Heat-curing polylactide for bone implants: Preparation and investigation on properties relevant to degradation

Abstract

Several processes have been used to produce polylactide for bone replacement. The challenge remains, however, to produce these devices by a simpler and more economical process. In this study, a method of combining powder and liquid parts was introduced. Star-shaped polylactides with molecular weights ranging from 3 to 16 kg/mol were synthesized and blended with a linear polylactide (Mw = 188 kg/mol) using the technique of emulsion solvent evaporation. The blends in a form of spherical powder were characterized by scanning electron microscopy, gel permeation chromatography, and particle size analysis. The heat-curing polylactide was fabricated by mixing the powder with triethylene glycol dimethacrylate, molded, and then heated in a hot water bath to solidify. The effects of powder composition in terms of amount and molecular weight of the star-shaped polylactide on mechanical properties were investigated. The results showed an increase in flexural strength with increase in the amount of star-shaped polylactide. The powder comprised star-shaped polylactide having the molecular weight of 10,770 g/mol, not less than 80wt%, offered the fabricated heat-curing polylactide with high strength ranging from 95 to 100 MPa. This formulation was further incorporated with hydroxyapatite to improve biocompatibility and subjected to degradation at 37°C. Mechanical test and weight loss determination together with biological test were conducted at certain times during degradation of the materials. Both materials with and without hydroxyapatite showed mechanical stability upon degradation for at least 6 months, but the one with hydroxyapatite revealed significantly better bioactivity at the end of 1-year follow-up study, making it the most promising material for bone implants.

Dual-Curing Polylactide for Resorbable Bone Cement

“…Powder Part: The star-shaped PLA (MW = 10,770 g/mol, L-form) was blended with the linear PLA (MW = 188,030 g/mol) at a weight ratio of 8/2. The blended PLA powder was prepared by emulsion technique to achieve a spherical powder [5]. Benzoyl peroxide (BPO), an initiator, was added in the powder part in various amounts as indicated in Table 1.…”

“…Its mechanical stability and bioactivity may enable a prospective application for bone implants. The 4-arm PLA was used in developing the heat-curing PLA [5]. Powder of the 4-arm and linear PLA blend was hardened by heat when mixed with the liquid of dimethacrylate.…”

Enhancing the mechanical properties of photosensitive binder jetting PLA via dual curing and thermal treatment

“…Dusunceli studied tensile relaxation on PLA and PLA/hydroxyapatite (HA) and found that both strain rate and temperature had great effects on the mechanical responses of the materials 26 . Our previous studies employed a three‐point bending test to investigate the flexural strength of PLA and PLA/HA under different degradation conditions 27,28 . Each mechanical testing method has its own benefits for certain applications.…”