NANO FORMULATIONS

Liposomes as nanopharmaceuticals are formed from phospholipids and cholesterol in aqueous medium. Liposomes have a spherical phospholipid liquid crystalline phase, and are simply produced by dispersion of phospholipid in water by shaking.  This results in the formation of multilayer structures consisting of several bilayers of lipids.  Liposomes can entrap both hydrophilic and hydrophobic drugs and drug release can be targeted to specific sites.  Biocompatibility, biodegradability and low toxicity are the main advantages of liposomal delivery systems.

Polymeric nanoparticles possess the advantage of stability – both in storage and in vivo application.  For polymeric particles, the drug is entrapped within the polymer matrix, usually a biodegradable polymeric matrix. Polymer nanomedines typically fall into one of two categories: (a) polymer-drug conjugates for increased drug half-life and bioavailability, and (b) degradable polymer architectures for controlled release applications.

Nanocrystals are composed of tiny particles of hydrophobic drug stabilized with a small amount of excipient or surfactant.  The saturation solubility of the nanocrystals is highly related to the particle size, and solubility increases with particle size reduction due to the increased surface area, especially when the nanocrystals are below 300 nm.  In these suspension formulations, the rate-limiting step for drug absorption is the speed for drug particle dissolution into the in vivo fluid surrounding the drug formulation.