Tris(2-aminoethyl)amine-based α-branched fatty acid amides - Synthesis of lipids and comparative study of transfection efficiency of their lipid formulations

Ionizable lipids based on branched fatty acids - An explorative study on Langmuir monolayers

Ionizable lipids are a class of pharmaceutical excipients with a main application in lipid nanoparticles for nucleic acid delivery. New ionizable lipids are needed to tune characteristics of lipid-based nucleic acid delivery systems, e.g. stability, nucleic acid loading capacity and binding strength, as well as bio-distribution. Herein, we present the synthesis of three novel ionizable lipids as putative excipients for lipid-based nucleic acid delivery systems. Langmuir monolayer experiments with classical surface pressure/area isotherm evaluation were used to understand the self-assembly behavior of the lipids. Additional experiments with surface sensitive techniques, namely grazing incidence x-ray scattering and infrared reflection-absorption spectroscopy (IRRAS), were performed to understand structural characteristics of lipid associates. The latter technique was also used to investigate the nucleic acid binding process between DNA and the ionizable lipids. Finally, first transfection experiments with the novel lipids formulated as cationic liposomes were performed providing first efficacy data. Although the alkyl chain pattern was comparable for all three ionizable lipids, the results demonstrated that with increasing head-group size the DNA binding capacity changed and the alkyl chain fluidity was increased. The lipid with the lowest phase transition temperature and the smallest packing parameter showed the highest DNA transfer efficiency.

Lipoplex-Functionalized Thin-Film Surface Coating Based on Extracellular Matrix Components as Local Gene Delivery System to Control Osteogenic Stem Cell Differentiation

A gene-activated surface coating is presented as a strategy to design smart biomaterials for bone tissue engineering. The thin-film coating is based on polyelectrolyte multilayers composed of collagen I and chondroitin sulfate, two main biopolymers of the bone extracellular matrix, which are fabricated by layer-by-layer assembly. For further functionalization, DNA/lipid-nanoparticles (lipoplexes) are incorporated into the multilayers. The polyelectrolyte multilayer fabrication and lipoplex deposition are analyzed by surface sensitive analytical methods that demonstrate successful thin-film formation, fibrillar structuring of collagen, and homogenous embedding of lipoplexes. Culture of mesenchymal stem cells on the lipoplex functionalized multilayer results in excellent attachment and growth of them, and also, their ability to take up cargo like fluorescence-labelled DNA from lipoplexes. The functionalization of the multilayer with lipoplexes encapsulating DNA encoding for transient expression of bone morphogenetic protein 2 induces osteogenic differentiation of mesenchymal stem cells, which is shown by mRNA quantification for osteogenic genes and histochemical staining. In summary, the novel gene-functionalized and extracellular matrix mimicking multilayer composed of collagen I, chondroitin sulfate, and lipoplexes, represents a smart surface functionalization that holds great promise for tissue engineering constructs and implant coatings to promote regeneration of bone and other tissues.

Malonic acid based cationic lipids - The way to highly efficient DNA-carriers

Cationic lipids play an important role as non-viral nucleic acid carriers in gene therapy since 3 decades. This review will introduce malonic acid derived cationic lipids as nucleic acid carriers which appeared in the literature dealing with lipofection 10years ago. The family of amino-functionalized branched fatty acid amides will be presented as well as different generations of malonic acid diamides. Both groups of cationic lipids yield lipid mixtures with highly efficient nucleic acid transfer activities in in-vitro cell culture models. The DNA transfer screening of lipid libraries with directed structural variations in the lipophilic as well as in the hydrophilic part of the amphiphiles yields structure/activity relationships. Furthermore, the detailed characterizations of selected lipid composites at the air/water interface and in bulk systems are summarized with regard to transfection determining physical-chemical properties. The findings are also discussed in comparison to results obtained with other families of cationic lipids.