Supercritical fluid technique (SCF), in this case using supercritical CO₂ as a medium, offers promising approach of morphology changes of materials  and moreover reduction of particle size at moderate operating conditions. Thus SCF could be suitable for treatment of many thermally unstable compounds, for example the pharmaceuticals [1]. In this study a commercially supplied device Spe-ed SFE-4 (Applied Separations, USA) has been used for size reduction of selected biologically active substances cimetidine and caffeine. Procedures were carried out by techniques of rapid expansion of supercritical mixtures (RESS) or using supercritical CO₂ as an anti-solvent (GAS).

Submicron particles and nanoparticles of caffeine were prepared using RESS procedure; moreover the increasing of temperature caused the reduction of caffeine nanoparticles size and had an impact on the shape of the resulting particles. Cimetidine submicron particles were obtained using GAS method. In this case higher pressure leads to the smaller particles which have enormous tendency to agglomerate; the influence of higher temperature could be summarized as positive.

It is evident that the use of supercritical CO₂ could lead to interesting morphology modification, as well as to reduction of the particles size. This has a positive impact on improvements in the terms of bioavailability of drugs.

This work was supported by MSMT projects LO1203, LO1404 and SP2016/65.

References:

¹ Michael Turk, Particle formation with supercritical fluids, Supercritical Fluid Science and Technology, Vol. 6, Editor: Erdogan Kiran, Elsevier 2014