Circulating Microplastics as Acute Triggers of Platelet Activation and Coagulation: Implications for Cardiovascular Risk

Abstract Background Microplastics and nanoplastics (MPs/NPs) have recently been detected in human blood and vascular tissues, yet their direct effects on thrombosis remain poorly defined. Given the central role of platelets in atherothrombotic disease, understanding how circulating NPs exposure influences platelet function is critical for cardiovascular health. Methods Washed platelets and citrated whole blood from healthy volunteers were exposed to fluorescent carboxylated polystyrene nanoplastics (PS-NPs; 100 nm). PS-NPs association, internalization, and activation were quantified by flow cytometry (side scatter, forward scatter, PS-NPs fluorescence, and CD63). Fluorescence microscopy visualized the PS-NPs uptake kinetics. A whole-blood coagulation assay assessed PS-NPs-induced clot formation under varying Ca²⁺ concentrations. Results PS-NPs rapidly associated with human platelets in a concentration and time-dependent manner, with near-maximal internalization achieved within 10 minutes. PS-NPs uptake induced marked structural remodeling (increased FSC/SSC), pseudopod formation, and concentration-dependent CD63 externalization, indicative of robust platelet activation comparable to that induced by thrombin stimulation. PS-NPs association remained non-saturable across tested doses (0.3–20 μg), suggesting high-capacity, non-specific uptake mechanisms. In whole blood, PS-NPs induced dense fibrin clot formation exclusively under Ca²-permissive conditions, and PS-NPs were incorporated into fibrin networks, consistent with their role as catalytic pro-coagulant surfaces. Supernatant fluorescence confirmed PS-NPs sequestration into clots. Conclusions PS-NPs rapidly bind and activate human platelets, promote pro-coagulant platelet phenotypes, and integrate into fibrin-rich thrombi. These findings provide mechanistic evidence that circulating MPs may function as previously unrecognized environmental cardiovascular risk factors capable of acutely enhancing thrombotic potential. Defining exposure thresholds and in vivo relevance is urgently needed to assess the cardiovascular impact of the rising human NPs burden. Clinical Perspective What Is New? Circulating nanoplastics rapidly bind to human platelets through high-capacity, non-specific membrane interactions, triggering cytoskeletal remodeling, granule release, and activation pathways similar to classical agonists such as thrombin. Nanoplastics serve as catalytic pro-coagulant surfaces that accelerate fibrin polymerization and become structurally embedded within thrombi, providing a direct mechanistic link between environmental microplastic exposure and thrombogenesis. Rapid, non-saturable platelet uptake suggests that rising global microplastic loads may proportionally increase human thrombotic susceptibility. What Are the Clinical Implications? Nanoplastic-induced platelet activation and clot formation identify microplastics as previously unrecognized, modifiable environmental cardiovascular risk factors with mechanistic plausibility for contributing to myocardial infarction, stroke, and microvascular thrombosis. Populations with heightened platelet reactivity, endothelial dysfunction, or chronic inflammatory states may be particularly vulnerable to thrombotic events triggered by acute or cumulative nanoplastic exposure. Public health efforts aimed at reducing environmental microplastic contamination and establishing exposure limits may become necessary components of cardiovascular disease prevention strategies.