Page 252 - Biodegradable Polyesters
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230  9 Environment-Friendly Methods for Converting Biodegradable Polyesters



                      (a)                             (b)











                                           2 μm                        50 μm



                      (c)                             (d)









                                            5 μm


                    Figure 9.11 SEM micrographs of (a) PLA  a growing cell on it, (c) scaffold manufac-
                    scaffold with a structure of 3-D nanoporous  tured using the NFC technique from PLLA,
                    nanofibrillar network prepared from PVA/PLA and (d) MC3T3-E1 cells grown for 7 days on
                    (70/30 wt%) blend after melt blending, cold  NFC scaffolds fabricated from PLLA (shown
                    drawing, and extraction with water, scaf-  here as (c)).
                    fold without cells, and (b) as (a) but with

                      The results [24, 25, 39–43] of biomedical testing with living cells, as shown in
                    Figure 9.11, are quite promising – the cells attach rather well to the scaffold surface
                    (Figure 9.11b,d), proliferate, and grow further.
                      What could be the next challenge? The first could be improvement of the
                    mechanical performance of the final nano-sized materials. As demonstrated
                    above, in the cases when H-bonding in polymer blends exists, the final nano-
                    morphology is similar to the 3-D nanofibrillar network, which does not possess
                    the superior mechanical properties of noninterconnected nanofibrils. Scaffolds
                    with high mechanical performance (e.g., for bones and tendons repair) are
                    frequently needed in tissue engineering, possibly prepared with the use of water
                    only as a solvent.
                      Keeping in mind the fact that practically all water-soluble polymers are inclined
                    to form hydrogen bonds with polyesters and polyamides, it follows that it is
                    hardly possible to convert the condensation polymers (to which most important
                    biodegradable biocompatible polyesters belong, Figure 9.8) into nano-sized
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