Eco-Friendly Organic Nanotubes Encapsulating Alkaline Phosphatase and Ecotoxicology of Nanotubes to Natural Bacterial Assemblages in Coastal Estuarine Waters
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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Phosphatase-encapsulated nanotubes have potential in environmental remediation of organophosphate contaminants e.g., pesticides, nerve agents. We investigated alkaline phosphatase AP activity when encapsulated in self-assembled lithocholic acid nanotubes LCA-AP in water samples along a transect from Cypress bog headwaters through estuarine waters and to Atlantic Ocean seawater. Apparent V-max V-appmax for both LCA-AP and unencapsulated AP Free-AP was most rapid at mid-estuary and most inhibited at the humic-rich bog. LCA-AP retained a higher-activity percentage, suggesting that encapsulation may afford some protection from denaturing effects of humics. Apparent K-m K-appm of Free-AP 1-2.3 mu M was largely unaffected by preincubation with transect water, whereas K-appm of LCA-AP was higher with bog water 5.3 mu M relative to other stations. When comparing Free-AP and LCA-AP, increasing salinity generally decreased the catalytic efficiency of the LCA-AP, but had little effect on that of the Free-AP. In addition, both showed the same pattern of lowest efficiency in bog water, which increased with salinity to 21 practical salinity units before decreasing at full-strength salinity. With the exception of the similarly low values in the bog water 1.04 for LCA-AP, 1.34 for Free-AP, absolute values of catalytic efficiency for LCA-AP were about 17 range 14.5-19.3 of that for Free-AP. Nanotube addition had little ecotoxicological effect on heterotrophic bacterial production in waters sampled along the transect. Microbially associated, intrinsic AP activity showed a similar pattern along the transect to LCA-AP, suggesting that AP environmental control and regulation in nature may inform study of nanomaterials.