Biomedical Engineering Reference
In-Depth Information
Table 1.1 Commonest types of tissue response to implanted materials
Predominant
agents
Type of response
Time frame
Examples
Infl ammatory response
Acute
Minutes to
48 hours
Opsonins,
complement,
neutrophils
Monocytes,
macrophages,
proteases
Vascular
implants,
stents
Chronic
Hours to
several
days
Immune response
Innate
Minutes to
24 hours
Complement,
coagulation
factors,
neutrophils,
macrophages,
NK cells
T and B
lymphocytes,
antibodies
Coronary
artery stents
Adaptive
Several
days
Ventricular
assist
devices
Hypersensitivity response
Type I
Minutes
IgE
Dacron,
titanium,
steel
Stent
thrombosis
Type IV
Over 12
hours
T cells
Thrombus formation
Hours to
several
days
Extracellular
proteins,
platelets
Prosthetic
heart valves
Biofi lm formation
(infection)
Days
Extracellular
proteins,
microorganisms
Prosthetic
heart valves
￿ ￿ ￿ ￿ ￿
Carcinogenesis
Several
years
Free oxygen
radicals
Polymers
The tissue response to implanted materials is a complex process. It entails
a variety of pathways that may include the generation and activation of
interacting humoral and molecular components. These processes may be
acute, taking place over minutes, or long term, spanning many years (Table
1.1). This chapter aims to present the commonest types of tissue response
to materials used for the construction of implantable medical devices. It
describes processes such as infl ammation, immune response, hypersensitiv-
ity, formation of thrombus or biofi lm and carcinogenesis. Each section
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