Use of thin film freezing to enable drug delivery: a review

Pharmaceutical Cryogenic Technologies

“…TFF was also referred as ultra-rapid freezing (URF), spray forming, thermal spray coating, splat cooling, slat quenching solidifi cation, plasma or powder spray deposition, etc. (Overhoff et al 2009 ) . Recently, TFF has been used as a particle engineering technique to improve the dissolution profi les of poorly watersoluble drugs.…”

“…In TFF, more concentrated and thus more viscous solutions may be processed, as the droplets are not atomized. However, the thickness profi le of the fi lm along the radius of the frozen disk may change with viscosity (Overhoff et al 2009 ) .…”

“…In TFF, collection of the frozen thin fi lms of the feed liquid droplets leads to nearly 100% yields, whereas in SFD process yields were about 80% because of the result of entrainment of uncaptured particles in the atomized aqueous stream, particles attaching to the walls of collection vessels, and ineffi cient separation of the cryogen from the 10-100-m m frozen particles (Johnson 1997 ;Overhoff et al 2009 ) .…”

“…To date, it is not sure which of the aforementioned cryogenic processes is the most cryogenically effi cient (Overhoff et al 2009 ) .…”

“…Increased supercooling, in turn, increases the nucleation rate of frozen solvent particles while minimizing the time for frozen solvent particle growth. When the supercooling is extremely high (rapid freezing rate), with permission from Elsevier the formation of a vitrifi ed solution may occur in which the nucleation of crystals may be minimized or fully prevented, leading to an amorphous material (Yu 2001 ;Overhoff et al 2009 ) .…”