Microfluidics: A Tool to Control the Size and Composition of Particles

Amstad, Esther

doi:10.2533/chimia.2017.334

Cited by 14 publications

(12 citation statements)

References 56 publications

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“…Glass capillaries have been widely used for production of different types of capsules, [32,36,37] including GUVs with ultra thin shells, [38,39] but the device production and operation are quite challenging: If capillaries are misaligned or not well sanded, instabilities can occur and double emulsions might not be produced because of uncontrolled encounter of the fluids. [40] Reproducible fabrication of microfluidic devices is more easily achieved if they are made from masks and molds, which is predominantly the case when soft lithography is employed to fabricate microchips made from PDMS. [41] However, despite rapid prototyping and easy replication, there are difficulties in modifying the chemical properties of PDMS surfaces to tune their wettability toward different fluids.…”

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confidence: 99%

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell‐Sized Compartments

et al. 2020

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optimize these pathways and thus to guarantee their maximum chance of survival, cells produce enzymes at precise and constant rates. [4] However, because of cellular complexity, determination of optimal enzyme levels is still unclear, in particular because specific enzymatic functions are strongly interconnected with their cascade effects. [5] A smart manner to study the behavior of enzymes, when involved in complex reactions, consists of taking advantage of synthetic micrometer-sized compartments shaped into spherical architectural bodies. [6-8] Though these idealized models favor even partitioning of membrane proteins and simplify diffusion gradients, similarly to cells, they provide the desired membrane selectivity and permeability. [9,10] Single specific functions have been presented by combining enzymes (the catalytic compounds) with synthetic supramolecular assemblies, either intrinsically semipermeable, such as lipid-coated porous silica particles, [11] protein cages, [12] layer-by-layer capsules, [13-15] and polydopamine capsules, [16,17] or rendered permeable by the insertion of biopores/membrane proteins (acting as "gates" for the passage of molecules), as in lipid-based [7,18,19] or polymer-based [8,20-22] giant unilamellar vesicles (GUVs). At present, GUVs formed with amphiphilic block copolymers are particularly appealing because they provide enhanced structural membrane properties compared to lipids, since they possess compartments with higher chemical versatility, controlled permeability, robustness, and stability. [23] Nevertheless, common approaches to form polymer GUVs by self-assembly, as electroformation [24] and film-rehydration, [25] rely on the statistical process of encapsulation of biomolecules with a probability of finding the designed amount of one type of enzyme inside the compartments ranging from 12-57%. In the context of elementary biochemical pathways where at least two enzymes are present, this scenario is even more unsatisfactory, with co-encapsulation of two enzymes inside one compartment as low as 10-22%. [26,27] These shortcomings are worsened by the fact that these probabilities have a large uncertainty induced by specific properties of enzymes (e.g., solubility and stability). To date, scientists have struggled to work with stateof-the-art average values for number/mass of enzymes that are vastly non-representative (limited by a small sample size) Cells rely upon producing enzymes at precise rates and stoichiometry for maximizing functionalities. The reasons for this optimal control are unknown, primarily because of the interconnectivity of the enzymatic cascade effects within multi-step pathways. Here, an elegant strategy for studying such behavior, by controlling segregation/combination of enzymes/ metabolites in synthetic cell-sized compartments, while preserving vital cellular elements is presented. Therefore, compartments shaped into polymer GUVs are developed, producing via high-precision double-emulsion microfluidics that enable: i) tight control over the absolute and...

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Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell‐Sized Compartments

et al. 2020

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“…These parameters can be tuned with the composition and dimensions of the capsule shells. The degree of control over these parameters depends on the fabrication route of capsules . Capsules are commonly fabricated from templates by sequentially depositing reagents on their surface, and from emulsion drops by solidifying reagents contained in their shells .…”

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Bioinspired Viscoelastic Capsules: Delivery Vehicles and Beyond

