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C H A P T E R 4
Biomaterials – Polymers,
Scaffolds, and Basic Design
Criteria
CHAPTER SUMMARY
Biomaterials constitute a major component in various strategies of tissue engineering and regeneration, as standalone treatments or in combination with cells and/or bioactive molecules. This chapter provides a brief summary of the “need to know” about biomaterials; such as the basic criteria for material selection and design, the type of natural and synthetic polymers in use, scaffold types, and their fabrication methodology. The goal here is to familiarize the readers with the basic terminology, concepts, and principles in the biomaterials research field as related to the tissue engineering strategy. The application of biomaterials in the different strategies of cardiac tissue engineering and regeneration will be described in the coming chapters.
4.1INTRODUCTION
Tissue engineering aims at regenerating a living functional tissue to restore or establish the normal and original function of the damaged or compromised tissue [1]. As such, this multidisciplinary field implements knowledge and tools from diversified fields, such as material science, engineering, as well as cell and developmental biology. Biomaterials and scaffolds are critical components in this strategy, as standalones or in combination with cells and/or bioactive molecules (Fig. 4.1). They have been used as: 1) ECM replacement in a-cellular strategies; 2) controlled delivery systems for bioactive molecules; 3) vehicles for stem cell delivery and enhanced retention in the damaged tissue; and 4) supporting and guiding matrix for cell organization into a functional tissue, in vitro and in vivo.
This chapter provides an overview on biomaterials, their chemistry and sources, the basic criteria for their selection, and the methodologies for their fabrication as scaffolds.
4.2BASIC BIOMATERIAL DESIGN CRITERIA
In general, the biomaterials used in each of the strategies for myocardial repair and regeneration (Fig. 4.1) should comply with the following basic criteria:
42 4. BIOMATERIALS – POLYMERS, SCAFFOLDS, AND BASIC DESIGN CRITERIA
Figure 4.1: Paradigms for the use of biomaterials in cardiac tissue engineering and regeneration. Basic components (biomaterials, cells, and bioactive molecules) can be designed in various forms of implantable constructs or injectable solutions. These design strategies can be used for cell delivery, preparation of cardiac patches/grafts, in situ tissue support in acellular forms, or as a platform for the delivery of bioactive molecules. Ultimately, the biomaterial constructs or solutions are being delivered to the infarcted heart by implantation, or by using less invasive techniques, such as intramyocardial or intracoronary injections.
Biocompatibility – This term refers to the ability of a material to perform with an appropriate host response in a specific situation (Williams definition) [2]. In tissue engineering, biocompatibility refers to the ability of a scaffold to perform as a substrate that will support the appropriate cellular activity, including the facilitation of molecular and mechanical signaling, in order to optimize tissue regeneration, without eliciting any undesirable effects in those cells, or inducing any undesirable local or systemic responses in the host.
Mechanical strength – The strength of a material is its ability to withstand an applied stress without failure. Scaffolds in tissue engineering should have the mechanical properties to contain and