Vol 4, No 2 (2018)





Table of Contents

Cover Image

Editorials

Bioprinting science
by Chee Kai Chua
254 Views, 85 PDF Downloads
Bioprinting science
PDF

Perspective Articles

by Jia Min Lee, Swee Leong Sing, Miaomiao Zhou, Wai Yee Yeong
1778 Views, 185 PDF Downloads
This article aims to provide further classification of cell-compatible bioprinting processes and examine the concept of 3D bioprinting within the general technology field of 3D printing. These technologies are categorized into four distinct process categories, namely material jetting, vat photopolymerization, material extrusion and free-form spatial printing. Discussion will be presented on the definition of classification with example of techniques grouped under the same category. The objective of this article is to establish a basic framework for standardization of process terminology in order to accelerate the implementation of bioprinting technologies in research and commercial landscape.
PDF

Review Articles

by Cijun Shuai, Wenjing Yang, Shuping Peng, Chengde Gao, Wang Guo, Yuxiao Lai, Pei Feng
1604 Views, 123 PDF Downloads
Physical stimulations such as magnetic, electric and mechanical stimulation could enhance cell activity and promote bone formation in bone repair process via activating signal pathways, modulating ion channels, regulating bone-related gene expressions, etc. In this paper, bioeffects of physical stimulations on cell activity, tissue growth and bone healing were systematically summarized, which especially focused on their osteogenesis-inducing mechanisms. Detailedly, magnetic stimulation could produce Hall effect which improved the permeability of cell membrane and promoted the migration of ions, especially accelerating the extracellular calcium ions to pass through cell membrane. Electric stimulation could induce inverse piezoelectric effect which generated electric signals, accordingly up-regulating intracellular calcium levels and growth factor synthesis. And mechanical stimulation could produce mechanical signals which were converted into corresponding biochemical signals, thus activating various signaling pathways on cell membrane and inducing a series of gene expressions. Besides, the equipments of physical stimulation system were discussed. The opportunities and challenges of physical stimulations were also presented from the perspective of bone repair.
PDF

Review Articles

by Deepak Choudhury, Shivesh Anand, May Win Naing
1837 Views, 529 PDF Downloads

The dawn of commercial bioprinting is rapidly advancing the tissue engineering field. In the past few years, new bioprinting approaches as well as novel bioinks formulations have emerged, enabling biological research groups to demonstrate the use of such technology to fabricate functional and relevant tissue models. In recent years, several companies have launched bioprinters pushing for early adoption and democratisation of bioprinting. This article reviews the progress in commercial bioprinting since the inception, with a particular focus on the comparison of different available printing technologies and important features of the individual technologies as well as various existing applications. Various challenges and potential design considerations for next generations of bioprinters are also discussed.

PDF

Review Articles

by Hooi Yee Ng, Kai-Xing Alvin Lee, Che-Nan Kuo, Yu-Fang Shen
1677 Views, 360 PDF Downloads
Vascular networks have an important role to play in transporting nutrients, oxygen, metabolic wastes and maintenance of homeostasis. Bioprinting is a promising technology as it is able to fabricate complex, specific multi-cellular constructs with precision. In addition, current technology allows precise depositions of individual cells, growth factors and biochemical signals to enhance vascular growth. Fabrication of vascularized constructs has remained as a main challenge till date but it is deemed as an important stepping stone to bring organ engineering to a higher level. However, with the ever advancing bioprinting technology and knowledge of biomaterials, it is expected that bioprinting can be a viable solution for this problem. This article presents an overview of the biofabrication of vascular and vascularized constructs, the different techniques used in vascular engineering such as extrusion-based, droplet-based and laser-based bioprinting techniques, and the future prospects of bioprinting of artificial blood vessels.
PDF

