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

In the pursuit of continuous improvement in the area of biomaterial design, blends of mixed-substituent polyphosphazenes and poly(lactic acid-glycolic acid) (PLGA) were prepared, and their morphology of phase distributions for the first time was studied. The degradation mechanism and osteocompatibility of the blends were also evaluated for their use as regenerative materials. Poly[(ethylphenylalanato)25(glycine ethylglycinato)75phosphazene] (PNEPAGEG) and poly[(glycine ethylglycinato)75(phenylphenoxy)25phosphazene] (PNGEGPhPh) were blended with PLGA at various weight ratios to yield different blends, namely PNEPAGEG-PLGA 25:75, PNEPAGEG-PLGA 50:50, PNGEGPhPh-PLGA 25:75, and PNGEGPhPh-PLGA 50:50. The molecular interactions, domain sizes, and phase distributions of the blends were confirmed by atomic force microscopy (AFM) as the PNEPAGEG-PLGA and PNGEGPhPh-PLGA blends showed different domain sizes and phase distributions. Because of the extensive hydrogen bonding within the two polymer components, PNEPAGEG-PLGA exhibited small-sized domains and well-distributed morphology. While for the PNGEGPhPh-PLGA blends, the presence of phenylphenol (PhPh) caused the formation of PLGA large-sized domains as the PLGA formed a continuous phase and PNGEGPhPh constituted a dispersed phase. In addition to AFM results, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy (FTIR) results demonstrated the miscibility of the blends. The PNEPAGEG-PLGA and PNGEGPhPh-PLGA blends presented in situ 3D interconnected porous structures upon degradation in phosphate-buffered saline (PBS) media at 37 °C. However, the blends showed different mechanistic pathways to the formations of the pores. The difference in the erosion patterns could be attributed to the nature of molecular attractions that exist in the blends. Furthermore, the novel blends were able to support cell growth as compared to PLGA and accommodate cell infiltrations, which ultimately augmented the surface area for better cell-material interactions.