Bioaccumulation and correspondent biochemical response of lumbriculus variegatus by exposure to fullerenes (C60)



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Nanotechnology is one of the most popular and promising technologies in this era. It has been developed from a novel concept to an integral aspect of product advancement. Engineered nanomaterials (NMs) have been massively produced and applied into groups of products, such as automotive, defense, aerospace, electronics and computers, energy production, environmental, food production, agriculture, housing and construction, medical devices, pharmaceuticals, personal care, cosmetics. In 1985, a spherical carbon allotrope fullerene (C60) was discovered by Kroto et al. It is a foundational carbon based NM, widely applied into products due to its physical and chemical properties. However, the likelihood of direct C60 release into the environment has increased due to its applications. In recent decades, research associated with potential C60 environmental and human health risks has been emphasized. However, environmental risks of C60 are not fully understood. This research evaluated the bioaccumulation and correspondent catalase (CAT) activity change in Lumbriculus variegatus exposed to C60. With the challenge to quantify C60 in our experimental matrix, a normal shaking method was developed in this study to extract C60 effectively. Recovery results revealed 90.7 ± 4.5 % efficiency using silanized glass vessels. With relatively low cost of the supplies, this method was applied throughout the subsequent bioaccumulation study. Since few studies have emphasized C60 uptake by organisms in the environment, bioaccumulation factors have not been determined for C60 to L. variegatus. With no mortality observed in the concentration range of 0.05 to 11.33 mg C60 / kg dry weight sediment, biota-sediment accumulation factor (BSAF) was determined. For C60 aggregates in micro-size ranges (µ-C60), BSAF was 0.032 ± 0.008 at day 28, while a negligible (0.003 ± 0.006) BSAF was associated with the bigger C60 aggregates (bulk-C60). In comparison, BSAF of pyrene at day 28 (1.62 ± 0.22) was measured as a reference to determine C60 accumulation risk in the environment. Results demonstrated a lower potential for C60 accumulation in L. variegatus than pyrene. However, size effect for C60 suggests smaller aggregates can increase the accumulation in living organisms. Although C60 shows little accumulation risk in the environment, biological response corresponding to C60 exposure was observed. CAT activity was evaluated after both C60 and pyrene exposure to L. variegatus. Results illustrated a significant CAT activity change (p=0.034) at day 14 for worms exposed to C60 aggregates. This elevation was associated with the highest C60 body residue (199 ± 80 µg/kg worm tissue). Worms exposed to pyrene showed no significant CAT activity change while 600-fold higher body residues were found as compared to C60. This suggests that L. variegatus is more susceptible to C60 even through accumulation risk is relatively low. Furthermore, the relationship between C60 body residues and increased CAT activity was analyzed in linear regression to predict biological risk to L. variegatus from exposure to C60. NMs also include other compounds besides C60, such as carbon-nanotubes (CNTs) and metal-based nanoparticles. Current research has demonstrated some potential environmental and human health risks from exposure to NMs due to their special properties. In order to prevent future adverse effects from nanotechnology, an integrated governance approach that is based on scientific research and life cycle assessment is suggested to formulate effective NMs regulation. Advanced scientific research, general public education and engagement, application of well defined agenda-setting theory in public policy are all important norms in this approach to push sustainable NMs management and to prevent any unfriendly accident due to NMs exposure. In sum, this research adds to the knowledge of C60 effects on aquatic invertebrates (Lumbriculus variegatus). Governance approach suggestion is summarized and helpful in a proactive NMs management to not only aquatic ecosystems but also human health.