Solid lipid microparticles as an approach to drug delivery

Introduction : Solid lipid particles have been introduced since the early 1990s as an alternative drug carrier system to emulsions, liposomes and polymeric microparticles. While lipid nanoparticles have been examined/the object of a substantial number of reviews, fewer are available on lipid microparticles despite their distinct advantages, including biocompatibility, ease of production and characterization, extended release properties and high loading. Areas covered : This review presents an overview of the advantages and drawbacks of lipid microparticles (LMs), i.e. lipid-based particles with dimensions in the micrometer range. Specific focus is on the role of the main excipients used for LMs formulations, lipids and surfactants, and their effect on LM properties. Furthermore, an update on preparation techniques and characterization methods are also presented, with particular emphasis on more recent technologies. The interaction of LMs with biological systems, and in particular with cells will be also reviewed. Moreover, the various LM administration routes will be examined, with special attention to most recent applications (i.e., pulmonary and nasal delivery). Expert opinion: LMs represents an attractive and versatile carrier system, however their pharmaceutical applicability has been rather limited. Investigation on the use of LMs for less established administration routes, such as pulmonary delivery, may provide further interest on the development of LM-based systems both in the industry and in the clinics.