Qi Lang

A liver-on-a-chip platform with bioprinted hepatic spheroids.

The inadequacy of animal models in correctly predicting drug and biothreat agent toxicity in humans has resulted in a pressing need for in vitro models that can recreate the in vivo scenario. One of the most important organs in the assessment of drug toxicity is liver. Here, we report the development of a liver-on-a-chip platform for long-term culture of three-dimensional (3D) human HepG2/C3A spheroids for drug toxicity assessment. The bioreactor design allowed for in situ monitoring of the culture environment by enabling direct access to the hepatic construct during the experiment without compromising the platform operation. The engineered bioreactor could be interfaced with a bioprinter to fabricate 3D hepatic constructs of spheroids encapsulated within photocrosslinkable gelatin methacryloyl (GelMA) hydrogel. The engineered hepatic construct remained functional during the 30 days culture period as assessed by monitoring the secretion rates of albumin, alpha-1 antitrypsin, transferrin, and ceruloplasmin, as well as immunostaining for the hepatocyte markers, cytokeratin 18, MRP2 bile canalicular protein and tight junction protein ZO-1. Treatment with 15 mM acetaminophen induced a toxic response in the hepatic construct that was similar to published studies on animal and other in vitro models, thus providing a proof-of-concept demonstration of the utility of this liver-on-a-chip platform for toxicity assessment.

Photocrosslinkable gelatin hydrogel for epidermal tissue engineering

Natural hydrogels are promising scaffolds to engineer epidermis. Currently, natural hydrogels used to support epidermal regeneration are mainly collagen- or gelatin-based, which mimic the natural dermal extracellular matrix but often suffer from insufficient and uncontrollable mechanical and degradation properties. In this study, a photocrosslinkable gelatin (i.e., gelatin methacrylamide (GelMA)) with tunable mechanical, degradation, and biological properties is used to engineer the epidermis for skin tissue engineering applications. The results reveal that the mechanical and degradation properties of the developed hydrogels can be readily modified by varying the hydrogel concentration, with elastic and compressive moduli tuned from a few kPa to a few hundred kPa, and the degradation times varied from a few days to several months. Additionally, hydrogels of all concentrations displayed excellent cell viability (>90%) with increasing cell adhesion and proliferation corresponding to increases in hydrogel concentrations. Furthermore, the hydrogels are found to support keratinocyte growth, differentiation, and stratification into a reconstructed multilayered epidermis with adequate barrier functions. The robust and tunable properties of GelMA hydrogels suggest that the keratinocyte laden hydrogels can be used as epidermal substitutes, wound dressings, or substrates to construct various in vitro skin models.

Enhanced particle trapping performance of induced charge electroosmosis

By increasing the number of floating electrodes or enlarging the width of single floating electrode, this work provides effective ways to strongly improve the particle trapping performance of induced charge electroosmosis (ICEO). Particle trapping with double or triple separate narrow floating electrodes increases the effective actuating range of ICEO flow and therefore enhance the optimum trapping ability to be 1.63 or 2.34 times of that with single narrow electrode (width of L=200μm ), and the ideal trapping frequency is independent of the electrode number due to the mutual independence of electrochemical ion relaxation over each electrode. Furthermore, using a single wide floating electrode with the effective width equal to three separate narrow floating electrodes ( L=600μm ) instead of a single narrow one slightly lowers the ideal trapping frequency due to an increase in the characteristic polarization length, but the trapping performance is only up to 1.59 times of that with original single narrow electrode, implying that vertical channel confinement effect may severely suppresses the effective actuating range of ICEO flow and renders the trapping performance not as expected. Trapping experiments over wide floating electrode with different channel height were carried out, showing that the trapping performance increases by correctly increasing the channel height.

In-plane microvortices micromixer-based AC electrothermal for testing drug induced death of tumor cells

Herein, we first describe a perfusion chip integrated with an AC electrothermal (ACET) micromixer to supply a uniform drug concentration to tumor cells. The in-plane fluid microvortices for mixing were generated by six pairs of reconstructed novel ACET asymmetric electrodes. To enhance the mixing efficiency, the novel ACET electrodes with rotating angles of 0°, 30°, and 60° were investigated. The asymmetric electrodes with a rotating angle of 60° exhibited the highest mixing efficiency by both simulated and experimental results. The length of the mixing area is 7 mm, and the mixing efficiency is 89.12% (approximate complete mixing) at a voltage of 3 V and a frequency of 500 kHz. The applicability of our micromixer with electrodes rotating at 60° was demonstrated by the drug (tamoxifen) test of human breast cancer cells (MCF-7) for five days, which implies that our ACET in-plane microvortices micromixer has great potential for the application of drug induced rapid death of tumor cells and mixing of biomaterials in organs-on-a-chip systems.

A dual-core double emulsion platform for osmolarity-controlled microreactor triggered by coalescence of encapsulated droplets

Droplet-based microfluidics has provided a means to generate multi-core double emulsions, which are versatile platforms for microreactors in materials science, synthetic biology, and chemical engineering. To provide new opportunities for double emulsion platforms, here, we report a glass capillary microfluidic approach to first fabricate osmolarity-responsive Water-in-Oil-in-Water (W/O/W) double emulsion containing two different inner droplets/cores and to then trigger the coalescence between the encapsulated droplets precisely. To achieve this, we independently control the swelling speed and size of each droplet in the dual-core double emulsion by controlling the osmotic pressure between the inner droplets and the collection solutions. When the inner two droplets in one W/O/W double emulsion swell to the same size and reach the instability of the oil film interface between the inner droplets, core-coalescence happens and this coalescence process can be controlled precisely. This microfluidic methodology enables the generation of highly monodisperse dual-core double emulsions and the osmolarity-controlled swelling behavior provides new stimuli to trigger the coalescence between the encapsulated droplets. Such swelling-caused core-coalescence behavior in dual-core double emulsion establishes a novel microreactor for nanoliter-scale reactions, which can protect reaction materials and products from being contaminated or released.

A multifunctional resealable perfusion chip for cell culture and tissue engineering

We describe a multifunctional resealable perfusion chip to mimic the human environment for cell or tissue culture in vitro and to increase the efficiency of culture in this study. To meet the culture requirement of a two-dimensional (2D) submerged cultures and an air–liquid interface perfusion cultures, a multifunctional resealable perfusion chip was designed and fabricated. Human embryonic kidney cells (HEK293T) and human colon carcinoma cells (SW620) were submerged cultured in the chip for 72 h. Cell viability and cell proliferation tests were used to evaluate the performance of the chip. Moreover, an artificial epidermis was developed, and it lasted for 7 days for the submerged culture immortal human keratinocyte (HaCaT) monolayer and 35 days for the air–liquid interface differentiated culture. The artificial epidermis cultured in the chip and in a conventional transwell were evaluated by the Live/Dead Viability/Cytotoxicity kit, histology, and hematoxylin and eosin staining. The stability and the benefits of our resealable chip were demonstrated by culture cells and epidermis tissue. Unlike a conventional static culture, no obvious advantage was observed in the 2D submerged culture of HEK293T and SW620 cells in the chip, but an outstanding advantage was observed in the 2D HaCaT cell culture with high density and a reconstructed epidermis. The cells grew well, and the epidermis was successfully reconstructed. This result implies that our multifunctional chip has great potential in cell culture and tissue engineering applications.