Characterization of Spherulites as a Lipidic Carrier for Low and High Molecular Weight Agents

Abstract

Purpose To develop spherulite formulations to achieve high entrapment efficiency for both small and macromolecules as well as cell-type specific delivery. Methods Spherulites of various compositions were prepared, and lipid-PEG was incorporated through post-insertion. Calcein and FITC-labeled albumin were employed as model drugs for small and macromolecules. The spherulites were characterized with respect to entrapment efficiency, size, structure, and release kinetics, and the morphology was examined via cryo-EM. Finally, SV119-decorated spherulites were examined for their selective uptake by cancer cells. Results The spherulites are 170 ~ 290 nm in size. A loading efficiency of 55 ~ 60% can be consistently achieved for both calcein and albumin under optimized conditions. Cryo-EM shows the onion-like morphology consistent with the structure of multilamellar liposomes. A t1/2 of 39.3 h and 69.7 h in cargo release in serum was observed before and after PEG decoration, and incorporation of SV119 led to selective delivery of rhodamine-labeled spherulites to PC-3 tumor cells. Conclusions Our optimized formulations may represent a platform with simple preparation approach, relatively small particle size, high drug loading efficiency for both low and high molecular weight agents, and slow release kinetics for selective delivery of various types of therapeutics to target cells.

Cryo-EM sample preparation method for extremely low concentration liposomes

“…It is critical to accurately characterize liposomes and drug-liposome interactions as biophysical properties of liposomes are known to influence biological activity, biodistribution, and toxicity. Among the available techniques (Dynamic Light Scattering (DLS), Size Exclusion Chromatography (SEC), Atomic Force Microscopy (AFM), and cryo-EM), cryo-EM is the most precise and direct method to determine liposome lamellarity, size, shape and ultrastructure, which may reveal clues to mechanism of action toward the clinical endpoints of efficacy and toxicity [32][33][34][35][36][37][38][39][40][41].…”

Cryo-EM sample preparation method for extremely low concentration liposomes

“…It is critical to accurately characterize liposomes and drug-liposome interactions as biophysical properties of liposomes are known to influence biological activity, biodistribution, and toxicity. Among the available techniques (Dynamic Light Scattering (DLS), Size Exclusion Chromatography (SEC), Atomic Force Microscopy (AFM), and cryo-EM), cryo-EM is the most precise and direct method to determine liposome lamellarity, size, shape and ultrastructure, which may reveal clues to mechanism of action toward the clinical endpoints of efficacy and toxicity (Aissaoui et al, 2011;Al-Ahmady et al, 2016;Baxa, 2018;Bonnaud et al, 2013;Crawford et al, 2011;De Carlo et al, 2004;Lepault et al, 1985;Uhl et al, 2017;Uhl et al, 2016;Zhang et al, 2013).…”

Engineering Lipid Spherulites for the Sustained Release of Highly Dosed Small Hydrophilic Compounds

“…[20] They are considered a special class of liposomes characterized by a closely packed and well-organized onion-like structure, where concentric lipid bilayers alternate with continuous aqueous compartments. [21,22] Spherulites possess the advantages of conventional liposomes (e.g., safety) while overcoming drawbacks related to the use of organic solvents or heat, and allowing a higher loading efficiency (LE). [22] So far, several drug-delivery applications employing the spherulite technology have been described, covering a wide range of molecules (low MW organic molecules, proteins and DNA) and functions (oral delivery, drug detoxification, immune stimulation and imaging).…”