A continues multi-material toolpath planning for tissue scaffolds with hollowed features

This paper presents a new multi-material based toolpath planning methodology for porous tissue scaffolds with multiple hollowed features. Ruled surface with hollowed features generated in our earlier work is used to develop toolpath planning. Ruling lines are reoriented to enable continuous and uniform size multi-material printing through them in two steps. Firstly, all ruling lines are matched and connected to eliminate start and stops during printing. Then, regions with high number of ruling lines are relaxed using a relaxation technique to eliminate over deposition. A novel layer-by-layer deposition process is progressed in two consecutive layers: The first layer with hollow shape based zigzag pattern and the next layer with spiral pattern deposition. Heterogeneous material properties are mapped based on the parametric distances from the hollow features

Application areas of 3D bioprinting

PubMedID: 27086009Three dimensional (3D) bioprinting has been a powerful tool in patterning and precisely placing biologics, including living cells, nucleic acids, drug particles, proteins and growth factors, to recapitulate tissue anatomy, biology and physiology. Since the first time of cytoscribing cells demonstrated in 1986, bioprinting has made a substantial leap forward, particularly in the past 10 years, and it has been widely used in fabrication of living tissues for various application areas. The technology has been recently commercialized by several emerging businesses, and bioprinters and bioprinted tissues have gained significant interest in medicine and pharmaceutics. This Keynote review presents the bioprinting technology and covers a first-time comprehensive overview of its application areas from tissue engineering and regenerative medicine to pharmaceutics and cancer research. © 2016 Elsevier LtdChina Scholarship Council: 201308360128 1462232, 1349716, 426 Pennsylvania State UniversityThis work has been supported by National Science Foundation CMMI Awards 1349716 and 1462232 , Diabetes in Action Research and Education Foundation grant #426 and the China Scholarship Council 201308360128 . Ibrahim Tarik Ozbolat is an Associate Professor in the Engineering Science and Mechanics Department and the Huck Institutes of the Life Sciences at Penn State University. He received his PhD from the University at Buffalo, New York, and dual BS degrees in mechanical and industrial engineering from Middle East Technical University, Turkey. Dr Ozbolat's major research effort is in the area of 3D bioprinting. He has published over 80 journal and conference articles, and his research has been featured in local, national and international media. He is the recipient of several prestigious international awards. Weijie Peng received his PhD degree from the Department of Pharmacology, Central South University, China, in 2005. He is an Associate Professor in the Department of Pharmacology, Nanchang University, China. He has recently joined the Ozbolat Lab at Penn State University as a visiting scholar supported by the Chinese Scholarship Committee. His major research work is on estrogen receptor, estrogenic substances and bioprinting for pharmaceutical research. Veli Ozbolat received his BS degree in mechanical engineering from the Middle East Technical University, Ankara, Turkey, in 2008; and his MS degree in industrial engineering from the University at Buffalo, New York, USA, in 2010. He obtained his PhD in mechanical engineering from Cukurova University, Adana, Turkey, in 2015. He will join Penn State University as a postdoctoral scholar in Summer 2016. His research mainly focuses on biomedical engineering, heat transfer and fluid mechanics

Extrusion-based printing of sacrificial Carbopol ink for fabrication of microfluidic devices

