Poly organo phosphazene Degradation

II. Degradation characteristics of hydrolysis-sensitive poly[(organo) phosphazenes]. Biomaterials 13 (9) (1992) 601-611. 

Crommen, J.H.L., Schacht, E.H. and Mense, E.H.G. (1992) Biodegradable poly mers. II. Degradation characteristics of hydrolysis-sensitive poly[(organo)phosphazenes]. Biomaterials, 13(9), 601-611. 

Figure 2.1 Basic structures for some groups of synthetic polymers commonly employed as degradable materials in medical applications a) polylactide-co-polyglycolides (also commonly used as their homopolymers (i.e., n/m = 0), b) polycaprolactones, c) polydioxanones, d) polyorthoesters, e) polyanhydrides, f) polyalkylcyanoacrylates, g) poly(organo)phosphazenes and h) polyphosphoesters...

Figure 2.2 The proposed mechanism for the hydrolytic degradation of poly(organo)phosphazenes...

The nature of the organic side groups has a decisive influence on the degradation rate of the resulting poly(organo)phosphazene. 

Figure 2.4 Some water-soluble, degradable poly(organo) phosphazenes...

Mildly basic conditions (pH 7-10) generally tend to slow the degradation rate of poly(organo)phosphazene in comparison to neutral pH, an observation consistent for a range of different organic substituents (Figure 2.8) [41, 51]. This is somewhat surprising for a hydrolysis reaction, but is reported for a number... 

Figure 2.8 Degradation profiles of PYRP showing the pH dependence a pattern of decreasing hydrolytic stability with lower pH is observed, as seen for many poly(organo)phosphazenes. Reproduced with permission from A.K. Andrianov, A. Marin and R Peterson, Macromolecules, 2005, 38,19, 7972. 2005, American Chemical Society [41]...

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]...

The data produced to date suggests that if the poly(organo) phosphazene side groups are carefully selected, the degradation products are nontoxic [25, 48, 69]. That the backbone degradation products consist of a benign mixture of phosphates and ammonia is well proven [46]. Phosphates have a well-known metabolic... 

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