CUSTOMIZED NANOCOMPOSITE SCAFFOLDS FABRICATED VIA SELECTIVE LASER SINTERING FOR BONE TISSUE ENGINEERING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 941

Figure 45.8. (a) Shape and morphology of BSA-loaded Ca-P/PHBV
nanocomposite microspheres, and (b) cross-sectional view of BSA-loaded
Ca-P/PHBV nanocomposite microsphere.
selected as a model biomolecule for the incorporation and release
studies in this investigation because it is a well-characterized pro-
tein and is inexpensive for model studies. The surface morphology
and internal structure of BSA-loaded Ca-P/PHBV nanocomposite
microsphereswereexaminedunderSEMandareshowninFig.45.8.
With the incorporation of BSA, small pores were observed on the
crosssectionsofmicrospheres,asdepictedinFig.45.8b,whichwere
notobserved in nanocompositemicrospheres without BSA loading.
The actual BSA loading in Ca-P/PHBV nanocomposite
microspheres, as was determined using a Micro BCA assay kit, was
6.13 ± 0.15 μ g/mg,andtheBSAencapsulatione ciency(EE)forCa-
P/PHBV nanocomposite microspheres was 24.51 ± 0.60%. The low
EEwasmainlyattributedtotheinherentlimitedchemicalandphys-
ical stability of BSA and relatively harsh microsphere fabrication
process for BSA. The widely known reasons for low EE of biomole-
cules in polymer microspheres obtained via emulsion processes
include (i) the use of organic solvents during the double-emulsion
process, (ii) biomolecule elution from the inner water phase into
the outer water phase during the solvent evaporation process, (iii)
exposure of the biomolecules to high shear forces during emul-
sion preparation, and (iv) generation of organic-aqueous interfaces.
These reasons could also be valid in the current investigation. In
addition, the hydrophobility of PHBV due to its high crystallinity
weakened the interaction between the PHBV polymer and BSA and
thus further decreased the EEvalue.