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Table of Contents

Special Section: Bioprinting of 3D Functional Tissue Constructs

Regular Section

Original Articles

by Hang Liu, Fan Wu, Renwei Chen, Yanan Chen, Kai Yao, Zengping Liu, Bhav Harshad Parikh, Linzhi Jing, Tiange Liu, Xinyi Su, Jie Sun, Dejian Huang

Age-related macular degeneration (AMD) is the leading cause of visual loss and affects millions of people worldwide. Dysfunction of the retinal pigment epithelium (RPE) is associated with the pathogenesis of AMD. The purpose of this work is to build and evaluate the performance of ultrathin scaffolds with an electrohydrodynamic jet (EHDJ) printing method for RPE cell culture. We printed two types of ultrathin (around 7 μm) polycaprolactone scaffolds with 20 μm and 50 μm pores, which possess mechanical properties resembling that of native human Bruch’s membrane and are biodegradable. Light microscopy and cell proliferation assay showed that adult human retinal pigment epithelial (ARPE-19) cells adhered and proliferated to form a monolayer on the scaffolds. The progress of culture matured on the scaffolds was demonstrated by immunofluorescence (actin, ZO-1, and Na+/K+-ATPase) and Western blot analysis of the respective proteins. The RPE cells cultured on EHDJ-printed scaffolds with 20 μm pores presented higher permeability, higher transepithelial potential difference, and higher expression level of Na+/K+-ATPase than those cultured on Transwell inserts. These findings suggest that the EHDJ printing can fabricate scaffolds that mimic Bruch’s membrane by promoting maturation of RPE cells to form a polarized and functional monolayered epithelium with potential as an in vitro model for studying retinal diseases and treatment methods.

Original Articles

by Xiaomin Duan, Wei Wang, Wenping Ma, Zhenhui Mao, Fangliang Xing, Xin Zhao

It is technically challenging for pediatric anesthesiologists to use bronchial blocker (BB) to isolate the lungs of infants during thoracoscopic surgery. Further, BB currently sold in the market cannot match the anatomical characteristics of the infants, especially on the right main bronchus. It may easily cause poor exhaustion of the right upper lobe, which leads to interference with the thoracoscopic surgical field. The two dimensional reconstruction data of 124 normal infants’ airways were extracted from the medical image database of Beijing Children’s Hospital for statistical analysis. After using linear fitting and goodness-of-fit test, a good linear relationship was detected between infant age and various parameters related to aid in designing a new BB for infants (R2=0.502). According to the growth and development rate of infants, the DICOM files of airway CT scan of 7 infants aged 30, 60, 90, 120, 180, 270, and 360 days were selected to print non-transparent convex and transparent concave 3D models. The non-transparent convex model was precisely measured to obtain the important parameters for BB design infants only, to complete the design of BB, to generate the sample, and to verify the blocking effect of produced sample in transparent concave three-dimensional (3D) model.

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Original Articles

by Reza Noroozi, Farzad Tatar, Ali Zolfagharian, Roberto Brighenti, Mohammad Amin Shamekhi, Abbas Rastgoo, Amin Hadi, Mahdi Bodaghi

Tissue engineering, whose aim is to repair or replace damaged tissues by combining the principle of biomaterials and cell transplantation, is one of the most important and interdisciplinary fields of regenerative medicine. Despite remarkable progress, there are still some limitations in the tissue engineering field, among which designing and manufacturing suitable scaffolds. With the advent of additive manufacturing (AM), a breakthrough happened in the production of complex geometries. In this vein, AM has enhanced the field of bioprinting in generating biomimicking organs or artificial tissues possessing the required porous graded structure. In this study, triply periodic minimal surface structures, suitable to manufacture scaffolds mimicking bone’s heterogeneous nature, have been studied experimentally and numerically; the influence of the printing direction and printing material has been investigated. Various multi-morphology scaffolds, including gyroid, diamond, and I-graph and wrapped package graph (I-WP), with different transitional zone, have been three-dimensional (3D) printed and tested under compression. Further, a micro-computed tomography (μCT) analysis has been employed to obtain the real geometry of printed scaffolds. Finite element analyses have been also performed and compared with experimental results. Finally, the scaffolds’ behavior under complex loading has been investigated based on the combination of μCT and finite element modeling.

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Original Articles

by Chanh Trung Nguyen, Van Thuy Duong, Chang Ho Hwang, Kyo-in Koo

Rapid construction of pre-vascular structure is highly desired for engineered thick tissue. However, angiogenesis in free-standing scaffold has been rarely reported because of limitation in growth factor (GF) supply into the scaffold. This study, for the 1st time, investigated angiogenic sprouting in free-standing two-vasculature-embedded scaffold with three different culture conditions and additional GFs. A two-core laminar flow device continuously extruded one vascular channel with human umbilical vein endothelial cells (HUVECs) and a 3 mg/ml type-1 collagen, one hollow channel, and a shell layer with 2% w/v gelatin-alginate (70:30) composite. Under the GF flowing condition, angiogenic sprouting from the HUVEC vessel had started since day 1 and gradually grew toward the hollow channel on day 10. Due to the medium flowing, the HUVECs showed elongated spindle-like morphology homogeneously. Their viability has been over 80% up to day 10. This approach could apply to vascular investigation, and drug discovery further, not only to the engineered thick tissue.

Review Articles

by Qiushi Liang, Yuanzhu Ma, Xudong Yao, Wei Wei

Chondral lesions caused by stressors, such as injury or inflammation, lead to osteoarthritis (OA). OA is a degenerative joint disease that has become a challenge worldwide. As the articular cartilage is incapable of self-regeneration due to the absence of vessels and nerves, novel cartilage repair techniques are urgently needed. Three-dimensional (3D) bioprinting, which allows the precise control of internal architecture and geometry of printed scaffolds, has stepped up to be a promising strategy in cartilage restoration. With regards to 3D bioprinting, bioinks with proper chemical and mechanical properties play one of the most critical roles in designing successful cartilage tissue constructs. In particular, hydrogels as 3D hydrophilic cross-linked polymer networks are highly recommended as bioinks because of their fine biocompatibility, easy fabrication, and tunable mechanical strength. Herein, we highlight the widely used polymers for hydrogel preparation and further provide a non-exhaustive overview of various functional modified additives (such as cells, drugs, bioactive factors and ceramic) to exploit the unique properties suitable for bioprinted cartilage. Finally, a prospective on future development for 3D-bioprinting in cartilage repair is elucidated in this review.

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