DYNAMIC CELL CULTURE METHODS FOR FUNCTIONALIZED BIOMATERIALS - Biologically-Responsive Hybrid Biomaterials - page 397

future studies to enable progress toward “organ printing,” where combining
multilayer photopatterning with optimized cell adhesion and function could
result in a viable tissue.
Huang et al. also used a rapid-prototyping technique to create a 3-D scaffold
with the ability to be cultured in a perfusion bioreactor [150]. Using a fully-
automated selective laser sintering (SLS) process, porous, salt-leached
polycaprolactone (PCL) tetrahedral scaffolds were created with and without
macro-sized flow channels. Then, two different forms of seeding were
investigated: avidin-biotin binding and collagen treatment. For the AB method,
the Hep G2 cells were treated with the biotin compound and the avidin was
allowed to adsorb into the scaffolds for 2 hours, followed by injection of the cell
suspension and a centrifugation seeding process [151]. The media perfusion
began at a flow rate of 2 mL/min for 2 hours, followed by 5 mL/min for the
remainder of the culture period. The initial seeding efficiency was slightly higher
using the AB seeding on the 3-D construct, but the remarkable differences
occurred at day 9 of culture, when the construct with fluid channels and AB
binding showed significantly higher cell numbers. In addition, the constructs
with channels and AB binding showed clear advantages in cell function, through
glucose consumption and albumin production, over the constructs with no
channels and over those treated with collagen adhesion. The monolayer control
culture nearly lost the ability to remove ammonium, one of the most important
functions for bioartificial liver function. The cells adhered using the AB binding
in the perfusion showed a higher detoxification capacity than the other perfusion
cultures, but lower than that of a shaking 3-D PCL disk culture. The perfusion
culture and the enhanced cell adhesion through avidin-biotin binding both enable
the cells to grow and function, showing promise for the development of in vitro
liver tissues [150].
4. Future Perspectives
It can be concluded that in most cases presented, the combination of a
biomimetic material as a scaffold with a physiologically relevant mechanical
microenvironment, results in a more functional, homogenous engineered tissue.
There are obviously still obstacles for the development of tissue engineered
grafts displaying the properties of native tissue, but the field continues to
advance to overcome the many complexities inherent in designing a biologically
relevant product.