Materials Characterization of Stereolithography 3D Printed Polymer to Develop a Self-Driven Microfluidic Device for Bioanalytical Applications.

Stereolithography (SLA) 3D printing is a rapid prototyping technique and reproducible manufacturing platform, which makes it a useful tool to develop advanced microfluidic devices for bioanalytical applications. However, limited information exists regarding the physical, chemical, and biological properties of the photocured polymers printed with SLA. This study demonstrates the characterization of a commercially available SLA 3D printed polymer to evaluate the potential presence of any time-dependent changes in material properties that may affect its ability to produce functional, capillary-action microfluidic devices. The printed polymer was analyzed with Fourier transform infrared-attenuated total reflectance, contact angle measurements, tensile test, impact test, scanning electron microscopy, and fluid flow analysis. Polymer biocompatibility was assessed with propidium iodide flow cytometry and an MTT assay for cell viability. The material characterization and biocompatibility results were then implemented to design and fabricate a self-driven capillary action microfluidic device for future use as a bioanalytical assay. This study demonstrates temporally stable mechanical properties and biocompatibility of the SLA polymer. However, surface characterization through contact angle measurements shows the polymer's wettability changes over time which indicates there is a limited postprinting period when the polymer can be used for capillary-based fluid flow. Overall, this study demonstrates the feasibility of implementing SLA as a high-throughput manufacturing method for capillary action microfluidic devices.

Review: Human stem cell-based 3D in vitro angiogenesis models for preclinical drug screening applications.

Vascular diseases are the underlying pathology in many life-threatening illnesses. Human cellular and molecular mechanisms involved in angiogenesis are complex and difficult to study in current 2D in vitro and in vivo animal models. Engineered 3D in vitro models that incorporate human pluripotent stem cell (hPSC) derived endothelial cells (ECs) and supportive biomaterials within a dynamic microfluidic platform provide a less expensive, more controlled, and reproducible platform to better study angiogenic processes in response to external chemical or physical stimulus. Current studies to develop 3D in vitro angiogenesis models aim to establish single-source systems by incorporating hPSC-ECs into biomimetic extracellular matrices (ECM) and microfluidic devices to create a patient-specific, physiologically relevant platform that facilitates preclinical study of endothelial cell-ECM interactions, vascular disease pathology, and drug treatment pharmacokinetics. This review provides a detailed description of the current methods used for the directed differentiation of human stem cells to endothelial cells and their use in engineered 3D in vitro angiogenesis models that have been developed within the last 10 years.

Development of in vitro cardiovascular tissue models within capillary circuit microfluidic devices fabricated with 3D Stereolithography printing.

Human cardiovascular tissue and diseases are difficult to study for novel drug discovery and fundamental cellular/molecular processes due to limited availability of physiologically-relevant models in vitro.[1-3] Animal models may resemble human heart structure, however there are significant differences from human cardiovascular physiology including biochemical signaling, and gene expression.[4-6] In vitro microfluidic tissue models provide a less expensive, more controlled, and reproducible platform for better quantification of isolated cellular processes in response to biochemical or biophysical stimulus.[6-12] The capillary driven-flow microfluidic device in this study was manufactured with a 3D stereolithography (SLA) printed mold and is a closed circuit system operating on principles of capillary action allowing continuous fluid movement without external power supply. Human umbilical vein endothelial cells (HUVECs) and human cardiomyocytes (AC16) were encapsulated into a fibrin hydrogel to form vascular (VTM) and cardiac (CTM) tissue models respectively. To determine response to biophysical stimulus, the 3D cardiovascular tissue was directly loaded into the device tissue culture chambers that either had no microposts (DWoP) or microposts (DWPG) for 1, 3 and 5 days. The tissues were analyzed with fluorescent microscopy for morphological differences, average tube length, and cell orientation between tissues cultured in both conditions. In DWPG VTMs displayed capillary-like tube formation with visible cell alignment and orientation, while AC16s continued to elongate around microposts by day 5. VTM and CTM models in devices with posts (DWPG) displayed cell alignment and orientation after 5 days, indicated the microposts induced biophysical cues to guide cell structure and specific organization.

Engineering approaches for cardiac organoid formation and their characterization.

Cardiac organoids are 3-dimensional (3D) structures composed of tissue or niche-specific cells, obtained from diverse sources, encapsulated in either a naturally derived or synthetic, extracellular matrix scaffold, and include exogenous biochemical signals such as essential growth factors. The overarching goal of developing cardiac organoid models is to establish a functional integration of cardiomyocytes with physiologically relevant cells, tissues, and structures like capillary-like networks composed of endothelial cells. These organoids used to model human heart anatomy, physiology, and disease pathologies in vitro have the potential to solve many issues related to cardiovascular drug discovery and fundamental research. The advent of patient-specific human-induced pluripotent stem cell-derived cardiovascular cells provide a unique, single-source approach to study the complex process of cardiovascular disease progression through organoid formation and incorporation into relevant, controlled microenvironments such as microfluidic devices. Strategies that aim to accomplish such a feat include microfluidic technology-based approaches, microphysiological systems, microwells, microarray-based platforms, 3D bioprinted models, and electrospun fiber mat-based scaffolds. This article discusses the engineering or technology-driven practices for making cardiac organoid models in comparison with self-assembled or scaffold-free methods to generate organoids. We further discuss emerging strategies for characterization of the bio-assembled cardiac organoids including electrophysiology and machine-learning and conclude with prospective points of interest for engineering cardiac tissues in vitro.

A combined hiPSC-derived endothelial cell and in vitro microfluidic platform for assessing biomaterial-based angiogenesis.

Human induced pluripotent stem cell (hiPSC) derived angiogenesis models present a unique opportunity for patient-specific platforms to study the complex process of angiogenesis and the endothelial cell response to biomaterial and biophysical changes in a defined microenvironment. We present a refined method for differentiating hiPSCs into a CD31 + endothelial cell population (hiPSC-ECs) using a single basal medium from pluripotency to the final stage of differentiation. This protocol produces endothelial cells that are functionally competent in assays following purification. Subsequently, an in vitro angiogenesis model was developed by encapsulating the hiPSC-ECs into a tunable, growth factor sequestering hyaluronic acid (HyA) matrix where they formed stable, capillary-like networks that responded to environmental stimuli. Perfusion of the networks was demonstrated using fluorescent beads in a microfluidic device designed to study angiogenesis. The combination of hiPSC-ECs, bioinspired hydrogel, and the microfluidic platform creates a unique testbed for rapidly assessing the performance of angiogenic biomaterials.