Krogman Nicholas R, Singh Anurima, Nair Lakshmi S, Laurencin Cato T, Allcock Harry R
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Biomacromolecules. 2007 Apr;8(4):1306-12. doi: 10.1021/bm061064q. Epub 2007 Mar 6.
We have previously demonstrated the feasibility of blending bioerodible polyphosphazenes with poly(lactide-co-glycolide) (PLGA) to form versatile polymeric materials with altered bioerosion properties. These studies demonstrated the effective neutralization of the acidic degradation products of PLGA by the polyphosphazene hydrolysis products. In the present study, five new polymers of dipeptide polyphosphazenes poly[(ethyl glycinato)x(glycyl-ethyl glycinato)yphosphazene] and novel blends of these polyphosphazenes with poly(lactide-co-glycolide) (PLGA) were synthesized and fabricated. The miscibility was analyzed using differential scanning calorimetry and scanning electron microscopy. Hydrogen bonding within the blends was assessed by attenuated total reflectance infrared spectroscopy. The phosphazene component of the blend contained varying ratios of the glycyl-glycine ethyl ester to the glycine ethyl ester. Poly[(ethyl glycinato)0.5(glycine ethyl glycinato)1.5phosphazene formed completely miscible blends with PLGA (50:50) and PLGA (85:15). This is ascribed to the multiple hydrogen-bonding sites within the side groups of the polyphosphazene. The components of the blend act as plasticizers for each other because a glass transition temperature for each blend was detected at a lower temperature than for each individual polymer. A hydrolysis study showed that unblended solid poly[(ethyl glycinato)0.5(glycyl ethyl glycinato)1.5phosphazene] hydrolyzed in less than 1 week. However, the blends degraded at a slower rate than both parent polymers. This is attributed to the buffering capacity of the polyphosphazene hydrolysis products, which increases the pH of the degradation media from 2.5 to 4, thereby slowing the degradation rate of PLGA.
我们之前已经证明了将可生物侵蚀的聚磷腈与聚（丙交酯-共-乙交酯）（PLGA）共混以形成具有改变的生物侵蚀特性的多功能聚合物材料的可行性。这些研究表明聚磷腈水解产物可有效中和PLGA的酸性降解产物。在本研究中，合成并制备了五种新型的二肽聚磷腈聚[（甘氨酸乙酯）x（甘氨酰-甘氨酸乙酯）y磷腈]以及这些聚磷腈与聚（丙交酯-共-乙交酯）（PLGA）的新型共混物。使用差示扫描量热法和扫描电子显微镜分析了其相容性。通过衰减全反射红外光谱法评估了共混物中的氢键。共混物的磷腈组分包含不同比例的甘氨酰-甘氨酸乙酯与甘氨酸乙酯。聚[（甘氨酸乙酯）0.5（甘氨酰-甘氨酸乙酯）1.5磷腈]与PLGA（50:50）和PLGA（85:15）形成了完全互溶的共混物。这归因于聚磷腈侧基内的多个氢键位点。共混物的组分彼此充当增塑剂，因为检测到每种共混物的玻璃化转变温度都比每种单独的聚合物低。一项水解研究表明，未共混的固体聚[（甘氨酸乙酯）0.5（甘氨酰-甘氨酸乙酯）1.5磷腈]在不到1周的时间内就发生了水解。然而，共混物的降解速度比两种母体聚合物都要慢。这归因于聚磷腈水解产物的缓冲能力，它将降解介质的pH从2.5提高到4，从而减缓了PLGA的降解速度。
