Preparation and characterization of hydroxyapatite/poly(ethylene glutarate) biomaterials

Abstract

Hydroxyapatite/poly(ethylene glutarate) (HAp/PEG) biomaterial composites were prepared by ring-opening polymerization (ROP) of cyclic oligo(ethylene glutarate) (C-PEG) in porous HAp scaffolds. The HAp/C-PEG precomposites were prepared by immersing the porous HAp scaffolds in the mixture solution of C-PEG and dibutyl tinoxide catalyst overnight and polymerizing at 200 degrees C for 24, 48, and 72 h under vacuum. The successful ROP of C-PEG in the porous HAp scaffolds was corroborated by the signals of hydroxyl end-group of PEG shown in the (1)H NMR spectrum of the ROP-products extracted from the composites. PEG in the composites was present as a thin layer coating on the HAp grains and was evenly distributed throughout the samples. The PEG content was about 13-16 wt % and decreased with increasing polymerization time. Its molecular weight (M(w), weight average) measured by gel permeation chromatography was in the range of 4300-6800 g/mol. Compressive strength of the HAp/PEG composites was significantly increased from 3 MPa of the porous HAp scaffold to 11-15 MPa, depending on the PEG content in the composites. In vitro bioactivity of the HAp/PEG composites was studied by soaking in simulated body fluid (SBF) at 36.5 degrees C for 7-28 days. After prolonged soaking, the HAp nanocrystals precipitated from the SBF solution and formed as a layer of globular aggregates, coated on the composite surfaces. This result suggested that the HAp/PEG composite was a bioactive material.

Effect of ring‐opening polymerization condition on the characteristic and mechanical properties of hydroxyapatite/poly(ethylene glutarate) biomaterials

“…The crystalline peaks of HAp around 2θ = 31.7–32° were broadened after prolonged soaking in the SBF solution because of the overlapping of the low crystallinity and nanocrystallite size of newly formed HAp as previously reported. 23 In addition, an increase in intensity of 002 reflection at 25.8° 2 θ after prolonged soaking was observed, corresponding to the preferred orientation of newly formed HAp crystals in the c ‐plane. These results are due to the unique behavior of HAp—its precipitation from the SBF solution by consuming the Ca 2+ and PO 4 3− ions to form the HAp nanocrystals on the composite surfaces 23, 29…”

“…The spectrum did not show the signal of C H 2 OH end group at δ 3.6–4.0 ppm, indicating the successful synthesis of C‐PEG via cyclodepolymerization of PEG under high dilution condition. 23, 24 The as‐prepared cyclic with a conversion of 88% was obtained as a yellowish solid product. The $ \overline {M_{\rm n} } $ and $ \overline {M_{\rm W} } $ of the C‐PEG measured by GPC were 430 and 570 g/mol, respectively.…”

“…The composites were then soaked in the SBF solution at 36.5°C for various times using slow‐flowing systems as previously reported. 23 After predetermined soaking time, the HAp/PEG composites were removed from the soaking systems, gently washed with distilled water and dried at room temperature. The surfaces of the soaked HAp/PEG composites were investigated by XRD and SEM.…”

“…In the previous research, the preparation of composites between porous HAp impregnated with poly (ethylene glutarate) (PEG) was studied using ring‐opening polymerization (ROP) temperature at 200°C for 24–72 h. 23 It was found that PEG could flow out from the HAp scaffold, resulting in different amount of PEG within the HAp/PEG composites. When longer polymerization time was applied, the amount of ROP‐PEG in the composites decreased, leading to lower compressive strength of HAp/PEG composites.…”

Bioelastomers (Synthetic Polyester): Tissue Engineering

“…[37] Erythritol is a sugar substitute that is approved by the FDA. [69][70][71][72][73][74][75][76] Due to such a wide spectrum of starting materials, the macromolecular characteristics of the poly(erythritol dicarboxylate) (PErD) are diverse. Erythritol is absorbed by the body and excreted unaltered, implying that normal metabolic pathways continue to be unaffected.…”