Biomedical Engineering Reference
In-Depth Information
The composites may have optimal porosity to support the attachment and growth of osteoblastic
cells with sufficient retention of plasticity for ease of filling defects while maintaining sufficient
mechanical strength for support.
Metallic nanoparticles such as copper and zinc have high antibacterial activity, low toxicity, and
chemical stability. Moreover, zinc has been shown to be an important trace element in bone
[37]
,
required for cell proliferation
[38]
and it has been suggested to play an important role in collagen
production and biomineralization
[39,40]
. Because of these properties, these metals have been uti-
lized in the fabrication of materials for bone tissue engineering. The addition of nanocopper and
zinc has been recently shown to significantly increase swelling, decrease degradation, increase
protein adsorption, and increase antibacterial activity in chitosan/nano-HA scaffolds
[41]
. These
composites have been shown to have no toxicity toward osteoprogenitor cells and have therefore
been postulated to have advantages over the chitosan nano-HA scaffolds without added metals for
use in osseous regeneration in many critical sites such as in the oral cavity where antimicrobial
effects might be particularly useful
[41]
. Although to date it does not appear that clinical studies
with chitosan/nano-HA composites of this type have been reported, the experimental in vitro stud-
ies do target them as promising scaffolds for use in oral bone tissue engineering. Their development
should be further pursued in order to optimize the bioresorbability and mechanical strength proper-
ties of the scaffold material for various craniofacial bone and periodontal intrabony defect sites.
19.6
Chitosan and nano-bioactive glass composites
Other variations of chitosan and nanoceramics have recently been developed and tested for bone
tissue engineering. In particular, a chitosan
gelatin/nano-bioactive glass ceramic composite has
been shown to have many excellent properties for use in alveolar bone tissue regeneration
[42]
. This
composite extends the valuable characteristics of chitosan discussed above with the blending of gela-
tin, a unique sequence of amino acids such as glycine, proline, and hydroxyproline that enhances cell
attachment and nanoparticles of glass ceramics that are osteoconductive and biodegradable.
Bioactive glass particles, particularly those synthesized by a sol
gel process, have been shown to
bond to hard tissues because of their ability to form a surface layer of hydroxycarbonate apatite and
produce no local or systemic toxicity or inflammatory or foreign-body response
[6,43,44]
. A compos-
ite of chitosan
gelatin and nanoglass ceramic can be fabricated to have pore sizes in the range of
150
m which should be optimal for migration of cells into the interior of the scaffold and osse-
ous ingrowths and vascularization
[45]
. The degradation and swelling behavior of the composite
scaffold also appeared optimized for cell attachment and spreading with biomineralization occurring
with the formation of an apatite layer on the surface of the composite
[42]
. These properties point to
the usefulness of these composites in tissue engineering applications in bone regeneration.
300
μ
19.7
Nanocalcium sulfate
Calcium sulfate (CS) is another highly biocompatible material with a long clinical history as a syn-
thetic ceramic material. The hemihydrate form of CS, also known as plaster of Paris, is one of the
