Tissue engineering polyphosphazenes

Polyphosphazenes can be considered as biomaterials in several different ways, depending on the type of utilization one can predict for these substrates. In this regard, we will consider three different topics concerning water-soluble POPs and their hydrogels, bioerodible POPs for drug delivery systems and for tissue engineering, and the surface implications of POP films. 

Table 19 also describes polyphosphazenes bearing oligopeptide side chains (Gly-Pro-Gly and Gly-Val-Ala tripeptides) [636], potentially useful for tissue engineering, and polymers bearing AT-acetylglycine substituents [637]. The... 

Concurrent with these investigations, polyphosphazene matrices, functionalized with aminoacid esters or with imidazole groups, became of importance because of their tissue engineering aspects in bone regeneration [655,656,679], treatment of periodontal diseases [657], and nerve reconstruction problems [680-682] in which the remarkable bio compatibility of POP matrices was coupled with their tuneable bio degradability. 

Liquid crystalline, ferroelectric, and photochromic systems Controlled drug-delivery from polyphosphazenes Use in bone tissue engineering... 

Recent developments in the polyphosphazene chemistry have been re-viewed. The role of polyphosphazenes as biodegradable polymers as hydrogels for tissue engineering and as induced helical polymers has been discussed. Preparation and application of poly(thionyl phosphazenes) are discussed in two review chapters. ... 

The ester protection technique has also been used in the preparation of amino acid derivatives of polyphosphazenes (70, 71). For example, eAyl glycinate reacts with poly(dichlorophosphazene) to link the amino function to e phosphorus atoms of the backbone. Subs uent exposure of the protected polymer to water in a biological environment leads to hydrolysis of the ester function and breakdown of the polymer to ethanol, glycine, phosphate, and ammonia. This has been used both for the controlled delivery of drugs and for stimulating the regrowth of bone in tissue engineering experiments (72). 

Nukavarapu, S.R Kumbar, S.G. Brown, J.L. Krogman, N.R. Weikel, A.L. Hindenlang, M.D. Nair, L.S. Allcock, H.R. Laurencin, C.T. Polyphosphazene/nano-hydroxyapatite composite microsphere scaffolds for bone tissue engineering. Biomacromolecules 2008, 9 (7), 1818-1825. 

This chapter on polyphosphazenes provides the reader an overview of the synthesis and side group chemistry in context to the degradation profile and biocompatibility. In addition, it reviews the medical applications developed using biodegradable polyphosphazenes specifically drug delivery matrices and tissue-engineering scaffolds. 

Polyphosphazene films, prepared by solvent casting of either polyphosphazene polymers or polyphosphazene blends, have been actively studied for periodontal or bone tissue engineering. Duan et al. prepared poly[(ethyl... 

M. Deng, et al.. Dipeptide-based polyphosphazene and polyester blends for bone tissue engineering. Biomaterials 31 (18) (2010) 4898 908. 

S. Bhattacharyya, et al.. Biodegradable polyphosphazene-nanohydroxyapatite composite nanofibers scaffolds for bone tissue engineering, J. Biomed. Nanaechnol. 5 (1) (2009) 69-75. 

M. Deng, et al., Polyphosphazene polymers for tissue engineering an analysis of material synthesis, characterization and apphcations. Soft Matter 6 (2010) 3119-3132. 

M.S. Peach, et al., Polyphosphazene functionalized polyester fiber matrices for tendon tissue engineering in vitro evaluation with human mesenchymal stem cells, Biomed. Mater. 7 (4) (2012) 045016. 

FIGURE 21.15 Polyphosphazene-based 3D matrices for tissue engineering, (a) Sintered polyphosphazene scaffolds, (b) SEM image of polyphosphazene microsphere scaffolds. 

A further major field of investigation for bioerodihle polymers is their use as scaffolds for tissue engineering. Tissue engineering is the use of a bioerodible polymer as an artificial extracellular matrix, supporting cell growth and organisation and will he discussed in Chapter 4, as it represents a major focus of polyphosphazene research. 

---