Biomedical Engineering Reference
In-Depth Information
a major concern. Basically this is due to the practical limitation in
supplying all the required nutrients to the cells on time. Of all, oxy-
gen is one of the most important elements for cell survival, yet it
remains the toughest challenge so far in designing a suitable mech-
anism to supply a su cient amount to cells. This is due to the gas
natureofoxygenanditslowsolubilityinaqueoussolution(
7.8mg
L 1 at25 C) 15 ,evenlowerinculturemediahavingvarioussolutes. 16
Asaresult,directsupplyoftendamagescellsduetosparging, 17 bub-
ble formation, 18 and forming, 19 unlike other nutrients that can dis-
solve directly into the media of the cells. In the absence of oxygen,
cells of living organisms undergo anaerobic metabolism that gener-
ates a large amount of lactic acid and subsequently harms or kills
the cells with the highly acidic condition. 20 Under normal physio-
logical conditions, oxygen is delivered to the body tissues via blood
circulation that comes under the control of the respiratory system.
The concentration of oxygen at the tissues is tightly maintained at
an optimumlevelinensuringhealthy, growing cells. Suchacomplex
systemiselegantinnaturebuthasturnedintooneofthebiggestlim-
itations in the field of tissue engineering as the formation of blood
vessels naturally is a slow process. As tissue starts to grow thicker,
cells imbedded more than 200 μ m from the oxygen source will face
necrosisbeforeeventhebloodvesselsareformed,duetooxygendif-
fusion limitations. 21 , 22 The incorporation of a system which mimics
the natural respiratory function is still far too complex to be made
realistic using the current engineering level, although measures are
undergoing, especially in the area of vascularization. Therefore, is
stillanadvantagetousescaffoldsinprovidingoxygentocellsfortis-
sue engineering and possibly via incorporating smart microspheres
into scaffoldsthat release oxygen in acontrolled manner.
32.2 Current Status and Development in Supplying
Oxygen for Tissue Engineering
The issue of the insu cient supply of oxygen for the cell survival
during the tissue engineering process has been known for a long
time but remains problematic. Numerous efforts have been made
 
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