Appeal No. 1997-2634
Application 08/222,662
1. As further explained on pages 5 through 8 of the specification (citations omitted, and
footnote added):
Poly(organophosphazenes) are high molecular weight polymers containing a
backbone of alternating phosphorous and nitrogen atoms. There are a wide
variety . . . derived from the same precursor polymer,
poly(dichlorophosphazene). The chlorine-substituted species can be
modified by replacement of the chlorine atoms by different organic
nucleophiles . . . The physical and chemical properties of the polymer can be
altered by adding various ratios of hydrolytic sensitive side chains such as
ethyl glycinate . . . This will affect the degradation of the polymer as an
implantable and biodegradable material as well as vary the support of
osteogenic cells for bone and tissue implants . . .
“[I]n order to maximize growth, increase cell attachment and promote permanent
fixation by ingrowth of living tissue,”
[a] highly porous three-dimensional biodegradable [polyphosphazene] matrix
with hydrolytically unstable side chains is prepared and used as a scaffold
for the growth of osteoblast cells . . . the polyphosphazene includes between
10 and 90% hydrolytically unstable side chains including glucosyl, glycinyl,
glyceryl, imidazolyl or ethoxy units . . . The addition of the glucosyl or glycinyl
side chains to the polymer can also be used generally to enhance growth
rates of cells adhered to the polymer, presumably through uptake and
metabolism of the simple sugar or alcohol units.
As demonstrated by the examples, [polyphosphazene] substituted with 40%
methylphenoxy and 60% ethyl glycinato side chains was fabricated into a
porous three-dimensional matrix with an average pore density of 165 µm
4
using a salt removal technique. Characterization by environmental scanning
electron microscopy (ESEM) revealed an interconnecting porous network
throughout the matrix with an even distribution of pores over the entire
surface of the matrix . . . light microscopy revealed [osteoblast] cells growing
4According to page 14 of the specification, “[a] particulate leaching process is
used to create a porous polymeric matrix . . . particles are suspended in a polymer
solution, the polymer solvent is removed, and the particles are leached out of the hardened
polymer.”
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