Applications of Supercritical Fluid in Alloplastic Bone Graft:  A Novel Method and in Vitro Tests

Abstract

In this study, supercritical fluid (SCF) technology is discussed in relation to biomaterial processing, especially the fabrication and processing of alloplastic bone graft. SCF offers excellent extraction properties for some compounds because of its favorable diffusivity, viscosity, zero surface tension, liquidlike density and solvating power, and other physical properties. The most desirable SCF solvent for extraction is supercritical carbon dioxide (SCCO 2 ), which is nontoxic, nonflammable, inexpensive, friendly to mankind, and environmentally benign and has mild supercritical conditions (T c ) 31.2 °C, P c ) 7.386 MPa). For the porous structure of porcine vertebra with its content of lipids, proteins, and inorganic substances in the cells and intercellular matrix, SCCO 2 combined with ethanol or glutaraldehyde (GA) is used to prepare novel porcine-derived bone grafts in three supercritical settings and one subcritical condition for control comparison. The biocompatibility of these novel bone grafts was tested with human MG63 osteoblast-like cells and mouse fibroblast 3T3 cells by MTT assay. The results revealed that materials processed by SCCO 2 combined with both ethanol and GA were not cytotoxic and allowed the differentiation and proliferation of test cells. The good performances of these novel bone grafts can be explained by the characteristics of SCF. Applications of SCF in biomaterials are very promising for bone regeneration and tissue engineering. Additional advanced in vitro and in vivo studies must be performed in the future for optimization.

Controlling the Porosity and Microarchitecture of Hydrogels for Tissue Engineering

“…Various techniques such as CO 2 -water emulsion templating [56][57][58][59][60] or the use of a cosolvent system have been developed to improve the ability of a dense gas to diffuse into a hydrophilic polymer and produce porosity. 61,62 Using dense gas CO 2 to generate porosity eliminates the use of surfactant or foam stabilizer that is required in conventional gas foaming techniques. 50,51 Emulsion templating involves forming a high internal phase emulsion (HIPE) that is composed of an external phase consisting of a curable polymer and an internal phase made of minute droplets.…”

Insight into Biological Apatite: Physiochemical Properties and Preparation Approaches

“…Once a substance reaches the supercritical state, its physical property becomes an intermediate between the fluid and gas phases. In particular, the substance shows fluid-like density and gas-like diffusivity and viscosity, which enables it to dissolve nonpolar solids [66, 74]. Even so, by adding certain modifiers such as ethanol and propane, the solubility of both non-polar and polar solids could increase in a supercritical fluid.…”

“…Such a resultant may be probably usable as a carrier or framework in bone engineering. However, it should be noted that most of the proteins like collagens cannot be extracted and would be remained in the bone samples [66] according to the extraction mechanism. In this case, most of the biological apatite crystals are embedded in the residual collagens and are hard to be observed (Figure 6).…”

Use of ozone on regeneration of 3D critical size bone defects

“…24 Thus, it is reasonable that these materials may soon replace autogenous bone as the material of choice in bone reconstruction. 44 However, some questions are still arguable. The main challenges for the manufacturability of 3D-printed alloplastic scaffolds lies in the alignment of factors such as crystallinity, pore interconnectivity, grain micro-geometry, cytotoxicity, and remodelability.…”