Lipids drug delivery applications

Amphipathic peptides contain amino acid sequences that allow them to adopt membrane active conformations [219]. Usually amphipathic peptides contain a sequence with both hydrophobic amino acids (e.g., isoleucine, valine) and hydrophilic amino acids (e.g., glutamic acid, aspartic acid). These sequences allow the peptide to interact with lipid bilayer. Depending on the peptide sequence these peptides may form a-helix or j6-sheet conformation [219]. They may also interact with different parts of the bilayer. Importantly, these interactions result in a leaky lipid bilayer and, therefore, these features are quite interesting for drug delivery application. Obviously, many of these peptides are toxic due to their strong membrane interactions. 

The force-mapping method directly measures the enhancement of the mechanical stability of phase-separated multicomponent lipid bilayers caused by the added PS- -PEO amphiphilic diblock copolymer. In addition, the lipid bilayer-(PS-b-PEO) systems mimic membrane-Pluronic systems and provide a platform for obtaining a fundamental understanding of the role of amphiphilic block copolymers in drug delivery applications as well as being a biological response modifier. 

Mehnert, W. and Mader, K. (2001) Solid lipid nanopartides. Production, characterization and applications. Advanced Drug Delivery Reviews, 47, 165. 

Takenaga, M., Application of lipid microspheres for the treatment of cancer, Advanced Drug Delivery Review, 1996, 20, 209-219. 

As one increases the size of the cages, the cavity becomes sufficiently large to be used as a nanoreactor. In fact, nanometer size capsules or spheres made of lipid bilayers have been investigated for other applications including drug delivery. However, without modification, such vesicles are probably not suitable as reactors since the lipid bilayer is rather fluid, and the lipid molecules exchange with free lipids in solution. In order to use such vesicles as reactors, it is necessary to convert them into a robust... 

In the past decades, it has become more and more obvious that students and scientists of chemistry and engineering should have some understanding of surface and colloid chemistry. The textbooks on physical chemistry tend to introduce this subject insufficiently. Modern nanotechnology is another area where the role of surface and chemistry is found of much importance. Medical diagnostics applications are also extensive, where both microscale and surface reactions are determined by different aspects of surface and colloid chemical principles. Drug delivery is much based on lipid vesicles (self-assembly structure) that are stabilized by various surface forces. 

At the most fundamental level, monolayers of surfactants at an air-liquid interface serve as model systems to examine condensed matter phenomena. As we see briefly in Section 7.4, a rich variety of phases and structures occurs in such films, and phenomena such as nucleation, dendritic growth, and crystallization can be studied by a number of methods. Moreover, monolayers and bilayers of lipids can be used to model biological membranes and to produce vesicles and liposomes for potential applications in artificial blood substitutes and drug delivery systems (see, for example, Vignette 1.3 on liposomes in Chapter 1). 

Microemulsions, and Lipid-Based Drug Delivery Systems for Drug Solubilization and Delivery—Part I Parenteral Applications... 

Azone (laurocapram) is used extensively as a transdermal permeation enhancer, and has also found use in buccal drug delivery. It is a lipophilic surfactant in nature (Figure 10.4). Permeation of salicylic acid was enhanced by the pre-application of an Azone emulsion in vivo in a keratinized hamster cheek pouch model [35]. Octreotide and some hydrophobic compounds absorption have also been improved by the use of Azone [36], Azone was shown to interact with the lipid domains and alter the molecular moment on the surface of the bilayers [37], In skin it has been proposed that Azone was able to form ion pairs with anionic drugs to promote their permeation [38],... 

For example, the use of a conically shaped lipid, dioleoylphos-phatidylethanolamine (DOPE), in cationic liposomes helps the destabilization of the cellular membranes, leading to a more efficient delivery of plasmid DNA in cell culture.84 The structural diversity of the lipidic colloids offers great flexibility in their applications as drug delivery and drug targeting systems. 

Boomer, J. A., and Thompson, D. H. Synthesis of acid-labile diplasmenyl lipids for drug and gene delivery applications. Chem. Phys. Lipids 99(2) 145—153. 1999. 

---