You have the wrong state of mind. You are already making yourself guilty, and they can spot that. I recon 1 vial and put it with my checked bag, with my personal items, along my perfume bottles and other liquids (eye drops, etc). I put syringes, alcohol, etc in a separate small wrap in the same checked bag ( I suggest 0.3/0.5cc syringes). Try to not make yourself look like a drug addict. And the whole story about 'research' does not stand a chance (IMO).
If they analyze the vial, it is not a 'controlled' substance. They can keep it, and I possibly will pay a fine. Worst case, I will be denied entry (and may have difficulty re-entering the next time). If you import a lot, its contraband and a crime. No powder in a vial, please.
Read the EU customs law, and for each other country. If you want to debate with a TSA or custom officer this is legitimate medicine, you need to make that statement up front. You need a prescription, written in the language of that country, with the evidence they want. Anything else, and you are begging to spend time in secondary inspection, lowering your odds and digging yourself a grave.
You need to be a cool cat, that can stare at an officer in the eyes, and say 'nothing to declare' because there is nothing to declare. Body temperature, eye pupil/movement, sweat, etc will give you up easily. The vials do not need to be refrigerated during transit. If you try to hide this too much, that means you know you are doing something wrong, and you are making yourself guilty.
By the way, its the lithium batteries that will betray you. They are paranoid about those now. None in checked bags, and keep them together with you. The scanners are so good, they can spot small, quarter size lithium batteries.