The Impact of Solvent Selection: Strategies to Guide the Manufacturing of Liposomes Using Microfluidics (original) (raw)
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A facile microfluidic method for production of liposomes
Anticancer research
Ethanol injection is widely used in liposome preparation. However, the parameters determining particle size distribution of the liposomal preparation has not been fully defined. A syringe pump-driven microfluidic injection device was used to produce liposomes under different conditions. Particle size of the liposomes was decreased with decrease in needle diameter (or increase in hydrodynamic pressure), decrease in lipid concentration in the alcohol solution, decrease in phase transition temperature (T(m)) of the lipid bilayer and the absence of cholesterol (or decrease in, membrane rigidity). The device used is simple to adopt and can be used for affordable production of liposomes with tunable particle size.
International journal of pharmaceutics, 2016
Despite the substantial body of research investigating the use of liposomes, niosomes and other bilayer vesicles for drug delivery, the translation of these systems into licensed products remains limited. Indeed, recent shortages in the supply of liposomal products demonstrate the need for new scalable production methods for liposomes. Therefore, the aim of our research has been to consider the application of microfluidics in the manufacture of liposomes containing either or both a water soluble and a lipid soluble drug to promote co-delivery of drugs. For the first time, we demonstrate the entrapment of a hydrophilic and a lipophilic drug (metformin and glipizide respectively) both individually, and in combination, using a scalable microfluidics manufacturing system. In terms of the operating parameters, the choice of solvents, lipid concentration and aqueous:solvent ratio all impact on liposome size with vesicle diameter ranging from ∼90 to 300nm. In terms of drug loading, microfl...
Synthesis of Nanoscale Liposomes via Low-Cost Microfluidic Systems
Micromachines
We describe the manufacture of low-cost microfluidic systems to produce nanoscale liposomes with highly uniform size distributions (i.e., low polydispersity indexes (PDI)) and acceptable colloidal stability. This was achieved by exploiting a Y-junction device followed by a serpentine micromixer geometry to facilitate the diffusion between the mixing phases (i.e., continuous and dispersed) via advective processes. Two different geometries were studied. In the first one, the microchannels were engraved with a laser cutting machine on a polymethyl methacrylate (PMMA) sheet and covered with another PMMA sheet to form a two-layer device. In the second one, microchannels were not engraved but through-hole cut on a PMMA sheet and encased by a top and a bottom PMMA sheet to form a three-layer device. The devices were tested out by putting in contact lipids dissolved in alcohol as the dispersed phase and water as the continuous phase to self-assemble the liposomes. By fixing the total flow r...
Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach
Materials (Basel, Switzerland), 2017
Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs). Although modelling evidenced the depe...
Evaluation of a static mixer as a new microfluidic method for liposome formulation
Frontiers in Bioengineering and Biotechnology, 2023
Introduction: Microfluidic formulation of liposomes has been extensively studied as a potential replacement for batch methods, which struggle with problems in scalability and difficulty in modulating conditions. Although microfluidic devices are considered to be able to combat these issues, an adequate replacement method has yet to be established. Methods: This paper examines the potential of a static mixer (SM) by comparing the encapsulation efficiency, loading, lamellarity, and user-friendliness with a commonly used microfluidic device, a staggered herringbone micromixer (SHM). Results: In both devices, it was found that as the initial lipid concentration increased, the particle size increased; however, the overall particle size was seen to be significantly larger in the liposomes prepared with SM. PDI remained significantly smaller in SM, however, signifying that better control of the particle size was accomplished in SM. In addition, the encapsulation efficiency was slightly smaller in SM compared to SHM, and in both devices, the values increased as the initial lipid concentration increased. The increase in encapsulation efficiencies was significantly smaller than that of the theoretical encapsulation efficiency, and this was found to be due to the increase in lamellarity as the initial lipid concentration increased. Discussion: In terms of user-friendliness, SM demonstrated significant advantages. The mixing elements could be taken out from the device, allowing for thorough cleaning of the element and device before and after experiments and ensuring experiments are conducted at virgin state in every round. Consequently, it was found that SM not only can produce uniformly distributed liposomes but has the potential to become a more practical method for liposome formulation with modifications in the mixing elements.
