Dear Colleagues,

Currently, more than half of all new drug candidates that enter the development pipeline fail because they are insoluble in water. This state results in a low dissolution of these drugs, affecting their pharmacokinetics and pharmacodynamics, resulting in low bioavailability when ingested. The low solubility of the active substance in water causes changes in the absorption of the drug in gastric environments in fasting and fed states, resulting in the appearance of fasting–fed variables. In addition, low solubility in water leads to the impaired dose–response proportionality of the drug, the unexpected collapse of the drug after administration, decreased patient compliance and, consequently, low bioavailability.

One of the most common approaches is to increase the solubility, dissolution and bioavailability of the drug by reducing the particle size and increasing the surface area. Nanocrystal or nanosuspension technology is a popular approach aiming to increase the solubility, dissolution, and thus bioavailability of BCS Class II and IV drugs by reducing the particle size of drugs to nanoscale dimensions without an additional carrier system.

Nanosuspensions offer potential advantages such as a reduction in dose and therapy cost and avoiding dose dumping in the body, minimizing fast/fed state plasma level fluctuation and intersubject variability. These advantages have driven the rapid development of nanosuspension technology in recent decades.

There are many possible nanosuspension administration routes besides oral administration.

Polymer-based nanoparticles, one of the nano drug delivery systems, have also recently gained importance.

Polymer-based nanoparticles, or polymeric nanoparticles, are tiny solid and colloidal particles with sizes ranging from a few nanometers to 1000 nm, with versatile structures and morphologies. The active ingredients can be trapped inside the polymeric core or adsorbed on the surface. Polymer-based nanoparticles are produced using both natural and synthetic polymers using different techniques for desired properties. Most important advantages offered by the polymeric-based  nanoparticles include the following: they (a) provide controlled release to the desired site, (b) provide stability to labile molecules (e.g., proteins), and (c) provide ability to modify surfaces with ligands for stealth and targeted drug delivery purposes. They have been tested to deliver a wide range of drugs, such as small hydrophilic and hydrophobic drugs, vaccines, peptides, and biological macromolecules, via several routes of administration. 

They are widely used as targeted drug delivery systems in the treatment of many diseases, including cancer treatments.

This Special Issue, entitled "Novel Approaches in Drug Delivery Systems: Nanosuspension and Polymer-Based Nanoparticles", consists of studies on production methods, characterizations, in vitro and in vivo evaluations of nanosuspensions and polymeric nanoparticles—which have many advantages—and different administration routes of nanosuspensions and polymeric nanoparticles.

Dr. Nevin Çelebi
Guest Editor

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• nanocrystal
• wet milling
• high-pressure homogenization
• solubility
• dissolution
• bioavailability
• oral
• dermal
• pulmonary, polymer-based nanoparticles
• natural and synthetic polymers