Tiny Plastics, Big Problem: New Biosensors Race to Detect Micro- and Nanoplastics

Plastic pollution has become one of the defining environmental challenges of the twenty-first century, but the most alarming threat may be invisible to the naked eye. A comprehensive review published in Environmental Monitoring and Assessment by researchers at the Birla Institute of Technology and Sciences, Pilani, examines how plastic debris progressively fragments into micro- and nanoplastics—collectively known as MNPs—through physical, chemical, and biological degradation processes. Once released, these particles pervade oceans, freshwater systems, soils, and even the atmosphere. Because of their minute dimensions, MNPs are extraordinarily difficult to track, and the review argues that the world’s ability to understand—and ultimately manage—this pollution crisis is being held back by a fundamental bottleneck: we still lack fast, cheap, and reliable ways to detect these particles where they matter most.

The physical and chemical properties of MNPs make them uniquely hazardous environmental actors. Their small size gives them an exceptionally high surface-area-to-volume ratio, while their hydrophobic surfaces readily attract and adsorb a wide range of other contaminants. In aquatic environments, microplastics act as vectors for heavy metals, binding cadmium, arsenic, and other toxic elements and transporting them into organisms that ingest the particles. Studies cited in the review document synergistic toxicity when fish, zebrafish, and the planktonic crustacean Daphnia magna are exposed to both microplastics and metals simultaneously, with effects that exceed those of either stressor alone. Similar interactions have been reported with antibiotics, organic pollutants, and pathogenic microbial communities that colonize plastic surfaces in the so-called plastisphere.

The consequences ripple through entire ecosystems. In soil, MNPs alter aggregate formation, change hydraulic properties and pore characteristics of compacted earth, and disrupt the carbon, nitrogen, and phosphorus cycles that sustain farmland productivity. Meta-analyses referenced in the review show shifts in soil microbial diversity and community structure following exposure, while rice seedlings suffer increased arsenic toxicity in the presence of plastic particles. Crop plants can take up submicrometre plastics through a crack-entry mode at their roots, raising concerns about the food chain. In freshwater and marine systems, microplastics affect grazing behavior and mortality in plankton, impair growth and immunity in fish such as the yellow seahorse, and alter neurobehavioral and molecular rhythms in fish exposed to clean nanoplastics, demonstrating that the particles themselves—not just their chemical passengers—can disrupt biology.

Perhaps the most sobering findings concern human exposure. Researchers have now identified microplastics in human blood, sputum, breast milk, and the placenta, with pyrolysis gas chromatography mass spectrometry confirming accumulation in placental specimens. Microplastics have been associated with microbiota in placentas and meconium, found in maternal amniotic fluid with links to gestational age, and detected in the feces of expectant mothers. Experimental evidence indicates that micro- and nanoplastics can breach the blood–brain barrier, with a biomolecular corona of proteins facilitating their passage. Reviews of health impacts point to endocrine-disrupting effects, risks to the central nervous system, and potential reproductive consequences, although the review is careful to note that the full clinical significance of these exposures remains an active area of investigation.

Against this backdrop, the review’s central contribution is its critical evaluation of how MNPs are actually detected. Conventional approaches rely on sophisticated laboratory instrumentation. Fourier transform infrared spectroscopy and Raman spectroscopy can identify polymer types by their vibrational fingerprints, and surface-enhanced Raman spectroscopy using silver nanoparticles and nanodendrites pushes sensitivity further, enabling on-site detection of microplastics in water. Thermal methods such as thermogravimetric analysis coupled with mass spectrometry quantify polyethylene and polypropylene in environmental samples, while pyrolysis gas chromatography mass spectrometry has proven powerful for complex biological matrices. Fluorescent staining with Nile Red offers a rapid screening approach for microplastic fibers, distinguishing synthetic from natural materials. Mass spectrometry techniques have recently achieved detection of micro- and nanoplastics in seconds, illustrating how far analytical speed has advanced.

Yet each of these conventional techniques carries inherent limitations. The instruments are expensive, the workflows demand skilled personnel and extensive sample preparation, and most methods are poorly suited to rapid on-site analysis. Spectroscopic identification struggles with particles below a few micrometres, precisely where nanoplastics dominate, and distinguishing true environmental contamination from background laboratory plastic pollution remains a persistent challenge. For environmental monitoring at scale—thousands of water bodies, agricultural fields, and food products—these constraints mean that the true distribution of MNPs is likely far worse than current measurements suggest. The review concludes that this detection gap underscores the urgent need for innovative strategies offering high sensitivity, high selectivity, and real-time analytical capability.

