**4. Applications of hybrid nanocarriers**

Hybrid systems combine properties of two or more materials, thus, appear superior to individual material system. Usually, one component of hybrid system is active, whereas other is used to improve biocompatibility, circulation life and targeting. Many new hybrid systems use second material to improve efficiency of first materials. By suitable selection of materials, hybrid systems find wider applications in medical field. Hydrophilic polymers have been widely used to impart stealth property to nanoparticles. However, stealth coating does not improve or impart new functional aspect of nanoparticles. Thus, many researchers do not regard PEG coated as hybrid systems. Similarly, nanoparticles conjugated with targeting ligands cannot be regarded as hybrid system.
