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| 2. |
- Cantoni, Federico, et al.
(författare)
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A perfusable multi-hydrogel vasculature on-chip engineered by 2-photon 3D printing and scaffold molding to improve microfabrication fidelity in hydrogels
- 2024
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Ingår i: Advanced Materials Technologies. - : John Wiley & Sons. - 2365-709X. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Engineering vasculature networks in physiologically relevant hydrogelsrepresents a challenge in terms of both fabrication, due to the cell–bioinkinteractions, as well as the subsequent hydrogel-device interfacing. Here, anew cell-friendly fabrication strategy is presented to realize perfusablemulti-hydrogel vasculature models supporting co-culture integrated in amicrofluidic chip. The system comprises two different hydrogels to specificallysupport the growth and proliferation of two different cell types selected for thevessel model. First, the channels are printed in a gelatin-based ink bytwo-photon polymerization (2PP) inside the microfluidic device. Then, ahuman lung fibroblast-laden fibrin hydrogel is injected to surround the printednetwork. Finally, human endothelial cells are seeded inside the printedchannels. The printing parameters and fibrin composition are optimized toreduce hydrogel swelling and ensure a stable model that can be perfused withcell media. Fabricating the hydrogel structure in two steps ensures that nocells are exposed to cytotoxic fabrication processes, while still obtaining highfidelity printing. In this work, the possibility to guide the endothelial cellinvasion through the 3D printed scaffold and perfusion of the co-culturemodel for 10 days is successfully demonstrated on a custom-made perfusionsystem.
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| 3. |
- Cantoni, Federico, et al.
(författare)
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Hydrogel membrane fabricated by 2-photon polymerization in a microfluidic chip for bio-interface investigations
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Current bio-interface models often rely upon a porous thin membrane integrated in a microfluidic system to combine the cell proximity with a precise delivery of biochemical and biophysical cues1. However, this strategy still fails to provide the cultured cells with a good mimic of the tissue physiology. Compared to a conventional porous membrane, a natural-sourced hydrogel represents a more suitable candidate to recapitulate the 3D environment of the biological counterpart2. The platform presented in this study includes a 200 µm thick methacrylated gelatin (GelMA) membrane fabricated with 2-photon polymerization3 in-between two microfluidic channels.
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| 4. |
- Ewald, Johannes, et al.
(författare)
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Acid-Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5
- 2020
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 26:13, s. 2947-2953
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Tidskriftsartikel (refereegranskat)abstract
- PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (Mn) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐dependent, rapid hydrolysis at pH 5–6 and long‐term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA‐Alexa488 can be tailored from a few hours to several days (hydrolysis half‐life time t1/2 at pH 5: 13 h to 51 h).
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| 5. |
- Fornell, Anna, et al.
(författare)
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Acoustic focusing of beads and cells in hydrogel droplets
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 6. |
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| 7. |
- Pohlit, Hannah, et al.
(författare)
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ACOUSTOFLUIDIC METHOD TO ALIGN POLYSTYRENE BEADS AND CELLS IN HYDROGEL DROPLETS
- 2021
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Ingår i: MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419031 ; , s. 887-888
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Konferensbidrag (refereegranskat)abstract
- We present a microfluidic system to control the position of particles (polystyrene beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves. Droplets comprising hydrogel precursor solution, photoinitiator and (bio-)particles were generated and acoustic forces focused the beads to the droplet center line. Droplets were cross-linked by exposure to UV-light. With the acoustics applied, 89 ± 19% of the particles were positioned in the center of the hydrogel droplet. As proof-of-principle for biological applications, astrocytes were focused in hydrogel droplets. The viability of the cells after 7 days was unaffected by the acoustic focusing (72 ± 22%).
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| 8. |
- Pohlit, Hannah, et al.
