Three-dimensional (3D) bioprinting of hydrogel-based constructs at adequate consistency and reproducibility can be obtained through a compromise between the hydrogel's inherent instability and printing fidelity.There is an increasing demand to develop bioprinting modalities that enable high-fidelity fabrication of 3D hydrogel structures that closely correspond to the envisioned design. In this work, we performed a systematic, in-depth characterization and optimization of embedded 3D bioprinting to create 3D gelatin-methacryloyl (gelMA) structures with highly controlled fidelity using Carbopol as suspension bath. The role of various embedded printing process parameters in bioprinting fidelity was investigated using a combination of experimental and theoretical approaches. We examined the effect of rheological properties of gelMA and Carbopol at varying concentrations, as well as printing conditions on the volumetric flow rate of gelMA bioink. Printing speed was examined and optimized to successfully print gelMA into the support bath at varying Carbopol concentrations. Printing fidelity was characterized in terms of printed strand diameter, uniformity, angle, and area. The optimal Carbopol solution that retained filament shape at highest fidelity was determined. The efficacy of developed bioprinting approach was then demonstrated by fabricating 3D hydrogel constructs with varying geometries and visualized using an advanced synchrotron-based imaging technique. We also investigated the influence of the Carbopol medium on cross-linking and the resulting stiffness of gelMA constructs. Finally, in vitro cytotoxicity of the developed bioprinting approach was assessed by printing human umbilical vein endothelial cells encapsulated in the gelMA bioink. These results demonstrate the significance of the close interplay between bioink−support bath rheology and printing parameters and help to establish an optimized workflow for creating 3D hydrogel structures with high fidelity and cytocompatibility via embedded bioprinting techniques. This robust platform could further expand the application of bioprinted soft tissue constructs in a wide variety of biomedical applications.

The human genome with all its ethnic variations contributes to differences in human development, aging, disease, repair, and response to medical treatments and is an exciting area of research and clinical study. The availability of well-characterized ethnically diverse stem cell lines is limited and has not kept pace with other advances in stem cell research. Here we derived xenofree ethnically diverse-human induced pluripotent stem cell (ED-iPSC) lines from fibroblasts obtained from individuals of African American, Hispanic-Latino, Asian, and Caucasian ethnic origin and have characterized the lines under a uniform platform for comparative analysis. Derived ED-iPSC lines are low passage number and evaluated in vivo by teratoma formation and in vitro by high throughput microarray analysis of EB formation and early differentiation for tri-lineage commitment to endoderm, ectoderm and mesoderm. These new xenofree ED-iPSC lines represent a well-characterized valuable resource with potential for use in future research in drug discovery or clinical investigations.

3D bioprinting techniques have shown great promise in various fields of tissue engineering and regenerative medicine. Yet, creating a tissue construct that faithfully represents the tightly regulated composition, microenvironment, and function of native tissues is still challenging. Among various factors, biomechanics of bioprinting processes play fundamental roles in determining the ultimate outcome of manufactured constructs. This review provides a comprehensive and detailed overview on various biomechanical factors involved in tissue bioprinting, including those involved in pre, during, and post printing procedures. In preprinting processes, factors including viscosity, osmotic pressure, and injectability are reviewed and their influence on cell behavior during the bioink preparation is discussed, providing a basic guidance for the selection and optimization of bioinks. In during bioprinting processes, we review the key characteristics that determine the success of tissue manufacturing, including the rheological properties and surface tension of the bioink, printing flow rate control, process-induced mechanical forces, and the in situ cross-linking mechanisms. Advanced bioprinting techniques, including embedded and multi-material printing, are explored. For post printing steps, general techniques and equipment that are used for characterizing the biomechanical properties of printed tissue constructs are reviewed. Furthermore, the biomechanical interactions between printed constructs and various tissue/cell types are elaborated for both in vitro and in vivo applications. The review is concluded with an outlook regarding the significance of biomechanical processes in tissue bioprinting, presenting future directions to address some of the key challenges faced by the bioprinting community.

BACKGROUND COVID-19 poses a risk to the endoscopic skull base surgeon. Significant efforts to improving safety have been employed, including the use of personal protective equipment, preoperative COVID-19 testing, and recently the use of a modified surgical mask barrier. OBJECTIVE To reduce the risks of pathogen transmission during endoscopic skull base surgery. METHODS This study was exempt from Institutional Review Board approval. Our study utilizes a 3-dimensional (3D)-printed mask with an anterior aperture fitted with a surgical glove with ports designed to allow for surgical instrumentation and side ports to accommodate suction ventilation and an endotracheal tube. As an alternative, a modified laparoscopic surgery trocar served as a port for instruments, and, on the contralateral side, rubber tubing was used over the endoscrub endosheath to create an airtight seal. Surgical freedom and aerosolization were tested in both modalities. RESULTS The ventilated mask allowed for excellent surgical maneuverability and freedom. The trocar system was effective for posterior surgical procedures, allowing access to critical paramedian structures, and afforded a superior surgical seal, but was limited in terms of visualization and maneuverability during anterior approaches. Aerosolization was reduced using both the mask and nasal trocar. CONCLUSION The ventilated upper airway endoscopic procedure mask allows for a sealed surgical barrier during endoscopic skull base surgery and may play a critical role in advancing skull base surgery in the COVID-19 era. The nasal trocar may be a useful alternative in instances where 3D printing is not available. Additional studies are needed to validate these preliminary findings.