PubMedID: 30884470Current technologies for manufacturing of microfluidic devices include soft-lithography, wet and dry etching, thermoforming, micro-machining and three-dimensional (3D) printing. Among them, soft-lithography has been the mostly preferred one in medical and pharmaceutical fields due to its ability to generate polydimethylsiloxane (PDMS) devices with resin biocompatibility, throughput and transparency for imaging. It is a multi-step process requiring the preparation of a silicon wafer pattern, which is fabricated using photolithography according to a defined mask. Photolithography is a costly, complicated and time-consuming process requiring a clean-room environment, and the technology is not readily accessible in most of the developing countries. In addition, generated patterns on photolithography-made silicon wafers do not allow building 3D intricate shapes and silicon direct bonding is thus utilized for closed fluid channels and complex 3D structures. 3D Printing of PDMS has recently gained significant interest due to its ability to define complex 3D shapes directly from user-defined designs. In this work, we investigated Carbopol as a sacrificial gel in order to create microfluidic channels in PDMS devices. Our study demonstrated that Carbopol ink possessed a shear-thinning behavior and enabled the extrusion-based printing of channel templates, which were overlaid with PDMS to create microfluidic devices upon curing of PDMS and removal of the sacrificial Carbopol ink. To demonstrate the effectiveness of the fabricated devices, channels were lined up with human umbilical vein endothelial cells (HUVECs) and human bone marrow endothelial cells (BMECs) in separate devices, where both HUVECs and BMECs demonstrated the formation of endothelium with highly aligned cells in the direction of fluid flow. Overall, we here present a highly affordable and practical approach in fabrication of PDMS devices with closed fluid channels, which have great potential in a myriad of applications from cancer treatments to infectious disease diagnostics to artificial organs. © 2019 IOP Publishing Ltd

Bone tissue bioprinting for craniofacial reconstruction

PubMedID: 28600873Craniofacial (CF) tissue is an architecturally complex tissue consisting of both bone and soft tissues with significant patient specific variations. Conditions of congenital abnormalities, tumor resection surgeries, and traumatic injuries of the CF skeleton can result in major deficits of bone tissue. Despite advances in surgical reconstruction techniques, management of CF osseous deficits remains a challenge. Due its inherent versatility, bioprinting offers a promising solution to address these issues. In this review, we present and analyze the current state of bioprinting of bone tissue and highlight how these techniques may be adapted to serve regenerative therapies for CF applications. Biotechnol. Bioeng. 2017;114: 2424–2431. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.National Science Foundation Division of Civil, Mechanical and Manufacturing Innovation: http://onlinelibrary.wiley.com/doi/10.1002/bit.26349/abstractConflicts of interest: The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. Correspondence to: Ibrahim T. Ozbolat Contract grant sponsor: National Science Foundation, Division of Civil, Mechanical and Manufacturing Innovation Contract grant number: 1600118 Received 3 April 2017; Revision received 3 June 2017; Accepted 6 June 2017 Accepted manuscript online 10 June 2017; Article first published online 29 August 2017 in Wiley Online Library (http://onlinelibrary.wiley.com/doi/10.1002/bit.26349/abstract). DOI 10.1002/bit.2634

Thermally-controlled extrusion-based bioprinting of collagen

PubMedID: 31041538Thermally-crosslinked hydrogels in bioprinting have gained increasing attention due to their ability to undergo tunable crosslinking by modulating the temperature and time of crosslinking. In this paper, we present a new bioink composed of collagen type-I and Pluronic® F-127 hydrogels, which was bioprinted using a thermally-controlled bioprinting unit. Bioprintability and rheology of the composite bioink was studied in a thorough manner in order to determine the optimal bioprinting time and extrusion profile of the bioink for fabrication of three-dimensional (3D) constructs, respectively. It was observed that collagen fibers aligned themselves along the directions of the printed filaments after bioprinting based on the results on an anisotropy study. Furthermore, rat bone marrow-derived stem cells (rBMSCs) were bioprinted in order to determine the effect of thermally-controlled extrusion process. In vitro viability and proliferation study revealed that rBMSCs were able to maintain their viability after extrusion and attached to collagen fibers, spread and proliferated within the constructs up to seven days of culture. [Figure not available: see fulltext.]. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.National Science Foundation: CMMI 1462232 Osteology Foundation: 15–042 BIDEP 2219 Türkiye Bilimsel ve Teknolojik Araştirma KurumuAcknowledgements This work was supported by the National Science Foundation Award (CMMI 1462232) and Osteology Foundation Award # 15–042. Dr. Veli Ozbolat acknowledges the support from the International Postdoctoral Research Scholarship Program (BIDEP 2219) of the Scientific and Technological Research Council of Turkey (TUBITAK). The authors would like to thank Dr. Albert Ratner (Mechanical and Industrial Engineering Department, University of Iowa, Iowa City, USA) providing the FLIR thermal camera system. The authors would like to thank Ethan M. Gerhard, Dr. Jian Yang and Kevin P. Godzik (Department of Biomedical Engineering, Penn State University, University Park, USA) for their assistance with the mechanical testing and the rheology study, respectively. The authors would like to also thank Mrs. Alyssa Sipos with her assistance to PSR and immunofluorescence staining. There has been no significant financial support for this work that could have influenced its outcome

