Nanotechnology Applications for Natural Products Delivery

Natural products are fascinating molecules in drug discovery for their exciting structure variability and for their interaction with various biological targets, which represent the best approach to develop successful medications for many diseases. The scarce water solubility, low lipophilicity and inappropriate molecular size of many natural compounds, which undergo structural instability in biological milieu, rapid clearance and high metabolic rate, have severely limited their use in clinic. Nanomedicine represents an excellent tool to increase bioavailability and activities of natural products. Generally, nanosized delivery systems provide large surface area increasing dissolution properties and can overcome anatomic barriers. In addition, passive and active targeting can optimize the performance of the nanocarriers. Passive targeting takes advantage of the unique pathophysiological characteristics of inflamed and tumor vessels, enabling nanodrugs to accumulate in the tissues. The effect is called enhanced permeation and retention, generally obtained by the decoration with polyethylene glycol the vector surface. An intriguing strategy is to decorate the nanocarriers with special ligands in order to recognize and bind to target cells through ligand– receptor interactions. Although the active targeting strategy looks intriguing, nanodrugs currently approved for clinical use are relatively simple and generally lack active targeting or triggered drug release components.