2019
Giant Unilamellar Vesicles (GUVs) are a versatile tool in many branches of science, including biophysics and synthetic biology. Octanol-Assisted Liposome Assembly (OLA), a recently developed microfluidic technique enables the production and testing of GUVs within a single device under highly controlled experimental conditions. It is therefore gaining significant interest as a platform for use in drug discovery, the production of artificial cells and more generally for controlled studies of the properties of lipid membranes. In this work, we expand the capabilities of the OLA technique by forming GUVs of tunable binary lipid mixtures of DOPC, DOPG and DOPE. Using fluorescence recovery after photobleaching we investigated the lateral diffusion coefficients of lipids in OLA liposomes and found the expected values in the range of 1 μm2/s for the lipid systems tested. We studied the OLA derived GUVs under a range of conditions and compared the results with electroformed vesicles. Overall...
Microfluidic Production of Lysolipid-Containing Temperature-Sensitive Liposomes
Journal of Visualized Experiments, 2020
The protocol presents the optimized parameters for preparing thermosensitive liposomes using the staggered herringbone micromixer microfluidics device. This also allows co-encapsulation of doxorubicin and indocyanine green into the liposomes and the photothermal-triggered release of doxorubicin for controlled/triggered drug release. ABSTRACT The presented protocol enables a high-throughput continuous preparation of low temperaturesensitive liposomes (LTSLs), which are capable of loading chemotherapeutic drugs, such as doxorubicin (DOX). To achieve this, an ethanolic lipid mixture and ammonium sulfate solution are injected into a staggered herringbone micromixer (SHM) microfluidic device. The solutions are rapidly mixed by the SHM, providing a homogeneous solvent environment for liposomes selfassembly. Collected liposomes are first annealed, then dialyzed to remove residual ethanol. An ammonium sulfate pH-gradient is established through buffer exchange of the external solution by using size exclusion chromatography. DOX is then remotely loaded into the liposomes with high encapsulation efficiency (> 80%). The liposomes obtained are homogenous in size with Zaverage diameter of 100 nm. They are capable of temperature-triggered burst release of encapsulated DOX in the presence of mild hyperthermia (42 °C). Indocyanine green (ICG) can also be co-loaded into the liposomes for near-infrared laser-triggered DOX release. The microfluidic approach ensures high-throughput, reproducible and scalable preparation of LTSLs. INTRODUCTION LTSL formulation is a clinically relevant liposomal product that has been developed to deliver the chemotherapeutic drug doxorubicin (DOX) and allows efficient burst drug release at clinically
Influence of micro-mixing on the size of liposomes self-assembled from miscible liquid phases
Chemistry and Physics of Lipids, 2013
Ethanol injection and variations of it are a class of methods where two miscible phases-one of which contains dissolved lipidsare mixed together leading to the self-assembly of lipid molecules to form liposomes. This method has been suggested, among other applications, for in-situ synthesis of liposomes as drug delivery capsules. However, the mechanism that leads to a specific size selection of the liposomes in solution based self-assembly in general, and in flow-focussing microfluidic devices in particular, has so far not been established. Here we report two aspects of this problem. A simple and easily fabricated device for synthesis of monodisperse unilamellar liposomes in a co-axial flow-focussing microfluidic geometry is presented. We also show that the size of liposomes is dependent on the extent of micro-convective mixing of the two miscible phases. Here, a viscosity stratification induced hydrodynamic instability leads to a gentle micro-mixing which results in larger liposome size than when the streams are mixed turbulently. The results are in sharp contrast to a purely diffusive mixing in macroscopic laminar flow that was believed to occur under these conditions. Further precise quantification of the mixing characteristics should provide the insights to develop a general theory for size selection for the class of ethanol injection methods. This will also lay grounds for obtaining empirical evidence that will enable better control of liposome sizes and for designing drug encapsulation and delivery devices.