Integrating microfluidics and streamlined remote drug loading: one step closer to continuous manufacturing of liposomal injectables containing small drugs

Abstract

The industrial manufacturing of liposomal injectables faces significant technical challenges. Traditional batch manufacturing methods, like ethanol injection and extrusion, are time-consuming, prompting a shift towards continuous manufacturing. To improve process efficiency, this study tested microfluidics, a technique widely used in lipid nanoparticle (LNP) production for nucleic acid delivery, to optimize doxorubicin liposome manufacturing, focusing on vesicle formation and remote drug loading. The formulation consisted of neutral phospholipids with minimal DSPE-PEG content and no negatively charged lipids, components typically considered critical for liposome self-assembly and colloidal stability, demonstrating that microfluidics can effectively produce stable liposomes under these challenging conditions. Detailed characterization by cryo-TEM confirmed the formation of unilamellar vesicles with internal drug nanocrystals by microfluidics. In addition, it yielded fewer multilamellar liposomes than the conventional process (18 % vs. 35 %), indicating better control of vesicle structure and lamellarity. Importantly, employing microfluidics instead of ethanol injection and extrusion reduced liposome formation time by 70 % while ensuring consistent particle size distribution, relative to ethanol injection and extrusion. Additionally, lowering the temperature during drug loading (45 °C vs. 65 °C) shortened this step by 20 %, due to faster heating and cooling. Consequently, the optimized process was at least 25 % faster and reduced cost by 15 %. Although conducted at a 100 mL scale, these improvements are expected to be amplified on an industrial scale. Hence, these findings highlight the relevance of decreasing process temperatures and underscore the potential of microfluidics to enhance the efficiency and scalability of continuous manufacturing of liposomes for small molecular weight drug delivery, a field in which this technology has been underexplored.