Host Response to Biomaterials

The Impact of Host Response on Biomaterial Selection

Stephen F. Badylak

• Publisher: Academic Press
• Year: 2015
• ISBN:
  9780128005002
• Topic: Medicina
• Subtopic: Tecnología y suministros médicos

Host Response to Biomaterials: The Impact of Host Response on Biomaterial Selection explains the various categories of biomaterials and their significance for clinical applications, focusing on the host response to each biomaterial. It is one of the first books to connect immunology and biomaterials with regard to host response.

The text also explores the role of the immune system in host response, and covers the regulatory environment for biomaterials, along with the benefits of synthetic versus natural biomaterials, and the transition from simple to complex biomaterial solutions.

Fields covered include, but are not limited to, orthopaedic surgery, dentistry, general surgery, neurosurgery, urology, and regenerative medicine.

• Explains the various categories of biomaterials and their significance for clinical applications
• Contains a range of extensive coverage, including, but not limited to, orthopedic, surgery, dental, general surgery, neurosurgery, lower urinary tract, and regenerative medicine
• Includes regulations regarding combination devices

Chapter 1

Factors Which Affect the Host Response to Biomaterials

Ricardo Londono^1,2 and Stephen F. Badylak^1,3, ¹McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA, ²School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA, ³Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA

The ability of a biomaterial to perform its intended in vivo function is ultimately dependent upon both the structural and biophysical properties of the material and the host response to the given material. Biomaterial-related factors affecting performance include its composition, mechanical and material properties, surface topography and molecular landscape, ability to resist infection, and proper surgical placement, among others. Host-related factors include age, nutritional status, body mass index, comorbidities such as diabetes, previous interventions at the treatment site, and medications being taken by the patient. The host response begins immediately upon implantation and consists of both the response to the inevitable iatrogenic tissue injury during device placement and the response to the material itself. The implantation-induced component resolves quickly as part of the normal wound healing process. However, the response to the material itself will last for the length of time the material is present in the host. The host response is the primary determinant of clinical success in most applications. Hence, the safety and efficacy of these technologies will be well served by placing emphasis upon the understanding of the host response and the dynamic interaction between biomaterial- and host-related factors that affect clinical outcomes.

Keywords

Host response; biomaterials; host–biomaterial interaction; immune response to biomaterials; biocompatibility; biotolerance; biomaterial-mediated tissue repair

Contents

Introduction 1

Biomaterial–Host Interaction 2

Host Factors 4

Age 4

Nutritional Status 6

Anatomic Factors 7

Comorbidities 8

Obesity 8

Diabetes 9

Chemotherapy and Radiation Therapy 9

Design Considerations 10

References 10

Introduction

The ability of a biomaterial to perform its intended in vivo function is dependent on many factors including its composition, mechanical and material properties, surface topography and molecular landscape, ability to resist infection, and proper surgical placement, among others. However, the ultimate determinant of success or failure is the host response to the biomaterial.

The host response begins immediately upon implantation and consists of both the response to the inevitable iatrogenic tissue injury during device placement and the response to the material itself. In most cases, the implantation-induced component resolves quickly as part of the normal wound healing process. However, the response to the material will last for the length of time the material is present in the host. Materials which elicit a persistent proinflammatory response are likely to be associated with abundant fibrous connective tissue deposition and the downstream consequences of the effector molecules secreted by recruited inflammatory cells. Materials which either rapidly degrade or reach a steady state of tolerance with adjacent host tissue (see Chapter 3) are typically associated with minimal scarring, a quiescent population of resident inflammatory cells, and tissue types appropriate for the anatomic location.

The host response to an implanted material includes factors that relate to the biomaterial itself and factors that relate to the host (Table 1.1). Biomaterial-related factors have been the focus of studies for many years. Such factors include the base composition of the material (e.g., polypropylene versus polytetrafluoroethylene versus extracellular matrix), surface texture, surface ligand landscape, degradability, and device design parameters such as pore and fiber size, among others. Host-related factors, on the other hand, have been underappreciated as a determinant of the response. These factors include age, nutritional status, body mass index, comorbidities such as diabetes, previous interventions at the treatment site, and medications being taken by the patient, among others. No biomaterial is inert and the interplay between material and host-related factors should be considered in the design and manufacture of all biomaterials.

Table 1.1

Host-related and biomaterial-related factors which affect the host response and chapters in which they are discussed

Factors that affect the host response to biomaterials
Biomaterial-related factors	Chapters	Host-related factors	Chapters
Composition (material)	2, 3	Age	11
Degradability	3	Anatomic location	12, 13,14
Mechanical properties		Previous interventions	14
Sterility		Comorbidities
Antigenicity	4, 5, 8, 10	Immune response	2, 6, 7, 8, 9
Active ingredients (drugs)		Medications

Biomaterial–Host Interaction

Although the physical and mechanical properties of a material at the time of implantation are important for obvious reasons, these properties are equally important at 1 month, 1 year, 5 years, and beyond, especially for those materials intended to remain in situ for the life span of the patient. The host response can degrade, destroy, encapsulate, or otherwise alter the composition of the biomaterial over time resulting in changes to the form and mechanical properties of the material itself (Figure 1.1) (Badylak, 2014). Hence, it is not the degree to which the physical characteristics of the material resemble the targeted anatomic location before implantation that determines the performance of a biomaterial, but rather the host response over time.

Figure 1.1 Host response to biomaterial implantation
The host response to implanted biomaterials depends upon many factors. Although the initial stages of the biomaterial–host interaction are shared among all materials and include tissue damage during implantation and protein adsorption to the surface of the material, the host response quickly transitions into complex phases that depend directly upon the type of material being implanted and other factors. These phases involve cellular and mole­cular components of the innate immune system and the wound healing response, and will ultimately determine the clinical outcome (i.e., encapsulation vs. scar formation vs. constructive remodeling).

The host response is initiated with the activation of the innate immune system as a result of cell and tissue damage during biomaterial implantation (see Chapters 2, 3, 4). Upon contact with the host tissues, the surface of the biomaterial is coated with blood and plasma proteins through a process known as the Vroman effect (Slack et al., 1987). Depending on the type of biomaterial and surface topography (i.e., type I collagen vs. polytetrafluoroethylene vs. titanium), the type and amount of adsorbed molecules will vary, and consequently, so will the composition and arrangement of the interface molecules that exist between the host tissues and the implant.

As a result of the Vroman ef...