PubMed · 14056248
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L SMITH. 1963. CERAMIC-PLASTIC MATERIAL AS A BONE SUBSTITUTE.. https://doi.org/10.1001/archsurg.1963.01310160115023
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Different biomaterials have been proposed as scaffolds for the delivery of cells and/or biological molecules to repair or regenerate damaged or diseased bone tissues. Particular attention is being given to porous bioceramics that mimic trabecular bone chemistry and structure. Chemical composition, density, pore shape, pore size, and pore interconnection are elements that have to be considered to improve the efficiency of these biomaterials. Commonly, two-dimensional (2D) systems of analysis such as scanning electron microscope (SEM) are used for the characterization and comparison of the scaffolds. Unfortunately, these systems do not allow a complete investigation of the three-dimensional (3D) spatial structure of the scaffold. In this study, we have considered two different techniques, that is, SEM and 3D synchrotron radiation (SR) micro-CT to extract information on the geometry of two hydroxyapatite (HA) bioceramics with identical chemical composition but different micro-porosity, pore size distribution, and pore interconnection pathway. The two scaffolds were obtained with two different procedures: (a) sponge matrix embedding (scaffold FB), and (b) foaming (scaffold EP). Both scaffolds showed structures suitable for tissue-engineering applications, but scaffold EP appeared superior with regard to interconnection of pores, surface on which the new bone could be deposited, and percentage of volume available to bone deposition.
Copolymers of (2-hydroxyethyl methacrylate) (HEMA) and methacrylamide monomers conjugated with amino acids were synthesized and crosslinked with ethylene glycol dimethacrylate. The resulting library of copolymers was mineralized in vitro using two distinct methods. In the first mineralization method, the copolymers were polymerized in the presence of a sub-micron hydroxyapatite (HA) suspension. In the second method, copolymers were mineralized with HA using a urea-mediated process. The mechanical properties of all of the copolymers, both mineralized and not, were determined using nanoindentation under both load and displacement control. A power law fit to the initial unloading curve was used to determine a reduced elastic modulus for each material. Between 30 and 300 indentations were performed on each material, and ANOVA analysis was run to determine the statistical significance of differences in modulus between samples. Using nanoindentation, the 22 different samples had reduced modulus values ranging from 840 MPa to 4.14 GPa. Aspartic acid-methacrylate (Asp-MA) copolymers were not distinguishable from the pHEMA control material. Polymerization in the presence of HA created a more uniform material than the urea method of mineralization. Several challenges and solutions encountered in the nanomechanical testing of soft, heterogeneous materials are discussed. These results demonstrate that with proper experimental design, the mechanical properties of tissue engineering scaffold materials based on polymer-ceramic composite materials can be determined using small samples and nanoindentation techniques.
Depending on the coating method utilized and subsequent heat treatments (such as through the use of plasma-spray deposition), inter-diffusion of atomic species across titanium (Ti) and hydroxyapatite (HA) coatings may result. These events may lead to structural and compositional changes that consequently cause unanticipated HA phase transformations which may clearly influence the performance of an orthopedic implant. Thus, the objective of the present in vitro study was to compare the cytocompatibility properties of chemistries that may form at the Ti:HA interface, specifically HA, tricalcium phosphate (TCP), HA doped with Ti, and those containing calcium titanate (CaTiO(3)). In doing so, results of this study showed that osteoblast (bone-forming cells) adhesion increased with greater CaTiO(3) substitutions in either HA or TCP. Specifically, osteoblast adhesion on HA and TCP composites with CaTiO(3) was almost 4.5 times higher than that over pure HA. Material characterization studies revealed that enhanced osteoblast adhesion on these compacts may be due to increasing shrinkage in the unit lattice parameters and decreasing grain size. Although all CaTiO(3) composites exhibited excellent osteoblast adhesion results, Ca(9)HPO(4)(PO(4))(5)OH phase transformation into TCP/CaTiO(3) increased osteoblast adhesion the most; because of these reasons, these materials should be further studied for orthopedic applications.