(författare)
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Evaluation of biocompatibility of acousticfocusing of cells in hydrogel droplets
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionDroplet microfluidics has become a powerful tool to generate miniaturized compartments suitable for biologicalexperiments.[1] For example, hydrogel droplets are a suitable platform to study 3D cell culture.[2] For thisapplication, it can be advantageous to prepare hydrogel constructs with an ordered cell architecture. Here, wepresent an acoustic method to align cells in hydrogel droplets and demonstrate its biocompatibility.Experimental procedure and ResultsTo position the cells in a line at the center of the droplets, we use acoustophoresis. The microfluidic chip wasfabricated using deep reactive ion etching of a Si wafer to form the channels and anodic bonding of a glass waferto seal the chip. A piezoelectric transducer was glued to the chip and actuated to generate bulk acoustic waves inthe channel. The channel dimensions were 380 μm x 100 μm (width x height), which corresponds to halfwavelength lateral resonance at 2 MHz. Droplets consisting of hydrogel precursor solution (3 wt% 4-arm-PEG(10000)-acrylate, 1 wt% gelatin methacrylate and 0.1 wt% photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP)) were formed. The cells, 5 × 106 astrocytes/mL encapsulated in the hydrogeldroplets, were focused at the center of the droplets (pressure nodal line) by the primary acoustic radiation force,Fig 1a). By exposing the cell-laden droplets to a short UV dose, the hydrogel precursor solution was cross-linkedand the cells were “frozen” in their position. Viability of acoustically focused cells and non-focused cells (noacoustics applied) encapsulated in the cross-linked droplets were evaluated by live/dead staining, demonstratingthat acoustic focusing and on-chip cross-linking with UV is a gentle process, see Fig. 1b).[3]Figure 1: a) The experimental procedure. b) Focused polystyrene beads in a cross-linked hydrogel droplet. c) Focusedastrocytes in a cross-linked hydrogel droplet. d) The viability of astrocytes in hydrogel droplets after 1, 3 and 7 days of culture.In blue, acoustically focused cells are shown, whereas in grey, the control group (astrocytes encapsulated in hydrogel dropletswithout acoustic focusing) is shown after 7 days of culture.ConclusionA microfluidic chip with an integrated piezoelectric transducer can be used to generate hydrogel dropletswhere the encapsulated cells are focused to the center line of the droplets· Acoustic focusing of cells do not decrease cell viability· The generated hydrogel droplets could be suitable cell culture scaffolds for advanced biological studies.
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| 9. |
- Pohlit, Hannah, et al.
(författare)
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Free-hanging hydrogel structures as more in vivo-like barrier model
- 2020
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Konferensbidrag (refereegranskat)abstract
- Biological barriers, such as the blood-brain barrier (BBB), restrict the passage of potentially harmful substances from the blood stream into the surrounding tissue while allowing important nutrients to pass. The high selectivity of the barrier is difficult to replicate and remains a severe obstacle in in vitro models currently available.Most models today use porous polymer membranes as the cell culture scaffolds, but using hydrogels as the scaffold instead would resemble the extracellular matrix to a higher extent and we hypothesize that this could lead to improvements in the obtained barrier tightness.
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| 10. |
- Pohlit, Hannah, et al.
(författare)
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Technology platform for facile handling of 3D hydrogel cell culture scaffolds
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogels are used extensively as cell-culture scaffolds for both 2D and 3D cell cultures due to their biocompatibility and the ease in which their mechanical and biological properties can be tailored to mimic natural tissue. The challenge when working with hydrogel-based scaffolds is in their handling, as hydrogels that mimic e.g. brain tissue, are both fragile and brittle when prepared as thin (sub-mm) membranes. Here, we describe a method for facile handling of thin hydrogel cell culture scaffolds by molding them onto a polycaprolactone (PCL) mesh support attached to a commonly used Transwell set-up in which the original membrane has been removed. In addition to demonstrating the assembly of this set-up, we also show some applications for this type of biological membrane. A polyethylene glycol (PEG)-gelatin hydrogel supports cell adhesion, and the structures can be used for biological barrier models comprising either one or multiple hydrogel layers. Here, we demonstrate the formation of a tight layer of an epithelial cell model comprising MDCK cells cultured over 9 days by following the build-up of the transepithelial electrical resistances. Second, by integrating a pure PEG hydrogel into the PCL mesh, significant swelling is induced, which leads to the formation of a non-adherent biological scaffold with a large curvature that is useful for spheroid formation. In conclusion, we demonstrate the development of a handling platform for hydrogel cell culture scaffolds for easy integration with conventional measurement techniques and miniaturized organs-on-chip systems.
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