ABSTRACT
The technical development and subsequent advancement of clinical
studies and ultimately commercial applications of various types of
nanoparticle drug formulations have accelerated over the last couple
of decades. These nanoparticle formulations have been pursued
as enabling technologies to achieve various modes of enhanced
drug delivery of therapeutic and diagnostic agents, including the
improved oral delivery of poorly water-soluble drugs in terms of
increased bioavailability, onset of action, and reduction of food
effects,1−3 improved targeted delivery of therapeutic agents,2−5 the reduction of toxicity, and enhancement in the efficacy of certain
agents2,3 and general improvements in dosing convenience and
compliance.1,2 In the field of drug delivery, the term nanoparticles encompasses a broad assortment of different types of nano-sized
particle structural motifs. Broadly speaking, the most common
nanoparticle structures used in oral drug delivery can be grouped
into two different categories: (i) pure drug nanoparticles consisting
of essentially 100% drug (with or without the addition of surface
stabilizers) in either a crystalline (nanocrystals)1,3 or noncrystalline
state6,7 and (ii) an assortment of different nano-sized structures in
which the drug is encapsulated or dispersed in a solid, semisolid, or
liquid state within a formulation matrix. In this latter category are
included polymeric nanoparticles,8 nanoemulsions,9 liposomes,10
and solid lipid nanoparticles,11 among others. Additional types of
nanostructured drug particles include dendrimers, quantum dots,
and various types of metal-based colloidal nanoparticles to which
a drug may be anchored via covalent or noncovalent mechanisms12
and which are outside the scope of this review.
