Porous poly(α-hydroxyacid)/Bioglass® composite scaffolds for bone tissue engineering. I: preparation and in vitro characterisation

Abstract

Highly porous composites scaffolds of poly-D,L-lactide (PDLLA) and poly(lactide-co-glycolide) (PLGA) containing different amounts (10, 25 and 50wt%) of bioactive glass (45S5 bioglass ® ) were prepared by thermally induced solid-liquid phase separation (TIPS) and subsequent solvent sublimation. The addition of increasing amounts of bioglass ® into the polymer foams decreased the pore volume. Conversely, the mechanical properties of the polymer materials were improved. The composites were incubated in phosphate buffer saline at 37°C to study the in vitro degradation of the polymer by measurement of water absorption, weight loss as well as changes in the average molecular weight of the polymer and in the pH of the incubation medium as a function of the incubation time. The addition of bioglass ® to polymer foams increased the water absorption and weight loss compared to neat polymer foams. However, the polymer molecular weight, determined by size exclusion chromatography, was found to decrease more rapidly and to a larger extent in absence of bioglass ® . The presence of the bioactive filler was therefore found to delay the degradation rate of the polymer as compared to the neat polymer foams. Formation of hydroxyapatite on the surface of composites, as an indication of their bioactivity, was recorded by EDXA, X-ray diffractometry and confirmed by Raman spectroscopy.

Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

“…The addition of 15 vol.% Bioglass® tended to reduce the porosity by ~1% when compared to that of 100% PDLLA and of 2 vol.% PDLLA/Bioglass® foams. This is consistent with previous work where the porosity was also shown to decrease with increasing filler content (up to 40 wt.% Bioglass®) [12]. However, it has been reported that at high filler loadings the pore shapes become increasingly rugose, thereby resulting in a moderately less well-ordered structure [2,12].…”

“…PDLLA and PDLLA/Bioglass®-filled composite foams were prepared by TIPS and subsequent solvent sublimation, which has been described in detail elsewhere [12,13]. Monolithic foams were produced with dimensions of 90 mm diameter and varying in thickness 7-10 mm due to the shape of the vessel base used in fabrication.…”

“…The following foam systems were investigated: pure PDLLA and composite foams filled with two different amounts of Bioglass® particles, nominally referred to as 2vol.% and 15 vol.% foams. These compositions were chosen based on previous studies conducted on similar composite systems [12,14]. The weight and volume percentages of the Bioglass® phase are given in Table 1.…”

“…A system currently being developed is based on poly(D,L-lactide) (PDLLA)/Bio-glass®-filled composite foams produced by thermally induced phase separation (TIPS) [12]. Processing of materials using the TIPS method enables the production of foams which exhibit pore anisotropy, which may be controlled to enable the fabrication of scaffolds with tailored porosity appropriate to the tissue concerned [2,13].…”

Repair of critical size defects in the rat cranium using ceramic‐reinforced PLA scaffolds obtained by supercritical gas foaming

“…Working with polymerbased composites offers a wider range of mechanical properties closer to bone, osteocondution induced by ceramics and a better control of resorption rate. [25][26][27] Polymer-based foams can be processed in different ways: solvent casting/particulate leaching, 28,29 thermally induced phase separation, or emulsion freezedrying, 30-33 gas foaming. [34][35][36] The latter technique has the main advantage of avoiding the use of potentially toxic organic solvents.…”