# Self-Assembly of a Therapeutic Peptide Surfactant: A Small-Angle X‑ray Scattering Study

## TL;DR

This study uses X-ray scattering to understand how a therapeutic lipidated peptide self-assembles into micelles in water.

## Contribution

The study reveals the self-assembly behavior of a bis-lipidated GLP-1 analogue using SAXS, showing stable micelle formation under various conditions.

## Key findings

- MEDI7219 forms small micelles with a core-and-shell structure in aqueous solutions.
- Aggregation numbers of the micelles range from 5 to 8 and are insensitive to environmental changes.
- The lipopeptide exhibits very low critical micelle concentrations.

## Abstract

Amphiphilic compounds are important in many fields including
pharmaceutical
processes and development. Synthetic surfactants are often toxic to
biological systems and frequently display poor biodegradability. Biosurfactants,
such as lipopeptides and bile salts, on the other hand, can offer
superior properties with regard to toxicity, biodegradability, and
efficiency. Lipidated peptides are also gaining interest as therapeutic
agents, as they can offer enhanced pharmacokinetic properties, compared
with native peptides. The amphiphilic nature of lipidated peptides
suggests that they may self-assemble into micellar structures, which
can influence formulation stability and biological performance. Understanding
the aggregation behavior of lipidated peptides is thus important for
identifying and avoiding stability issues that could affect drug efficacy
and safety. Structural characterization of self-assembled aggregates
provides insight into aggregation mechanisms, which is valuable for
identifying potential challenges during the production, storage,
and administration of pharmaceutical peptides. By using small-angle
X-ray scattering (SAXS), we have investigated the size and morphology
of aggregates formed by MEDI7219, a bis-lipidated glucagon-like peptide-1
(GLP-1) analogue, in various aqueous solutions. We demonstrate that
the lipopeptide MEDI7219 behaves as a surfactant with high spontaneous
curvature that forms small micelles with a clear core-and-shell structure
in aqueous solvents. The aggregation numbers of the micelles vary
in the range of 5–8 and are found to be surprisingly insensitive
to environmental conditions such as type of electrolyte and tonicity
modifier, different buffers, and temperature, while exhibiting very
low critical micelle concentrations (cmc).