3D bioprinting for drug discovery and development in pharmaceutics

PubMedID: 28501712Successful launch of a commercial drug requires significant investment of time and financial resources wherein late-stage failures become a reason for catastrophic failures in drug discovery. This calls for infusing constant innovations in technologies, which can give reliable prediction of efficacy, and more importantly, toxicology of the compound early in the drug discovery process before clinical trials. Though computational advances have resulted in more rationale in silico designing, in vitro experimental studies still require gaining industry confidence and improving in vitro-in vivo correlations. In this quest, due to their ability to mimic the spatial and chemical attributes of native tissues, three-dimensional (3D) tissue models have now proven to provide better results for drug screening compared to traditional two-dimensional (2D) models. However, in vitro fabrication of living tissues has remained a bottleneck in realizing the full potential of 3D models. Recent advances in bioprinting provide a valuable tool to fabricate biomimetic constructs, which can be applied in different stages of drug discovery research. This paper presents the first comprehensive review of bioprinting techniques applied for fabrication of 3D tissue models for pharmaceutical studies. A comparative evaluation of different bioprinting modalities is performed to assess the performance and ability of fabricating 3D tissue models for pharmaceutical use as the critical selection of bioprinting modalities indeed plays a crucial role in efficacy and toxicology testing of drugs and accelerates the drug development cycle. In addition, limitations with current tissue models are discussed thoroughly and future prospects of the role of bioprinting in pharmaceutics are provided to the reader. Statement of Significance Present advances in tissue biofabrication have crucial role to play in aiding the pharmaceutical development process achieve its objectives. Advent of three-dimensional (3D) models, in particular, is viewed with immense interest by the community due to their ability to mimic in vivo hierarchical tissue architecture and heterogeneous composition. Successful realization of 3D models will not only provide greater in vitro-in vivo correlation compared to the two-dimensional (2D) models, but also eventually replace pre-clinical animal testing, which has their own shortcomings. Amongst all fabrication techniques, bioprinting- comprising all the different modalities (extrusion-, droplet- and laser-based bioprinting), is emerging as the most viable fabrication technique to create the biomimetic tissue constructs. Notwithstanding the interest in bioprinting by the pharmaceutical development researchers, it can be seen that there is a limited availability of comparative literature which can guide the proper selection of bioprinting processes and associated considerations, such as the bioink selection for a particular pharmaceutical study. Thus, this work emphasizes these aspects of bioprinting and presents them in perspective of differential requirements of different pharmaceutical studies like in vitro predictive toxicology, high-throughput screening, drug delivery and tissue-specific efficacies. Moreover, since bioprinting techniques are mostly applied in regenerative medicine and tissue engineering, a comparative analysis of similarities and differences are also expounded to help researchers make informed decisions based on contemporary literature. © 2017 Acta Materialia Inc.China Scholarship Council: 201308360128 BIDEP 2219 Jiangxi University of Science and Technology Diabetes Action Research and Education Foundation: 426 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu 1624515This work has been supported by National Science Foundation Awards # 1624515, Diabetes in Action Research and Education Foundation grant # 426 and the China Scholarship Council 201308360128 and the Oversea Sailing Project from Jiangxi Association for Science and Technology ( 2013 ). The authors also acknowledge Department of Science and Technology , Government of India, INSPIRE Faculty Award to P.D. The authors are grateful to the support from the Turkish Ministry of National Education for providing graduate scholarship to B. A. and International Postdoctoral Research Scholarship Program (BIDEP 2219) of the Scientific and Technological Research Council of Turkey for providing scholarship to V. O. The authors thank Dr. Christopher Barnatt from http://www.explainingthefuture.com for the bioprinting concept image used in the graphical abstract. In the graphical abstract, the drug screening image was reproduced/adapted with permission from [161] and the ADME assay image was reproduced/adapted from [162] . The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome

