Polyanion-induced, microfluidic engineering of fragmented collagen microfibers for reconstituting extracellular environments of 3D hepatocyte culture

3D bioprinting of dECM-incorporated hepatocyte spheroid for simultaneous promotion of cell-cell and -ECM interactions

The cell spheroid technology, which greatly enhances cell-cell interactions, has gained significant attention in the development of in vitro liver models. However, existing cell spheroid technologies still have limitations in improving hepatocyte-extracellular matrix (ECM) interaction, which have a significant impact on hepatic function. In this study, we have developed a novel bioprinting technology for decellularized ECM (dECM)-incorporated hepatocyte spheroids that could enhance both cell-cell and -ECM interactions simultaneously. To provide a biomimetic environment, a porcine liver dECM-based cell bio-ink was developed, and a spheroid printing process using this bio-ink was established. As a result, we precisely printed the dECM-incorporated hepatocyte spheroids with a diameter of approximately 160-220 μm using primary mouse hepatocyte (PMHs). The dECM materials were uniformly distributed within the bio-printed spheroids, and even after more than 2 weeks of culture, the spheroids maintained their spherical shape and high viability. The incorporation of dECM also significantly improved the hepatic function of hepatocyte spheroids. Compared to hepatocyte-only spheroids, dECM-incorporated hepatocyte spheroids showed approximately 4.3- and 2.5-fold increased levels of albumin and urea secretion, respectively, and a 2.0-fold increase in CYP enzyme activity. These characteristics were also reflected in the hepatic gene expression levels of ALB, HNF4A, CPS1, and others. Furthermore, the dECM-incorporated hepatocyte spheroids exhibited up to a 1.8-fold enhanced drug responsiveness to representative hepatotoxic drugs such as acetaminophen, celecoxib, and amiodarone. Based on these results, it can be concluded that the dECM-incorporated spheroid printing technology has great potential for the development of highly functional in vitro liver tissue models for drug toxicity assessment.

Recent Advances on Cell Culture Platforms for In Vitro Drug Screening and Cell Therapies: From Conventional to Microfluidic Strategies

The clinical translations of drugs and nanomedicines depend on coherent pharmaceutical research based on biologically accurate screening approaches. Since establishing the 2D in vitro cell culture method, the scientific community has improved cell-based drug screening assays and models. Those advances result in more informative biochemical assays and the development of 3D multicellular models to describe the biological complexity better and enhance the simulation of the in vivo microenvironment. Despite the overall dominance of conventional 2D and 3D cell macroscopic culture methods, they present physicochemical and operational challenges that impair the scale-up of drug screening by not allowing a high parallelization, multidrug combination, and high-throughput screening. Their combination and complementarity with microfluidic platforms enable the development of microfluidics-based cell culture platforms with unequivocal advantages in drug screening and cell therapies. Thus, this review presents an updated and consolidated view of cell culture miniaturization's physical, chemical, and operational considerations in the pharmaceutical research scenario. It clarifies advances in the field using gradient-based microfluidics, droplet-based microfluidics, printed-based microfluidics, digital-based microfluidics, SlipChip, and paper-based microfluidics. Finally, it presents a comparative analysis of the performance of cell-based methods in life research and development to achieve increased precision in the drug screening process.

A multiscale, vertical-flow perfusion system with integrated porous microchambers for upgrading multicellular spheroid culture

Spheroid formation assisted by microengineered chambers is a versatile approach for morphology-controlled three-dimensional (3D) cell cultivation with physiological relevance to human tissues. However, the limitation in diffusion-based oxygen/nutrient transport has been a critical issue for the densely packed cells in spheroids, preventing maximization of cellular functions and thus limiting their biomedical applications. Here, we have developed a multiscale microfluidic system for the perfusion culture of spheroids, in which porous microchambers, connected with microfluidic channels, were engineered. A newly developed process of centrifugation-assisted replica molding and salt-leaching enabled the formation of single micrometer-sized pores on the chamber surface and in the substrate. The porous configuration generates a vertical flow to directly supply the medium to the spheroids, while avoiding the formation of stagnant flow regions. We created seamlessly integrated, all PDMS/silicone-based microfluidic devices with an array of microchambers. Spheroids of human liver cells (HepG2 cells) were formed and cultured under vertical-flow perfusion, and the proliferation ability and liver cell-specific functions were compared with those of cells cultured in non-porous chambers with a horizontal flow. The presented system realizes both size-controlled formation of spheroids and direct medium supply, making it suitable as a precision cell culture platform for drug development, disease modelling, and regenerative medicine.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

Clinical study of injectable collagen scaffold with autologous fat cells for repair of severe vocal fold injury

Cell retention and survival after transplantation remains a major problem for long-term efficiency in therapy of severe vocal fold injury with autologous cells. In this study, injectable collagen scaffold was used to deliver autologous fat cells (AFCs) for repairing of severe vocal fold injury. We found injectable collagen scaffold could enhance the retention and survival of green fluorescent protein (GFP) labeled fat cells in the transplantation sites in rats. Based on these data, a randomized controlled clinical trial was conducted to evaluate the safety and efficiency of transplantation of collagen scaffold with AFCs for severe vocal fold injury. Ten patients with vocal fold paralysis were randomly assigned to control (AFCs only) and intervention (AFCs + collagen) groups. AFCs with or without collagen scaffold were injected into vocal folds of patients under general anesthesia, respectively. The safety and efficacy were regularly assessed during 24 months post-surgery. No obvious complications occurred in all patients during the follow-up. The collagen scaffold maintained the stability of implants after injection and reconstructed the vocal fold structure. The improvement of voice quality of patients was observed through voice quality evaluation with the voice handicap index (VHI) questionnaire, as well as acoustic analysis of maximum phonation time, jitter, and shimmer. The VHI score of patients in AFCs + collagen group improved significantly than those in AFCs group at 6, 12 and 24 months post-surgery. It demonstrates the injectable collagen scaffold is safe and efficient for delivering AFCs for vocal fold injury.

Production of Janus/Hecate microfibers by microfluidic photopolymerization and evaluation of their potential in dye removal

The microfluidic production of Janus/Hecate polymer microfibers with well-defined interfaces from miscible phases is reported. The process offers tunability of the width and composition of each part of the fibers by controlling the flow rate and nature of the monomers in a single step. The enhanced performances of the fibers are outlined for the simultaneous removal of dyes of opposite charges using amphoteric Janus fibers.

Formation of 3D tissues of primary hepatocytes using fibrillized collagen microparticles as intercellular binders

Numerous attempts have been made to organize isolated primary hepatocytes into functional three-dimensional (3D) constructs, but technologies to introduce extracellular matrix (ECM) components into such assemblies have not been fully developed. Here we report a new approach to forming hepatocyte-based 3D tissues using fibrillized collagen microparticles (F-CMPs) as intercellular binders. We created thick tissues with a thickness of ∼200 μm simply by mixing F-CMPs with isolated primary rat hepatocytes and culturing them in cell culture inserts. Owing to the incorporated F-CMPs, the circular morphology of the formed tissues was stabilized, which was strong enough to be manually manipulated and retrieved from the chamber of the insert. We confirmed that the F-CMPs dramatically improved the cell viability and hepatocyte-specific functions such as albumin production and urea synthesis in the formed tissues. The presented approach provides a versatile strategy for hepatocyte-based tissue engineering, and will have a significant impact on biomedical applications and pharmaceutical research.