Biomedical Engineering Reference
In-Depth Information
normal cartilage growth. 189 Thus, surgical strategies for cartilage repair have
focused on accessing the regenerative signaling molecules and cells within
the subchondral bone marrow 112 but this requires invasive drilling or abrasion
through the overlying articular cartilage into the bone marrow. This causes even
further cartilage tissue damage before achieving any therapeutic effect. Besides
that, the properties of the resulting tissue are inferior to that of the uninjured
cartilage due to the growth of fibrocartilage.
Biomaterials are very important in engineering tissue regeneration and
repair. 190 To grow an entire organ or a tissue for transplantation, it requires a pre-
designed scaffold with the patient-specific anatomy. 191 In some cases, irregular
shaped defects and wounds need to be filled and repaired in clinics. 192 In such
situations, injectable materials are useful because they are easily manipulated
and can be sued in minimally invasive procedures to reduce complications and
to improve patient comfort and satisfaction. 193 One of the flexible and manipu-
lable materials that have been explored for such purpose is hydrogel which has
limitations that are being tackled by various approaches. 194-198 However, these
materials are not yet in clinical use.
One material that is being studied as scaffold for cartilage tissue engineering
is that electrospun polymeric nanofibers have emerged as potential scaffolds
for cartilage tissue engineering 199,200 because these mimic the natural ECM
making them suitable candidates for cartilage tissue engineering. 201,202 Poly-
ε-caprolactone (PCL) nanofiber sheets are flexible and can be rolled or folded
and contoured to cover the surface of a joint making them excellent candidates
for cartilage tissue engineering. The study by Liu 192 demonstrated that it is pos-
sible to seed PCL nanofiber scaffolds with periosteal cells in vivo and subse-
quently produce engineered cartilage in vitro.
Other nanomaterials including polymeric nanomaterials, nanocomposites,
and natural nanomaterials have also been studied for cartilage regeneration. 112
Human cartilage cells attached and proliferated well on HA nanocrystals that
were homogeneously dispersed in poly(lactic acid) (PLA) nanocomposites. 35
Increased chondrocyte adhesion and migration were observed in anodized
nanomaterial metals (such as Ti) with nanometer-sized pores. 203
6.3.3 Nanomaterials for Vascular Applications
Polymeric nanomaterials have also promoted the responses of vascular cells
(such as endothelial and smooth muscle cells). 112 PLGA that were treated with
various concentrations of NaOH for selected period of time generated nano-
structured PLGA with altered surface chemistry while retaining nanostructured
topographies by using silastic mold-casting techniques. Their results demon-
strated that endothelial and smooth muscle cell densities increased on nano-
structured PLGA as a result of the nanometer surface features. 204 Additionally,
nanometals prepared by powder metallurgy techniques also demonstrated
increased endothelialization compared with conventional metals 205 showing
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