Bioprinting

The following sections are included:

• Dedication
• Foreword
• Preface
• Acknowledgements
• About the Authors
• List of Abbreviations
• Contents

Tissue engineering (TE), an interdisciplinary technology which emerged thirty years ago, has increasingly drawn significant attention from numerous scientists, engineers, technologists and physicians around the world due to its ability to construct biological substitutes to repair and replace diseased and damaged tissues. Tissue engineering technology has already been used in clinical applications, developing effective therapies, particularly for skin, blood vessels and livers. An important branch of tissue engineering has been the incorporation of new techniques such as microfabrication and additive manufacturing that will enable future breakthroughs. This chapter introduces the current therapies for tissue substrates and highlights the beginning of the tissue engineering field, which leads to the emergence of the three-dimensional printing concept.

With the ever increasing demand for suitable replacements and organ transplantation, tissue engineering (TE) has become a feasible solution, bringing great hope to patients who are desperate to look for tissue and organ substitutes [1]. In order to obtain substitutes, a popular approach is to fabricate a three-dimensional (3D), biocompatible, biodegradable and porous scaffold functioning as a temporary 3D template for tissue ingrowth [2-8]. Biocompatible polymers, peptides, proteins and hydrogels are the common raw materials for producing scaffolds [9]. In addition to material properties, the scaffold fabrication techniques can largely determine the final characteristics of the scaffold such as porosity and mechanical strength. This chapter describes a number of established processing and fabrication methods including conventional and additive manufacturing (AM) methods. The advantages and disadvantages of the scaffold-based method are also discussed.

Three-dimensional (3D) cell bioprinting is an emerging technology, which has now been initially used to design and generate 3D cell constructs for transplantation therapies. The most attractive advantage of this technology is the ability to create 3D structures with living biological elements such as cells and nutrients. This chapter presents a number of companies with particular attention on their bioprinting systems and processes for delivering cells and biomaterials in preclinical studies, which have shown promising improvements as compared to the scaffold-based fabrication methods presented in Chapter 2. These systems are classified based on the printing techniques such as inkjet printing, extrusion and combinational techniques. Starting with the introduction of the bioprinting definition, this chapter describes the printing process principles and mechanisms, followed by discussion of the process advantages and disadvantages. Finally, the applications of the bioprinting techniques are outlined.

Biomaterials science and engineering has expanded, advanced and evolved dramatically since the late 1960s. It now covers fundamental aspects of physical, chemical, mechanical, electrical and even biological properties of both the natural and synthetic biomaterials. This chapter aims to introduce the most popular biomaterials in relation to tissue engineering (TE). Most of these biomaterials have been proven to be available for bioprinting. The requirements of biomaterials specifically in tissue engineering are first presented, followed by polymers, ceramics and glasses. Finally, this chapter pays particular attention to hydrogels and their unique properties.

Cells are an essential part in the approach of tissue engineering (TE). In the scaffold-based approach, cells are seeded secondarily after the scaffold is constructed. In bioprinting, cells are added onto the construct during the printing process. In both approaches, the selection and supply of cells will affect the success of the implementation. Cells can be categorised in different ways such as source, potential and maturation state. For bioprinting, the added variance comes in the form of the cell format, in which individual or aggregates of cells are added into hydrogel matrix or cells can be deposited as cell spheroids. In this chapter, cell sources, the potential for expansion and differentiation, together with different formats of cells for printing are presented and discussed.

Over the past decades, three-dimensional (3D) cell culture has been adopted by tissue engineers, cancer researchers, stem cell scientists and cell biologists, mostly in university settings. New materials and methods have continuously been developed. The pioneers of 3D cell culture technology have gained the benefits of better data with extensive knowledge of tissue and cancer behaviour. 3D cell culture methods used to be very expensive, laborious, messy and difficult to adapt to existing procedures. Nowadays, researchers and scientists can select viable 3D cell culture tools to fit their specific requirements and needs. In this chapter, readers will find useful information on the principles and major techniques/tools used for 3D cell culture.

Today's computer-aided technologies together with medical imaging have assisted and enhanced the advances in tissue engineering (TE), creating new possibilities in the TE development [1]. Such possibilities include, for instance, using magnetic resonance imaging (MRI) and non-invasive computed tomography (CT) techniques to generate tissue structural images for tissue classification, trauma and tumour identification [2, 3], and three-dimensional anatomical models. These are achieved by using computer-aided design/manufacturing (CAD/CAM) as well as additive manufacturing (AM) technology to manufacture the physical models of hard tissues, scaffolds, and furthermore the customised implant prostheses [4, 5], and applying the physical and anatomical modelling for reconstructive tissue implementation and surgeons [6]. The utilisation of computer-aided technologies has led to the emergence of a new field named computer-aided tissue engineering (CATE) [7, 8]. The advances in biology, biomedicine and information technology for TE application have stimulated the development of CATE [9]. This chapter presents the recent development of CATE with particular interest in computational modelling for bioprinting.

Direct printing of living functional organs is the ultimate goal of the three-dimensional (3D) bioprinting technology. If this becomes true eventually, it will be a revolutionary technology for medical industry. As this technology is still at the initial stage of development at present, it is early and unrealistic to speculate when these printed organs will become available. Kidneys, livers and hearts are commonly believed to be the organs that bioprinting should aim for in the future. Based on the waiting lists of kidney, liver and heart transplants in the USA and Europe, the bioprinted organ market is expected to increase with an annual growth of over 100% [1]…

The following section is included:

• Index