Nanocapsules are nanoparticles with a core/shell structure. Nanocapsules consist of two major parts. The inner part is the core material comprised of one or more active ingredients, which may be solids, liquids, or gases. The outer part is the coating material that is usually a high molecular weight polymer (or a combination of such polymers), carbon, or oxide. The polymer can be chosen from a wide variety of natural and synthetic polymers. Normally, the coating material must be nonreactive to the core material, preferably biodegradable, and nontoxic if used for medicine. Other components, such as plasticizers and surfactants, may also be added to the nanocapsules.

Nanocapsules can be prepared by various methods with different mechanisms, including physical, chemical, physico-chemical, and mechanical ones. The structural, physical, and biomedical properties of nanocapsules depend sensitively on the processes used for sample preparation. For instance, the preparation procedure could control the size of the nano-capsules, the size distribution of the particles, the thickness of the shell, the size of the grains, the morphology of the nanocapsules, etc. Different nanocapsules may need to be synthesized by different types of preparation techniques. Some methods may be suitable for synthesis of only some typical nanocapsules.

In this section, we describe the most applicable nano-encapsulation procedures, including physical methods such as heat evaporation, arc discharge, laser/electron beam heating, sputtering, etc.; chemical methods such as chemical vapor deposition, solid-state reactions, sol-gel, precipitation, hydrothermal process, solvent process, latex process, oxidation process, polymerization, etc.; physicochemical methods such as coacervation-phase seperation, etc.; mechanical methods such as air suspension, pan coating, spray-drying and congealing, and multiorifice centrifugation. In this section, we concentrate mainly on the preparation procedures and leave the detailed description of the physical and biomedical properties to next two sections.

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