Amphiphilic Oligomers Based on Diesters of Pyromellitic Acid for the Solubilization of Lipophilic Agents

New amphiphilic oligomeric surfactants, diesters of pyromellitic acid (DEPA), were synthesized from pyromellitic dianhidryde, polyethylene glycol methyl ethers of different chain lengths, and alkanols/cholesterol. The synthesis resulted in amphiphilic oligomers containing hydrophilic (polyethylene glycol methyl ether, MPEG) and hydrophobic (residues of alkanol/cholesterol) fragments with a defined length. We demonstrated that DEPA oligomers form micelles in an aqueous solution, and that the surface activity of DEPA depends on the nature and length of its hydrophilic and hydrophobic constituents (the hydrophilic-lipophilic balance of DEPA). Above their critical micelle concentration, the DEPA oligomers solubilize water-insoluble substances (including the lipophilic drug, curcumin), which confirms their potential for improving the solubility of poorly water-soluble (lipophilic) agents (drugs), for example in drug delivery systems.