Wound Healing Biomaterials - Volume 2

Functional Biomaterials

Magnus Ågren

• Publisher: Woodhead Publishing
• Year: 2016
• ISBN:
  9780081006061
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Wound Healing Biomaterials: Volume Two, Functional Biomaterials discusses the types of wounds associated with trauma, illness, or surgery that can sometimes be extremely complex and difficult to heal. Consequently, there is a prominent drive for scientists and clinicians to find methods to heal wounds opening up a new area of research in biomaterials and the ways they can be applied to the challenges associated with wound care.

Much research is now concerned with new therapies, regeneration methods, and the use of biomaterials that can assist in wound healing and alter healing responses. This book provides readers with a thorough review of the functional biomaterials used for wound healing, with chapters discussing the fundamentals of wound healing biomaterials, films for wound healing applications, polymer-based dressing for wound healing applications, and functional dressings for wound care.

• Includes more systematic and comprehensive coverage on the topic of wound care
• Provides thorough coverage of all specific therapies and biomaterials for wound healing
• Contains clear layout and organization that is carefully arranged with clear titles and comprehensive section headings
• Details specific sections on the fundamentals of wound healing biomaterials, films for wound healing applications, polymer-based dressing for wound healing applications, and more

Part One

Fundamentals of wound healing biomaterials

Outline

1. Introduction to biomaterials for wound healing

2. Modelling of cell–tissue interactions in skin

3. Biofilms in wounds and wound dressing

4. The importance of preventing and controlling biofilm in wounds: biofilm models and nanotechnology in antibiofilm approaches

5. Control and treatment of infected wounds

1

Introduction to biomaterials for wound healing

P. Aramwit Chulalongkorn University, Phatumwan, Bangkok, Thailand

Abstract

The advantageous biocompatibility and cell proliferative effects of synthetic and natural biomaterials have promoted their broad use in various medical areas, including wound healing. Most synthetic biomaterials show excellent physical properties but are, in general, complicated to fabricate, whereas natural biomaterials normally show no cell toxicity or elicit foreign body responses but show high natural variability. This chapter gives an overview of existent biomaterials used for wound healing purposes, especially the naturally obtained categories such as polysaccharide-based, protein-based, nanofiber-based, and marine biomaterials, which have been investigated in depth in vivo and in clinical studies. The potentials, but also the limitations, of novel biomaterials for wound healing applications are also discussed.

Keywords

Biomaterials; Nanofiber based; Polysaccharide based; Protein based; Wound healing

1.1. Definition of biomaterial

Biomaterial by definition is “a non-drug substance suitable for inclusion in systems which augment or replace the function of bodily tissues or organs” (Nicolai and Rakhorst, 2008). These materials are capable of being in contact with bodily fluids and tissues for prolonged periods, while eliciting minimal if any adverse reactions (Heness and Ben-Nissan, 2004). In this sense, biomaterials are classified as synthetic or natural substances. Hence, in this chapter a biomaterial is defined as any substance (other than a drug) or combination of substances, synthetic or natural in origin, which can be used as a whole or as a part of a system which treats, augments, or replaces any tissue, organ, or function of the body (von Recum and LaBerge, 1995). The field of biomaterials working under biological constraints is rapidly expanding and represents 2–3% of the overall health expenses in developed countries. This field covers many different materials: cardiac artificial valves; artificial vessels; cardiac stimulators; stents; artificial hips, knees, shoulders, and elbows; materials for internal fracture fixation; scoliosis treatment; materials for urinary tract reconstruction; artificial crystalline lenses; skin; ear ossicles; and dental roots (Sedel, 2004).

1.2. Types of biomaterials

Since the introduction of sutures for wound closure (Davis, 2003), the use of biomaterials has expanded intensively. Biomaterials can be divided into synthetic or natural.

1.2.1. Synthetic biomaterials

The most common synthetic biomaterials used for implants are titanium, silver products, polyester, and porcelain. Synthetic biomaterials can be divided into the following four categories (Agrawal, 1998).

1.2.1.1. Metals

Metals are the most widely used for load-bearing implants such as artificial joints for hips and knees. Although many metals and alloys are used for medical device applications, the most commonly used metals are stainless steel, pure titanium, and titanium alloys.

