Bioconjugate-based molecular umbrellas.

Molecular umbrellas are "amphomorphic" compounds that can produce a hydrophobic or hydrophilic exterior when exposed to a hydrophobic or hydrophilic microenvironment, respectively. Such molecules are composed of two or more facial amphiphiles that are connected to a central scaffold. Molecular umbrellas that have been synthesized to date, using bile acids as umbrella "walls", polyamines such as spermidine and spermine as scaffold material, and l-lysine as "branches", have been found capable of transporting certain hydrophilic peptides, nucleotides, and oligonucleotides across liposomal membranes by passive diffusion. They have also have been shown to increase water solubility and hydrolytic stability of a hydrophobic drug, and to exhibit significant antiviral activity. The ability of a fluorescently labeled molecular umbrella to readily enter live HeLa cells suggests that such conjugates could find use as drug carriers.