3D Printing of PDMS Improves Its Mechanical and Cell Adhesion Properties

Despite extensive use of polydimethylsiloxane (PDMS) in medical applications, such as lab-on-a-chip or tissue/organ-on-a-chip devices, point-of-care devices, and biological machines, the manufacturing of PDMS devices is limited to soft-lithography and its derivatives, which prohibits the fabrication of geometrically complex shapes. With the recent advances in three-dimensional (3D) printing, use of PDMS for fabrication of such complex shapes has gained considerable interest. This research presents a detailed investigation on printability of PDMS elastomers over three concentrations for mechanical and cell adhesion studies. The results demonstrate that 3D printing of PDMS improved the mechanical properties of fabricated samples up to three fold compared to that of cast ones because of the decreased porosity of bubble entrapment. Most importantly, 3D printing facilitates the adhesion of breast cancer cells, whereas cast samples do not allow cellular adhesion without the use of additional coatings such as extracellular matrix proteins. Cells are able to adhere and grow in the grooves along the printed filaments demonstrating that 3D printed devices can be engineered with superior cell adhesion qualities compared to traditionally manufactured PDMS devices. © 2017 American Chemical Society.National Institutes of Health National Institutes of Health: https://3dprint.nih.gov/, Slic3r, http://slic3r.org/ BIDEP 22192.4. 3D Printing of Models. The mesh files of human hand, ear and femur were downloaded from National Institutes of Health (NIH) 3D Print Exchange (https://3dprint.nih.gov/) and the print paths were generated after scaling down mesh models using a slicer package Slic3r (http://slic3r.org/). The print paths for the human nose and blood vessel were taken from Cellink (Sweden), and the print path for the bifurcated vessel was generated in-house. 3D complex models were printed using Ink 8:2 with a 510 µm nozzle tip at a constant printing speed and extrusion pressure of 160 mm/min and 300 kPa, respectively.The authors thank Dr. Jian Yang and Ethan Gerhard from Biomedical Engineering Department at Pennsylvania State University for their assistance with mechanical testing experiments. The authors also thank Bruce Perrulli and Julia-Grace Polish from Anton-Paar USA, Inc., for their assistance with the rheology experiments. The authors are grateful to Dr. Dino Ravnic (Department of Surgery at the Pennsylvania State University) for providing the INCREDIBLE 3D bioprinter. The authors also thank Dr. Thomas Neuberger with his assistance with the MRI scan. Veli Ozbolat acknowledges the support from the International Postdoctoral Research Scholarship Program (BIDEP 2219) of the Scientific and Technological Research Council of Turkey (TUBITAK), and Bugra Ayan acknowledges support from the Turkish Ministry of National Education. The authors are also thankful to Materials Research Institute at the Pennsylvania State University in supporting the porosity experiments

Essential steps in bioprinting: From pre- to post-bioprinting

PubMedID: 29909085An increasing demand for directed assembly of biomaterials has inspired the development of bioprinting, which facilitates the assembling of both cellular and acellular inks into well-arranged three-dimensional (3D) structures for tissue fabrication. Although great advances have been achieved in the recent decade, there still exist issues to be addressed. Herein, a review has been systematically performed to discuss the considerations in the entire procedure of bioprinting. Though bioprinting is advancing at a rapid pace, it is seen that the whole process of obtaining tissue constructs from this technique involves multiple-stages, cutting across various technology domains. These stages can be divided into three broad categories: pre-bioprinting, bioprinting and post-bioprinting. Each stage can influence others and has a bearing on the performance of fabricated constructs. For example, in pre-bioprinting, tissue biopsy and cell expansion techniques are essential to ensure a large number of cells are available for mass organ production. Similarly, medical imaging is needed to provide high resolution designs, which can be faithfully bioprinted. In the bioprinting stage, compatibility of biomaterials is needed to be matched with solidification kinetics to ensure constructs with high cell viability and fidelity are obtained. On the other hand, there is a need to develop bioprinters, which have high degrees of freedom of movement, perform without failure concerns for several hours and are compact, and affordable. Finally, maturation of bioprinted cells are governed by conditions provided during the post-bioprinting process. This review, for the first time, puts all the bioprinting stages in perspective of the whole process of bioprinting, and analyzes their current state-of-the art. It is concluded that bioprinting community will recognize the relative importance and optimize the parameter of each stage to obtain the desired outcomes. © 2018 Elsevier Inc.National Science Foundation: 1600118, BIDEP 2219This work has been supported by National Science Foundation Award # 1600118 awarded to I.T.O. The authors also acknowledge Department of Science and Technology , Government of India, INSPIRE Faculty Award to P.D. The authors are grateful to International Postdoctoral Research Scholarship Program ( BIDEP 2219 ) of the Scientific and Technological Research Council of Turkey for providing scholarship to V. O and the support from the Turkish Ministry of National Education for providing graduate scholarship to B. A. The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome

