Acoustic Cell Patterning for Structured Cell-Laden Hydrogel Fibers/Tubules

Abstract

Cell-laden hydrogel fibers/tubules are one of the fundamentals of tissue engineering. They have been proven as a promising method for constructing biomimetic tissues, such as muscle fibers, nerve conduits, tendon and vessels, etc. However, current hydrogel fiber/tubule production methods have limitations in ordered cell arrangements, thus impeding the biomimetic configurations. Acoustic cell patterning is a cell manipulation method that has good biocompatibility, wide tunability, and is contact-free. However, there are few studies on acoustic cell patterning for fiber production, especially on the radial figure cell arrangements, which mimic many native tissue-like cell arrangements. Here, an acoustic cell patterning system that can be used to produce hydrogel fibers/tubules with tunable cell patterns is shown. Cells can be pre-patterned in the liquid hydrogel before being extruded as cross-linked hydrogel fibers/tubules. The radial patterns can be tuned with different complexities based on the acoustic resonances. Cell viability assays after 72 h confirm good cell viability and proliferation. Considering the biocompatibility and reliability, the present method can be further used for a variety of biomimetic fabrications.

Keywords: acoustofluidic; biofabrication; cell patterning; hydrogel fibers.

Figure 1

Schematic of the hydrogel fiber/tubule production with acoustic cell patterning. A) (i) Cells are randomly distributed in a liquid hydrogel solution when injected into the capillary. (ii) The designed acoustic pressure fields enable cell patterning in the liquid hydrogel. (iii) The UV light irradiates the liquid hydrogel with cell patterns, within which the photo‐initiators cross‐link the polymer networks, thus the liquid hydrogel will be cured. B) Continuous flow of cell‐laden hydrogel is driven by a syringe pump to the transparent glass capillary. When the flow passes through the acoustic‐activated capillary, the cells will be assembled to the desired pattern. After that, the structural hydrogel fibers/tubules are generated with the cross‐linking by ultraviolet (UV) light.

Figure 2

The numerical simulation results of acoustic pressure fields in capillaries with different shapes and materials. The acoustic pressure field distribution in the glass capillary. with different shapes of different inner cross‐sections: A) rectangle capillary. B) circle capillary. and C) coaxial circle capillary. The acoustic pressure field distribution in the coaxial circle capillary. with different materials of D) steel and E) plastic. Scale bar: 500 µm.

Figure 3

The principle of acoustically controlled particle pattern in a glass capillary. A) The schematic diagram of PMMA particles patterning process under acoustic on. B) The corresponding PMMA particles dynamic patterning experiment after under acoustic at 0, 1.7, and 4.4 s. C) The effect of input voltage on the patterning velocity of particles in glass capillaries under different acoustic modes. D) The effect of the input voltage on the patterning velocity of particles in coaxial glass capillaries under different acoustic modes. E) The simulation results of acoustic pressure field and ARF distribution in glass capillaries as well as the corresponding experiment results of particle patterns for different acoustic modes. F) The simulation results of acoustic pressure field and ARF distribution in coaxial glass capillaries as well as the corresponding experiment results of particle patterns for different acoustic modes. Scale bar: 500 µm.

Figure 4

Results of continuous production of hydrogel fibers with patterned fluorescent PS particles. A–C) The different structures (Green: PS particles, Red: Hydrogel) under various acoustic modes (first mode, second mode, third mode) from different views (Left: Top view, Middle: Front view, Right: 3D view). Scale bar: 500 µm.

Figure 5

Results of continuous production of hydrogel tubules with patterned fluorescent PS particles. A–C) The different structures (Green: PS particles, Red: hydrogel) under various acoustic modes (first mode, second mode, third mode) from different views (left: top view, middle: front view, right: 3D view). Scale bar: 500 µm.

Figure 6

Results of continuous production of hydrogel fibers and tubules with patterned cells. A–C) The different structures (Blue: 293T cell, Red: Hydrogel) under various acoustic modes (first mode, second mode, third mode) from different views (left: top view, middle: front view, right: 3D view) of hydrogel fibers. D–F) The different structures (blue: 293T cell, red: hydrogel) under various acoustic modes (first mode, second mode, third mode) from different views (left: top view, middle: front view, right: 3D view) of hydrogel tubules. Scale bar: 500 µm.

Figure 7

Cell viability tests show that cells grow and proliferate in the acoustically patterned cell‐laden hydrogels. A) The results of the cell toxicity test for four different samples treated with different acoustic conditions (acoustic off, first mode, second mode, third mode) at 6, 24, 48, and 72 h indicate the normal proliferation of viable cells. B–D) Fluorescence images of acoustically patterned 293T after 24 h from different views (B: top view, C: front view, D: 3D view), which demonstrate that cells survive in the acoustically patterned assemblies in the 3D hydrogels, the green region represents the live cells, the red region represents the dead cells. Scale bar: 100 µm.