Effect of Formulation Method, Lipid Composition, and PEGylation on Vesicle Lamellarity: A Small-Angle Neutron Scattering Study

Nele, Valeria; Holme, Margaret N.; Kauscher, Ulrike; Thomas, Michael R.; Doutch, James; Stevens, Molly M.

doi:10.1021/acs.langmuir.8b04256

Cited by 80 publications

(87 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly, any factor that lowers the bilayer adhesion energy, such as increasing interlamellar repulsion with charged lipids (12), also favors separation of layers and should therefore increase the fraction of unilamellar vesicles after extrusion. It is likely that bending energy also contributes to an increased probability of unilamellar vesicles upon hydration (i.e., prior to extrusion), as recently proposed (13). Indeed, we found that the lipid with the largest bending modulus (ESM) had the greatest fraction of unilamellar vesicles both before and after extrusion (Table S2).…”

Section: Statement Of Significancesupporting

confidence: 80%

“…The presence of multilamellar structures in extruded vesicles has been sporadically reported in the literature, often evidenced by their clear experimental signature in scattering studies (9,13,21). Some factors that can potentially influence multilamellarity are the number of freeze-thaw cycles (22), membrane lipid composition (9), and modification of lipid headgroups, for example by PEG polymers (13,(22)(23)(24).…”

Section: Statement Of Significancementioning

confidence: 93%

See 1 more Smart Citation

On the mechanism of bilayer separation by extrusion; or, why your large unilamellar vesicles are not really unilamellar

Scott

Skinkle

Kelley

et al. 2019

Preprint

View full text Add to dashboard Cite

Extrusion through porous filters is a widely used method for preparing biomimetic model membranes. Of primary importance in this approach is the efficient production of single bilayer (unilamellar) vesicles that eliminate the influence of interlamellar interactions and strictly define the bilayer surface area available to external reagents such as proteins. Sub-microscopic vesicles produced using extrusion are widely assumed to be unilamellar, and large deviations from this assumption would dramatically impact interpretations from many model membrane experiments. Using three probe-free methods—small-angle X-ray and neutron scattering (SAXS and SANS) and cryogenic electron microscopy (cryoEM)—we report unambiguous evidence of extensive multilamellarity in extruded vesicles composed of neutral phosphatidylcholine lipids, including for the common case of neutral lipids dispersed in physiological buffer and extruded through 100 nm diameter pores. In such preparations, only ~35% of lipids are externally accessible, and this fraction is highly dependent on preparation conditions. Charged lipids promote unilamellarity, as does decreasing solvent ionic strength, indicating the importance of electrostatic interactions in determining the lamellarity of extruded vesicles. Smaller extrusion pore sizes also robustly increase the fraction of unilamellar vesicles, suggesting a role for membrane bending. Taken together, these observations suggest a mechanistic model for extrusion, wherein formation of unilamellar vesicles involves competition between bilayer bending and adhesion energies. The findings presented here have wide-ranging implications for the design and interpretation of model membrane studies, especially ensemble-averaged observations relying on the assumption of unilamellarity.STATEMENT OF SIGNIFICANCEExtruded vesicles are a ubiquitous tool in membrane research. It is widely presumed that extrusion produces unilamellar (i.e., single bilayer) vesicles, an assumption that is often crucial for data analysis and interpretation. Using X-ray and neutron scattering and cryogenic electron microscopy, we show that a substantial amount of lipid remains inaccessible after extrusion due to an abundance of multilamellar vesicles (MLVs). While this is a general phenomenon for neutral lipids, MLV contamination can be reduced by several complementary approaches such as including charged lipids in the mixture, reducing the ionic strength of the aqueous medium, and reducing the extrusion pore size. These observations together suggest a mechanism by which extrusion strips MLVs of their layers.

show abstract

Section: Statement Of Significancesupporting

confidence: 80%

Section: Statement Of Significancementioning

confidence: 93%

On the mechanism of bilayer separation by extrusion; or, why your large unilamellar vesicles are not really unilamellar

