Solubility of Hydrophobic Compounds in Aqueous Solution Using Combinations of Self-assembling Peptide and Amino Acid

Self-assembling peptides (SAPs) are promising vehicles for the delivery of hydrophobic therapeutics for clinical applications; their amphipathic properties allow them to dissolve hydrophobic compounds in the aqueous environment of the human body. However, self-assembling peptide solutions have poor blood compatibility (e.g., low osmolarity), hindering their clinical application through intravenous administrations. We have recently developed a generalized platform for hydrophobic drug delivery, which combines SAPs with amino acid solutions (SAP-AA) to enhance drug solubility and increase formulation osmolarity to reach the requirements for clinical uses. This formulation strategy was thoroughly tested in the context of three structurally different hydrophobic compounds - PP2, rottlerin, and curcumin - in order to demonstrate its versatility. Furthermore, we examined effects of changing formulation components by analyzing 6 different SAPs, 20 naturally existing amino acids at low and high concentrations, and two different co-solvents dimethyl sulfoxide (DMSO) and ethanol. Our strategy proved to be effective in optimizing components for a given hydrophobic drug, and therapeutic function of the formulated inhibitor, PP2, was observed both in vitro and in vivo. This manuscript outlines our generalized formulation method using SAP-AA combinations for hydrophobic compounds, and analysis of solubility as a first step towards potential use of these formulations in more functional studies. We include representative solubility results for formulation of the hydrophobic compound, curcumin, and discuss how our methodology serves as a platform for future biological studies and disease models.