Synthesis, Structures, and Emerging Uses for Poly(organophosphazenes)

Biomedical applications of polyphosphazenes

“…Since mechanical strength is one of the required criteria for the suitability of biomaterials for biomedical applications, a number of investigations have confirmed the mechanical competence of polyphosphazene-based biomaterials (Deng et al, 2011;. For example, Deng et al (Deng et al, 2011) (Allcock, 2018;Ogueri, Escobar Ivirico, et al, 2019). These stringent conditions pose a formidable hurdle to the manufacturing process development and scale-up (Ogueri et al, 2020a).…”

“…The first step starts with the controlled thermal ROP of commercially available hexachlorocyclotriphosphazene monomers (HCCTP) at 250°C under vacuum (Ogueri, Escobar Ivirico, et al, 2019). This initial step results in a highly reactive organic precursor, called poly(dichloro)phosphazene (PDCP) with labile P–Cl bonds that are later utilized to substitute in organic nucleophiles for chlorine atoms (Allcock, 2016, 2018; Ogueri, Escobar Ivirico, et al, 2019). Though ROP is the conventional synthetic route to obtain a linear and high molecular weight PDCP, other alternative technique routes such as living cationic polymerization and direct synthesis have been reported to yield PDCP intermediates with low molecular weight (Ogueri et al, 2019, 2020a).…”

“…Despite the remarkable progress in the development and utility of polyphosphazene‐based biomaterials in biomedicine, there are still concerns regarding their scale‐up and commercialization (Ogueri et al, 2020a). The conventional synthetic technique of a linear polyphosphazene is cumbersome and requires severe reaction conditions such as high temperature, anhydrous environment and an airtight closed system (Allcock, 2018; Ogueri, Escobar Ivirico, et al, 2019). These stringent conditions pose a formidable hurdle to the manufacturing process development and scale‐up (Ogueri et al, 2020a).…”

“…This is because most organic polymers (with few exceptions) lack the design flexibility and property tunability as materials scientist and engineers often focus on harnessing and optimizing the physicochemical properties of polymers during design, scale‐up, and commercialization (Ogueri, Ivirico, Nair, Allcock, & Laurencin, 2017; Ogueri, Jafari, et al, 2019; Song et al, 2018). Meanwhile, the biocompatibility and degradability are often ignored and not considered as target properties (Allcock, 2018; Ogueri, Jafari, et al, 2019). Thus, polyphosphazenes provide a versatile tool that can manage this trade‐off, and they offer an optimal biologic interface between the surface of medical implants and native tissues (Z. Huang et al, 2018; Ogueri, Ogueri, Allcock, & Laurencin, 2020a; Potta, Chun, & Song, 2010).…”

A Regenerative Polymer Blend Composed of Glycylglycine Ethyl Ester-Substituted Polyphosphazene and Poly(lactic-co-glycolic acid)

“…PLGA and its derivatives are FDA-approved materials used for many medically related applications, and as such, they have been extensively investigated for regenerative engineering. − However, PLGA and formulations are not ideal biomaterial platforms and face limitations because of the lingering issues of acidic degradation products arising from bulk erosion. − The local accumulation of these acidic products (lactic and glycolic acids) often elicits a prolonged inflammatory response in the tissue microenvironment surrounding the implant, which may result in sudden structural failures. , Also, the rise of regenerative engineering and its complexity and demands have caused a paradigm shift and stimulated innovation in the design of new biomaterials with diverse properties that can meet the ever-changing requirements of this approach. , So an ideal polymeric biomaterial should possess excellent initial mechanical properties, appropriate degradability, neutral degradation products, and the ability to present interconnected porous structures for cell infiltration, tissue in-growth, and vascularization. , However, no polymers have satisfied all the listed criteria. Because biomaterials are not a “one-size-fits-all” system, materials with a wide range of degradation rates and physicochemical properties are sought after.…”