Semaglutide: reagent form, reconstitution and storage

Physical form and specification

Semaglutide is a synthetic, lipidated analogue of glucagon-like peptide-1 (GLP-1) and an agonist at its receptor. As a reagent it is supplied as a white to off-white lyophilized (freeze-dried) powder. Batch purity is confirmed by HPLC (typically ≥98 %) and identity by mass spectrometry. It ships in 20 mg and 50 mg per-vial formats.

Reconstitution

The lyophilizate is reconstituted directly in the vial. In laboratory practice, bacteriostatic water (water with 0.9 % benzyl alcohol) or sterile water is used; a phosphate-buffered saline at slightly alkaline pH is also suitable for stock solutions. Add the diluent slowly, directing the stream against the vial wall rather than onto the powder, then swirl the vial gently without shaking until fully dissolved. Semaglutide is readily soluble in aqueous buffers; vigorous shaking generates foam and can cause mechanical denaturation and aggregation of the peptide, so it should be avoided.

Storage

A sealed lyophilized vial is stable in a freezer (−20 °C) and remains usable for months; short-term storage at 2–8 °C is acceptable. Protect the material from light and moisture. Once reconstituted, keep the solution at 2–8 °C: a bacteriostatic diluent limits microbial growth and extends the working life of the stock to several weeks. For long-term storage, prepare aliquots and freeze them, avoiding repeated freeze-thaw cycles, which reduce activity.

Stability

Semaglutide is notable for its high metabolic stability. Substitution of alanine with 2-aminoisobutyric acid (Aib) at position 8 protects the molecule from cleavage by dipeptidyl peptidase-4, while the attached C18 diacid chain confers reversible binding to albumin — together these account for the long half-life of roughly 7 days observed in research models. In solution the peptide is susceptible to oxidation and aggregation at room temperature, so working solutions are best prepared immediately before an experiment.

Research applications

The reagent is used in studies of GLP-1 receptor signaling, glucose metabolism, satiety mechanisms and energy homeostasis, both in vitro and in animal models. Stock solutions are standardized by concentration to construct dose-response curves in cell lines expressing the GLP-1 receptor. The 50 mg vial is convenient for preparing a wider range of concentrations, while the 20 mg vial suits smaller experimental series.