Lipid nanocarriers as drug delivery systems

Nanotechnologies dedicated to medical applications are today defined under the term "nanomedicine". This discipline exploits the physical, chemical and/or biological properties of materials on the nanometric scale, which often differ from those observed on the micro- or macroscopic scale. Nanomedicine offers new hope for the prevention, early and reliable diagnosis and treatment of many diseases. The three main areas of application for nanomedicine are in vitro or in vivo diagnosis, therapy and regenerative medicine. This science was born over 40 years ago, even though it was not called nanomedicine, with Bangham's discovery of liposomes. Its development has benefited from nanotechnology concepts involving multidisciplinary research fields such as chemistry (organic, inorganic and polymeric), physical chemistry and pharmaceutical and medical sciences (pharmacists and clinicians).

When it comes to delivering active ingredients, the nanotechnologies developed must meet the requirements of vectorization, i.e. the need for better orientation of active ingredients towards their biological site of action, in order to increase efficacy and reduce toxicity. To meet this challenge, we are developing nanometric colloidal particulate systems resulting from the self-assembly of biodegradable molecules. Acting as cargo vessels for the transport, delivery and targeting of active ingredients, they are often referred to as nanovectors, nanocargos and, more recently, as "nanomedicines". Today, there are some 30 approved nanomedicines in the U.S., and more than 100 clinical trials involving nano-objects worldwide.

Nanoparticles used in nanomedicine can be divided into two main families: organic nanoparticles and inorganic nanoparticles. Among organic nanoparticles, lipid-based nanoparticles (liposomes) were the first to be developed, as they are composed of natural lipids already present in large quantities in the body, making them biocompatible and biodegradable. Taking advantage of this similarity with the living environment, a category of lipid systems has been developed and will be the subject of this article.

The purpose of this file is to present :

• the various lipid systems developed in research and clinical practice;

• lipid nanoemulsions by describing their manufacturing methods, as well as their formulation and stability ranges;

  the main parameters governing their encapsulation/loading properties for molecules of diagnostic or therapeutic interest, as well as their interaction behavior with the biological environment;

  examples of biomedical applications in oral and parenteral drug delivery, and in medical imaging....