Surface Roughness Values Closer to Bone for Titania Nanoparticle/Poly-lactic-co-glycolic Acid (PLGA) Composites Increase
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Surface Roughness Values Closer to Bone for Titania Nanoparticle/Poly-lactic-co-glycolic Acid (PLGA) Composites Increases Bone Cell Adhesion Huinan Liu1, Elliott B. Slamovich1 and Thomas J. Webster1,2 1 School of Materials Engineering, 501 Northwestern Avenue, 2 Weldon School of Biomedical Engineering, 500 Central Drive, Purdue University, West Lafayette, IN 47907, U.S.A. ABSTRACT Bone substitutes are often required to replace damaged tissue due to injuries, diseases and genetic malformations. Traditional bone substitutes, such as autografts, allografts, xenografts and metal implants, are far from ideal as each have their own specific problems and limitations. Bone tissue engineering offers a promising opportunity for bone regeneration in a natural way. However, currently the scientific challenges of bone tissue engineering lie in the development of suitable scaffold materials that can improve bone cell adhesion, proliferation and differentiation. The design of nanophase titania/polymer composites offers an exciting approach to combine the advantages of a degradable polymer with nano-size ceramic grains that optimize biological properties for bone regeneration. Importantly, nanophase titania mimics the size scale of constituent components of bone since bone itself is a nanostructured composite composed of nanometer hydroxyapatite crystals well-dispersed in a mostly collagen matrix. Previous studies have shown significant improvement in protein adsorption, osteoblast (bone-forming cell) adhesion and long-term functions on nano-grain ceramic materials compared to traditional micron-grain ceramic materials. This study used nanometer grain size titania dispersed in a model polymer (PLGA or poly-lactic-co-glycolic acid) matrix by using various sonication powers to increase osteoblast adhesion. The surface characteristics of the composites, such as topography, titania surface area coverage and surface roughness, were studied by scanning electron microscopy and atomic force microscopy. Of all the composites formulated in this study, osteoblast adhesion was the greatest on nanophase titania/PLGA (30/70 wt.%) sonicated at 118.75 for 10 minutes; this composite was the closest in terms of nanometer surface roughness compared to bone of all the composites formulated. In this manner, this study suggests that nanophase titania sonicated in PLGA under these conditions should be further studied for orthopedic applications. INTRODUCTION Bone itself is a nanostructured material composed of entities like proteins (collagen Type I) and hydroxyapatite crystals that have nanometer dimensions. For example, the dimensions of crystalline hydroxyapatite (HA) in natural bone are from 50-100 nm in length and 1-10 nm in diameter. Recent research in this field suggested that better osteoconductivity could be achieved if synthetic materials resembled the size of constituent components of bone.1-2 For example, Du et al. synthesized nano-HA/collagen composites with a similar porous microstructure to bone, and showed that cells within the c
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