Low salt concentration inside the liposomes (≤ 100 mM) or low solubility (≤ 1.9 mM) leads to medium loading. Basically, the variable salt concentration inside the liposomes resembles the variable of in/out gradient magnitude. Increase in the intraliposome salt concentration leads to higher loading efficiency until the curve reaches a plateau (when the concentration is ≥ 250 mM).