Biomaterials polyphosphazenes

Allcock HR, Kwon S, Riding GH, Fitzpatrick RJ, and Bennett JL. Hydrophilic polyphosphazenes as hydrogels Ration cross-linking and hydrogel characteristics of poly [bis(methoxyethoxyethoxy)phos-phazene. Biomaterials, 1988, 9, 509. 

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. 

The third topic in polyphosphazene biomaterials that will be described in this article concerns surface implications. One of the major problems in the utilization of polyphosphazenes in solid state is their exploitation in the construction of implantable devices, for which good physical properties, minimum biological response, and good resistance to fungal or bacterial colonization may be required. 

On this basis, five classes of different polyphosphazenes are considered as outstanding examples of this type of macromolecules, in which skeletal and substituent features overlap to the highest extent. The reported materials are elastomers, flame retardants and self-extinguishing macromolecules, polymeric ionic conductors, biomaterials, and photosensitive polymeric compounds all of them based on the polyphosphazene structure. 

Understanding the relationship between molecular structure and materials piroperties or biological activity is one of the most important facets of biomaterials synthesis and new-drug design. This is especially true for polyphosphazenes, where the molecular structure and properties can be varied so widely by small modifications to the substitutive method of synthesis. 

It has been demonstrated that a variety of different polyphosphazenes can be developed as biomaterials, membranes or hydrogels, bioactive polymers, and bioerodible polymers. As with most new areas of polymer chemistry and biomaterials science, molecular design forms the basis of most new advances, but the rate-controlling step is the testing and evaluation of the materials in both in vitro and in vivo environments. This is particularly true for polyphosphazenes where the availability of research quantities only has limited the... 

Allcock, H. R., Gebura, M., Kwon, S., and Neenan, T. X., Amphiphilic polyphosphazenes as membrane materials Influence of side group on radiation crosslinking, semipermeability, and surface morphology. Biomaterials. 19. 500, 1988. 

AG Scopelianos. Polyphosphazenes as new biomaterials. In SW Shalaby, ed. Biomedical Polymers Designed-to-Degrade Systems. Cincinnati, OH Hanser/Gardner, 1994, pp 153-172. 

Scopelianos, A.G. (1994). Polyphosphazenes as New Biomaterials. In Shalaby, S.W. (ed.) Biomedical Polymers Designed-to-Degrade Systems. Hanser/Gardner Publishers, Inc., Cincinnati, OH, 153-171. 

Veronese, F. M., Marsillo, F., et al. Polyphosphazene membranes and microspheres in periodontal diseases and implant surgery. Biomaterials 20(l) 91-98, 1999. 

Applications of polyphosphazenes as flame retardants, electrolytes for special batteries, and biomaterials have been described. Some cyclophosphazene derivatives can serve as hosts for small molecule Clathration. ... 

This basic structure provides for considerable flexibility in the design of biomaterials, as described in a recent review [27]. By selection of the side groups on the polymer chain, both hydrophobic and hydrophilic polymers can be produced. Hydrophobic polyphosphazenes may be useful as the basis of implantable biomaterials, such as heart valves. The hydrophilic polymers can be used to produce materials with a hydrophilic surface or, when the polymer is so hydrophilic that it dissolves in water, cross-linked to produce hydrogels or solid implants. In addition, a variety of bioactive compounds can be linked to polyphosphazene molecules allowing the creation of bioactive water-soluble macromolecules or polymer surfaces with biological activity. 

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

C.T. Laurencin, et al.. The biocompatibility of polyphosphazenes. Evaluation in Bone, in 24th Annual Meeting in Conjunction with 30th International Symposium, San Diego, United States, Society for Biomaterials, 1998. 

A.L. Weikel, et al.. Miscibility of choline-substituted polyphosphazenes with PLGA and osteoblast activity on resulting blends. Biomaterials 31 (33)(2010) 8507-8515. 

Ambrosio, A. M. A., Allcock, H. R., Katti, D. S. Laurencin, C. T. 2002. Degradable polyphosphazene/poly(alpha-hydroxyester) blends degradation studies. Biomaterials, 23, 1667-1672. 

Verret, V., Wassef, M., Pelage, J.P., Ghegediban, S.H., Jouneau, L., Moine, L., et al., 2011. Influence of degradation on inflammatory profile of polyphosphazene coated PMMA and trisacryl gelatin microspheres in a sheep uterine artery embolization model. Biomaterials 32 (2), 339—351. 

Weikel, A.L., Owens, S.G., Morozowich, N.L., Deng, M., Nair, L.S., Laurencin, C.T., et al., 2010. Miscibility of choline-substituted polyphosphazenes with PLGA and osteoblast activity on resulting blends. Biomaterials 31 (33), 8507—8515. 

A wide range of polyphosphazenes have been used for a number of biomedical applications. Examples are inert biomaterials for cardiovascular and dental uses, bioerodible and water soluble polymers for controlled drug delivery applications (Allcock et al, 1990). 

Studies were made by Laurencin et al (1993) to examine the possible use of polyphosphazenes for skeletal tissue regeneration. Polyphosphazenes with imidazole or ethylglycinate side groups next to methylphenoxy groups were evaluated. The in vitro evaluation on several cell cultures of these materials suggested that these poly thosphazene materials could be suitable candidate biomaterials for the reconstruction of a cell-polymer matrix for tissue regeneration. 

Lora, S., Palma, G., Bozio, R., Caliced, P. and Pezzin, G. (1993) Polyphosphazenes as biomaterials smTace modification of poly(bis(trifluoroethoxy)phosphazene) with polyethylene glycols. Biomaterials, 14(6), 430-436. 

Andrianov, A. K., J. Chen and L. G. Payne, 1998, Preparation of hydrogel microspheres by coacervation of aqueous polyphosphazene solutions. Biomaterials 19 109-115. 

Figure 2.10 The relative pH of the degradation products is shown by the amount of sodium hydroxide required to neutralise the acid released during the degradation of the PLGA-polyphosphazene blends and its parent polymers PLGA and the poly(organo) phosphazene-PPHOS-EG50. Reproduced with permission from A.M.A. Ambrosio, H.R. Allcock, D.S. Katti and C.T. Laurencin, Biomaterials, 2002, 23, 7, 1667. 2002, Elsevier [62]...

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