Lipids and their derivatives: by-products used as essential building blocks for modern drug delivery systems

Lipids, one of the major natural products, usually have high biocompatibility and low toxicity. Due to their proper physicochemical properties, they are the most commonly used materials for building modern drug delivery systems, especially nanocarriers. However, to impart new functions or to satisfy special requirements, the lipids can be modified or synthesized. Using lipids or lipid derivatives, various lipid-based drug or gene delivery systems have been developed and show potential in pre-clinical and clinical applications. In this article, the most commonly used lipids are discussed in terms of their properties and functions as drug carrier components, their chemical modifications, the formulation or composition of lipid-based nanocarriers, and their biomedical applications. This article provides a critical view and possible future directions of lipid-based drug delivery strategies.