Dragging 3D printing technique controls pore sizes of tissue engineered blood vessels to induce spontaneous cellular assembly.

To date, several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel (SDV) replacement. However, conventional artificial blood vessel grafts lack endothelium and, thus, are not ideal for SDV transplantation as they can cause thrombosis. In addition, a successful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external stresses. Here, we developed a spontaneous cellular assembly SDV (S-SDV) that develops without additional intervention. By improving the dragging 3D printing technique, SDV constructs with free-form, multilayers and controllable pore size can be fabricated at once. Then, The S-SDV filled in the natural polymer bioink containing human umbilical vein endothelial cells (HUVECs) and human aorta smooth muscle cells (HAoSMCs). The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV construct. The antiplatelet adhesion of the formed endothelium on the luminal surface was also confirmed. In addition, this S-SDV had sufficient mechanical properties (burst pressure, suture retention, leakage test) for transplantation. We believe that the S-SDV could address the challenges of conventional SDVs: notably, endothelial formation and mechanical properties. In particular, the S-SDV can be designed simply as a free-form structure with a desired pore size. Since endothelial formation through the pore is easy even in free-form constructs, it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes, and in other tubular tissues such as the esophagus.

Biohybrid 3D Printing of a Tissue-Sensor Platform for Wireless, Real-Time, and Continuous Monitoring of Drug-Induced Cardiotoxicity.

Drug-induced cardiotoxicity is regarded as a major hurdle in the early stages of drug development. Although there are various methods for preclinical cardiotoxicity tests, they cannot completely predict the cardiotoxic potential of a compound due to the lack of physiological relevance. Recently, 3D engineered heart tissue (EHT) has been used to investigate cardiac muscle functions as well as pharmacological effects by exhibiting physiological auxotonic contractions. However, there is still no adequate platform for continuous monitoring to test acute and chronic pharmacological effects in vitro. Here, a biohybrid 3D printing method for fabricating a tissue-sensor platform, composed of a bipillar-grafted strain gauge sensor and EHT, is first introduced. Two pillars are three-dimensionally printed as grafts onto a strain gauge-embedded substrate to promote the EHT contractility and guide the self-assembly of the EHTs along with the strain gauge. In addition, the integration of a wireless multi-channel electronic system allows for continuous monitoring of the EHT contractile force by the tissue-sensor platform and, ultimately, for the observation of the acute and chronic drug effects of cardiotoxicants. In summary, biohybrid 3D printing technology is expected to be a potential fabrication method to provide a next-generation tissue-sensor platform for an effective drug development process.

Modular assembly of bioprinted perfusable blood vessel and tracheal epithelium for studying inflammatory respiratory diseases.

In vitroorgan models allow for the creation of precise preclinical models that mimic organ physiology. During a pandemic of a life-threatening acute respiratory disease, an improved trachea model (TM) is required. We fabricated a modular assembly of the blood vessel and TMs using 3D bioprinting technology. First, decellularized extracellular matrix (dECM) were prepared using the porcine trachea and blood vessels. A trachea module was fabricated based on the tracheal mucosa-derived dECM and microporous membrane. Further, a blood vessel module was manufactured using the prepared vascular-tissue-derived dECM. By assembling each manufactured module, a perfusable vascularized TM simulating the interface between the tracheal epithelium and blood vessels was fabricated. This assembled model was manufactured with efficient performance, and it offered respiratory symptoms, such as inflammatory response and allergen-induced asthma exacerbation. These characteristics indicate the possibility of manufacturing a highly functional organ model that mimics a complex organ environment in the future.

Au Hierarchical Nanostructure-Based Surface Modification of Microelectrodes for Improved Neural Signal Recording.

