Functional 3D Tissue Engineering Scaffolds

Materials, Technologies, and Applications

Ying Deng, Jordan Kuiper

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN: 9780081009796
• eBook ISBN: 9780081009802
• Topic: Technology & Engineering
• Subtopic: Biomedical Science
• Index: Technology & Engineering

In order to grow replacement tissues, 3D scaffolds are widely used as a template for tissue engineering and regeneration. These scaffolds, which are typically 'seeded' with cells, support the growth of new tissues. However, in order to achieve successful tissue growth, the scaffold must meet specific requirements and are often 'functionalized' to accentuate particular properties. Functional 3D tissue engineering scaffolds: materials, technologies, and applications, is a comprehensive review of functional 3D scaffolds, providing information on the fundamentals, technologies, and applications.Part 1 focuses on the fundamentals of 3D tissue scaffolds, examining information on materials, properties, and trends. Part 2 discusses a wide range of conventional technologies for engineering functional 3D scaffolds, leading the way to a discussion on CAD and advanced technologies for functional 3D scaffold engineering. Chapters in part 3 study methods for functionalizing scaffolds to support a variety of in vivo functions whilst the final set of chapters provides an important review of the most significant applications of functional 3D scaffolds within tissue engineering.This book is a valuable resource for biomaterial scientists and biomedical engineers in academia and industry, with interests in tissue engineering and regenerative medicine.- Provides a self-contained work for the field of biomaterials and tissue engineering- Discusses all the requirements a scaffold must meet and a wide range of strategies to create them- Highlights significant and successful applications of functional 3D scaffolds

1

Mechanical and biological properties of scaffold materials

Naznin Sultana, Universiti Teknologi Malaysia (UTM), Johor, Malaysia

Abstract

In tissue engineering, cells are seeded onto a porous three-dimensional scaffold that will provide support and guide cells toward the growth of new tissue-like structures. These scaffolds can provide a platform for the delivery of growth factors release and drug delivery under controlled conditions. The efficacious construction of scaffolds for tissue engineering applications is essential. Scaffolds must possess certain properties. Amongst the properties, mechanical and biological properties of tissue engineering scaffolds are very important. This chapter addresses some of the biomaterials that are commonly used to fabricate scaffolds and describes their mechanical and biological properties. The chapter also includes illustrated examples, the structure and mechanical properties of scaffolds as well as the cellular interactions with scaffolds.

Keywords

Bioceramics; biopolymers; cell scaffold interaction; composite scaffolds; mechanical properties; scaffolds; tissue engineering

1.1 Introduction

Tissue engineering (TE) has emerged as an alternative to conventional approaches to restoring and repairing tissue function, such as autografts, allografts, and xenografts. TE involves the use of biomaterial scaffolds, cells, and bioactive agents to regenerate and restore damaged tissues. Generally, the strategies of tissue engineering involve (1) isolation of healthy cells from the body; (2) insertion of tissue-inducing substances, such as growth factors; and (3) seeding the expanded cells onto a scaffold [1] (Fig. 1.1). In the field of TE, scaffolds are used to provide a suitable environment for the regeneration of cells or tissues [2]. These scaffolds are seeded with cells and, sometimes, with growth factors. Fig. 1.2 shows a general appearance of tissue engineering scaffold and its microstructure. This chapter focuses on the mechanical and biological properties of scaffolds. The chapter concludes with future perspectives of the properties of new scaffolds for affluent tissue engineering.

Figure 1.1 Components and fundamental tissue engineering concept.

Figure 1.2 (A) General appearance and (B) A scanning electron micrograph of a scaffold.

1.2 Potential biomaterials for tissue engineering

Biomaterials are generally materials that are used in biomedical and tissue engineering applications. They include metals, ceramics, polymers, and composites (a combination of different material types, such as ceramics and polymers). Polymers are a long chain of molecular weight composed of small repeating units linked together by covalent bonds. Polymers are divided into two groups: synthetic polymers and natural polymers. Table 1.1 shows the commonly used natural and synthetic polymers and their properties. There are a wide variety of natural polymers (e.g., cellulose and collagen) and synthetic materials (e.g., polyethylene) deployed for tissue engineering applications including wound healing and bone regeneration. In applications where the biodegradation of implants is desired, biocompatible and biodegradable polymers can be used. These polymers include poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and polyhydroxybutyrate (PHB) and its copolymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). In choosing a biodegradable polymer, other than the generally required properties of a scaffold, the degradation rate of the material is also very important; it should have a favorable correlation with the growth rate of the new tissue [3]. Table 1.2 shows some bone regeneration materials and their properties [4].

Table 1.1

The commonly used natural and synthetic polymers for the fabrication of tissue engineering scaffolds

Origin	Material	Properties
Natural	Fibrin, collagen type I, chitosan, polyhydroxybutyrate (PHB), polyhydroxybutyrate-co-hydroxyvalerate (PHBV), alginate	Hydrophilic, cell adhesive, low mechanical properties
Synthetic	Polylactide (PLA), polyglycolide (PGA), polylactide-co-glycolide (PLGA), polycaprolactone (PCL)	Slow degrading, high mechanical properties, satisfactory biological property

Table 1.2

Some bone regeneration polymers and their properties [4,5]

Material	Compressive strength (MPa)	Modulus (MPa)	Porous (µm)	Support cell adhesion
PLA	NR	NR	100–500	Yes
PLGA	60±20	0.5 (tensile), 2.4 (Young’s)	150–710	Yes
Poly (orthoester)	4–16	NR	NR	Yes
PLA/HA	6–9	NR	NR	Yes
PLA/Ca phosphate	NR	5 (Young’s)	100–500	Yes
PLGA/Ca phosphate	NR	0.25	100–500	Yes

NR indicates “not reported”.

A family of linear aliphatic polyesters that are most frequently used in tissue engineering include PGA, PLA, and their copolymers polylactic acid-co-glycolic acid (PLGA). Hydrolysis of the ester bonds causes the polymers to degrade. PGA is one of the most widely used scaffolding polymers. PGA degrades rapidly in aqueous solutions or in vivo due to its relatively hydrophilic nature, losing its mechanical integrity after 2–4 weeks. The most widely used scaffolds derived from this polymer are the nonwoven fibrous fabrics. PLA is another widely used polymer for scaffold fabrication.

PLA scaffolds or implants have very high mechanical integrity in vitro or in vivo due their slower degradation rate, often taking years to degrade. This is the consequence of the additional methyl...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Preface
• 1. Mechanical and biological properties of scaffold materials
• 2. Instructive proteins for tissue regeneration
• 3. Bioinspired scaffolds for bone and neural tissue and interface engineering
• 4. Melt-molding technologies for 3D scaffold engineering
• 5. Phase-separation technologies for 3D scaffold engineering
• 6. Gas foaming technologies for 3D scaffold engineering
• 7. Freeze-drying technologies for 3D scaffold engineering
• 8. Textile technologies for 3D scaffold engineering
• 9. 3D printing technologies for 3D scaffold engineering
• 10. Extrusion-based 3D printing technologies for 3D scaffold engineering
• 11. Scaffold functionalization to support a tissue biocompatibility
• 12. Functional three-dimensional scaffolds for skeletal muscle tissue engineering
• 13. 3D functional scaffolds for cardiovascular tissue engineering
• 14. 3D functional scaffolds for skin tissue engineering
• 15. 3D functional scaffolds for tendon tissue engineering
• 16. 3D functional scaffolds for cartilage tissue engineering
• 17. 3D Functional scaffolds for dental tissue engineering
• Index