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Eco-friendly organic nanotubes encapsulating alkaline phosphatase and ecotoxicology of nanotubes to natural bacterial assemblages in coastal estuarine waters

350 263 Stroud Water Research Center

Montgomery, M.T., G.E. Collins, T.J. Boyd, C.L. Osburn, D. Oviedo-Vargas, and Q. Lu. 2019. American Chemical Society Omega 4(1):2196–2205.

http://doi.org/10.1021/acsomega.8b02650

Abstract

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 Vmax (appVmax) 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 Km (appKm) of Free-AP (1–2.3 μM) was largely unaffected by preincubation with transect water, whereas appKm of LCA-AP was higher with bog water (5.3 μM) 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.