Controlled release of poorly soluble compounds from alginate hydrogels

Alginate gels are widely investigated for delivery of drugs and nutraceuticals. However, because of its hydrophilic nature, many hydrophobic entities cannot be solubilized in the hydrogel. The problem of delivering hydrophobic compounds is not a trivial one; over 40% of the drugs developed in the past two decades are extremely hydrophobic. Although those lipophilic drugs can act as efficient therapeutic agents, their low bioavailability inhibits their implementation. Similar difficulty exists while attempting to deliver many other compounds that promote health, such as bioactive lipids, antioxidants, and vitamins, which are poorly soluble in water. In order to be able to exploit alginate gels as a matrix for these bioactive agents, clever schemes have to be implemented. This chapter will focus on some of the approaches to deliver poorly water soluble compounds in alginate. These include hydrophobically modifying the alginate, and incorporating micro- and nano-particles into the hydrogel. A special emphasis will be given to drug-containing microemulsions embedded in alginate hydrogels.