Stabilizers used in nanocrystal based drug delivery systems

Nanocrystals have emerged as a viable tool to enhance oral bioavailability of poorly water soluble drugs. They also enable parenteral administration of these drugs as nanosuspensions. The high surface free energy due to the large surface area to volume ratio of nanocrystals, makes them prone to aggregation, that can lead to physical instability and loss of solubility/dissolution advantage. Stabilizers are incorporated into nanocrystalline formulations to prevent aggregation and these include excipients such as polymers and surfactants. They achieve stabilization by electrostatic repulsion and/or steric hindrance. This article focuses on phenomenon of aggregation in nanocrystal based formulations, stabilizers for inhibition of aggregation, classification of stabilizers, properties of stabilizers and the mechanisms involved in stabilization. A compilation of stabilizers, drugs stabilized, formulation types and techniques used for generation of nanocrystals have been presented. Current challenges and future trends in the field of stabilizers have also been highlighted.