Biomedical Engineering Reference
In-Depth Information
acid are used in surgery. Gels and hydrogels used for tissue engineering
applications are prepared starting from natural biopolymers (polysaccharides,
e.g., hyaluronic acid derivative), synthetic polymers (e.g., poly(hydroxyethyl
methacrylate)) or semi-synthetic derivatives (e.g., collagen-PLA composites). 3D
network formation is performed via radical or photopolymerization induced by
ultraviolet irradiation. It has been demonstrated that self-assembling peptide
hydrogel structures support the differentiation and transdifferentiation of cells.
Stem or progenitor cells are encapsulated within these self-assembling peptide
hydrogel structures. The peptide hydrogel nanoscale environment renders the cells
available for instruction by differentiation factors such as growth factors or ECM
components, enabling the cells to differentiate or transdifferentiate within the
structures. Due to limited mechanical and viscoelastic properties, hydrogels are
mainly used for controlled drug release [
104
].
Polymeric foams can be used as both scaffolds and drug delivery matrices. One
of the few synthetic polymers approved for human clinical use are porous foams
made of a racemic poly(lactide-co-glycolide) copolymer. Microcellular foams are
made from biodegradable or non-biodegradable polymers with pores throughout
the material having a diameter of about 1-200 lm[
105
]. In addition, polymer
surfaces may be textured as a result of foaming. This is of vital interest, since
surface morphology and roughness have been demonstrated to influence the
physiological response to an implant, including cell attachment, morphology, and
differentiation [
106
].
3.3 Nanomaterials and Novel Fabrication Methods
The discovery of fullerenes and carbon nanotubes produced a tremendous
development of novel nanomaterials and their investigation for use in many dif-
ferent applications [
107
]. Nanostructured biomaterials including nanoparticles,
nanofibers, nanosurfaces, nanocomposites, and nanosphere-immobilized bioma-
terials have gained increasing interest in regenerative medicine, since these
materials often mimic the ECM. Nanomaterials have thus been intensively studied
in the last decade for utilization in tissue engineering and scaffold fabrication.
Preparation, characterization, and invitro analysis of novel structured nanofibrous
scaffolds for bone tissue engineering have recently been reviewed by Wang and
co-workers [
108
].
Nanomaterials. Materials designed in nanoscale used for bone regeneration
include nanospheres and nanoparticles [
109
,
110
], nanotubes, in particular carbon
nanotubes [
111
-
113
], and nanodendrimers based on carboxymethylchitosan/
poly(amido amine) [
114
]. Applications are mainly focused on utilization of
nanomaterials to improve mechanical properties of scaffold materials [
115
].
Lim studied micropatterning and characterization of electrospun PCL/gelatine
nanofiber tissue scaffolds by femtosecond laser ablation for tissue engineering
applications [
116
]. Nanofibers are prepared via electrospinning, phase separation
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