Interactions of novel, nonhemolytic surfactants with phospholipid vesicles.

PEG-12-acyloxystearates constitute a novel class of pharmaceutical solubilizers and are synthesized from polyethylene glycol and 12-hydroxystearic acid, which has been esterified with a second acyl chain. The hemolytic activity of these surfactants decreases drastically with increasing pendant acyloxy chain length, and surfactants with an acyloxy chain of 14 carbon atoms or more are essentially nonhemolytic. In this paper, the interactions of PEG-12-acyloxystearates (acyloxy chain lengths ranging from 8 to 16 carbon atoms) with phosphatidylcholine vesicles, used as a model system for erythrocyte membranes, were studied in search of an explanation for the large variations in hemolytic activity.

Membrane destabilizing properties of cell-penetrating peptides.

Although cell-penetrating peptides (CPPs), also denoted protein transduction domains (PTDs), have been widely used for intracellular delivery of large and hydrophilic molecules, the mechanism of uptake is still poorly understood. In a recent live cell study of the uptake of penetratin and tryptophan-containing analogues of Tat(48-60) and oligoarginine, denoted TatP59W, TatLysP59W and R(7)W, respectively, it was found that both endocytotic and non-endocytotic uptake pathways are involved [Thoren et al., Biochem.

Vesicle size-dependent translocation of penetratin analogs across lipid membranes.

The recent discoveries of serious artifacts associated with the use of cell fixation in studies of the cellular uptake of cell-penetrating peptides (CPPs) have prompted a reevaluation of the current understanding of peptide-mediated cellular delivery. Following a report on the differential cellular uptake of a number of penetratin analogs in unfixed cells, we here investigate their membrane translocation abilities in large and giant unilamellar vesicles (LUVs and GUVs, respectively). Surprisingly, in contrast to the behavior in living cells, all peptides readily entered the giant vesicles (>1 microm) as proved by confocal microscopy, while none of them could cross the membranes of LUVs (100 nm).

Vesicle membrane interactions of penetratin analogues.

Reports on serious artifacts associated with the use of cell fixation in studies of the cellular uptake of cell-penetrating peptides, also denoted protein transduction domains, have demonstrated the need for a reevaluation of the current understanding of peptide-mediated cellular delivery of large, hydrophilic molecules. In a recent study on the internalization in unfixed cells of penetratin and its analogues in which tryptophans are substituted for phenylalanines (Pen2W2F), lysines for arginines (PenArg), and arginines for lysines (PenLys), we revealed large dissimilarities in cell interactions among the peptides [Thorén et al. (2003) Biochem.

Membrane binding and translocation of cell-penetrating peptides.

Cell-penetrating peptides (CPPs) have been extensively studied during the past decade, because of their ability to promote the cellular uptake of various cargo molecules, e.g., oligonucleotides and proteins.

Uptake of analogs of penetratin, Tat(48-60) and oligoarginine in live cells.

Cell-penetrating peptides are regarded as promising vectors for intracellular delivery of large, hydrophilic molecules, but their mechanism of uptake is poorly understood. Since it has now been demonstrated that the use of cell fixation leads to artifacts in microscopy studies on the cellular uptake of such peptides, much of what has been considered as established facts must be reinvestigated using live (unfixed) cells. In this work, the uptake of analogs of penetratin, Tat(48-60), and heptaarginine in two different cell lines was studied by confocal laser scanning microscopy.

Application of a novel analysis to measure the binding of the membrane-translocating peptide penetratin to negatively charged liposomes.

The binding of penetratin, a peptide that has been found useful for cellular delivery of large hydrophilic molecules, to negatively charged vesicles was investigated. The surface charge density of the vesicles was varied by mixing zwitterionic dioleoylphosphatidylcholine (DOPC) and negatively charged dioleoylphosphatidylglycerol (DOPG) at various molar ratios. The extent of membrane association was quantified from tryptophan emission spectra recorded during titration of peptide solution with liposomes.