Scaffold

J O U R N A L O F M A T E R I A L S S C I E N C E : M A T E R I A L S I N M E D I C I N E 1 6 (2 0 0 5 ) 189 – 195

Hydroxyapatite porous scaffold engineered with biological polymer hybrid coating for antibiotic Vancomycin release
HAE-WON KIM 1,2 ∗, JONATHAN C. KNOWLES 2 , HYOUN-EE KIM 1 1 School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea 2 Divisionof Biomaterials and Tissue Engineering, Eastman Dental Institute, University College London, 256 Gray’s Inn Road, London WC1X 8LD, UK E-mail: hwkim@snu.ac.kr

The purpose of this study is to improve hydroxyapatite (HA) porous scaffolds via coating with biological polymer-HA hybrids for use as wound healing and tissue regeneration. Highly porous HA scaffolds, fabricated by a polyurethane foamreticulate method, were coated with hybrid coating solution, consisting of poly(ε-caprolactone) (PCL), HA powders, and the antibiotic Vancomycin. The PCL to HA ratio was fixed at 1.5 and the drug amounts were varied [drug/(PCL + HA) = 0.02 and 0.04]. For the purpose of comparison, bare HA scaffold without the hybrid coating layer was also loaded with Vancomycin via an immersion-adsorption method. Thehybrid coating structure and morphology were observed with Fourier transformed infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The effects of the hybrid coating on the compressive mechanical properties and the in vitro drug release of the scaffolds were investigated in comparison with bare HA scaffold. The PCL-HA hybrid coating altered the scaffold pore structure slightly,resulting in thicker stems and reduced porosity. With the hybrid coating, the HA scaffold responded to an applied compressive stress more effectively without showing a brittle failure. This was attributed to the shielding and covering of the framework surface by the coating layer. The encapsulated drugs within the coated scaffold was released in a highly sustained manner as compared to the rapidrelease of drugs directly adsorbed on the pure HA scaffold. These findings suggest that the coated HA scaffolds expand their applicability in hard tissue regeneration and wound healing substitutes delivering bioactive molecules. C 2005 Springer Science + Business Media, Inc.

1. Introduction Over the last a few years, the field of Tissue Engineering (TE) has expanded noticeably due to the increasingdemands of artificial tissues and organs [1]. A multitude of biological materials, such as bioactive ceramics and degradable polymers have been developed and designed to fulfill the requirements for specific uses [2]. The bioactive ceramics, such as calcium phosphates and silica or phosphate-glasses, are considered useful for hard tissue regeneration due to their physicochemical similarity to teethand bones [3–6]. In oral, maxillofacial, and orthopaedic applications, hydroxyapatite (HA) ceramics have been used mainly as non-load-bearing parts in the form of powders and granules [2, 3], or else, as composites with resins and polymers, offering systems with good osteoconductivity and bioactivity [7, 8]. Compared
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to dense bodies orgranules, the porous scaffolds are highly attractive for their biological benefits, such as osteoconductivity and fast bone ingrowth, due to high surface area and sufficient blood circulation [4, 5]. However, the intrinsically poor mechanical properties of HA, such as low compressive strength and fracture toughness restrict its application only to small sizes of granules and powders or non-load bearingimplant [2, 3]. In order to expand its applicability in hard tissue applications, the brittleness of HA needs to be overcome. The biological performance of HA can be improved by the administration of drugs, such as antibiotics, antitumor, and growth factors [9, 10]. The encapsulated drugs enhance the wound healing and tissue regeneration. Several trials have been made to entrap drugs within the...