Effect of blending tricalcium phosphate on hydrolytic degradation of a block polyester containing poly(L-lactic acid) segment

Resorbable composites with bioresorbable glass fibers for load-bearing applications. In vitro degradation and degradation mechanism

An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past.

Biological performance of a new β-TCP/PLLA composite material for applications in spine surgery:In vitro andin vivo studies

The objective of this research was to carry out an in vitro and in vivo study of the biological performance of PLLA/beta-TCP composite materials, to estimate the scope of their potential applications in bone surgery. Samples with increasing beta-TCP (0-60% w/w) contents were processed by injection molding. The in vitro study consisted of an evaluation of inflammatory potential by assaying the IL-1alpha secreted by monocytes, and then cell proliferation (counting) and phenotype expression (PAL and I collagen) in human osteogenous cells. The in vivo study was carried out using cylindrical implants of composite materials composed of composite materials containing 0 or 60% beta-TCP and pure beta-TCP, respectively. The implants were inserted in femoral sites in rabbits, using the Kathagen protocol. Each animal received a 60% implant, with either a 0 or a 100% implant in the contralateral femur, so that the materials could be compared with one another. Five animals were examined for each material and implantation period, giving a total of 30 animals. This study showed that adding increasing percentages of beta-TCP to a lactic acid polymer matrix stimulated the proliferation of human osteogenous cells and synthesis of the extracellular bone matrix in a dose-dependent manner. In vivo results indicate that, in comparison with pure PLA, tricalcium phosphate-containing composite materials had faster degradation kinetics, caused less inflammatory reaction, and promoted contact osteogenesis. The composite material containing 60% beta-TCP demonstrated a similar performance to pure tricalcium phosphate bone grafts in terms of osteogenesis, and is apparently compatible with the production of intra-osseous implants for situations representing high levels of mechanical strain.

In vitro degradation behavior of a novel bioresorbable composite material based on PLA and a soluble CaP glass

Poly(alpha-hydroxy acids), and in particular polylactic acid (PLA), are nowadays amongst the most used bioabsorbable materials. However, this polymer may not meet some application requirements due to inadequate mechanical properties and or its degradation characteristics. A possible strategy to tackle this problem is the incorporation of an inorganic phase into the polymeric matrix. In this work a new fully biodegradable composite material made with PLA and calcium phosphate soluble glass particles has been developed. The behaviour of the PLA/glass composite has been analysed during its degradation in simulated physiological conditions by means of weight loss, molecular weight and thermal properties analysis and electron microscopy observation. The results showed that the incorporation of phosphate glass particles into the polymer significantly accelerated the degradation of the PLA and induced the formation of calcium phosphate precipitates at the composite surface.

Novel polymer-synthesized ceramic composite-based system for bone repair: Anin vitro evaluation

The emergence of synthetic bone repair scaffolds has been necessitated by the limitations of both autografts and allografts. Several candidate materials are available including degradable polymers and ceramics. However, these materials possess their own limitations that at least in part may be overcome by combining the two materials into a composite. Toward that end, a novel approach to forming a polymer/ceramic composite has been developed that combines degradable poly(lactide-co-glycolide) microspheres and a poorly crystalline calcium phosphate that is synthesized within the microspheres, which are then fused together to form a porous three-dimensional scaffold for bone repair. The design, fabrication, and characterization of the composite microspheres, the calcium phosphate formed within these microspheres, and the formation of scaffolds were studied. The calcium phosphate formed was analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy, and was shown to be similar to native bone in both composition and crystallinity by controlling certain processing parameters such as mixing time, solution pH, and mixing temperature. Scaffolds with porous interconnected structures and mechanical properties in the range of trabecular bone were fabricated via precise control of polymer/ceramic ratios within the microspheres and scaffold heating times. This composite scaffold represents a new and important vehicle for bone-tissue engineering.

Effect of blending calcium compounds on hydrolytic degradation of poly(DL-lactic acid-co-glycolic acid)

To clarify the effect of blending calcium compounds with different acidity or basicity on the degradation of poly(DL-lactic acid-co-glycolic acid) (PLGA). composite materials composed of PLGA incorporated with 30 mass% of calcium dihydrogenphosphate (CDHP), calcium hydrogenphosphate, calcium phosphate, and calcium carbonate (CC) were prepared by mixing in dioxane followed by freeze-drying. The porous composite materials were then compressed to yield nonporous films with 0.5 mm thickness. The blend films and the unfilled films as a control were immersed in phosphate-buffered saline (pH 7.4) at 37 degrees C. Specimens were removed at 1, 2, 3, 4, 6, and 8 weeks and subjected to measuring of water absorption, mass loss, thickness change, and molecular weight. The temporal changes in appearance and measurements for the five materials differed from each other; especially, the CC blend differed from the other four materials. The degradation of PLGA decreased with increasing basicity of the calcium compounds blended. The most basic CC was most effective to delay the degradation, while the most acidic CDHP was least effective. However, even CDHP had appreciable degradation-delaying effects compared with unfilled PLGA. Thus, the findings of the present study suggest that degradation of PLGA can be varied by blending inorganic compounds with different basicity.