Microelectrodes are widely used for neural signal analysis because they can record high-resolution signals. In general, the smaller the size of the microelectrode for obtaining a high-resolution signal, the higher the impedance and noise value of the electrodes. Therefore, to improve the signal-to-noise ratio (SNR) of neural signals, it is important to develop microelectrodes with low impedance and noise. In this research, an Au hierarchical nanostructure (AHN) was deposited to improve the electrochemical surface area (ECSA) of a microelectrode. Au nanostructures on different scales were deposited on the electrode surface in a hierarchical structure using an electrochemical deposition method. The AHN-modified microelectrode exhibited an average of 80% improvement in impedance compared to a bare microelectrode. Through electrochemical impedance spectroscopy analysis and impedance equivalent circuit modeling, the increase in the ECSA due to the AHN was confirmed. After evaluating the cell cytotoxicity of the AHN-modified microelectrode through an in vitro test, neural signals from rats were obtained in in vivo experiments. The AHN-modified microelectrode exhibited an approximate 9.79 dB improvement in SNR compared to the bare microelectrode. This surface modification technology is a post-treatment strategy used for existing fabricated electrodes, so it can be applied to microelectrode arrays and nerve electrodes made from various structures and materials.

3D bioprinting of stem cell-laden cardiac patch: A promising alternative for myocardial repair.

Stem cell-laden three-dimensional (3D) bioprinted cardiac patches offer an alternative and promising therapeutic and regenerative approach for ischemic cardiomyopathy by reversing scar formation and promoting myocardial regeneration. Numerous studies have reported using either multipotent or pluripotent stem cells or their combination for 3D bioprinting of a cardiac patch with the sole aim of restoring cardiac function by faithfully rejuvenating the cardiomyocytes and associated vasculatures that are lost to myocardial infarction. While many studies have demonstrated success in mimicking cardiomyocytes' behavior, improving cardiac function and providing new hope for regenerating heart post-myocardial infarction, some others have reported contradicting data in apparent ways. Nonetheless, all investigators in the field are speed racing toward determining a potential strategy to effectively treat losses due to myocardial infarction. This review discusses various types of candidate stem cells that possess cardiac regenerative potential, elucidating their applications and limitations. We also brief the challenges of and an update on the implementation of the state-of-the-art 3D bioprinting approach to fabricate cardiac patches and highlight different strategies to implement vascularization and augment cardiac functional properties with respect to electrophysiological similarities to native tissue.

Fabrication of Oblique Submicron-Scale Structures Using Synchrotron Hard X-ray Lithography.

Oblique submicron-scale structures are used in various aspects of research, such as the directional characteristics of dry adhesives and wettability. Although deposition, etching, and lithography techniques are applied to fabricate oblique submicron-scale structures, these approaches have the problem of the controllability or throughput of the structures. Here, we propose a simple X-ray-lithography method, which can control the oblique angle of submicron-scale structures with areas on the centimeter scale. An X-ray mask was fabricated by gold film deposition on slanted structures. Using this mask, oblique ZEP520A photoresist structures with slopes of 20° and 10° and widths of 510 nm and 345 nm were fabricated by oblique X-ray exposure, and the possibility of polydimethylsiloxane (PDMS) molding was also confirmed. In addition, through double exposure with submicron- and micron-scale X-ray masks, dotted-line patterns were produced as an example of multiscale patterning.

Multi-layered Free-form 3D Cell-printed Tubular Construct with Decellularized Inner and Outer Esophageal Tissue-derived Bioinks.

The incidences of various esophageal diseases (e.g., congenital esophageal stenosis, tracheoesophageal fistula, esophageal atresia, esophageal cancer) are increasing, but esophageal tissue is difficult to be recovered because of its weak regenerative capability. There are no commercialized off-the-shelf alternatives to current esophageal reconstruction and regeneration methods. Surgeons usually use ectopic conduit tissues including stomach and intestine, presumably inducing donor site morbidity and severe complications. To date, polymer-based esophageal substitutes have been studied as an alternative. However, the fabrication techniques are nearly limited to creating only cylindrical outer shapes with the help of additional apparatus (e.g., mandrels for electrospinning) and are unable to recapitulate multi-layered characteristic or complex-shaped inner architectures. 3D bioprinting is known as a suitable method to fabricate complex free-form tubular structures with desired pore characteristic. In this study, we developed a extrusion-based 3D printing technique to control the size and the shape of the pore in a single extrusion process, so that the fabricated structure has a higher flexibility than that fabricated in the conventional process. Based on this suggested technique, we developed a bioprinted 3D esophageal structure with multi-layered features and converged with biochemical microenvironmental cues of esophageal tissue by using decellularizedbioinks from mucosal and muscular layers of native esophageal tissues. The two types of esophageal tissue derived-decellularized extracellular matrix bioinks can mimic the inherent components and composition of original tissues with layer specificity. This structure can be applied to full-thickness circumferential esophageal defects and esophageal regeneration.

