Background: In the current pharmaceutical industry, overcoming drug insolubility
is a daunting formulation challenge. The most active drugs (with receptor affinity and
specificity and low toxicity) are not necessarily the most druggable, lacking high solubility,
stability, permeability or absorption. Since insoluble drug particles show poor bioavailability,
one of the solutions to this problem is to aid dissolution rate (kinetic) and solubility
(thermodynamic) by nanosizing the drug. Thus, during the past few decades, several strategies
based on nanotechnology have been adopted to overcome these problems, which increase
production costs and require administration of large doses resulting in higher
cost/dose ratios. This review discusses techniques to improve bioavailability and solubility
through nanosuspensions, nanoparticles (NPs) as well as using various nanocarriers.
Methods: Bibliographic databases were screened for peer-reviewed research literature of recent
origin. The papers were selected based on the relevance to nanotechnological methods
for improving drug solubility.
Results: Synthesis of metal-based drug encapsulant or a drug conveyor constituting a metallo-
drug can affect the drug release potential and the rate of drug release. Carrier-free
nanocrystal colloidal delivery systems are found to efficiently solubilize drugs. Furthermore,
solid dispersions which are comprised of two components where a drug crystal (diameter D
50% < 20 μm) along with a carrier/disintegrant have been successfully employed. In the
area of self-emulsifying hydrophilic and hydrophobic drugs, micelles, liposomes, selfdispersing
tablets and emulsions as well as solid lipid NPs are good candidates for efficiently
transporting drugs. In addition, drug complexes with cyclodextrins, calixarenes, cucurbiturils
and dendrimers have also led to better solubility and bioavailability.
Conclusion: These approaches present significant improvements to the solubility and
bioavailability of existing drugs and future discoveries.