2019

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range of rheological properties of capsulecontaining solutions that can be accessed; the formulation of capsule-based solutions displaying a pronounced shear thinning or a yield stress would be key to use them as 3D printable inks. Capsules with much thinner, flexible shells whose structure and surface composition can be varied over a wide range can be fabricated from emulsion drops by solidifying reagents at their surface. This can be achieved, if appropriate reagents are dispersed in the drop and complementary ones in the continuous phase. Once these reagents meet at the drop surface, they solidify through polymerization [21][22][23] or coacervation reactions. [24][25][26][27] Capsules with thin shells can also be produced from a single type of reagent, namely from chemically reactive surfactants, that are cross-linked at the drop surface. [28][29][30][31][32] However, the number of reagents that can be employed to form thin polymeric capsules through these approaches is limited. Flexible capsules that display a narrow size distribution, low permeability toward encapsulants, allow controlled exchanges of reagents, and are mechanically sufficiently stable to withstand significant shear stresses such that they can be processed into macroscopic materials through additive manufacturing techniques remain to be established. These capsules would open up a new field of their use as principal building blocks of macroscopic granular materials with well-defined micrometer-sized structures and locally varying compositions that go far beyond their current use as individually dispersed delivery vehicles.Here, we introduce a new type of viscoelastic, mechanically stable capsules that are composed of bioinspired ionically crosslinked catechol-functionalized block-copolymer surfactants. These capsules present Fe 3+ complexed catechols at their surface such that they have a high affinity to each other. Therefore, they cannot only be used as individually dispersed mobile carrier vehicles that enable triggered release of reagents, but also as principal building blocks of macroscopic soft materials. We demonstrate for the first time that these capsules are mechanically sufficiently stable to serve as principal building blocks of inks that can be 3D printed into macroscopic granular materials with well-defined micrometer-length-scale structures.Emulsion drops are often stabilized with polymeric surfactants that are crucial during drop production and storage. However, once the drops are converted into capsules, surfactants are usually superfluous or even devastating because they irreproducibly change the surface wettability of the Microcapsules are often used as individually dispersed carriers of active ingredients to prolong their shelf life or to protect premature reactions with substances contained in the surrounding. This study goes beyond this application and employs microcapsules as principal building blocks of macroscopic 3D materials with well-defined granular structures. To achieve this goal and inspired by nature, capsules ...

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“…To provide examples of achievable propulsion velocities for symmetric and asymmetric Janus capsules we chose a realistic capsule size of about 10 μm and a stiffness of 8 10 N m 4 1 --, which fits the values of common capsules [25,43,44]. A higher mass density for capsules than for the liquid can be achieved if salt is dissolved in the liquid inside the capsule [45], whereby water with dissolved salt can reach densities up to three times higher than pure water (without salt).…”

Section: Discussionmentioning

confidence: 99%

Engineering passive swimmers by shaking liquids

et al. 2019

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The locomotion and design of microswimmers are topical issues of current fundamental and applied research. In addition to numerous living and artificial active microswimmers, a passive microswimmer was identified only recently: a soft, Λ-shaped, non-buoyant particle propagates in a shaken liquid of zero-mean velocity (Jo et al 2016 Phys. Rev. E 94 063116). We show that this novel passive locomotion mechanism works for realistic non-buoyant, asymmetric Janus microcapsules as well. According to our analytical approximation, this locomotion requires a symmetry breaking caused by different Stokes drags of soft particles during the two half periods of the oscillatory liquid motion. It is the intrinsic anisotropy of Janus capsules and Λ-shaped particles that break this symmetry for sinusoidal liquid motion. Further, we show that this passive locomotion mechanism also works for the wider class of symmetric soft particles, e.g. capsules, by breaking the symmetry via an appropriate liquid shaking. The swimming direction can be uniquely selected by a suitable choice of the liquid motion. Numerical studies, including lattice Boltzmann simulations, also show that this locomotion can outweigh gravity, i.e. non-buoyant particles may be either elevated in shaken liquids or concentrated at the bottom of a container. This novel propulsion mechanism is relevant to many applications, including the sorting of soft particles like healthy and malignant (cancer) cells, which serves medical purposes, or the use of non-buoyant soft particles as directed microswimmers.

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Microfluidics: A Tool to Control the Size and Composition of Particles

Cited by 14 publications

References 56 publications

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell‐Sized Compartments

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell‐Sized Compartments

Bioinspired Viscoelastic Capsules: Delivery Vehicles and Beyond

Engineering passive swimmers by shaking liquids

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