I appreciate the thorough response! Bought some sterile vials and syringe filters. Is it a good idea to filter most of the peptides into new vials or is it just a big thing with Tesamorelin? Thanks!
I'm filtering all my peptides now, based on what I've learned. This is an increasing concern with commercial pharma producers as peptides become more widespread therapeutics. Most of the aggregation appears to happen in the final product container once it's in the hands of the user.
I ended up going down this rabbit hole for a few reasons, and a "cloudy" batch of PIP inducing Tesa was one.
The TLDR version is that all protein based therapeutics are susceptible to this aggregation process. Visible particles are the final stage. It's a concern because, at the least, aggregates don't work the way the peptide is intended. It's an altered version of the original product. Depending on various factors, those altered products can cause negative reactions as the immune system responds, maybe something you can feel, maybe not. Finally, aggregates can "train" the immune system to attack the original, unmodified peptide creating "tolerance" and reducing the effect you're seeking. This is referred to as "immunogenicity".
It impossible for end users to filter out all aggregates, especially the smaller ones like dimer. But the common .2um filters will eliminate the largest aggregates, without filtering out even the longest peptides. .1um may be even better. Only "Size Exclusion Chromatography" can eliminate all aggregates leaving behind pure peptide.
Here's a rough diagram showing the concept of proteins subject to various stresses like temp cycling (freeze thaw) contamination(especially silicone from stoppers and syringes), and agitation causing shear stress, all leading to aggregates forming, which then trigger an immune response.
This shows the approximately
aggregate size, with 100um being "visible", aka "cloudy solution", and the smallest aggregates 1um. Often, the larger the aggregate the worse the reaction and greater possibility of immunogenicity developing.
One final thing, developing immunity to a peptide does not typically seem to be anywhere near as long as immunity from something like a vaccine, but still best to be avoided or you could be pointlessly injecting a peptide with diminished or no effects at all.