On-chip background dilution in droplets with high particle recovery using acoustophoresis

Liu, Zhenhua; Fornell, Anna; Barbe, Laurent; Hjort, Klas

doi:10.1063/1.5129256

Cited by 8 publications

(6 citation statements)

References 26 publications

(22 reference statements)

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“…In this work we selected to use mineral oil as the continuous phase, since it has similar acoustic properties 33 as the dispersed phase. Mineral oil has previously been used in several studies to generate droplets with cells encapsulated 34 – 36 .…”

Section: Introductionmentioning

confidence: 99%

Acoustic focusing of beads and cells in hydrogel droplets

Fornell

Pohlit

Shi

2021

Sci Rep

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The generation of hydrogel droplets using droplet microfluidics has emerged as a powerful tool with many applications in biology and medicine. Here, a microfluidic system to control the position of particles (beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves is presented. The chip consisted of a droplet generator and a 380 µm wide acoustic focusing channel. Droplets comprising hydrogel precursor solution (polyethylene glycol tetraacrylate or a combination of polyethylene glycol tetraacrylate and gelatine methacrylate), photoinitiator and particles were generated. The droplets passed along the acoustic focusing channel where a half wavelength acoustic standing wave field was generated, and the particles were focused to the centre line of the droplets (i.e. the pressure nodal line) by the acoustic force. The droplets were cross-linked by exposure to UV-light, freezing the particles in their positions. With the acoustics applied, 89 ± 19% of the particles (polystyrene beads, 10 µm diameter) were positioned in an area ± 10% from the centre line. As proof-of-principle for biological particles, astrocytes were focused in hydrogel droplets using the same principle. The viability of the astrocytes after 7 days in culture was 72 ± 22% when exposed to the acoustic focusing compared with 70 ± 19% for samples not exposed to the acoustic focusing. This technology provides a platform to control the spatial position of bioparticles in hydrogel droplets, and opens up for the generation of more complex biological hydrogel structures.

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Section: Introductionmentioning

confidence: 99%

Acoustic focusing of beads and cells in hydrogel droplets

Fornell

Pohlit

Shi

2021

Sci Rep

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“…Washing in droplet‐based microfluidics is limited to relying on continuous droplet splitting to dilute the unwanted reagents. [ 43,45,47–48 ] Here, we demonstrate an alternative that completely removes the liquid droplet inside that traps after co‐encapsulation while keeping the hybridoma cell with the target cells in the trap using electrostatic forces. In contrast to previous reports, [ 76–78 ] which use an emulsion destabilizer or a diluted surfactant (0.001% wt [ 77 ] ) in the oil phase, we individually disrupt droplets by electrostatic forces avoiding unwanted droplet coalescence and prevent any change in the medium/oil constituents that might adversely affect the viability or functionality of the cells.…”

Section: Resultsmentioning

confidence: 99%

“…Most work with droplet-based microfluidics has avoided incorporating these challenging steps due to the droplets being coated with surfactant which make it difficult to break. There are several techniques that have been implemented to address the challenge of solution exchange and washing in conventional droplet microfluidics, [9,[41][42][43][44] including the use of acoustophoretic, [45][46][47] magnetic, [48][49][50][51] dielectrophoretic (DEP) [43] force, electro-coalescence, [51][52][53] pico-washing, [54] and chemical demulsifiers like perfluorooctanol. [40,[55][56] However, chemical demulsifiers compromise cell viability [44,[52][53] and irreversibly impact the singularity of the isolated cells, and acoustic and magnetic methods suffer from limitations in device materials and sample types, respectively.…”

Section: Introductionmentioning

confidence: 99%

An Automated Single‐Cell Droplet‐Digital Microfluidic Platform for Monoclonal Antibody Discovery

Ahmadi,

Tran,

Letourneau

et al. 2024

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Monoclonal antibody (mAb) discovery plays a prominent role in diagnostic and therapeutic applications. Droplet microfluidics has become a standard technology for high‐throughput screening of antibody‐producing cells due to high droplet single‐cell confinement frequency and rapid analysis and sorting of the cells of interest with their secreted mAbs. In this work, a new method is described for on‐demand co‐encapsulation of cells that eliminates the difficulties associated with washing in between consecutive steps inside the droplets and enables the washing and addition of fresh media. The new platform identifies hybridoma cells that are expressing antibodies of interest using antibody‐characterization assays to find the best‐performing or rare‐cell antibody candidates.

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“…The channels were dry-etched on a silicon wafer following standard microfabrication processes as previously reported. 36 The chip was heated to 100 °C on a hot plate, and a low-temperature solder (No. 158, Indium Corporation) was injected in the electrode channels.…”

Section: Methodsmentioning

confidence: 99%

A droplet acoustofluidic platform for time-controlled microbead-based reactions

Liu

Fornell

2021

Biomicrofluidics

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Droplet microfluidics is a powerful method used to characterize chemical reactions at high throughput. Often detection is performed via in-line optical readout, which puts high demands on the detection system or makes detection of low concentration substrates challenging. Here, we have developed a droplet acoustofluidic chip for time-controlled reactions that can be combined with off-line optical readout. The principle of the platform is demonstrated by the enzymatic conversion of fluorescein diphosphate to fluorescein by alkaline phosphatase. The novelty of this work is that the time of the enzymatic reaction is controlled by physically removing the enzymes from the droplets instead of using chemical inhibitors. This is advantageous as inhibitors could potentially interact with the readout. Droplets containing substrate were generated on the chip, and enzyme-coupled microbeads were added into the droplets via pico-injection. The reaction starts as soon as the enzyme/bead complexes are added, and the reaction is stopped when the microbeads are removed from the droplets at a channel bifurcation. The encapsulated microbeads were focused in the droplets by acoustophoresis during the split, leaving the product in the side daughter droplet to be collected for the analysis (without beads). The time of the reaction was controlled by using different outlets, positioned at different lengths from the pico-injector. The enzymatic conversion could be measured with fluorescence readout in a separate PDMS based assay chip. We show the ability to perform time-controlled enzymatic assays in droplet microfluidics coupled to an off-line optical readout, without the need of enzyme inhibitors.

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On-chip background dilution in droplets with high particle recovery using acoustophoresis

Cited by 8 publications

References 26 publications

Acoustic focusing of beads and cells in hydrogel droplets

Acoustic focusing of beads and cells in hydrogel droplets

An Automated Single‐Cell Droplet‐Digital Microfluidic Platform for Monoclonal Antibody Discovery

A droplet acoustofluidic platform for time-controlled microbead-based reactions

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