The emergence of nanocomposite hydrogels allow for more site-specific and time-controlled delivery of drugs of different sizes at improved safety and specificity. Depending on the method of inserting drugs into the material, for example, dissolved, encased, or attached, the drug carrier will be named differently: nanoparticles, nanospheres (where the drug is evenly dispersed throughout the polymeric network), or nanocapsules (where the drug is surrounded by a polymer shell structure). The elastomeric nature of this material allows the hydrogels to obtain the shape of the targeted site and thus the hydrogels can be manufactured identically and used on all patients.
Hydrogels are controlled drug delivery agents that can be engineered to have desired properties. Specifically, hydrogels can be designed to release drugs or other agents in response to physical characteristics of the environment like temperature and pH. The responsiveness of hydrogels is a result of their molecular structure and polymer networks.
Hydrogel nanoparticles have a promising future in the drug delivery field. Ideally, drug delivery systems should, “…maximize the efficacy and the safety of the therapeutic agent, delivering an appropriate amount at a suitable rate and to the most appropriate site in the body”. Nanotechnology incorporated within hydrogels has the potential to meet all the requirements of an ideal drug delivery system. Hydrogels have been studied with a variety of nanocomposites including: clay, gold, silver, iron oxide, carbon nanotubes, hydroxyapatite, and tricalcium phosphate.
Nanoparticles, largely due to their size related physical properties, are highly useful as drug delivery agents. They can overcome physiological barriers and reach specific targets.  Nanoparticles’ size, surface charge and properties enable them to penetrate biological barriers that most other drug carriers cannot. To become even more specified, nanoparticles can be coated with targeting ligands. The ability of nanoparticles to deliver drugs to specific targets suggests the potential to limit systemic side-effects and immune responses.
The ability of nanoparticles to carry and release drugs is also largely dependent on characteristics which result from the small size and unique surface area to volume ratio of nanoparticles. Nanoparticles can generally carry drugs in two ways: drugs can either be bound to the outside of the nanoparticles or packed within the polymeric matrix of the nanoparticles. Smaller nanoparticles have higher surface area ratios and can thus bind a high quantity of drug, while larger nanoparticles can encapsulate more of the drug within its core. The best method of drug loading is dependent on the structures of the drug to be bound. Also, drug loading can occur as the nanoparticles are produced, or the drugs can be added to pre-existing nanoparticles. The release of drugs, depends largely on the size of the nanoparticle carrying it. Because nanoparticles can be bound to the surface of nanoparticles, which is large relative to the volume of the particles, drugs can be released quickly. In contrast, drugs that are loaded within nanoparticles are released more slowly.