Table of Contents

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Editorials

Call for special issues
by Chee Kai Chua
53 Views, 35 PDF Downloads
Call for special issues
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Perspective Articles

by Rong Feng Zhang, Peng Yun Wang, Ming Yang, Xuebo Dong, Xue Liu, Yiguang Sang, An Tong
95 Views, 43 PDF Downloads

Additive manufacturing has been used in complex spinal surgical planning since the 1990s and is now increasingly utilized to produce surgical guides, templates, and more recently customized implants. Surgeons report beneficial impacts using additively manufactured biomodels as pre-operative planning aids as it generally provides a better representation of the patient’s anatomy than on-screen viewing of computed tomography (CT) or magnetic resonance imaging (MRI). Furthermore, it has proven to be very beneficial in surgical training and in explaining complex deformity and surgical plans to patients/ parents. This paper reviews the historical perspective, current use, and future directions in using additive manufacturing in complex spinal surgery cases. This review reflects the authors’ opinion of where the field is moving in light of the current literature. Despite the reported benefits of additive manufacturing for surgical planning in recent years, it remains a high niche market. This review raises the question as to why the use of this technology has not progressed more rapidly despite the reported advantages – decreased operating time, decreased radiation exposure to patients intraoperatively, improved overall surgical outcomes, pre-operative implant selection, as well as being an excellent communication aid for all medical and surgical team members. Increasingly, the greatest benefits of additive manufacturing technology in spinal surgery are customdesigned drill guides, templates for pedicle screw placement, and customized patient-specific implants. In view of these applications, additive manufacturing technology could potentially revolutionize health care in the near future.

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Perspective Articles

by Yi Zhang
45 Views, 29 PDF Downloads

As microfluidic devices are designed to tackle more intricate tasks, the architecture of microfluidic devices
becomes more complex, and more sophisticated fabrication techniques are in demand. Therefore, it is sensible to fabricate
microfluidic devices by three-dimensional (3D)-printing, which is well-recognized for its unique ability to monolithically
fabricate complex structures using a near-net-shape additive manufacturing process. Many 3D-printed microfluidic platforms
have been demonstrated but can 3D-printed microfluidics meet the demanding requirements in today’s context, and has
microfluidics truly benefited from 3D-printing? In contrast to 3D-printed microfluidics, some go the other way around and
exploit microfluidics for 3D-printing. Many innovative printing strategies have been made possible with microfluidicsenabled
3D-printing, although the limitations are also largely evident. In this perspective article, we take a look at the current
development in 3D-printed microfluidics and microfluidics-enabled 3D printing with a strong focus on the limitations of the
two technologies. More importantly, we attempt to identify the innovations required to overcome these limitations and to
develop new high-value applications that would make a scientific and social impact in the future.

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Original Articles

by Mishbak H. H, Glen Cooper, Paulo Jorge Da Silva Bartolo
105 Views, 70 PDF Downloads

Alginate is a biocompatible material suitable for biomedical applications, which can be processed under mild conditions upon irradiation.  This paper investigates the preparation and the rheological behaviour of different pre-polymerised and polymerised alginate-methacrylate systems for 3D photopolymerisation bioprinting. The effect of the functionalization time on the mechanical, morphological, swelling and degradation characteristics of crosslinked alginate hydrogel is also discussed.  Alginate was chemically-modified with methacrylate groups and different reaction times considered. Photocurable alginate systems were prepared  by dissolving functionalized alginate with 0.5-1.5% photoinitiator solution and crosslinked by ultraviolet (UV) light (8 mW/cm2).

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Original Articles

by Daisuke Takagi, Waka Lin, Takahiko Matsumoto, Hidekazu Yaginuma, Natsuko Hemmi, Shigeo Hatada, Manabu Seo
90 Views, 65 PDF Downloads
In recent years, bioprinting has emerged as a promising technology for the construction of three-dimensional (3D) tissues to be used in regenerative medicine or in vitro screening applications. In the present study, we present the development of an inkjet-based bioprinting system to arrange multiple cells and materials precisely into structurally organized constructs. A novel inkjet printhead has been specially designed for live cell ejection. Droplet formation is powered by piezoelectric membrane vibrations coupled with mixing movements to prevent cell sedimentation at the nozzle. Stable drop-on-demand dispensing and cell viability were validated over an adequately long time to allow the fabrication of 3D tissues. Reliable control of cell number and spatial positioning was demonstrated using two separate suspensions with different cell types printed sequentially. Finally, a process for constructing stratified Mille-Feuille-like 3D structures is proposed by alternately superimposing cell suspensions and hydrogel layers with a controlled vertical resolution. The results show that inkjet technology is effective for both two-dimensional patterning and 3D multilayering and has the potential to facilitate the achievement of live cell bioprinting with an unprecedented level of precision.
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Original Articles

