Abstract
The application of dense gases in particle formation processes has attracted great attention due to documented advantages over conventional technologies. In particular, the use of dense CO2 in the process has been subject of many works and explored in a variety of different techniques. This article presents a review of the current available techniques in use in particle formation processes, focusing exclusively on those employing dense CO2 as a solute, co-solute or co-solvent during the process, such as PGSS (Particles from gas-saturated solutions®), CPF (Concentrated Powder Form®), CPCSP (Continuous Powder Coating Spraying Process), CAN-BD (Carbon dioxide Assisted Nebulization with a Bubble Dryer®), SEA (Supercritical Enhanced Atomization), SAA (Supercritical Fluid-Assisted Atomization), PGSS-Drying and DELOS (Depressurization of an Expanded Liquid Organic Solution). Special emphasis is given to modifications introduced in the different techniques, as well as the limitations that have been overcome.
Highlights
The application of dense gases in particle formation processes has attracted great attention due to documented advantages over conventional technologies
Smaller particles with a narrower size distribution were obtained which the authors explained to be due to the fact that the system solute/acetone/CO2 exist in one phase liquid solution for a wide range of CO2 molar fractions and added that, in systems with this behavior, the DELOS process is an alternative to the Gaseous Anti-solvent (GAS) process
Since Weidner and co-workers patented the Particles from Gas Saturated Solution (PGSS) process in 1994, several variations based on the same concept were developed in which dense CO2 plays different roles; as a solute in CPF and Continuous Powder Coating Spraying Process (CPCSP); as a co-solute for CAN-BD, SEA, SAA and PGSS-drying; and as a co-solvent in the DELOS
Summary
Particle formation processes using dense gases have emerged within the last two decades as a promising alternative technology to overcome some technical problems and limitations related to the use of conventional methodologies [1,2,3,4,5,6,7]. The PGSS technique was patented [21] by Weidner and co-workers in 1994 and presented [22] in the Third International Symposium on Supercritical Fluids in Strasbourg in the same year It is considered one of the most attractive CO2 based micronization processes because it does not rely on the solvent strength of CO2, it employs relatively low operating pressures and can totally eliminate the need for organic solvents [9]. PEG is a widely used hydrophilic polymer due to its biocompatibility and non-toxicity; it is used as a carrier material in the development of pharmaceutical and cosmetic formulations and was used by Weidner and co-workers to improve understanding on how process parameters influence final product properties For this purpose, dependencies of particle size distribution, morphology and bulk density on process parameters like pre-expansion pressure, pre-expansion temperature and gas to product ratio (GTP) were studied [20]. Melting Atomization (GAMA) process, in which the introduction of a co-axial air injection device in the typical PGSS precipitation vessel facilitated the yield of insulin-loaded solid lipid submicron particles and avoided agglomeration
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