Lipids are fundamental components of cells in organisms. Recent studies reveal that lipids are also present in cell-free bioadhesives. Examples include barnacle cement, sea star footprints, hairy and smooth pads of insects and gecko setae. Whether reliance on lipids is universal in bioadhesion is not known. In the present study, we demonstrated, for the first time, the involvement of lipids in mussel adhesion. We extracted, identified and localized lipids in the byssal threads. The lipids were confirmed as fatty acids by gas chromatograpy mass spectrometry. δ13C measurements of the fatty acids in the byssus were also conducted. Results show that byssal fatty acids, with concentrations ranging from 1.10-2.51 mg g-1 by thread dry weight depending on the mussel species, are localized both on the surface of and inside the byssal thread and plaque. Over half of the fatty acids were loosely attached to the surface while a small portion were tightly bound to the byssus. Most of the surface fatty acids disappear within a week of thread deposition. δ13C values of byssal fatty acids show isotope fractionation suggesting that thread fatty acids are derived from the foot. It is possible that fatty acids are key players in expelling water and preparing the substrate surface for adhesion. Using lipids in the adhesion process might be a common strategy for organisms in need of temporary or permanent attachment. The process of lipid participation may be as important as adhesive components for developing more efficient man-made glues.
MoS2 quantum dots (QDs) functionalized g-C3N4 nanosheets (MoS2@CNNS) were prepared through a protonation-assisted ion exchange method, which were developed as a highly efficient biomimetic catalyst. Structural analysis revealed that uniformly-dispersed MoS2 QDs with controllable size and different loading amount grew in-situ on the surface of CNNS, forming close-contact MoS2@CNNS nanostructures and exhibiting distinct surface properties. Compared to MoS2 QDs and CNNS, the MoS2@CNNS nanocomposites exhibited a more than four times stronger peroxidase-like catalytic activity, which could catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue oxide. Among the MoS2@CNNS nanocomposites, MoS2@CNNS(30) was verified to present the best intrinsic peroxidase-like performance, which could be attributed to the more negative potential and larger specific surface area. A simple, rapid and ultrasensitive system for colorimetric detection of H2O2 was thus successfully established based on MoS2@CNNS, displaying nice selectivity, reusability, and stability. The detection limit of H2O2 could reach as low as 0.02 μM. Furthermore, the kinetic and active species trapping experiments indicated the peroxidase-like catalytic mechanism of MoS2@CNNS. This work develops a novel, rapid, and ultrasensitive approach for visual assay of H2O2, which has a potential application prospect on clinical diagnosis and biomedical analysis.
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