**1. Introduction**

82 Cellulose – Medical, Pharmaceutical and Electronic Applications

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A biomaterial is defined as a material, either man-made or natural, intended to interact with biological systems. It does not have a chemical effect in the organism, nor thus it need to be metabolised to be active like for example drugs 1. When inserted into the body, a local tissue inflammatory reaction called foreign body reaction is induced 2. This reaction may either favour or adversely affect the tissue repair process.

Cellulose and its derivatives are well tolerated by most tissues and cells 3-5. These nontoxic materials have good biocompability, therefore, they offer several possibilities in medical applications. Regenerated cellulose sponges have also been used in experimental surgery for decades as it does not affect the healing process, but acts as a chemoattractant inducing cells involved in the repair process to migrate towards it 6-8.

We have studied different biomaterials including cellulose in search for an optimal bone substitute. In bone defects, regenerated cellulose supported with cotton fibres was shown to allow new bone in-growth to some degree 9-11. Oxidation with periodate and hydrogen peroxide, or carbamination further improved its biocompability but not enough to be used as bone substitutes. We also expected to increase the osteostimulating property of regenerated cellulose by coating it with a silica-rich hydroxyapatite (HA) as it resembles the mineral composition of bone. To our disappointment, the HA-coated cellulose did not promote bone formation but favoured instead inflammation and fibroplasia. Since the bone implant study revealed unexpectedly an enormous ability of the HA-implants to induce granulation tissue, the coated cellulose was tested subcutaneously as well. These studies showed that the HA-coated cellulose not only attracted inflammatory cells but also bone marrow-derived progenitor cells of both haematopoietic and mesenchymal origin (see box 1). In this chapter, we will discuss cellulose as implant material with emphasis on the cell guiding properties of regenerated cellulose coated with silica-rich HA.

© 2013 Ekholm et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Ekholm et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
