Liposome disposition in vivo II: Dose dependency

Area of Science:

• Pharmacokinetics and Drug Delivery
• Nanomedicine
• Biomedical Engineering

Background:

• Liposomes are crucial nanocarriers for drug delivery.
• Understanding liposome disposition is vital for optimizing therapeutic efficacy.
• Extruded multilamellar liposomes offer controlled particle size and charge.

Purpose of the Study:

• To investigate the dose-dependent disposition of negatively charged liposomes in vivo.
• To evaluate the impact of liposomal lipid dose on biodistribution and cellular uptake.
• To determine the extent of intracellular delivery of entrapped substances.

Main Methods:

• Administered radiolabeled [14C]inulin-loaded liposomes intravenously to mice at varying doses (15, 300, 1500 mumoles lipid/kg).
• Quantified Carbon 14 levels in blood, liver, spleen, and carcass over 72 hours.
• Analyzed dose-dependent saturation effects and tissue-specific accumulation patterns.

Main Results:

• Observed pronounced dose-dependent saturation effects at early time points, with higher concentrations in blood and spleen but lower in the liver at increased doses.
• Noted attenuation of dose effects in the liver over time, while spleen saturation persisted.
• [14C]inulin decline in the liver (first 48 hr) suggested leakage from extracellular liposomes; plateau levels indicated intracellular delivery.

Conclusions:

• Liposome biodistribution exhibits dose-dependent saturation, similar to other colloidal systems.
• Early decline in liver [14C]inulin suggests liposome instability and content leakage.
• Later plateau levels of [14C]inulin approximate successful intracellular liposomal drug delivery.