Biomedical Engineering Reference
In-Depth Information
2
Definitions and Special Properties
Drug nanocrystals are particles consisting of pure drug only, and being by definition
in the nano size range, i.e. below 1,000 nm to a few nm. They are in the crystalline
state, due to this they are of cuboid shape. Trade names are NanoCrystal ® (élan, prev.
Nanosystems), DissoCubes ® (SkyePharma, prev. PharmaSol) and smartCrystal ®
(Soliqs/Abbott, prev. PharmaSol). Drug nanoparticles can also be amorphous.
In this case, in a strict sense they should not be called nanocrystals, trade name is
Nanomorph (Soliqs/Abbott). Because of the amorphous state and lack of ordered,
periodically repeating structure, they are spherical (Fig. 1 ).
There are different views how big a nanoparticle is. The above definition is based
on dimensional considerations, i.e. the complete nanometer range, and typically
used by most pharmacists. The US Food and Drug Administration (FDA), the
National Nanotechnology Initiative (NNI) and the new European Cosmetic regu-
lations consider nanoparticles as particles below 100 nm (Regulation (EC) No
1223 /2009; National Nanotechnology Initiative (NNI) 2001 ). This can be rationa-
lized by the increased toxicity risk when going below this size threshold (cf. 5, NCS
classes). Some colloid scientists consider a “real” nanoparticle below about 20 nm.
In case the nanocrystals or amorphous drug nanoparticles are dispersed in a
liquid, this is called “nanosuspension”. Nanocrystals can be dispersed in either
water or in non-aqueous dispersion media. Examples for non-aqueous media are
oils, paraffins, liquid polyethylene glycols (PEGs) but also solid PEGs. In the latter
case it is a solid nanosuspension or solid nanodispersion, analogous to classical
solid dispersions of particles or solid dispersions of solutes.
Fig. 1 Crystalline nanocrystals with cuboid shape ( left , Courtesy by Böhm ( 1999 ), Modified)
and nanoMorph amorphous drug nanoparticles of spherical shape due to lack of ordered crystal
structure ( right , Courtesy by Soliqs, Ludwigshafen, Germany)
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