Biomaterials from Nature for Advanced Devices and Therapies

Nuno M. Neves, Rui L. Reis, Nuno M. Neves, Rui L. Reis

• Publisher: Wiley
• Year: 2016
• Print ISBN: 9781118478059
• eBook ISBN: 9781119178071
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

In-depth information on natural biomaterials and their applications for translational medicine!

• Undiluted expertise: edited by world-leading experts with contributions from top-notch international scientists, collating experience and cutting-edge knowledge on natural biomaterials from all over the world
• A must-have on the shelf in every biomaterials lab: graduate and PhD students beginning their career in biomaterials science and experienced researchers and practitioners alike will turn to this comprehensive reference in their daily work
• Link to clinical practice: chapters on translational research make readers aware of what needs to be considered when a biomaterial leaves the lab to be routinely used

Part I

1
Collagen-Based Porous Scaffolds for Tissue Engineering

Guoping Chen and Naoki Kawazoe

Tissue Regeneration Materials Group, International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan

1.1 Introduction

Collagen is one of the main components of extracellular matrices that provide mechanical support and biological signals to cells for cellular activities [1]. Collagen has attracted wide attention for biomedical applications because of its versatile property [2–5]. It has been used to construct scaffolds in different forms either with or without hybridization with other biodegradable synthetic or naturally derived materials for tissue engineering. Collagen-based porous scaffolds have been developed through many methods and widely used for tissue engineering of a variety of tissues and organs such as skin [3], bone [5], cartilage [6], ligament [7], blood vessel [8] and nerve [9]. Their pore structures have been well designed and controlled to meet the requirements for cell distribution and cell interaction to promote functional tissue regeneration [10–15]. Hybridization of collagen with mechanically strong synthetic polymers has also developed to improve its mechanical property. Some of the latest developments of collagen-based scaffolds with controlled pore structures and composite structures are summarized and highlighted in this chapter.

1.2 Collagen Sponges

Collagen is a water-soluble polymer and is very easy to prepare its porous sponge by using freeze-drying method [16]. Collagen aqueous solution or collagen gel can be frozen at a low temperature, subsequently freeze-dried at a low pressure and finally cross-linked to prepare collagen porous sponges. During freezing process, freezing temperature may affect the formation and growth of ice crystals in the aqueous solution. Therefore, controlling of freezing temperature has been used to control the porous structure of collagen sponges. Fast freezing at a lower temperature induces cracking, uniform small channels and formation of a fibrous structure. Slow freezing at a higher temperature results in nonuniformity and large pores with more collapsed pores than continuous channels. A unidirectional freezing-drying method has been developed to prepare unidirectionally structured collagen sponge [17]. Collagen sponge resembling the extracellular matrix structure of a particular tissue has been prepared by specific freezing regimes [18]. Although some methods have been deve-loped to prepare collagen sponges with partially controlled pore structures, it has been pursued by many researchers to make the sponge pore open and increase the interconnectivity. Recently a method by using embossing ice particulates as a temperature to precisely control the pore structure of collagen sponges has been developed [10].

The preparation scheme using embossing ice particulates is shown in Figure 1.1. At first, water droplets are prepared by spraying pure water on the surface of a hydrophobic film and water droplets are formed on the surface. The size of the water droplets can be controlled by spraying condition such as spraying speed and spraying time. Or the water droplet can be printed on the hydrophobic surface by a dispenser and the size of the ice droplets can be controlled by the volume of injected volume of water. Subsequently, the water droplets are frozen at a low temperature to form ice particulates embossing the membrane surface. The size and density of embossing ice particulates are controllable. Finally, collagen aqueous solution is eluted onto the embossing ice particulates, frozen, freeze-dried and cross-linked to prepare collagen sponges with a controlled pore structure. Usually the temperature of ice particulates and collagen aqueous solution should be balanced before eluting collagen aqueous solution onto the ice particulates. The prepared collagen porous sponges have large open pores on the surface and interconnected bulk pores underlying the large surface pores. Such structure is very similar to a funnel and therefore the collagen sponges prepared by this method are referred as funnel-like collagen sponges.

Figure 1.1 Preparation scheme of the funnel-like collagen sponge using embossing ice particulates. Adapted and reproduced from Ref. 10 (DOI: 10.1177/0883911510370002).

The photo of funnel-like collagen sponge prepared with 398 μm-diameter ice particulates and 1.0% collagen aqueous solution shows clear large pores are evenly distributed on the surface of the collagen sponge (Fig. 1.2a). Scanning electron microscopy images show that large pores are formed on the top surface and interconnected bulk pores are formed beneath the surface pores (Fig. 1.2b and c). The mean diameter of the large surface pores is almost the same as that of the embossing ice particulates which are used as templates because the large surface pores should be the replicas of the embossing ice particulates.

Figure 1.2 Photograph (a) and SEM photomicrographs (b, c) of top surface (b) and cross-section (c) of funnel-like collagen sponge prepared with 398 μm-diameter ice particulate template at –3°C. Adapted and reproduced from Ref. 10 (DOI: 10.1177/0883911510370002).

The underlying bulk pores are interconnected with the large surface pores and extend into the bulk body of the sponge from the surface pores. The underlying bulk pores are the replicas of the ice crystals that are formed during freeze-drying. Therefore, the pore structure of the funnel-like collagen sponges is mainly dependent on the size and density of embossing ice particulates and the freezing temperature. The size and density of surface large pores are determined by the size and density of embossing ice particulates. The size and interconnectivity of underlying bulk pores are dependent on the freezing temperature. Funnel-like collagen sponges prepared with the same size of ice particulates (398 μm) but four different freezin...

Table of contents

• Cover
• Wiley - Society for Biomaterials
• Title Page
• Copyright
• Contributors
• Preface
• Part I
• Part II
• Part III
• Part IV
• Part V
• Part VI
• Index
• EULA