Synthesis, characterization, and osteocompatibility evaluation of novel alanine‐based polyphosphazenes

Abstract

This study deals with the synthesis and in vitro osteocompatibility evaluation of two novel alanine-containing biodegradable ester polyphosphazenes as candidates to form self-setting composites with hydroxyapatite (HAp) precursors. The two novel biodegradable polyphosphazenes synthesized were poly[(ethyl alanato)1.0(ethyl oxybenzoate)1.0 phosphazene] (PN-EA/EOB) and poly[(ethyl alanato)1.0(propyl oxybenzoate)1.0 phosphazene] (PN-EA/POB). The polymers were characterized by multinuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Biodegradability and percentage water absorption of the polymers were evaluated by following the mass change in phosphate buffer (pH 7.4) at 37 degrees C. PN-EA/POB underwent faster degradation and showed higher water absorption compared to PN-EA/EOB. Both polymers became insoluble in common organic solvents following hydrolysis presumably due to crosslinking reactions accompanying the degradation process. Osteoblast cell adhesion and proliferation on PN-EA/EOB and PN-EA/POB was followed by scanning electron microscopy (SEM) and by using a biochemical assay. Both PN-EA/EOB and PN-EA/POB supported the adhesion and proliferation of primary rat osteoblast cells in vitro. Furthermore, the enzymatic activity of the osteoblast cells cultured on the polymers was confirmed by the alkaline phosphatase activity. Thus, these biodegradable amino-acid-based polyphosphazenes are promising new materials for forming self-setting bone cements.

Polyphosphazene/Nano-Hydroxyapatite Composite Microsphere Scaffolds for Bone Tissue Engineering

“…5,6 A series of polyphosphazenes in the form of two dimensional films showed good osteoblast cell adhesion and proliferation. 7,8 We have further demonstrated the tissue compatibility and the in vivo degradation of alanine ethyl ester based polyphosphazenes in a rat model. 9 The in vitro and in vivo observations confirmed the osteocompatibility nature of polyphosphazenes and hence these materials are good candidates for bone tissue engineering applications.…”

“…We have previously reported glycine and alanine ethyl ester side group polyphosphazenes that showed excellent biocompatibility but lacked the required mechanical strength due to their lower glass transition temperatures. [7][8][9] In this study we have synthesized three different polyphosphazene single-substituent polymers with amino acid side groups, namely leucine, valine and phenylalanine ethyl esters. Among these, poly[bis(ethyl phenylalanato)phosphazene] had a T g around 41.6 °C which is above the physiological temperature and hence has the potential to be used as scaffold material for load bearing tissue engineering.…”

“…3,7 Hexachlorotriphosphazene was purified by recrystallization, followed by sublimation. This was then polymerized under vacuum in a sealed silica tube at 255 °C to obtain poly (dichlorophosphazene) (PDCP), followed by sublimation of unreacted hexachlorocyclotriphosphazene.…”

Miscibility and in vitro osteocompatibility of biodegradable blends of poly[(ethyl alanato) (p-phenyl phenoxy) phosphazene] and poly(lactic acid-glycolic acid)

“…The PNEA 50 PhPh 50 polymer was found to have a moderate molecular weight ( Mw = 1,570 ±20 kDa) with a polydispersity of 2.41±0.07, which is typical for polyphosphazenes obtained by the ring-opening polymerization of hexachlorocyclotriphosphazene [27]. The polymer had a high glass transition temperature of 24.6°C, which is due to the steric bulk and the possibility of π − π stacking of the biphenyl units [14].…”

Electrospun Polyphosphazene Nanofibers for In Vitro Osteoblast Culture

“…Despite these properties, there are few works related to the use of biodegradable polyphophazenes as materials in tissue engineering applications. Laurencin and co-workers reported that polyphosphazenes promote the growth, adhesion, and spreading of osteoblast cells (Laurencin et al, 1993Nair et al, 2004Nair et al, , 2006. Kajiwara studied the culture of Bowes and Chinese hamster ovary cell lines onto a polyphosphazene membrane (Kajiwara, 1992).…”