Scott

Skinkle

Kelley

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Earlier investigations of liposome production by millifluidics have predominately focused on a limited number of model lipid formulations. Since liposomes’ properties are very often dependent upon their lipid compositions [ 61 ], a further verification of the reactor’s performance was carried out by producing liposomes of different formulations comprising PC, DPPC, Chol, ODA, and PEG-40. PC (soybean) is one of the most common lipids used in liposomal formulations due to its abundance in animals and plants, and DPPC is often used in thermosensitive formulations and is often a key constituent in membrane models [ 62 ].…”

Section: Resultsmentioning

confidence: 99%

Continuous-Flow Production of Liposomes with a Millireactor under Varying Fluidic Conditions

et al. 2020

View full text Add to dashboard Cite

Continuous-flow production of liposomes using microfluidic reactors has demonstrated advantages compared to batch methods, including greater control over liposome size and size distribution and reduced reliance on post-production processing steps. However, the use of microfluidic technology for the production of nanoscale vesicular systems (such as liposomes) has not been fully translated to industrial scale yet. This may be due to limitations of microfluidic-based reactors, such as low production rates, limited lifetimes, and high manufacturing costs. In this study, we investigated the potential of millimeter-scale flow reactors (or millireactors) with a serpentine-like architecture, as a scalable and cost-effective route to the production of nanoscale liposomes. The effects on liposome size of varying inlet flow rates, lipid type and concentration, storage conditions, and temperature were investigated. Liposome size (i.e., mean diameter) and size dispersity were characterised by dynamic light scattering (DLS); z-potential measurements and TEM imaging were also carried out on selected liposome batches. It was found that the lipid type and concentration, together with the inlet flow settings, had significant effects on the properties of the resultant liposome dispersion. Notably, the millifluidic reactor was able to generate liposomes with size and dispersity ranging from 54 to 272 nm, and from 0.04 to 0.52 respectively, at operating flow rates between 1 and 10 mL/min. Moreover, when compared to a batch ethanol-injection method, the millireactor generated liposomes with a more therapeutically relevant size and size dispersity.

show abstract

“…In order to t the SANS data for PEGMA x -b-BuMA y -b-DEGMA z above the T degel , we used a BroadPeak model, which provided the best-t position of the Bragg peak. 60 This model is a combination of a Lorentzian-peak function and a power law decay and could suggest the presence of a bicontinuous structure 61 above the T degel . As is seen in Fig.…”

Section: Rheological Properties and Self-assembly Behaviourmentioning

confidence: 97%

Novel thermoresponsive polymer outperforming Pluronic® F127

Constantinou¹,

Nele²,

Doutch³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Thermoresponsive polymers featuring the appropriate combination of structural characteristics, i.e. architecture, composition, and molar mass (MM), can form physically crosslinked networks in a solvent upon changes in temperature. This fascinating class of polymers finds utility in various sectors such as formulation science and tissue engineering. Here, we report a novel thermoresponsive triblock terpolymer which out-performs the most commonly used and commercially available thermoresponsive polymer, Poloxamer P407 (also known as Pluronic® F127) in terms of gelation concentration. Specifically, the in-house synthesised polymer forms gels at lower concentrations that is an advantage in biomedical applications. To elucidate the differences in their macroscale gelling behaviour, we investigate their micellization via differential scanning calorimetry, and their nanoscale self-assembly behaviour in detail by means of small-angle neutron scattering by simultaneously recording their rheological properties (Rheo-SANS). Two different gelation mechanisms for the two polymers are revealed and proposed. Ex vivo gelation study upon intracameral injections demonstrated excellent potential for its application to improve drug residence in the eye.

show abstract

Effect of Formulation Method, Lipid Composition, and PEGylation on Vesicle Lamellarity: A Small-Angle Neutron Scattering Study

Cited by 80 publications

References 39 publications

On the mechanism of bilayer separation by extrusion; or, why your large unilamellar vesicles are not really unilamellar

On the mechanism of bilayer separation by extrusion; or, why your large unilamellar vesicles are not really unilamellar

Continuous-Flow Production of Liposomes with a Millireactor under Varying Fluidic Conditions

Novel thermoresponsive polymer outperforming Pluronic® F127

Contact Info

Product

Resources

About