A liposome-based nanodevice for sequestering siderophore-bound Fe

Nanometer-scale engineered liposomes provide a powerful platform for developing chemical sensors of trace metals in marine systems. We present here preliminary findings on liposome-based nanodevices designed to sequester iron that is complexed by the siderophore desferrioxamine B (DFB). Previous work shows that iron availability to eukaryotic phytoplankton can vary inversely with DFB additions, so quantifying DFB-Fe concentrations might provide key insights to the scenario of iron nutrition facing these organisms. The liposome-based devices are selective for DFB-Fe and form chemically and coagulation stable suspensions in synthetic buffers and full seawater for at least several weeks. Iron uptake was measured when the ionophore carrier molecule lasalocid was incorporated into the liposome membranes, although uptake efficiencies decreased with increasing seawater salt concentrations. Liposome devices fabricated from only natural phosphatidyl choline proved to be fragile but incorporating polymerizable diacetylene phospholipids increased their robustness markedly. These preliminary findings serve as a foundation for developing self-reporting iron acquisition devices that, in turn, could be calibrated to provide analytical measures of Fe availability in seawater.