3D Bioprinting Strategies for the Regeneration of Functional Tubular Tissues and Organs.

It is difficult to fabricate tubular-shaped tissues and organs (e.g., trachea, blood vessel, and esophagus tissue) with traditional biofabrication techniques (e.g., electrospinning, cell-sheet engineering, and mold-casting) because these have complicated multiple processes. In addition, the tubular-shaped tissues and organs have their own design with target-specific mechanical and biological properties. Therefore, the customized geometrical and physiological environment is required as one of the most critical factors for functional tissue regeneration. 3D bioprinting technology has been receiving attention for the fabrication of patient-tailored and complex-shaped free-form architecture with high reproducibility and versatility. Printable biocomposite inks that can facilitate to build tissue constructs with polymeric frameworks and biochemical microenvironmental cues are also being actively developed for the reconstruction of functional tissue. In this review, we delineated the state-of-the-art of 3D bioprinting techniques specifically for tubular tissue and organ regeneration. In addition, this review described biocomposite inks, such as natural and synthetic polymers. Several described engineering approaches using 3D bioprinting techniques and biocomposite inks may offer beneficial characteristics for the physiological mimicry of human tubular tissues and organs.

Modulation of saliva pattern and accurate detection of ovulation using an electrolyte pre-deposition-based method: a pilot study.

We developed an electrolyte pre-deposition-based saliva pattern modulation method to detect ovulation with high accuracy and reliability. Ovulation tests using human saliva have advantages in terms of the earlier ovulation detection and more convenient sample collection procedure; however, accuracy is low, which is a critical limitation given that the concentrations of salivary constituents can vary depending on the health status of the tested individual and subjective user judgement of the test result. In this study, we quantitatively analyzed saliva patterns according to the concentrations of electrolytes and proteins in the ovulation test and found that changes in the saliva pattern during the ovulatory period can be controlled by sodium chloride (NaCl) pre-deposition, which directly affects the accuracy of ovulation detection. The 100 nmol NaCl pre-deposition condition proved optimal, being two-fold more sensitive to changes in saliva pattern versus the non-pre-deposition condition (accuracy of ovulation detection = 66.6% and 33.3%, respectively). Although accuracy remained insufficient for actual applications compared to the urine-based ovulation detection method, we expect that the electrolyte pre-deposition method will greatly contribute to enhancing the performance of saliva-based ovulation detection tests, toward a commercially satisfactory level of accuracy.

Cell behaviour on a polyaniline nanoprotrusion structure surface.

The extracellular matrix provides mechanical support and affects cell behaviour. Nanoscale structures have been shown to have functions similar to the extracellular matrix. In this study, we fabricated nanoprotrusion structures with polyaniline as cell culture plates using a simple method and determined the effects of these nanoprotrusion structures on cells.

Replicable and shape-controllable fabrication of electrospun fibrous scaffolds for tissue engineering.

Controlling the architecture of electrospun fibers is one of the key issues in tissue engineering. This report describes a rapid and reproducible patterning method for the fabrication of an electrospun fibrous scaffold. The electrospun fibers were deposited on a patterned electrode. The patterned scaffold was fabricated using a thin insulating film between layers of this electrode. For a tissue engineering application, poly(lactic-co-glycolic acid) (PLGA), a biocompatible and biodegradable material, was electrospun. Fibroblast cells were cultured on the fibrous PLGA scaffold and the viability, morphology, and distribution of the cells were studied.