Biomedical Engineering Reference
In-Depth Information
engineering, closer mimicking of the physiological environment is required
and needs to include control of parameters such as the turnover of nutrients,
the regulation of pH and gas partial pressures and biomechanical stimuli.
all these different parameters have been taken into account and integrated
in the development of bioreactors.
14.6 Bioreactors
the future development of tissue engineered products depends on scalable
production processes with standards of safety and efficacy similar to those
established for the pharmaceutical industry. Many of the bioreactor design
principles established for production of biopharmaceuticals can be applied to
production of tissue engineering products. Bioreactors integrating dynamic
conditions such as stirrings, perfusion or microfluidic bioreactors have the
potential to address efficiently the clinical need for the production of tissue
engineering products (Godara
et al
., 2008b).
It is widely accepted that the behaviour of cells is significantly affected
by the hydrodynamic environment and mechanical stimuli. to this purpose,
computer modelling and bioreactor systems have been developed to set the
appropriate conditions in bioreactors for tissue engineering.
Computational fluid dynamic (CFD) studies have been performed to provide
the scientific community with a more detailed description of fluid mechanics
and nutrient transport within bioreactor equipments (Hutmacher and Singh,
2008). The definitions of CFD parameters will certainly have an impact on
the understanding of the cellular response to fluid flow processes.
the study of the parameters affecting tissue repair at the cellular level
should also be accompanied by investigations satisfying the requirements for
engineering customised, anatomically shaped and histologically differentiated
(e.g. osteochondral tissue including bony and cartilagineous layers) grafts.
the design of these grafts should take into account the need for an immediate
functionality (e.g. load bearing, structural support) and long-term regeneration
(i.e. graft formation, integration and remodeling) (Grayson
et al
., 2008).
MSCs and differentiated bone cells (osteoblasts and osteocytes) are able
to sense mechanical stimuli deriving from the surrounding environment. the
importance of mechanical stimuli has been observed in both bone homeostasis
and osteogenesis, but the mechanisms responsible for osteogenic induction
in response to mechanical signals are still poorly understood. Studies have
tried to discern the effect of biomechanical stimuli on osteoblasts in 3D
scaffolds. Electrospun PCL scaffolds were seeded with osteoblasts and
subjected to different levels of externally applied compressive force (Rath
et al
., 2008). the study showed that progenitor cells adhered, proliferated
and differentiated in the scaffolds and deposited new ECM. the biochemical
stimuli led to an enhanced expression of genes and proteins required for the
