Chapter 16 - Lipid-based nanocarriers for ocular drug delivery

Abstract

Ocular drug delivery remains challenging because of the complex nature and structure of the eye. Conventional systems, such as eye drops and ointments, are inefficient, whereas systemic administration requires high doses resulting in significant toxicity. There is a need to develop novel drug delivery carriers capable of increasing ocular bioavailability and decreasing both local and systemic cytotoxicity. Recently, the emergence of lipid-based nanocarriers has provided a viable means of enhancing the bioavailability of ophthalmic formulations. A number of these formulations have been found to be clinically active. Many nanostructured systems have been employed for ocular drug delivery and yielded some promising results. Solid lipid nanoparticles (SLNs) have been looked at as a potential drug carrier system since the 1990s. SLNs do not show biotoxicity as they are prepared from physiological lipids and are especially useful in ocular drug delivery as they can enhance the corneal absorption of drugs and improve the ocular bioavailability of both hydrophilic and lipophilic drugs. Also, SLNs allow autoclave sterilization, a necessary step toward formulation of ocular preparations. Recently, nanostructured lipid carriers (NLCs) and lipid drug conjugates (LDCs) have emerged as a new generation of SLNs to overcome problems of low entrapment efficiency and drug expulsion during storage.