Hydroxyapatite/poly( ε-caprolactone) composite coatings on hydroxyapatite porous bone scaffold for drug delivery

• Published in: Biomaterials 2004-03, Vol.25 (7), p.1279-1287
• Main Authors: Kim, Hae-Won, Knowles, Jonathan C., Kim, Hyoun-Ee
• Format: Article
• Language: English
• Subjects: Absorbable Implants; Anti-Bacterial Agents - administration & dosage; Anti-Bacterial Agents - chemistry; Body Fluids - chemistry; Bone Substitutes - chemical synthesis; Bone Substitutes - chemistry; Coated Materials, Biocompatible - chemical synthesis; Coated Materials, Biocompatible - chemistry; Composite coating; Compressive Strength; Diffusion; Drug Delivery Systems - methods; Drug Implants - administration & dosage; Drug release; Durapatite - chemistry; Elasticity; Hydroxyapatite (HA); Manufactured Materials; Materials Testing; Mechanical properties; Poly( ε-caprolactone) (PCL); Polyesters - chemistry; Porosity; Porous bone scaffold; Tetracycline - administration & dosage; Tetracycline - chemistry
• ISSN: 0142-9612; 1878-5905
• DOI: 10.1016/j.biomaterials.2003.07.003

Hydroxyapatite (HA) porous scaffold was coated with HA and polycaprolactone (PCL) composites, and antibiotic drug tetracycline hydrochloride was entrapped within the coating layer. The HA scaffold obtained by a polymeric reticulate method, possessed high porosity (∼87%) and controlled pore size (150–200 μm). Such a well-developed porous structure facilitated usage in a drug delivery system due to its high surface area and blood circulation efficiency. The PCL polymer, as a coating component, was used to improve the brittleness and low strength of the HA scaffold, as well to effectively entrap the drug. To improve the osteoconductivity and bioactivity of the coating layer, HA powder was hybridized with PCL solution to make the HA–PCL composite coating. With alteration in the coating concentration and HA/PCL ratio, the morphology, mechanical properties, and biodegradation behavior were investigated. Increasing the concentration rendered the stems thicker and some pores to be clogged; as well increasing the HA/PCL ratio made the coating surface be rough due to the large amount of HA particles. However, for all concentrations and compositions, uniform coatings were formed, i.e., with the HA particles being dispersed homogeneously in the PCL sheet. With the composite coating, the mechanical properties, such as compressive strength and elastic modulus were improved by several orders of magnitude. These improvements were more significant with thicker coatings, while little difference was observed with the HA/PCL ratio. The in vitro biodegradation of the composite coatings in the phosphate buffered saline solution increased linearly with incubation time and the rate differed with the coating concentration and the HA/PCL ratio; the higher concentration and HA amount caused the increased biodegradation. At short period (