Biomedical Engineering Reference
In-Depth Information
platelets was calculated according to the methods reported previously [14]. Figure 11 shows
the number of platelets that adhered to the samples. The platelet number was estimated
from the acid phosphatase reaction [47]. There was a linear relationship between the PRP
concentration and the absorbance values at 405 nm, indicating that the acid phosphatase
reaction of the platelets may be considered a reliable indicator of platelet number (data not
shown). The results demonstrate that the platelet adhesion rates were markedly low on the
e-BC gel when compared to the fibrinogen-coated or polystyrene surfaces. The e-SC gel also
showed an adhesion rate as low as the e-BC gel. We are separately studying the fabrication
of a vascular graft using the e-SC gel [16]. Consequently, the e-BC gel can potentially be
used for the fabrication of tissue-engineered vascular graft.
Considering that the platelets adhered better to the collagen-coated than to the gelatin-
coated surface [14], the anticoagulant ability of the e-BC gel may have been due to heat
denaturation. The e-BC gel was prepared by heat treatment at 60°C resulting in collagen
denaturation (gelatinization). Polanowska-Grabowska and coworkers reported that the
platelet adhesion rate on a gelatin-coated surface was lower than on collagen- coated or
fibrinogen-coated surfaces [48]. However, blood coagulation is known to depend on
material properties, such as surface-free energy, surface charge, and wettability; these
properties govern protein adsorption involving platelet adhesion [49, 50]. Experiments
using human whole blood are needed to test the clinical applications of the gels. Further
examinations are necessary to ensure the blood compatibility of the e-BC gel.
6. Conclusion
In conclusion, we successfully fabricated an elastic collagen material from EDC cross-linked
BC fibrillar gel by heat treatment. “Bio-inspired crosslinking” used in this study involves
collagen fibril formation in the presence of EDC as a crosslinking reagent, which was
developed in an attempt to mimic the in vivo simultaneous occurrence of fibril formation
and crosslinking. We successfully prepared the bio-inspired crosslinked BC gels by
adjusting the NaCl and EDC concentrations during collagen fibril formation. An advantage
of bio-inspired crosslinking is the achievement of homogenous intrafibrillar crosslinking as
well as interfibrillar one, providing higher mechanical properties compared to the
traditional sequential crosslinking in which monomeric collagen initially forms fibril, then
subsequently crosslinked using chemical or physical methods. Another advantage is the
elastic properties of bio-inspired crosslinked BC gels after heat treatment. Although
common collagen materials dissolved in water at a temperature above their denaturation
temperature, we found that the bio-inspired cross-linked BC gel drastically shrank at a high
temperature without remarkable dissolution. The collagen gel obtained interestingly
showed rubber-like elasticity and high stretchability. The human cells showed good
attachment and proliferation on this elastic material, suggesting its potential to be utilized in
biomaterials for tissue engineering. Additionally, the elastic material demonstrated excellent
blood compatibility. Our future work will focus on fabrication of small-caliber tubes (inner
diameter < 6 mm) for small-caliber vascular grafts and preclinical animal studies to further
assess the safety and effectiveness of the collagen-based vascular grafts.
7. Acknowledgment
This study was supported by Grants-in-Aid for Young Scientists (B) (20700393) from the
Ministry of Education, Science, and Culture, Japan.
