Biomedical Engineering Reference
In-Depth Information
(a)
(b)
10 µm
(c)
(d)
10 µm
FIgurE 18.9
(
See color insert.
) SHG microscopy images of cellulose scaffolds seeded with osteoblasts to obtain
a construct intended as a bone tissue replacement. (a) SHG image of cellulose scaffold measured 4 days after cell
seeding (b) overlay with simultaneously measured CARS image (orange color), showing a group of osteoblasts
located on the scaffold. (c) SHG image measured 8 days after seeding, when ECM collagen fibers could be detected
in regions of high cell density. (d) Corresponding SHG/CARS overlay image showing the collagen fibers located in
between the cells.
contact with a mesh of interconnected fibers from both materials, confirming adaptation of the graft
in
vivo
after implantation.
18.3.2.2 Biosynthesized cellulose as a Scaffold for Bone Regeneration
The potential for using biosynthesized cellulose as a bone graft material has also been investigated
(Zaborowska et al. 2010). For this purpose, a porous version of the material was manufactured using particle
leaching with paraffin wax particles added as porogens during fermentation. Figures 18.9a and 18.9c show
SHG images measured on cellulose scaffolds with osteoblasts, 4 and 8 days after cell seeding, respectively.
In Figure 18.9a, the SHG signal is obtained from the cellulose material surrounding a group of cells, whose
positions are indicated by the dark region in the image. After 8 days of growth when denser confluent cell
regions could be observed on the scaffold, SHG images also showed ECM collagen fibers as shown in Figure
18.9c. The osteoblasts can be imaged by CARS microscopy probing their hydrocarbon content via the CH
2
symmetric stretch vibration at wavenumber 2845 cm
−1
, in this case using combined excitation at 817 and
1064 nm. By means of simultaneous SHG and CARS microscopy, the combined arrangement of cells, cellu-
lose, and collagen can be visualized as shown in the overlay images of Figures 18.9b and 18.9d. In the overlay
image in Figure 18.9d, it can be seen that the detected ECM collagen fibers are located in between the cells.
18.4 Silk Fibroin
Silk fibroin is a natural biopolymer spun into fibers by silk worms such as the
Bombyx mori
and
Antherea
mylitta
. Properties such as high mechanical strength and low inflammatory effects when implanted
in vivo
(Mandal and Kundu 2010, Murphy and Kaplan 2009) make it of interest as a tissue engineering
scaffold material. For this purpose, silk can either be used in its raw form obtained from worm spinning
or, more commonly, in regenerated form. A number of tissue engineering applications using silk as scaf-
fold material has been presented in recent years. Some examples are vascular tissue (Enomoto et al. 2010,
Zhou et al. 2010), cartilage (Chao et al. 2010), ligament (Liu et al. 2008), bone (MacIntosh et al. 2008,
Weska et al. 2009), cornea (Lawrence et al. 2009), and nerve grafts (Yang et al. 2007).