by Fan Feng, Jiankang He, Jiaxin Li, Mao Mao, Dichen Li
49 Views, 4 PDF Downloads
Multimaterial bioprinting provides a promising strategy to recapitulate complex heterogeneous architectures of native tissues in artificial tissue analogs in a controlled manner. However, most of the existing multimaterial bioprinting techniques relying on multiple printing nozzles and complicate control program make it difficult to flexibly change the material composition during the printing process. Here, we developed a multicomponent bioprinting strategy to produce heterogeneous constructs using a microfluidic printhead with multiple inlets and one outlet. The composition of the printed filaments can be flexibly changed by adjusting volumetric flow rate ratio. Heterogeneous hydrogel constructs were successfully printed to have predefined spatial gradients of inks or microparticles. A rotary microfluidic printhead was used to maintain the heterogeneous morphology of the printed filaments as the printing path direction changed. Multicellular concentric ring constructs with two kinds of cell types distribution in the printed filaments were fabricated by utilizing coaxial microfluidic printhead and rotary collecting substrate, which significantly improves the printing efficiency for multicomponent concentric structures. The presented approach is simple and promising to potentially print multicomponent heterogeneous constructs for the fabrication of artificial multicellular tissues.
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Original Articles

by Cijun Shuai, Wenjing Yang, Youwen Yang, Chengde Gao, Chongxian He, Hao Pan
37 Views, 36 PDF Downloads

Mg alloys degrade rather rapidly in a physiological environment, although they have good biocompatibility and
favorable mechanical properties. In this study, Ti was introduced into AZ61 alloy fabricated by selective laser melting,
aiming to improve the corrosion resistance. Results indicated that Ti promoted the formation of Al-enriched eutectic α phase
and reduced the formation of β-Mg17Al12 phase. With Ti content reaching to 0.5 wt.%, the Al-enriched eutectic α phase
constructed a continuous net-like structure along the grain boundaries, which could act as a barrier to prevent the Mg matrix
from corrosion progression. On the other hand, the Al-enriched eutectic α phase was less cathodic than β-Mg17Al12 phase in
AZ61, thus alleviating the corrosion progress due to the decreased potential difference. As a consequence, the degradation
rate dramatically decreased from 0.74 to 0.24 mg·cm-2·d-1. Meanwhile, the compressive strength and microhardness were
increased by 59.4% and 15.6%, respectively. Moreover, the Ti-contained AZ61 alloy exhibited improved cytocompatibility.
It was suggested that Ti-contained AZ61 alloy was a promising material for bone implants application.

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Original Articles

by Yu Fang Shen
18 Views, 10 PDF Downloads
With the development of 3D printing, many commercial 3D printing materials have been applied in the fields of biomedicine and medical. MED610 is a clear, biocompatible PolyJet material that is medically certified for bodily contact. In this study, the poly dopamine (PDA)/ hydroxyapatite (HA) coating was added to the printed MED610 objects to evaluate its physical properties, cell proliferation, cell morphology, and alkaline phosphatase (ALP) expression level. The results show that the PDA/HA coating helps printed objects to enhance the hardness, biocompatibility and osteogenic differentiation potential. We expect that PDA/HA coatings contribute to the applicability of MED610 in biomedical and medical applications.
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Original Articles

by Wafaa Arab, Kowther Kahin, Zainab Khan, Charlotte Hauser
50 Views, 31 PDF Downloads