The most promising candidates, according to the review, are biosensors, and in particular aptamer-based platforms. Aptamers are short single-stranded DNA or RNA molecules selected to bind specific targets with antibody-like affinity, first described in 1990 through in vitro selection experiments. They are generated through SELEX—Systematic Evolution of Ligands by Exponential Enrichment—an iterative process of binding, partitioning, and amplification, with newer non-SELEX approaches and computational, in silico library design strategies accelerating discovery. Chemical modifications can dramatically increase binding affinity and nuclease resistance, and structured library approaches are producing a next generation of aptamers with improved performance. Because aptamers are chemically synthesized, they are cheaper, more reproducible, and more easily engineered than antibodies, making them attractive for mass-deployed environmental sensors.

Recent demonstrations show how aptamers can be coupled to different transduction modes for MNP detection. Colorimetric aptasensors exploit gold nanoparticle aggregation to produce visible readouts, including a gold nanoparticle-assisted platform for rapid sensing of polyethylene terephthalate microplastics. Electrochemical and photoelectrochemical designs include a switch-type aptasensor built on a two-dimensional organic–inorganic heterojunction for detecting micro- and nanoplastics. Surface plasmon resonance biosensors have measured very low microplastic concentrations through bioaffinity-induced particle retention, and engineered peptide biosensors have achieved sensitive, specific capture of polystyrene and polypropylene particles. Perhaps most strikingly, CRISPR-based colorimetric aptasensors combined with smartphone imaging and deep learning now enable selective recycling and visual prediction of microplastics in the environment, while a label-free electrochemical aptasensor uses CRISPR/Cas12a-mediated cascade strand displacement for sensitive and selective detection. Smartphone-enabled quantification and low-cost microfluidic identification further point toward field-deployable, citizen-accessible monitoring.

The review is candid about the obstacles that remain. Selecting aptamers against chemically heterogeneous, weathered plastic particles is far harder than selecting them against purified biomolecules, and critical evaluations of past aptamer work have shown that some celebrated binding claims do not survive scrutiny. Reproducibility of SELEX outcomes, the stability of aptamers in complex environmental matrices, and the challenge of distinguishing polymer types in mixtures all limit current platforms. Scaling from laboratory prototypes to robust, large-scale applications will require standardized target materials, validated binding characterization, and integration of sample preparation with sensing. The authors identify these knowledge gaps explicitly and outline future research directions, including non-SELEX selection methods, computational modeling of aptamer-target interactions, and hybrid systems that combine aptamer recognition with machine learning-assisted readout.

The stakes of closing the detection gap could hardly be higher. Plastic production continues to grow, tire wear, plastic mulches, landfill liners, and wastewater treatment plants all release MNPs into the environment, and atmospheric deposition now carries microplastics into remote coastal zones. Without accurate, affordable, real-time monitoring, regulators cannot set meaningful exposure limits, wastewater operators cannot optimize removal, and the public cannot judge the safety of drinking water, tap water, or food. The Birla Institute team argues that aptamer-based biosensors, by combining molecular specificity with low cost and portability, could transform MNP monitoring from a specialized laboratory pursuit into routine environmental practice—giving researchers and policymakers, for the first time, the measurement infrastructure needed to confront a pollutant that has already reached human blood, brains, and the placenta.

Subject of Research: Environmental impacts of micro- and nanoplastics and advances in aptamer-based biosensor detection strategies

Article Title: Effect of micro/nano-plastics on environment and recent advances in their detection strategies

Article References: S., L. J., Manjuladevi, V., Panwar, J., & Verma, S. K. (2026). Effect of micro/nano-plastics on environment and recent advances in their detection strategies. Environmental Monitoring and Assessment, 198(11), Article 1174. https://doi.org/10.1007/s10661-026-15995-7

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15995-7

Keywords: microplastics, nanoplastics, plastic pollution, biosensors, aptamers, SELEX, environmental monitoring, Raman spectroscopy, CRISPR, heavy metals, toxicology, water quality