Appeal No. 1997-2634
Application 08/222,662
proteins and gels, “polymers usable in a pocket or other containment structures . . . include,
without limitation, poly(Amides), poly(Esters), poly(Orthoesters), poly(Anhydrides),
poly(Ureas), poly(ALkyl 2-Cyancryolates), poly(Dihydropyrans), poly(Acetals),
poly(Phosphazenes), and poly(Dioxinones).” Column 13, lines 34-40.
Laurencin teaches that polyphosphazenes, with the hydrolytically unstable side
chains required by the claims, “are a class of bioerodible polymers whose use has only
been explored for a limited number of biomedical applications . . . [primarily] in the area of
controlled drug delivery and as material for encapsulation applications.” Pages 969-970
(citations omitted). As a “first step[] toward . . . the construction of an osteoblast-
biodegradable polymer composite for skeletal regeneration,” “[a]n in vitro tissue culture
model was chosen to investigate the potential of [polyphosphazene] to support osteoblast
growth” and “provide a greater understanding of how the nature of polymeric surfaces
influences cell attachment and growth.” Page 964. Cells were grown on polyphosphazene
discs of various compositions, and Laurencin concluded that “osteoblast cell adhesion and
growth can be modulated on [polyphosphazene] systems by varying the nature of the
hydrolytically unstable side chain . . . [f]urther, the degradation rate of the polymer appears
to be governed by the nature of the side chain . . . [t]hus, polyphosphazenes represent a
system whereby modulation of cell growth and polymer degradation can occur
simultaneously.” There is no indication that Laurencin’s hydrolytically unstable
polyphosphazene polymers are processed to form pores of any size.
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