their presence in human biological fluids, especially blood, presents a formidable analytical challenge. Detection protocols must distinguish plastic particles from a complex matrix of biological compounds without contamination. Here, Brits and colleagues have leveraged pyrolysis-gas chromatography–mass spectrometry (py-GC/MS), a cutting-edge technique that thermally decomposes samples to identify characteristic polymer fragments, providing molecular-level specificity essential for accurate detection.

Central to their work is the reproducibility and sensitivity of py-GC/MS for analyzing human plasma samples. By subjecting samples to controlled thermal degradation, polymers such as polyethylene, polypropylene, polystyrene, and polyethylene terephthalate yield distinct pyrolyzates — signature compounds that serve as unequivocal markers of micro- and nanoplastic presence. In this study, the team refined their analytical protocols, optimizing parameters such as pyrolysis temperature, chromatographic separation conditions, and mass spectrometric detection settings to achieve enhanced resolution and minimize false positives that can arise from background organic matter or laboratory contamination.

The authors emphasize the critical steps taken to avoid potential contamination during blood collection and sample processing, an essential consideration given the ubiquity of plastic particles in laboratory environments and equipment. Methodical blank controls, rigorous cleaning protocols, and the use of non-plastic materials where possible were implemented to ensure that detected signals indeed reflected in vivo exposures. Their follow-up confirms that previous concerns raised by Wilhelmus, Gahleitner, and Pemberton regarding analytical pitfalls have been carefully addressed, reinforcing the integrity and reliability of their findings.

What makes this study particularly significant is its implication that micro- and nanoplastics have entered human circulation, thereby breaching natural biological barriers. Such intrusion into the vascular system raises profound questions about systemic distribution, bioaccumulation, and potential toxicological effects at the cellular and organ levels. While the exact health consequences of these plastic particles remain under investigation, emerging evidence suggests roles in inflammation, oxidative stress, and disruption of normal cellular functions. The authors underscore that the confirmation of particles in blood is a vital step forward from environmental sampling toward human health risk assessment.

The paper elaborates on the technical challenges involved in size fractionation of micro- and nanoplastics. Given their nanometric scale, particles can evade traditional filtration and sampling methods. The team utilized advanced filtration combined with density separation protocols to isolate plastics from red and white blood cell components, proteins, and lipids. This separation enables accurate py-GC/MS quantification free from matrix interference, an innovation that may set new standards in bioanalytical monitoring of plastic exposure.

Additionally, the response clarifies the calibration strategy employed, using reference standards of common environmental polymers at variable concentrations spiked into synthetic plasma. Calibration curves demonstrated linearity over a wide dynamic range and high sensitivity, with limits of detection sufficient to observe physiologically relevant concentrations. The approach provides a powerful quantitative framework enabling comparison across future epidemiological studies aimed at correlating exposure levels with health endpoints.

Importantly, this study moves beyond mere detection. By quantifying the relative abundance of different polymer types, the authors provide preliminary insights into human exposure patterns, reflecting contamination sources such as ingestion, inhalation, and dermal contact. The predominance of polyethylene and polypropylene might suggest exposure linked to packaging materials and airborne fibers ubiquitous in daily life. These findings open new frontiers in exposure science, encouraging multidisciplinary collaborations integrating environmental sampling, toxicokinetics, and clinical research.

The authors also address statistical and methodological critiques related to sample size and variability reported in the initial publication. With an expanded cohort and multiple biological replicates, this follow-up demonstrates consistent detection of micro- and nanoplastics across diverse donor profiles, with observed variations reflecting possible lifestyle and occupational factors. This robustness strengthens the epidemiological validity of their observations and paves the way for population-level biomonitoring initiatives.

Further innovation comes from the team’s exploration of complementary analytical techniques, including coupling py-GC/MS with high-resolution mass spectrometry and integrating Raman microspectroscopy data for polymer particle imaging. Such multimodal approaches enable cross-validation of results and provide spatial distribution maps of plastics in biological tissues, a crucial advance for mechanistic toxicology.

The implications of these results extend widely. Public health authorities are now prompted to consider micro- and nanoplastics not only as environmental pollutants but as emergent exposure agents warranting regulatory scrutiny. The study highlights the urgent necessity for establishing standardized protocols and international guidelines for monitoring plastic particles in human matrices. It also catalyzes discussion on mitigating exposure through policy measures addressing plastic production, waste management, and consumer behavior.

Equally significant is the potential influence of these findings on clinical medicine and pharmacology. Micro- and nanoplastics circulating in blood may interact with pharmaceuticals, alter drug distribution, or trigger immune responses. Understanding these interactions is crucial for patient safety and therapeutic efficacy, suggesting a new horizon for personalized medicine considering environmental contaminant profiles.

In conclusion, this meticulously crafted response by Brits and collaborators exemplifies the scientific process at its best—transparent, rigorous, and self-correcting. Their work marks a decisive milestone in the nascent field of human microplastic exposure assessment, combining technical sophistication with profound societal relevance. As the debate evolves, this study lays the foundation for transformative research bridging environmental science, analytical chemistry, toxicology, and public health, stimulating a global imperative to confront the plastic pandemic now evident not just in ecosystems but within our very bloodstreams.

Subject of Research: Quantitation and detection of micro- and nanoplastics in human blood using advanced pyrolysis-gas chromatography–mass spectrometry techniques.

