Rhodamine DHPE

More reeently, u-GalNAc liposomes were formulated by the incorporation of D-GalNAc-linked citronellol to L-a-phosphatidylcholine and rhodamine-DHPE (Fig. 10). In vitro studies on HepG2 cells, monitored by fluorescence (rhodamine), pointed out the preferentially endocytose manner of uptake. This could lead to apoptosis with the appropriate drug (Dox for example) delivered into the parenchymal cells carcinoma. 

Figure 14.3 A vesicle, sucked up in a pipette, as observed under a microscope working in a fluorescence regime. The diameter of the vesicle is 20 pm, while the inner diameter of the pipette is 6 pm. The vesicle matrix is SOPC, with 5 mol % PEG2000 lipid and 1.5 mol % rhodamine DHPE.

The following fluorescent molecules were used to study GUV membrane properties ANS, coumarin 6, coumarin 35, and the labeled lipids rhodamine DHPE and dansyl egg PE (Figures 30.1 and 30.2). Such probes are excellent tools with which to analyse membrane dynamics as well as to monitor the interaction of membranes and proteins. 

Figure 30.2 Fluorescence images of POPC GUVs (bar = 50 nm) labeled with (A) ANS (6 X 10 M), (B) coumarin 6 (1 x 10 M), (C) coumarin 35 (6 x 10" M). Fluorescence images of POPC GUVs and the following colipids (D) dansyl-egg PE (mol ratio POPC labeled lipid = 40 1), (E) rhodamine DHPE (mol ratio TOPC labeled = lipid 270 1).

Dansyl-labeled lipids (Figure 30.2(D)) are useful probes for investigating the assembly of proteins on and within membranes, either by monitoring the spectral shift of dansyl fluorescence or via fluorescence resonance energy transfer measurements using protein-inherent tryptophan as donor [9]. Rhodamine DHPE (Figure 2(E)) does not easily transfer between separated lipid bilayers. Therefore this label is extensively used for membrane fusion assays [8]. 

Figure 8. Confocal micrograph Hydrophobic PTMC stained with red Rhodamine DHPE and the water phase stained with green BODIPY.

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