Biomimetic scaffolds based on chitosan in bone regeneration. A review.

Anna Kołakowska¹, Agnieszka Gadomska-Gajadhur¹*, Paweł Ruśkowski¹

¹ Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.

KEYWORDS: chitosan, scaffolds, biocompatibility, bone regeneration

ABSTRACT:

The article focuses on a polysaccharide of natural origin – chitosan and its application in tissue engineering. The preparation process and physicochemical properties of the saccharide are described. The degradation of chitosan and the properties influencing the process both outside and in living organism were examined. Four applications in bone tissue engineering can be distinguished: preparation of cell scaffolds exclusively from chitosan, from a chitosan composite or from a chitosan polyelectrolyte complex. The fourth way is to modify the surface of scaffolds made of other materials by covering them with a layer of chitosan. At the end of the article, the processes taking place after placing the implant inside the body are described, how the structure of chitosan affects the behaviour of bone cells in the adhesion process and life processes.

INTRODUCTION

Bone lesions are common injuries. In some cases, with a sufficiently small size of the defect, the bone is able to regenerate itself.¹ In optimal conditions, healing can take place without scarring, i.e. in such a way that the regenerated tissue is indistinguishable from the state before the damage.²There are also injuries that cannot regenerate spontaneously, despite surgical intervention and stabilisation, they require special treatment. Such injuries are called critical defects. It is assumed that the size of such lesions is approx. 1–2 cm and more than 50% of the bone volume is affected.³ Regeneration of such defects is complicated, difficult to control, until now it has involved autologous bone transplant surgery.⁴ This technique is relatively good due to its histocompatibility and non-immunogenicity. It also has its disadvantages, such as the formation of damage at the site of extraction of the implant tissue, risk of secondary damage, scarring, distortion, and others.^5,6 Tissue engineering is also involved in the treatment of such critical lesions and is an alternative to conventional transplants. It is possible to use scaffolds made from biomaterials, which will provide a place for attachment for new bone cells and form the basis for the reconstruction process.^7,8

Biomaterials are the basic materials used in tissue engineering. It is a group of compounds that can come into direct contact with tissues and are well tolerated by the body. Biomaterials must be biocompatible, effective and sterilisable.^9,10 There are three generations of biomaterials, chronologically these are inert materials, bioactive materials and biomimetic materials. The inert materials replace the damaged organ or its fragment without interacting with the body. Bioactive materials combine with tissue through biochemical reactions and can replace the damaged element. Biomimetic materials are designed to stimulate the growth and proliferation of cells on the surface of the material. They are characterised by both bioactivity and bioresorbability. This group includes biodegradable scaffolds, which are a place for cell attachment, later tissue development and decay over time.^11,12 The aim of the literature review was to study the popular polysaccharide of natural origin – chitosan, its properties, behaviour in contact with body cells and applications in bone tissue engineering.

Chitosan (CS) is a derivative of the natural polysaccharide – chitin (Figure 1). CS is obtained by partial deacetylation of chitin in which at least half of the acetyl groups are removed. Chitosan is a linear cationic polymer, a copolymer composed ofN– acetyl–D– glucosamine and D– glucosamine units linked by β‑1,4‑glycosidic bonds.

The source of chitosan is chitin – the second most common polysaccharide in nature.¹³ CI is one of the main building blocks of arthropod skeletons, some molluscs and fungal cell walls.^14,15 Industrial chitin is most often obtained from food industry waste, crustaceans or sea molluscs (shrimps, lobsters, crabs, squid, mussels),^16–19 it may also be of fungal origin.²⁰