Bioprinting functional tissues

PubMedID: 30639351Despite the numerous lives that have been saved since the first successful procedure in 1954, organ transplant has several shortcomings which prevent it from becoming a more comprehensive solution for medical care than it is today. There is a considerable shortage of organ donors, leading to patient death in many cases. In addition, patients require lifelong immunosuppression to prevent graft rejection postoperatively. With such issues in mind, recent research has focused on possible solutions for the lack of access to donor organs and rejections, with the possibility of using the patient's own cells and tissues for treatment showing enormous potential. Three-dimensional (3D) bioprinting is a rapidly emerging technology, which holds great promise for fabrication of functional tissues and organs. Bioprinting offers the means of utilizing a patient's cells to design and fabricate constructs for replacement of diseased tissues and organs. It enables the precise positioning of cells and biologics in an automated and high throughput manner. Several studies have shown the promise of 3D bioprinting. However, many problems must be overcome before the generation of functional tissues with biologically-relevant scale is possible. Specific focus on the functionality of bioprinted tissues is required prior to clinical translation. In this perspective, this paper discusses the challenges of functionalization of bioprinted tissue under eight dimensions: biomimicry, cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and strives to inform the reader with directions in bioprinting complex and volumetric tissues. Statement of Significance: With thousands of patients dying each year waiting for an organ transplant, bioprinted tissues and organs show the potential to eliminate this ever-increasing organ shortage crisis. However, this potential can only be realized by better understanding the functionality of the organ and developing the ability to translate this to the bioprinting methodologies. Considering the rate at which the field is currently expanding, it is reasonable to expect bioprinting to become an integral component of regenerative medicine. For this purpose, this paper discusses several factors that are critical for printing functional tissues including cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and inform the reader with future directions in bioprinting complex and volumetric tissues. © 2019 Acta Materialia Inc.Eunice Kennedy Shriver National Institute of Child Health and Human Development: K12HD055882 Pennsylvania State University Health Research 1624515This work was supported by the US National Science Foundation CMMI Award 1624515 (I.T.O.) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under BIRCWH award K12HD055882 ‘‘Career Development Program in Women’s Health Research at Penn State’’ (D.J.R.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the above-mentioned funding agencies

Recent advances in bioprinting technologies for engineering hepatic tissue

In the sphere of liver tissue engineering (LTE), 3D bioprinting has emerged as an effective technology to mimic the complex in vivo hepatic microenvironment, enabling the development of functional 3D constructs with potential application in the healthcare and diagnostic sector. This review gears off with a note on the liver's microscopic 3D architecture and pathologies linked to liver injury. The write-up is then directed towards unmasking recent advancements and prospects of bioprinting for recapitulating 3D hepatic structure and function. The article further introduces available stem cell opportunities and different strategies for their directed differentiation towards various hepatic stem cell types, including hepatocytes, hepatic sinusoidal endothelial cells, stellate cells, and Kupffer cells. Another thrust of the article is on understanding the dynamic interplay of different hepatic cells with various microenvironmental cues, which is crucial for controlling differentiation, maturation, and maintenance of functional hepatic cell phenotype. On a concluding note, various critical issues and future research direction towards clinical translation of bioprinted hepatic constructs are discussed