Microfluidic Fabrication of Click Chemistry-Mediated Hyaluronic Acid Microgels: A Bottom-Up Material Guide to Tailor a Microgel’s Physicochemical and Mechanical Properties

Heida, Thomas; Otto, Oliver; Biedenweg, Doreen; Hauck, Nicolas; Thiele, Julian

doi:10.3390/polym12081760

Cited by 17 publications

(31 citation statements)

References 78 publications

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“…In the following, we summarize conventional strategies for determining the mechanical properties of aqueous microgels. This includes techniques such as micropipette aspiration [ 11 , 12 ], optical tweezer and stretcher [ 13 ], atomic force microscopy [ 14 , 15 , 16 ], and, more recently, microfluidic-based approaches to provide distribution of the mechanical properties [ 17 , 18 , 19 ], and also Brillouin scattering based imaging [ 20 ]. Schematic presentations of some of these strategies are shown in Figure 1 .…”

Section: Introductionmentioning

confidence: 99%

On the Determination of Mechanical Properties of Aqueous Microgels—Towards High-Throughput Characterization

Oevreeide

Szydlak

Luty

et al. 2021

Gels

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Aqueous microgels are distinct entities of soft matter with mechanical signatures that can be different from their macroscopic counterparts due to confinement effects in the preparation, inherently made to consist of more than one domain (Janus particles) or further processing by coating and change in the extent of crosslinking of the core. Motivated by the importance of the mechanical properties of such microgels from a fundamental point, but also related to numerous applications, we provide a perspective on the experimental strategies currently available and emerging tools being explored. Albeit all techniques in principle exploit enforcing stress and observing strain, the realization differs from directly, as, e.g., by atomic force microscope, to less evident in a fluid field combined with imaging by a high-speed camera in high-throughput strategies. Moreover, the accompanying analysis strategies also reflect such differences, and the level of detail that would be preferred for a comprehensive understanding of the microgel mechanical properties are not always implemented. Overall, the perspective is that current technologies have the capacity to provide detailed, nanoscopic mechanical characterization of microgels over an extended size range, to the high-throughput approaches providing distributions over the mechanical signatures, a feature not readily accessible by atomic force microscopy and micropipette aspiration.

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Section: Introductionmentioning

confidence: 99%

On the Determination of Mechanical Properties of Aqueous Microgels—Towards High-Throughput Characterization

Oevreeide

Szydlak

Luty

et al. 2021

Gels

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show abstract

“…As shown by others [60][61][62], in situ gelling of droplets with dimensions beyond the height and/or width of a microfluidic channel can be utilized to form non-spherical microgels, such as disks, rods and threads.…”

Section: Merging Of Polymer and Crosslinker Droplets Or Injection Of Continuous Stream Of Crosslinking Solution Into Polymer Dropletsmentioning

confidence: 99%

“…Spherical beads are formed if the droplet volume, , is smaller than ℎ 3 /6, where ℎ is the channel height which is smaller than the channel width. Non-spherical beads are generated from confined droplets [61]. Plugs (rods) and threads are formed from droplets, which are confined in two directions and have the roundness, (= 4 / 2 ) greater than unity, where is the projected surface area of the beads and is the projected bead perimeter [63].…”

Section: Merging Of Polymer and Crosslinker Droplets Or Injection Of Continuous Stream Of Crosslinking Solution Into Polymer Dropletsmentioning

confidence: 99%

Crosslinking Strategies for Microfluidic Production of Microgels

Chen¹,

Bolognesi²,

Vladisavljević³

2021

Preprint

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This article provides a systematic review of the crosslinking strategies used to produce microgel particles in microfluidic chips. Various ionic crosslinking methods for gelation of charged pol-ymers are discussed, including external gelation via crosslinkers dissolved or dispersed in the oil phase, internal gelation methods using crosslinkers added to the dispersed phase in their non-active forms, such as chelating agents, photo-acid generators, sparingly soluble or slowly hydrolyzing compounds, and methods involving competitive ligand exchange, rapid mixing of polymer and crosslinking streams, and merging polymer and crosslinker droplets. Covalent crosslinking methods using enzymatic oxidation of modified biopolymers, photo-polymerization of crosslinkable monomers or polymers, and thiol-ene “click” reactions are also discussed, as well as the methods based on sol-gel transitions of stimuli responsive polymers triggered by pH or temperature change. In addition to homogeneous microgel particles, the production of structurally heterogeneous particles such as composite hydrogel particles entrapping droplet interface bi-layers, core-shell particles, organoids, and Janus particles are also discussed. Microfluidics offers the ability to precisely tune chemical composition, size, shape, surface morphology, and internal structure of microgels by bringing in contact multiple fluid streams in a highly controlled fashion using versatile channel geometries and flow configurations and allowing controlled crosslinking.

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“…As shown by others [ 65 , 66 , 67 ], in situ gelling of droplets whose dimensions are beyond the height and/or width of a microfluidic channel can be utilized to form non-spherical microgels, such as disks, rods, and threads.…”

Section: Microfluidic Production Of Spherical Matrix-type Microgelsmentioning

confidence: 99%

“…Spherical beads are formed if the droplet volume,

, is smaller than

, where

is the channel height, which is smaller than the channel width. Non-spherical beads are generated from confined droplets [ 66 ]. Plugs (rods) and threads are formed from droplets, which are confined in two directions and have a roundness,

greater than unity, where

is the projected surface area of the beads and

is the projected bead perimeter [ 68 ].…”

Section: Microfluidic Production Of Spherical Matrix-type Microgelsmentioning

confidence: 99%

Crosslinking Strategies for the Microfluidic Production of Microgels

2021

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This article provides a systematic review of the crosslinking strategies used to produce microgel particles in microfluidic chips. Various ionic crosslinking methods for the gelation of charged polymers are discussed, including external gelation via crosslinkers dissolved or dispersed in the oil phase; internal gelation methods using crosslinkers added to the dispersed phase in their non-active forms, such as chelating agents, photo-acid generators, sparingly soluble or slowly hydrolyzing compounds, and methods involving competitive ligand exchange; rapid mixing of polymer and crosslinking streams; and merging polymer and crosslinker droplets. Covalent crosslinking methods using enzymatic oxidation of modified biopolymers, photo-polymerization of crosslinkable monomers or polymers, and thiol-ene “click” reactions are also discussed, as well as methods based on the sol−gel transitions of stimuli responsive polymers triggered by pH or temperature change. In addition to homogeneous microgel particles, the production of structurally heterogeneous particles such as composite hydrogel particles entrapping droplet interface bilayers, core−shell particles, organoids, and Janus particles are also discussed. Microfluidics offers the ability to precisely tune the chemical composition, size, shape, surface morphology, and internal structure of microgels by bringing multiple fluid streams in contact in a highly controlled fashion using versatile channel geometries and flow configurations, and allowing for controlled crosslinking.

show abstract

Microfluidic Fabrication of Click Chemistry-Mediated Hyaluronic Acid Microgels: A Bottom-Up Material Guide to Tailor a Microgel’s Physicochemical and Mechanical Properties

Cited by 17 publications

References 78 publications

On the Determination of Mechanical Properties of Aqueous Microgels—Towards High-Throughput Characterization

On the Determination of Mechanical Properties of Aqueous Microgels—Towards High-Throughput Characterization

Crosslinking Strategies for Microfluidic Production of Microgels

Crosslinking Strategies for the Microfluidic Production of Microgels

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