Question

(Marks 10 X4-40) Answer all questions: " Biocompatibility" of materials. Also describe the tenm 1, (o) Describe what you u know about "Biocompatibility" of materials. A foreign body reaction in light of healing upon implantation of a biomaterial . (b) Discuss the role of mechanical stimuli in growing engineered tissue. How do cells in engineered bone or ligament tissue sense the mechanical stimuli and how do they respond do it?

Answer 1

a) A substance that elicits no unfavourable reaction from tissues is called a biocompatible material. The quality of being compatible with living tissue or a living system by not being toxic or injurious and not causing immunological rejection is called as biocompatibility.

For example biomaterials and cells for cardiac tissue engineering. Biocompatible materials in cardiac tissue engineering can be used alone to mechanically support the ventricular wall, or as scaffolds for the delivery of bioactive molecules or cells. Beyond their mechanical properties to facilitate contraction, biomaterials for cardiac tissue engineering are also required to be electrophysiologically stable and to favour cell attachment, growth, differentiation and electromechanical integration with the host tissue (Jawad et al., 2008). They should also support in vivo revascularization and safely degrade at an appropriate rate to sufficiently support the damaged tissue until the formation of the new tissue (Wu et al., 2006). A variety of synthetic and natural biomaterials have been used in cardiac tissue engineering.

The "foreign body reaction" composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial. There are a number of factors that modulate the interaction of macrophages and foreign body giant cells on synthetic surfaces where the chemical, physical, and morphological characteristics of the synthetic surface are considered to play a role in modulating cellular events. These events in the foreign body reaction include protein adsorption, monocyte/macrophage adhesion, macrophage fusion to form foreign body giant cells, consequences of the foreign body response on biomaterials, and cross-talk between macrophages/foreign body giant cells and inflammatory/wound healing cells. Biomaterial surface properties play an important role in modulating the foreign body reaction in the first two to four weeks following implantation of a medical device, even though the foreign body reaction at the tissue/material interface is present for the in vivo lifetime of the medical device. An understanding of the foreign body reaction is important as the foreign body reaction may impact the biocompatibility (safety) of the medical device, prosthesis, or implanted biomaterial and may significantly impact short- and long-term tissue responses with tissue-engineered constructs containing proteins, cells, and other biological components for use in tissue engineering and regenerative medicine.

The incorporation of biological components of allogeneic or xenogeneic origin, as well as stem cells into tissue-engineered or regenerative approaches, opens up a myriad of other challenges. An in-depth understanding of how the immune system interacts with these cells and how biomaterials or tissue-engineered constructs influences these interactions may prove pivotal to the safety, biocompatibility, and function of the device or system under consideration.