Review Articles

by Cavin Tan, Wei Yan Toh, Gladys Wong, Li Lin
1566 Views, 425 PDF Downloads

To help people with dysphagia increase their food intake, 3D printing can be used to improve the visual appeal of pureed diets. In this review, we have looked at the works done to date on extrusion-based 3D food printing with an emphasis on the edible materials (food inks) and machinery (printers) used. We discuss several methods that researchers have employed to modify conventional food materials into printable formulations. In general, additives such as hydrocolloids may modify the rheological properties and texture of a pureed food to confer printability. Some examples of such additives include starch, pectin, gelatin, nanocellulose, alginate, carrageenan etc. In the second part, we have looked at various food printers that have been developed for both academic and commercial purposes. We identified several common advantages and limitations that these printers shared. Moving forward, future research into food printer development should aim to improve on these strengths, eliminate these limitations and incorporate new capabilities.

PDF

Original Articles

by Wafaa Arab, Sakandar Rauf, Ohoud Al-Harbi, Charlotte Hauser
1407 Views, 128 PDF Downloads
The ability of skeletal muscle to self-repair after a traumatic injury, tumor ablation, or muscular disease is slow and limited, and the capacity of skeletal muscle to self-regenerate declines steeply with age. Tissue engineering of functional skeletal muscle using 3D bioprinting technology is promising for creating tissue constructs that repair and promote regeneration of damaged tissue. Hydrogel scaffolds used as biomaterials for skeletal muscle tissue engineering can provide chemical, physical and mechanical cues to the cells in three dimensions thus promoting regeneration. Herein, we have developed two synthetically designed novel tetramer peptide biomaterials. These peptides are self-assembling into a nanofibrous 3D network, entrapping 99.9% water and mimicking the native collagen of an extracellular matrix. Different biocompatibility assays including MTT, 3D cell viability assay, cytotoxicity assay and live-dead assay confirm the biocompatibility of these peptide hydrogels for mouse myoblast cells (C2C12). Immunofluorescence analysis of cell-laden hydrogels revealed that the proliferation of C2C12 cells was well-aligned in the peptide hydrogels compared to the alginate-gelatin control. These results indicate that these peptide hydrogels are suitable for skeletal muscle tissue engineering. Finally, we tested the printability of the peptide bioinks using a commercially available 3D bioprinter. The ability to print these hydrogels will enable future development of 3D bioprinted scaffolds containing skeletal muscle myoblasts for tissue engineering applications.
PDF

Original Articles

by Cijun Shuai, Youwen Yang, Pei Feng, Shuping Peng, Wang Guo, Anjie Min, Chengde Gao
1829 Views, 251 PDF Downloads

It is critical to develop a fabrication technology for precisely controlling an interconnected porous structure of scaffolds to mimic the native bone microenvironment. In this work, a novel combined process of additive manufacturing (AM) and chemical etching was developed to fabricate graphene oxide/poly(L-lactic acid) (GO/PLLA) scaffolds with multi-scale porous structure. Specially, AM was used to fabricate an interconnected porous network with pore sizes of hundreds of microns. And the chemical etching in sodium hydroxide solution constructed pores with several microns or even smaller on scaffolds surface. The degradation period of the scaffolds was adjustable via controlling the size and quantity of pores. Moreover, the scaffolds exhibited surprising bioactivity after chemical etching, which was ascribed to the formed polar groups on scaffolds surfaces. Furthermore, GO improved the mechanical strength of the scaffolds.

PDF

Original Articles

by Xiaoxiao Han, Julien Courseaus, Jamel Khamassi, Nadine Nottrodt, Sascha Engelhardt, Frank Jacobsen, Claas Bierwisch, Wolfdietrich Meyer, Torsten Walter, Jürgen Weisser, Raimund Jaeger, Richard Bibb, Russell Harris
1873 Views, 143 PDF Downloads