Background Tetralogy of Fallot with major aortopulmonary collateral arteries is a heterogeneous form of pulmonary artery (PA) stenosis that requires multiple forms of intervention. We present a patient‐specific in vitro platform capable of sustained flow that can be used to train proceduralists and surgical teams in current interventions, as well as in developing novel therapeutic approaches to treat various vascular anomalies. Our objective is to develop an in vitro model of PA stenosis based on patient data that can be used as an in vitro phantom to model cardiovascular disease and explore potential interventions. Methods and Results From patient‐specific scans obtained via computer tomography or 3‐dimensional (3D) rotational angiography, we generated digital 3D models of the arteries. Subsequently, in vitro models of tetralogy of Fallot with major aortopulmonary collateral arteries were first 3D printed using biocompatible resins and next bioprinted using gelatin methacrylate hydrogel to simulate neonatal vasculature or second‐order branches of an older patient with tetralogy of Fallot with major aortopulmonary collateral arteries. Printed models were used to study creation of extraluminal connection between an atretic PA and a major aortopulmonary collateral artery using a catheter‐based interventional method. Following the recanalization, engineered PA constructs were perfused and flow was visualized using contrast agents and x‐ray angiography. Further, computational fluid dynamics modeling was used to analyze flow in the recanalized model. Conclusions New 3D‐printed and computational fluid dynamics models for vascular atresia were successfully created. We demonstrated the unique capability of a printed model to develop a novel technique for establishing blood flow in atretic vessels using clinical imaging, together with 3D bioprinting–based tissue engineering techniques. Additive biomanufacturing technologies can enable fabrication of functional vascular phantoms to model PA stenosis conditions that can help develop novel clinical applications.

The realization of personalized medicine through human induced pluripotent stem cell (iPSC) technology can be advanced by transcriptomics, epigenomics, and bioinformatics that inform on genetic pathways directing tissue development and function. When possible, population diversity should be included in new studies as resources become available. Previously we derived replicate iPSC lines of African American, Hispanic-Latino and Asian self-designated ethnically diverse (ED) origins with normal karyotype, verified teratoma formation, pluripotency biomarkers, and tri-lineage in vitro commitment. Here we perform bioinformatics of RNA-Seq and ChIP-seq pluripotency data sets for two replicate Asian and Hispanic-Latino ED-iPSC lines that reveal differences in generation of contractile cardiomyocytes but similar and robust differentiation to multiple neural, pancreatic, and smooth muscle cell types. We identify shared and distinct genes and contributing pathways in the replicate ED-iPSC lines to enhance our ability to understand how reprogramming to iPSC impacts genes and pathways contributing to cardiomyocyte contractility potential.

Neuroblastoma (NB) is the most common extracranial tumor in children resulting in substantial morbidity and mortality. A deeper understanding of the NB tumor microenvironment (TME) remains an area of active research but there is a lack of reliable and biomimetic experimental models. This study utilizes a 3D bioprinting approach, in combination with NB spheroids, to create an in vitro vascular model of NB for exploring the tumor function within an endothelialized microenvironment. A gelatin methacryloyl (gelMA) bioink is used to create multi‐channel cubic tumor analogues with high printing fidelity and mechanical tunability. Human‐derived NB spheroids and human umbilical vein endothelial cells (HUVECs) are incorporated into the biomanufactured gelMA and cocultured under static versus dynamic conditions, demonstrating high levels of survival and growth. Quantification of NB‐EC integration and tumor cell migration suggested an increased aggressive behavior of NB when cultured in bioprinted endothelialized models, when cocultured with HUVECs, and also as a result of dynamic culture. This model also allowed for the assessment of metabolic, cytokine, and gene expression profiles of NB spheroids under varying TME conditions. These results establish a high throughput research enabling platform to study the TME‐mediated cellular‐molecular mechanisms of tumor growth, aggression, and response to therapy.

To date, the fields of biomaterials science and tissue engineering have shown great promise in creating bioartificial tissues and organs for use in a variety of regenerative medicine applications. With the emergence of new technologies such as additive biomanufacturing and 3D bioprinting, increasingly complex tissue constructs are being fabricated to fulfill the desired patient-specific requirements. Fundamental to the further advancement of this field is the design and development of imaging modalities that can enable visualization of the bioengineered constructs following implantation, at adequate spatial and temporal resolution and high penetration depths. These in vivo tracking techniques should introduce minimum toxicity, disruption, and destruction to treated tissues, while generating clinically relevant signal-to-noise ratios. This article reviews the imaging techniques that are currently being adopted in both research and clinical studies to track tissue engineering scaffolds in vivo, with special attention to 3D bioprinted tissue constructs.