Injured skeletal muscles which lose more than 20% of their volume, known as volumetric muscle loss, can no longer regenerate cells through self-healing. The traditional solution for recovery is through regenerative therapy. As the technology of three-dimensional (3D) bioprinting continues to advance, a new approach for tissue transplantation is using biocompatible materials arranged in 3D scaffolds for muscle repair. Ultrashort self-assembling peptide hydrogels compete as a potential biomaterial for muscle tissue formation due to their biocompatibility. In this study, two sequences of ultrashort peptides were analyzed with muscle myoblast cells (C2C12) for cell viability, cell proliferation, and differentiation in 3D cell culture. The peptides were then extruded through a custom-designed robotic 3D bioprinter to create cell-laden 3D structures. These constructs were also analyzed for cell viability through live/dead assay. Results showed that 3D bioprinted structures of peptide hydrogels could be used as tissue platforms for myotube formation – a process necessary for muscle repair.

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Original Articles

by Ao Fang, Zhiyan Hao, Ling Wang, Dichen Li, Jiankang He, Lin Gao, Xinggang Mao, Ruben Paz
97 Views, 31 PDF Downloads
The trauma of central nervous system (CNS) can lead to glial scar, and it can limit the regeneration of neurons at the injured area, which is considered to be a major factor affecting the functional recovery of patients with CNS injury. At present, the study of the glial scar model in vitro is still limited to two-dimensional culture, and the state of the scar in vivo cannot be well mimicked. Therefore, we use a collagen gel and astrocytes to construct a three-dimensional (3D) model in vitro to mimic natural glial scar tissue. The effects of concentration changes of astrocytes on cell morphology, proliferation, and tissue performance were investigated. After 8 days of culture in vitro, the results showed that the tissue model contracted, with a measured shrinkage rate of 4.5%, and the compressive elastic modulus increased to nearly 4 times. Moreover, the astrocytes of the 3D tissue model have the ability of proliferation, hyperplasia, and formation of scar clusters. It indicates that the model we constructed has the characteristics of glial scar tissue to some extent and can provide an in vitro model for the research of glial scar and brain diseases.
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Original Articles

by Sarah Ghalayini, Hepi Hari Susapto, Sophie Hall, Kowther Kahin, Charlotte Hauser
99 Views, 52 PDF Downloads

Nanoparticles (NPs) have left their mark on the field of bioengineering. Fabricated from metallic, magnetic, and metal oxide materials, their applications include drug delivery, bioimaging, and cell labeling. However, as they enter the body, the question remains – where do they go after fulfilling their designated function? As most materials used to produce NPs are not naturally found in the body, they are not biodegradable and may accumulate overtime. There is a lack of comprehensive, long-term studies assessing the biodistribution of non-biodegradable NPs for even the most widely studied NPs. There is a clear need for NPs produced from natural materials capable of degradation in vivo. As peptides exist naturally within the human body, their non-toxic and biocompatible nature comes as no surprise. Ultrashort peptides are aliphatic peptides designed with three to seven amino acids capable of self-assembling into helical fibers within macromolecular structures. Using a microfluidics flow-focusing approach, we produced different peptide-based NPs that were then three-dimensional (3D) printed with our novel printer setup. Herein, we describe the preparation method of NPs from ultrashort self-assembling peptides and their morphology in both manual and 3D-printed hydrogels, thus suggesting that peptide NPs are capable of withstanding the stresses involved in the printing process

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Methods

by Laurene Lenoir, Frederic Segonds, Kim-Anh Nguyen, Pablo Bartolucci
37 Views, 12 PDF Downloads

Today, additive manufacturing (AM) is implemented in medical industry and profoundly revolutionizes this area. This approach consists of producing parts by additions of layers of successive materials and offers advantages in terms of rapidity, complexity of parts, competitive costs that can be exploited and can lead to a significant advancement in biological research. Everything becomes technically feasible and gives way to a “techno-centered” approach. Many parameters must be controlled in this field, so it is necessary to be guided for the development of such a product. This article aims to present a state of the art of existing design methodologies focused on AM to create medical devices. Finally, a development method is proposed that consists of producing vascular geometry using AM, based on patient data, designed for cell culture in vitro studies.

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Retraction Note

Retraction: Application of 3D printing technology in orthopedic medical implant - Spinal surgery as an example
by Chee Kai Chua
73 Views, 30 PDF Downloads
Retraction: Application of 3D printing technology in orthopedic medical implant - Spinal surgery as an example
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