How to store peptides: powder, solution and spray

01

What breaks peptides down

Four things drive most degradation:

• Water, which drives reactions such as deamidation. A 1999 study found that the deamidation rate of a model peptide rose with the water content of its dry solid.
• Heat, which speeds every degradation reaction.
• Oxygen and light, which oxidize sensitive residues such as methionine, cysteine and tryptophan.
• Freeze–thaw cycles and shaking, which can drive aggregation and particles.

A 2014 review of peptide impurities catalogs the degradation products these processes leave behind.

Sources: [1] Journal of Pharmaceutical Sciences · 1999 · [3] Journal of Pharmaceutical and Biomedical Analysis · 2014

02

Storing lyophilized powder

Dry powder is the most stable form. Keep vials sealed, dry, dark and cold until you need them; short periods at room temperature, such as shipping, are tolerated by dry powder.

For long-term storage, many labs keep dry stock at −20 °C or colder. A 2015 FDA laboratory study stored a lyophilized peptide hormone at −20 °C, 4 °C, 25 °C, and 25 °C with 60% humidity. It measured content losses within eight weeks, and in the warm, humid condition particles grew within one week after reconstitution.

Let a cold vial reach room temperature before opening it, so moisture from the air does not condense on the powder.

Sources: [2] International Journal of Pharmaceutics · 2015 · [1] Journal of Pharmaceutical Sciences · 1999

03

Storing a reconstituted peptide

Once dissolved, a peptide is exposed to water full time, so reconstituted vials are usually refrigerated and used within a limited period. How long depends on the peptide and the solvent; follow the documentation for your material.

Bacteriostatic water, such as , contains benzyl alcohol to limit bacterial growth between entries, and the opened vial has its own time limit: how long bacteriostatic water lasts.

Avoid freezing and thawing a solution repeatedly. If a solution must be frozen, split it into single-use portions first.

04

Storing premixed nasal sprays

A spray is already a solution, so it follows the rules for dissolved peptides: keep it capped, cool and out of light, and follow the storage directions for the product.

How sprays and vials differ: peptide nasal spray vs vial.

05

Five habits that prevent most problems

Small routines matter more than equipment:

• Label each vial with its reconstitution date and concentration.
• Record the lot number with your experiment notes, so results trace back to a COA.
• Disinfect the stopper and use a new needle and syringe for every entry, as CDC injection-safety guidance requires in healthcare.
• Store vials upright in a dedicated, temperature-stable spot, not a refrigerator door.
• Discard anything cloudy or discolored, or with visible particles.

Sources: [4] CDC · Injection Safety Checklist