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
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.
Preparation and chemical
structure
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