Supercritical fluid processing applications in biomaterials

Abstract

Event Abstract Back to Event Supercritical fluid processing applications in biomaterials Michael Favaloro1, Hans Schonemann2 and Val Krukonis2 1 CompositeTechs, LLC, United States 2 Phasex, United States Introduction: The Supercritical Fluid (SCF) Process has been used as an enabling technology in the processing of biomaterials. Significant success has been achieved in the utilization of this process; however, the lack of understanding and knowledge of the technology has prevented increased usage. This paper describes the process in detail, provides advantages and disadvantages of the process as well as examples of existing applications, and discusses possible areas of further exploitation in the biomaterials community. Materials and Methods: An SCF is any substance above its critical point, i.e., above the temperature and pressure where distinct liquid and gas phases do not exist. It is a super-solvent, in that it can effuse through solid materials like a gas, and it can dissolve materials like a liquid. [1] SCF's are used in biomaterials for many applications. When compared to solvent extraction, supercritical fluids leave no trace solvents. Solvent residues and contaminants can be removed from polymers and high molecular weight oils. SCF's can separate, or fractionate organic materials into narrow bands of molecular weight, in some cases better than the molecular distillation process. Reactive monomers and molded implants can be purified. Materials can be dissolved and recrystallized into narrow particle size distributions. Similarly, organic materials can be dissolved and infused into microporous solids at low temperature, eliminating risk of thermal degradation.[3] Results and Discussion: Management of SCF's allows one to tailor a process for a variety of organic materials and applications, as shown in the following examples: SCF's can fractionate some polymers and chemicals that are unable to be separated even by molecular distillation. Some applications, such as medical implants, require extremely high levels of purification which are possible with SCF but not with conventional methods. The high temperatures required to increase vapor pressure of the monomers would result in degradation of the polymers, or, in some cases, the polymerization process would be affected. . Similar purification processing is in production for silk-like orthopedic structures used in medical implant applications. In the particle formation process, an organic material is ‘dissolved’ in the SCFand transferred to a chamber with lower pressure. The material precipitates, or recrystallizes, out of solution, and particle size is controlled. One example is with Beta- estradiol, a medical grade organic material. A fine, uniform particle size was achieved by recrystallization.[4] SCF's with dissolved polymers or organic constituents can be used to infiltrate microporous solids, and by reduction of pressure, the dissolved constituents that come out of solution remain within the solid.This process can be utilized to incorporate antibiotics and immunosuppressant or other anti-reject drugs into implants. The drugs could be utilized to reduce the risk of rejection of the implant by the body, or to provide a long term, slowly diffused antibiotic. Conclusion: SCF processing offers significant value to biomaterials engineers as a novel tool. . The process can be used to extract monomers and contaminants, purify raw materials and molded parts, manage particle size distribution, and infiltrate microporous components. Applications have been demonstrated and production is ongoing for medical implants.