CELL - BASED NANOCOMPOSITES AND BIOMOLECULES FOR BONE TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 554

change, enabling cellular processes to take place. The authors postulated that the
mineralized collagen may play a role in neutralizing the acidic PLA products 73 .
The porous nature of the scaffold is a conducive environment for the deposition
of bone matrix and mineralized collagen and may act as anchors for osteoblast
adhesion. Further bone regeneration could be aided by the bone-cells in the scaf-
fold 62,87,88 . Nutrient and waste transport are made possible via these pores as well.
One study had reported that spinal fusion was achieved when rhBMP-2 in a col-
lagen carrier was more homogeneous and underwent more remodeling than
when rhBMP-2 was in an autograft regardless of the presence of a collagen
carrier. In addition, the incorporation of rhBMP-2 led to a stiffer and stronger
spinal fusion than those using autogenous grafts 89 .

16.3.4 Nanofi brous Composites
Electrospun nanofi brous scaffolds were fabricated from a mixture of PCL, type I
collagen and HA nanoparticles with an average fi ber diameter of 180 50 nm,

characteristic of the collagen fi ber bundle diameter of native bone. The presence
of collagen in the nanofi bers further improved the stiffness of the scaffold. In
addition, the apatite particles were uniformly distributed on the fi bers 90 . Electro-
spinning technology was also employed in producing hybrid membranes made of
PLLA and HA. The presence of HA particles enhanced the tensile strength of
the hybrid membranes and the increased elastic modulus and lower strain at
failure were indicative of the fact that HA nanoparticles had made the nanofi ber
matrix stiffer and less plastic in deformation 91 . Table 16.4 shows some examples
of various types of nanofi brous composites that have been successfully fabricated
using electrospinning 92 - 96 .
One of the advantages of nanofi brous scaffolds was that biomineralization
was signifi cantly enhanced on nanofi brous scaffolds than on solid-walled
scaffolds 97 . Nanofi brous poly(L-lactic acid) (PLLA) scaffolds with intercon-
nected pores were made using a phase separation method. Osteoblasts were
seeded on the scaffolds and higher ALP activity and an earlier and enhanced
expression of RUNX-2 protein and bone sialoprotein were observed on the
nanofi brous scaffolds than on solid-walled scaffolds. In addition, the nanofi brous
scaffolds seemed to promote the adsorption of proteins such as fi bronectin and
vitronectin as integrins associated with fi bronectin (

±

α v β 3), vitronectin ( α v β 3) and

collagen - binding ( α 2 β 1) were present at higher amounts than those grown on

TABLE 16.4. Electrospun Nanofi brous Composites with Calcium Salts

Calcium Salts (Nanoparticles) Matrix References

Ref 92

Hydroxyapatite Polyhydroxybutyrate - co - valerate

Polylactic acid Ref 93

β - calcium phosphate

Hydroxyapatite Polycaprolactone Ref 94

Hydroxyapatite Silk Fibroin Ref 95

Calcium carbonate Polycaprolactone Ref 96