This paper demonstrates the essential and efficient methods to design, and fabricate optimal vascular network for tissue engineering structures based on their physiological conditions. Comprehensive physiological requirements in both micro and macro scales were considered in developing the optimisation design for complex vascular vessels. The optimised design was then manufactured by stereolithography process using materials that are biocompatible, elastic and surface bio-coatable. The materials are self-developed photocurable resin consist of BPA-ethoxylated-diacrylate, lauryl acrylate and isobornylacrylate with Irgacure® 184, the photoinitiator. The optimised vascular vessel offers many advantages: 1) it provides the maximum nutrient supply; 2) it minimises the recirculation areas and 3) it allows the wall shear stress on the vessel in a healthy range. The stereolithography manufactured vascular vessels were then embedded in the hydrogel seeded with cells. The results of in vitro studies show that the optimised vascular network has the lowest cell death rate compared with a pure hydrogel scaffold and a hydrogel scaffold embedded within a single tube in day seven. Consequently, these design and manufacture routes were shown to be viable for exploring and developing a high range complex and specialised artificial vascular networks. 

PDF

Original Articles

by Denise Mandt, Peter Gruber, Marica Markovic, Maximillian Tromayer, Mario Rothbauer, Sebastian Rudi Adam Krayz, Faheem Ali, Jasper van Hoorick, Wolfgang Holnthoner, Severin Mühleder, Peter Dubruel, Sandra Van Vlierberghe, Peter Ertl, Robert Liska, Aleksandr Ovsianikov
2766 Views, 359 PDF Downloads
The placenta is a transient organ, essential for development and survival of the unborn fetus. It interfaces the body of the pregnant woman with the unborn child and secures transport of endogenous and exogenous substances. Maternal and fetal blood are thereby separated at any time, by the so-called placental barrier. Current in vitro approaches fail to model this multifaceted structure, therefore research in the field of placental biology is particularly challenging. The present study aimed at establishing a novel model, simulating placental transport and its implications on development, in a versatile but reproducible way. The basal membrane was replicated using a gelatin-based material, closely mimicking the composition and properties of the natural extracellular matrix. The microstructure was produced by using a high-resolution 3D printing method – the two-photon polymerization (2PP). In order to structure gelatin by 2PP, its primary amines and carboxylic acids are modified with methacrylamides and methacrylates (GelMOD-AEMA), respectively. High-resolution structures in the range of a few micrometers were produced within the intersection of a customized microfluidic device, separating the x-shaped chamber into two isolated cell culture compartments. Human umbilical-vein endothelial cells (HUVEC) seeded on one side of this membrane simulate the fetal compartment while human choriocarcinoma cells, isolated from placental tissue (BeWo B30) mimic the maternal syncytium. This barrier model in combination with native flow profiles can be used to mimic the microenvironment of the placenta, investigating different pharmaceutical, clinical and biological scenarios. As proof-of-principle, this bioengineered placental barrier was used for the investigation of transcellular transport processes. While high molecular weight substances did not permeate, smaller molecules in the size of glucose were able to diffuse through the barrier in a time-depended manner. We envision to apply this bioengineered placental barrier for pathophysiological research, where altered nutrient transport is associated with health risks for the fetus.
PDF

Original Articles

by Leonardo Azael Garcia-Garcia, Marisela Rodriguez-Salvador
1400 Views, 150 PDF Downloads
A scientometric analysis as part of a Competitive Technology Intelligence methodology was used to determine the main research efforts in 3D bioprinting. Papers from Scopus and Web of Science (WoS) published between 2000 and 2017 were analysed. A network map of the most frequently occurring keywords in these articles was created, and their average publication year (APY) was determined. The analysis focused on the most relevant keywords that occurred at least five times. A total of 1,759 keywords were obtained, and a co-occurrence analysis was developed for APYs with more keywords: 2011–2016. The results indicated that Polylactic Acid (PLA) is the material used most often. Applications mainly focused on bone tissue engineering and regeneration. The most frequently used technique was inkjet printing, and the main cell sources were Mesenchymal Stem Cells (MSC). From a general perspective, ‘Treatment’ and ‘Bioink’ were the most frequent keywords. The former was mainly related to cancer, regenerative medicine, and MSC and the latter, to multicellular spheroid deposition and the use of hydrogels like GelMA (gelatin methacryloyl). This analysis provides insights to stakeholders involved in 3D bioprinting research and development who need to keep abreast of scientific progress in the field.
PDF