Accelerated Formation of Bone-Like Apatite on Biodegradable Polymer Substrates

Abstract

Using an acellular simulated body fluid (SBF), bone-like apatite can be formed on a variety of biomaterials, bioactive or bioinert, after these materials have undergone appropriate treatment(s). This biomimetic apatite-forming process is now applied to tissue engineering scaffolds in an attempt to make the scaffolds osteoconductive. In the current investigation, to form bone-like apatite on polymers such as poly(L-lactic acid) (PLLA) and poly(glycolic acid) (PGA) which degrade fast in aqueous environment, a solution (5SBF) of five times the ion concentrations of SBF was used so that an accelerated apatite formation could be achieved on PLLA and PGA. It was shown that indeed apatite could be formed on PLLA and PGA in 5SBF within 24 hours and that the apatite formed in 5SBF was similar in morphology and composition to that formed in the classical biomimetic process employing SBF or 2SBF. Results obtained in this investigation are very useful for producing osteoconductive scaffolds for bone tissue engineering.

Nature-inspired discontinuous calcium coatings on polyglycolic acid for orthopaedic applications

“…The PGA meshes were maintained at the air-solution interface of a supersaturated solution of Ca(HCO 3 ) 2 and heat-treated at 33 °C for 6 h. The saturation gradient that formed due to evaporation and CO 2 degassing enabled the heterogeneous nucleation/growth of CaCO 3 along the PGA mesh at the air-solution interface. This technique overcomes several challenges presented by the existing techniques to coat PGA with hard minerals: the deposition temperature is below the onset of the glass transition temperature of PGA (35 °C) [1], and the exposure time is relatively short, thereby avoiding hydrolytic degradation [11], 12,13].…”

“…The low onset of the glass transition temperature of PGA (35 °C [1]) represents a key technical challenge in forming a mineral coating on the mesh. Hence, lowtemperature wet chemical techniques are a common way to coat PGA with apatite [11], 12,13]. However, these methods typically require extended exposure (up to 16 days) to simulated bodily fluids (SBF), which could severely compromise the mechanical strength of PGA due to hydrolytic degradation [14].…”

Composite Scaffolds for Bone Tissue Engineering

“…However, as polymers such as PLA degrades fast in the aqueous environment, normal biomimetic processes that have been developed for coating apatite on metals or ceramics [19] are not suitable for these polymers. Therefore, an accelerated biomimetic process was developed to coat PLLA scaffolds with a thin layer of apatite [20,21] . Apatite was found to form on PGA meshes and PLLA scaffolds (Fig.7), and with a dynamic environment, biomimetic apatite coatings could be produced on pores inside the scaffolds.…”