Biomedical Engineering Reference
In-Depth Information
liquid affects the porosity of the final construct. PLGA constructs made using
emulsion freeze-drying have average pore sizes between 30 and 50m. Using
different amounts of emulsifying liquid and using different polymers can
manipulate the final polymer structure. Matrices produced using emulsion
freeze-drying typically have good connectivity of the internal pores (Baker et
al., 2009).
10.5.4 Gas foaming
Gas foaming is a method for creating synthetic matrices that avoids the use of
solvents. Consequently, it is a good technique for incorporating sensitive
molecules into matrices without drastically reducing their bioactivity (Lee et al.,
2008). The first step of gas foaming is high temperature compression molding of
the polymer into a solid disc. After the disc is formed, the solid polymer then
rests in a high pressure carbon dioxide chamber for several days. During this
period, the gas infiltrates the polymer creating pores for tissue ingrowth
(Mooney et al., 1996). An advantage of gas foaming is the absence of caustic
solvents, so their residual presence is not a factor in the final scaffold and it is
possible to incorporate sensitive bioactive molecules.
10.5.5 Electrospinning
In the past five to ten years, electrospinning has emerged as a popular fabrication
method for creating synthetic matrices. The appeal of electrospinning rests in its
ability to produce an artificial polymer matrix that is reminiscent of the native
ECM collagen (Fig. 10.1). Electrospun scaffolds offer a balance between micro
and macro characteristics by providing sufficient gross mechanical support for
10.1 A scanning electron micrograph of an electrospun type I collagen matrix
(Matthews et al., 2002).
