The solubility dependent bioavailability problem has become a major hurdle in drug development processes. Drug nanocrystals have been widely accepted by the pharmaceutical industry to improve the bioavailability of poorly water-soluble drugs. Poorly water soluble drugs show many problems in formulating a dosage form. Micronization does not sufficiently to enhance bioavailability and so next step is nanocrystalization i.e. drug nanocrystals having size of 1-1000 nm whose main application is to enhance the saturation of solubility, rate of dissolution and bioavailability of poorly soluble or poorly permeable drugs. Pure drug nano crystals, generated by “bottom up” or “top down” technologies, facilitate a significant improvement on dissolution behavior of poorly soluble drugs due to their enormous surface area, which in turn lead to substantial improvement in oral bioavaibility. In this review article we are focusing on Bottom-up techniques due to its simplicity and more applicability towards industrial use. The final product from this process is a suspension of drug nanocrystals in a liquid stabilized by a surfactant or polymer so called nan-suspension and after solidification of nano-suspension, nano-crystals can be formulated. The main objective behind this review articles was to provide bottom-up techniques for the preparation of nano-crystals with various critical parameters which affects the process, the final particle size and stability of nanocrystal.
