How to Store Peptides

Lyophilised (Dry) Peptide Storage

Lyophilised peptide in its sealed, dry form is substantially more stable than reconstituted solution. Unopened vials can be stored at room temperature for short periods, but refrigeration or freezing is recommended for anything beyond a few weeks. Key principles apply regardless of storage location:

• Keep vials away from direct light and moisture at all times.
• If storing multiple vials together, include a desiccant pack in the storage container to absorb ambient moisture.
• Do not open the vial until you are ready to reconstitute — exposure to air introduces moisture and shortens shelf life.

Reconstituted Peptide Storage

Once a peptide has been dissolved in bacteriostatic water, its stability decreases significantly compared to dry powder. The benzyl alcohol preservative in BAC water extends usable life, but the peptide is now in aqueous solution and subject to hydrolysis and degradation over time.

Most research handling guidelines report that reconstituted peptide in BAC water remains viable for 28–30 days when refrigerated. Some sources report up to 60 days for more robust peptide sequences, but a conservative 28-day window is widely used as the standard. After this period, potency cannot be assumed.

Freeze-Thaw Cycles

Each freeze-thaw cycle subjects a peptide solution to mechanical stress from ice crystal formation and re-dissolution, which can progressively degrade potency. Repeated cycling is therefore something to minimise.

If storing reconstituted peptide for extended periods does require freezing, the preferred approach is to aliquot the solution into individual single-dose volumes in small amber vials before freezing. Only the quantity needed for a given session is then thawed, preserving the integrity of the remaining aliquots. This is especially important for peptides with known sensitivity to temperature cycling.

Light Sensitivity

Most peptides are sensitive to ultraviolet light. UV exposure can cause photodegradation of specific amino acid residues, particularly tryptophan, phenylalanine, and tyrosine. Both dry and reconstituted peptides should be stored in amber (dark) glass vials, or the vial should be wrapped in aluminium foil if an amber vial is not available.

Do not leave reconstituted peptide on a bench in direct sunlight or under a bright laboratory lamp for any extended period. When drawing doses, minimise the time the vial spends out of the refrigerator and away from light.

Temperature Excursions

Occasional brief exposure to temperatures outside the target range — for example, a short power outage affecting a refrigerator — is generally tolerable for lyophilised powder, which is inherently stable in dry form. A few hours at room temperature are unlikely to significantly affect an unopened dry vial.

Reconstituted peptide that has been at room temperature for a few hours should generally remain usable, provided the total time does not exceed approximately 24 hours. If a reconstituted vial has been left at room temperature for longer than this, or if the solution appears cloudy, discoloured, or contains visible particles, it should be discarded rather than used.

Travel Tips

• Carry lyophilised powder when possible. Dry peptide is significantly more stable during transit than reconstituted solution and does not require continuous cold chain maintenance for short journeys.
• Use an insulated case with an ice pack for any reconstituted peptide that must be transported. Small medical-grade insulated pouches are widely available and keep contents at 2–8°C for several hours.
• Reconstitute at the destination where possible. Travelling with the dry vial and a separate BAC water vial, then reconstituting on arrival, avoids the cold chain challenge entirely.
• Airport security: security agencies generally permit medical supplies including syringes and vials when accompanied by appropriate documentation. Policies vary by jurisdiction — verify requirements before travelling.

Common Mistakes

• Storing reconstituted peptide at room temperature — even a few days at room temperature can meaningfully reduce potency. Keep reconstituted vials refrigerated at all times when not in use.
• Repeated freeze-thaw cycles — each cycle degrades the solution. Aliquot into single-dose volumes before freezing if long-term frozen storage is required.
• Not labelling vials with the date of reconstitution — without a date, there is no way to know whether a vial is within its viable window. Always label immediately after reconstitution.
• Leaving peptides exposed to light on the bench — UV exposure causes photodegradation. Store in amber vials or wrapped in foil, and minimise time in light during dose preparation.