Highly Stable Liposomes Based on Tetraether Lipids as a Promising and Versatile Drug Delivery System

Abstract

Conventional liposomes often lack stability, limiting their applicability and usage apart from intravenous routes. Nevertheless, their advantages in drug encapsulation and physicochemical properties might be helpful in oral and pulmonary drug delivery. This study investigated the feasibility and stability of liposomes containing tetraether lipids (TEL) from Thermoplasma acidophilum. Liposomes composed of different molar ratios of TEL:Phospholipon 100H (Ph) were produced and exposed to various temperature and pH conditions. The effects on size, polydispersity index, and zeta potential were examined by dynamic and electrophoretic light scattering. Autoclaving, which was considered an additional process step after fabrication, could minimize contamination and prolong shelf life, and the stability after autoclaving was tested. Moreover, 5(6)-carboxyfluorescein leakage was measured after incubation in the presence of fetal calf serum (FCS) and lung surfactant (Alveofact). The incorporation of TEL into the liposomes significantly impacted the stability against low pH, higher temperatures, and even sterilization by autoclaving. The stability of liposomes containing TEL was confirmed by atomic force microscopy as images revealed similar sizes and morphology before and after incubation with FCS. It could be concluded that increasing the molar ratio in the TEL:Ph liposome formulations improved the structural stability against high temperature, low pH, sterilization via autoclaving, and the presence of FCS and lung surfactant.

Pulmonary inhalation for disease treatment: Basic research and clinical translations

“…Conventional liposomes are studied dosage forms and have extended drug half-life, good biocompatibility, and high versatility, making them suitable carriers for drug delivery systems [ [171] , [172] , [173] ]. However, conventional liposomes frequently lack stability, restricting their use and application outside the intravenous route [ 174 ]. The active substance on the alveolar surface is dipalmitoyl phosphatidylcholine.…”

“…Therefore, the advantages of liposomes regarding drug encapsulation and physicochemical properties could reduce irritation and damage to the lungs, likely contributing to pulmonary drug delivery. Tetraether lipids, when constituting more than 50 % of the formulation, can enhance liposome stability, sterilize them by autoclaving, provide considerable advantages for clinical applications, and facilitate pulmonary drug delivery [ 174 ]. The movement of liposomes as carriers of inhaled formulations in the lungs is affected by gravitational settling, Brownian motion, and inertial impact ( Fig.…”