1.2.1.2. Polymers

Polymers are widely used for several applications such as facial prostheses, tracheal tubes, and kidney and liver parts. They are also used for medical adhesives and sealants or for coating of other materials to modify their function.

Polyester, polytetrafluoroethylene, and polyurethane are the most commonly used biomaterials for artificial devices. According to US Food and Drug Administration standards, these polymers are considered biocompatible biomaterials. The biocompatibility response of synthetic biomaterials in vivo is signified by hydrolysis via inflammatory cells and by the formation of a fibrous capsule that is the body’s response to a foreign intruder (Mathur et al., 1997; Anderson et al., 1998). In practice the biocompatibility of a material is defined by its ability to fill space and assist the body in regenerating tissue to develop permanent solutions to reconstruction and to reduce abnormal chronic wound healing (Mathur, 2009).

The newer biodegradable biomaterials, including polylactic acid (PLA) and polyglycolic acid (PGA), also have a polyester chemistry, and they are degraded by hydrolysis that results in large amounts of by-products that lower the pH of the local microenvironment. This may influence wound healing (Mathur, 2009). PGA provides a biocompatible surface for the cells to proliferate and has been widely used for tissue engineering of artificial arteries. PGA does not provide a mechanically robust matrix which would enable the cells to withstand the in vivo shear and compressive loads, and it also results in dedifferentiation of cells (Higgins et al., 2003).

Polyethylene glycol (PEG) lacks the chemistry for cellular interface unless ligand-presenting entities are introduced (Gobin and West, 2003). Classical tissue engineers prepared a cell-seeded biomimetic hydrogel such as ligand-modified PEG and studied the cell response by measuring proliferation and differentiation (Gobin and West, 2003). In this situation, most cells can adhere to the adhesion ligands and secrete a protease whose cleavage sequence is incorporated within the gel, which renders the hydrogel completely nonresponsive. From this case, the gel has all the characteristics of a synthetic nondegradable biomaterial and only two characteristics out of many of being a biologically responsive biomaterial. This indicates that cells need multiple signals in a tissue-engineered scaffold to mimic their in vivo behavior (Mathur, 2009).

1.2.1.3. Ceramics

Ceramic is primarily used as a restorative material in dentistry. Due to its poor fracture toughness, other uses are limited.

1.2.1.4. Composites

Composite materials are used extensively for prosthetic limbs wherein their low density/weight and high strength make them ideal materials for prosthetic applications.

Table 1.1

Biomaterials for medical applications

Biomaterial	Advantages	Disadvantages	Examples
Metal	Strong, tough, and ductile	Corrodible, dense, and complicated to fabricate	Joint replacement, bone plates and screws, dental root implants, pacers, and sutures
Polymers	Resilient and easy to fabricate	Fragile, deformable, and degradable	Blood vessels; sutures; tissue engineering for ear, nose, and soft tissues
Ceramics	Very biocompatible, inert, and strong in compression	Difficult to fabricate, brittle, and not resilient	Dental coatings and orthopedic implants, such as femoral head of neck
Composites	Strong in compression	Difficult to fabricate	Joint implants, heart valves

The advantages and disadvantages of each biomaterial category are shown in Table 1.1.

1.2.2. Natural biomaterials

Natural biomaterials are derived from animals, microbials, or plants. One advantage of natural biomaterials is that they are similar to materials familiar to the body (Davis, 2003). In this regard the field of biomimetics, or mimicking nature, is growing. There is seldom a toxicity issue with the use of natural materials in contrast to synthetic materials. Moreover, natural biomaterials may carry specific protein binding sites and other biochemical signals that may assist in tissue healing or integration. The major concerns of using these materials are immunogenicity and decomposition at temperatures below their melting points. This severely limits their fabrication into implants of different sizes and shapes (Ige et al., 2012).

Natural biomaterials are typically similar to macromolecular substances which are prepared for metabolic pathways. As a result, the problems of toxicity and simulation of a chronic inflammatory reaction which is provoked by many synthetic polymers are sup...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Biomaterials
• Part One. Fundamentals of wound healing biomaterials
• Part Two. Biomaterial films for wound healing
• Part Three. Polymer biomaterials and dressings for wound healing
• Part Four. Other functional biomaterial dressingsfor wound healing
• Index