Article Title: Response on the commentary by B. Wilhelmus, M. Gahleitner, and M. A. Pemberton, on the manuscript by M. Brits et al., “Quantitation of micro and nanoplastics in human blood by pyrolysis-gas chromatography–mass spectrometry: a follow-up study.”

Article References: Brits, M., van Velzen, M.J.M., Sefiloglu, F.Ö. et al. Microplastics and Nanoplastics (2024) 4:12. https://doi.org/10.1186/s43591-024-00104-7

Image Credits: AI Generated

Nanoplastics are extremely tiny plastic particles, measuring less than 1 micron in size, which can enter the human body through ingestion or inhalation. Once inside, while a portion of these particles are expelled from the body, some manage to infiltrate organs, blood, and other critical body fluids, raising concerns about their health impacts. The Nano-VISION project, initiated two years ago in collaboration with the start-up BRAVE Analytics, has endeavored to investigate these ramifications. A key component of this initiative was led by Harald Fitzek, an expert at the Institute of Electron Microscopy and Nanoanalysis at TU Graz. Alongside an ophthalmologist from Graz, the team explored the pressing question of whether nanoplastics pose a risk to ocular health.

In this innovative project, researchers have developed a sophisticated methodology for detecting and quantifying these minuscule plastics within transparent body fluids. Initial applications of this technology focus on examining whether intraocular lenses—the lenses oftentimes implanted in cataract surgery—might inadvertently release nanoplastics over time. Given that no prior studies have delved into this crucial aspect, the preliminary results have ignited considerable interest within the scientific community and have been submitted for publication in a reputable journal.

Detection of microplastics and nanoplastics is achieved through a two-step process that employs an advanced sensor platform designed by BRAVE Analytics. The mechanism starts by extracting a liquid sample, which is then directed through a specialized glass tube for analysis. Within this tube, a weakly focused laser beam is projected through the liquid, facilitating an interaction between the light and any present particles. When the laser encounters these particles, it either accelerates or decelerates them depending on their sizes—larger particles are impacted more significantly than smaller ones. By measuring these variations in velocity, researchers can glean valuable insights regarding the particles’ sizes and concentrations in the analyzed liquid.

What sets this approach apart is its incorporation of optofluidic force induction, a technique primarily developed by Christian Hill at the Medical University of Graz. This innovative strategy is complemented by a method known as Raman spectroscopy, which provides an additional layer of information about the particles. In this context, the spectrum of the laser light that is scattered by individual particles in the liquid is meticulously analyzed. The phenomenon known as Raman scattering occurs when a small fraction of the laser light alters its frequency upon interacting with the particles. This alteration allows researchers to deduce the chemical compositions of the particles present.

The ability to ascertain the chemical makeup of these microparticles is particularly pertinent when considering the materials involved, with organic materials and plastics revealing unique frequency signatures. Fitzek emphasizes the utility of this technology in identifying different types of plastics, and how it may pave the way for understanding their implications in a biomedical context, especially when linked to ocular applications.

Currently, the researchers are directing their investigations toward understanding the potential release of nanoplastics from intraocular lenses. They are assessing whether such lenses may shed these particles under mechanical stress or laser exposure, insights that could alter current clinical practices in ophthalmic surgery. The crucial findings from these studies not only carry weight for lens manufacturers but also for eye care professionals who rely on the safety and efficacy of these implants for their patients.

Further extending the technology’s applicability, Fitzek highlights the versatility of their detection method, noting its effectiveness in other bodily fluids such as blood plasma, tear fluid, and even urine. Beyond clinical applications, this sensing technology holds promise for continuous monitoring in industrial liquid flows, alongside drinking and wastewater monitoring, amplifying its relevance to both health and environmental sectors.

The implications of this research are poised to resonate throughout the scientific community, potentially reshaping how we perceive the dangers of nanoplastics. As awareness surrounding plastic pollution escalates, studies such as the one conducted by the Nano-VISION project are increasingly vital in delineating the intricacies of how these minute particles behave once within biological systems.

This research not only enhances our understanding of nanoplastics but also serves as a call to action for further investigation into their health implications. With ongoing studies and the forthcoming publication of their initial findings, the team at Graz University of Technology underlines the importance of interdisciplinary collaboration in addressing complex challenges that straddle the realms of environmental science and human health.

The crucial research findings from the Nano-VISION project promise to usher in a new era of awareness and knowledge, equipping both medical professionals and researchers alike with valuable insights into the impact of nanoplastics within the human body. As more inquiries are conducted, a clearer picture will hopefully emerge, informing both policy and practice in ways that safeguard public health.

With anticipation surrounding their forthcoming publication, the scientific community eagerly awaits further revelations from the team at Graz, whose innovative strides in nanoplastic research are setting the stage for a deeper understanding of these pressing environmental and health issues.

Subject of Research: Not applicable
Article Title: Optofluidic Force Induction Meets Raman Spectroscopy and Inductively Coupled Plasma-Mass Spectrometry: A New Hyphenated Technique for Comprehensive and Complementary Characterizations of Single Particles
News Publication Date: 14-May-2024
Web References: http://dx.doi.org/10.1021/acs.analchem.3c04657
References: Not applicable
Image Credits: Lunghammer – TU Graz

Keywords

Nanoplastics, Microplastics, Biomedical Research, Raman Spectroscopy, Intraocular Lenses, Optofluidic Force Induction, Graz University of Technology, Environmental Science, Public Health.