When the DPPC/Chol-MBP nanosheets dispersion is diluted to 0.2 wt%, spherical aggregates of less than 100 nm in diameter are observed on TEM (Fig. ). Meanwhile, the nanosheet structure is maintained upon the same dilution process after the addition of 2.0 equivalents of Cu 2+ ions (Fig. ), indicating that Cu 2+ -mediated crosslinking of Chol-MBP significantly improves the stability of DPPC/Chol-MBP nanosheets in the diluted condition. The structurally stable DPPC/Chol-MBP/Cu nanosheets can be used to investigate the dependence of the phospholipid assembling morphologies on the blood circulation profiles. Fluorescent Cy5-labeled DPPC vesicles and DPPC/Chol-MBP/Cu nanosheets filtered through a membrane with 200-nm pores are administered to mice via the tail vein ( FL DPPC vesicle and FL DPPC/Chol-MBP/Cu nanosheet, respectively, total content: 5.0 wt% before the injection). Observation of the blood circulation profile by confocal laser scanning microscopy of the earlobe of the mice (IV-CLSM) showed contrasting circulation properties of the vesicles and nanosheets. The FL DPPC vesicles were aggregated and clogged (Fig. ), whereas FL DPPC/Chol-MBP/Cu nanosheets were homogeneously dispersed in the blood vessels (Fig. ). The self-assembling approach of Chol-MBP is thus advantageous for stabilizing the bicelle morphology to enable prolonged circulation in the blood vessel relative to the spherical vesicles, demonstrating a suitable carrier to the whole body by blood administration.