Efficient production of uniform nanometer‐sized polymer vesicles in stirred‐tank reactors

Engineering in Life Sciences

2016

Self Cite

Polymersomes have some fundamental advantages compared to their liposomal counterparts. Due to the increased stability of the polymeric membrane, polymersomes are intended to be reasonably applicable as carrier‐systems and universal reaction compartments for diverse medical and biotechnological applications. Regardless of the application area, suitable methods to produce large vesicle quantities in a controlled and cost‐effective manner have to be developed to put polymersome technology into action at the industrial scale. In this work, the amphiphilic triblock copolymer poly(2‐methyloxazoline)15‐poly(dimethylsiloxane)68‐poly(2‐methyloxazoline)15 was formed into uniform polymersomes. A recently established production process, based on the use of miniaturized stirred‐tank reactors at the milliliter‐scale (12 mL), was successfully scaled‐up to the liter‐scale (1.5 L) based on solid process engineering parameters. Dynamic light scattering measurements show that using standard propeller stirrers with a dimensionless diameter dD−1≥0.65 in an unbaffled stirred‐tank reactor led to a narrow particle size distribution when providing a Froude number of Fr= 6.52 at the same time. Polymersomes with a mean diameter of 180 nm and a low polydispersity index (PDI<0.2) were generated within about 1 h in one single production step. Thus, this work provides the fundamental basis for further scale‐up purposes, regarding polymersome production in stirred‐tank reactors at the industrial scale.

“…S1 in Table , and Supporting Information Table S1), fixed at the stirrer shaft on top of each other (

h_{s, 1}

= 0.06 m,

h_{s, 2}

= 0.12 m,

h_{s, 3}

Section: Resultsmentioning

confidence: 99%

“…A constant volumetric power input

P V^{- 1}

Section: Resultsmentioning

confidence: 99%

P V^{- 1}

= 12.3 W/L was investigated in a baffled reactor at first.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

d D^{- 1}

= 0.72,

h H^{- 1}

= 0.64 and

h d^{- 1}

= 1.9 the S‐stirrer has a very special geometry that is far away from most standardized stirrer geometries.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Polymersomes for biotechnological applications: Large‐scale production of nano‐scale vesicles

Poschenrieder

Schiebel

Engineering in Life Sciences

2016

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Polymersome formation mechanism and formation rate in stirred‐tank reactors

Poschenrieder

Hanzlik

J of Applied Polymer Sci

2017

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Uniform polymersomes (polymer vesicles) made of poly(2-methyloxazoline) 15 -b-poly(dimethylsiloxane) 68 -b-poly(2-methyloxazoline) 15 (PMOXA15-PDMS68-PMOXA15) can be formed in miniaturized-stirred tank reactors by the aid of a recently published process. In this study, the occurring self-assembly mechanism was elucidated by using transmission electron microscopy. Subsequent to the initial formation of small spherical micelles and the following fusion to worm-like micelles, two simultaneously occurring pathways, describing the transformation of further intermediate structures to the desired vesicles, were found. The resulting particle increase was followed by dynamic light scattering. Thus, the vesicle formation rate was judged by the linear increase of the particle diameter over time. While temperature showed no influence, higher initial polymer concentrations and lower final solvent concentrations accelerated the polymersome formation. Besides, the process was crucially dependent on the agitation speed. While spherical micelles did not transform into polymersomes when no stirring or too slow stirring is applied, the self-assembly process was accelerated by increasing the agitation speed. Uniform polymeric vesicles can be formed under vigorous stirring in stirred-tank reactors in short process times. In this study, the underlying mechanisms of vesicle formation were elucidated, showing that the polymer forms small micellar structures before undergoing two separate pathways to form the desired vesicular structures. The formation rate of the polymer vesicles was mainly dependent on the agitation speed but also on the polymer and solvent concentrations, highlighting the need for controlled formation conditions.

Polymersomes as Nanoreactors Enabling the Application of Solvent‐Sensitive Enzymes in Different Biphasic Reaction Setups

Golombek

2020

Biotechnology Journal

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There is an increasing interest in biocatalysis to perform chemical reactions in biphasic systems, consisting of an aqueous phase and a water‐immiscible organic solvent or ionic liquid. In most cases, the hydrophobic phase is used as reservoir for poorly water‐soluble substrates or for in situ product removal. However, many enzymes are solvent‐sensitive and cannot be used in such systems. In this study, the solvent‐sensitive enzyme mandelate racemase is exemplarily protected from the organic phase by its entrapment in (crosslinked) polymersomes. The covalent crosslinking of the individual chains of the block copolymer poly(2‐methyloxazoline)15‐poly(dimethylsiloxane)68‐poly(2‐methyloxazoline)15 via terminal methacrylates leads to enhanced membrane stability. This effect is especially pronounced for long‐time incubation in the presence of organic solvents and ionic liquids. By using a gentle polymerization initiator at its minimal necessary concentration, the prior encapsulated enzymes remain intact during crosslinking. Although the insertion of natural channel proteins into the membrane improves the mass transport into the vesicles, it is non‐essential. Mandelate racemase in (crosslinked) polymersomes remains active in different highly dispersed biphasic systems for more than 24 h. The free enzyme, on the other hand, gets completely inactivated within 1 h, thus illustrating the potential of polymersomes as nanoreactors in biphasic reaction setups.