Hi Everyone
I am trying to calculate needed lipid amount from initial D:L ratio prior to remote loading.
I have a drug compound with a concentration of 1mg/mL (volume=1ml) with an MW=521.6 which i am going to load into liposomes.
I have an initial 0.5mM lipid stock solution.
I have calculated the compound concentration to be 1917micromolar which gives me for a Drug-to-lipid ratio of 1:4 an addition of 15.3mL from the 0.5mM lipid stock.
However it seems quite high amount of lipid and i am therefore not sure of the calculations are correct.
Any input or clarification is highly appreciated
Thanks!
Hi,
This seems about right. You initially have 1 mL of a 1 mg/mL solution of the drug, which has a MW = 521.6 g/mol, so you have indeed a 1916 uM or 1.916 mM solution of the drug.
When you add the 15.3 mL of the 0.5 mM lipid solution to your 1 mL drug solution, you end up diluting the drug solution to a concentration of 117.62 uM (1917 uM/(1 mL + 16.3 mL) = 117.62 uM).
Your initial lipid solution (15.3 mL) has a concentration of 0.5 mM, but you slightly dilute this solution with the 1 mL of drug solution, you end up having a concentration of 0.46933 mM or 469.33 uM of the lipid (0.5 mM * (15.3 mL/16.3 mL) = 0.46933 mM).
Since you have 117.62 uM of the drug and 469.33 uM of the lipid, you have 117.62 uM drug/469.33 uM lipid = 0.2506, which is indeed about 1/4.
It may seem like you have way too much lipid, but this ratio makes sense. You start with about 2 mM drug solution and a 0.5 lipid solution, so you have about a 4:1 drug : lipid concentration initially, but you have 15.3 mL of the lipid solution and only a 1 mL drug solution, so you have about a 1:16 drug : lipid volume. When you take both a volume and the initial concentration into account, you indeed have a 1:4 drug : lipid ratio.
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