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Lipid-Based Nanoparticles for siRNA Delivery
Published in Yubing Xie, The Nanobiotechnology Handbook, 2012
Bo Yu, L. James Lee, Robert J. Lee
In this model, after endocytosis, cationic lipids interact with anionic phospholipids within the endosome membrane, forming ion pairs that adopt non-bilayer structures. These interactions result in destabilization of both the LNP and endosome membranes. Electrostatic interaction between cationic lipid and anionic lipid further promotes the formation of an inverted hexagonal HII phase, which is a destabilizing structure. Molecular shape is used to describe the lipid polymorphism (Hafez and Cullis 2001). Lipids with a large head group and a small hydrocarbon tail can self-assemble into micelles (Figure 24.4a). Lipids with nearly equal head group and hydrocarbon cross-sectional areas, i.e., of cylindrical shape, prefer to form bilayers (Figure 24.4b). Meanwhile, lipids with a small head group and bulky cis-unsaturated hydrocarbon groups favor the HII phase (Figure 24.4c; Hafez and Cullis 2001, Hafez et al. 2001). Poly-cis-unsaturated lipids are the most effective in this regard. For instance, cationic lipids with C18:2 alkyl chains have been shown to have higher transfection efficiency than comparable cationic lipids with C18:1 chains (Heyes et al. 2005, Huang and Liu 2011).
Solid Lipid Nanoparticles for Anti-Tumor Drug Delivery
Published in Mansoor M. Amiji, Nanotechnology for Cancer Therapy, 2006
Ho Lun Wong, Yongqiang Li, Reina Bendayan, Mike Andrew Rauth, Xiao Yu Wu
The occurrence of lipid polymorphism is a phenomenon fairly unique to SLN as compared to other lipid formulations. Lipid polymorphism is referred to the multiple crystalline forms of solid lipids. One of these polymorphic forms, usually the one that forms perfect crystalline lattice, is more thermodynamically stable. For example, triglyceride has three forms, i.e., α-form, β-form, and β′-form. Among them, only the β-form is stable.36 The relatively less stable or meta-stable forms would eventually transform to the stable polymorphic form, leading to a number of challenges in the development of SLN formulations. Drug molecules are primarily loaded into SLN in the defects of the lattices of solid lipids. When the lipid molecules are converted from the metastable forms into the stable form, they become more orderly packed, and some of the defects in the lattices disappear. As a result, drug expulsion from the lipid core to the particle surface may occur, contributing to high initial burst release and drug leakage during storage.
Lipid-based liquid crystalline films and solutions for the delivery of cargo to cells
Published in Liquid Crystals Reviews, 2019
Marilyn Porras-Gomez, Cecilia Leal
Lipid polymorphism is particularly relevant when designing lipid-based lyotropic liquid crystals (LLCs) for biomedical applications such as drug and gene delivery. Most LLCs are lyotropic (i.e. resulting from the self-assembly of amphiphilic lipid molecules present in water or in a humid environment) [4]. LLCs can exist in bulk form, thin films or as particles suspended in solution and the stability of the phases depends sensitively upon the surfactant counterion [5,6]. The lamellar (i.e. composed by layers) [7], inverted [8] and normal [9] hexagonal, as well as cubic [10] LLCs phases have all been applied for the delivery nucleic acids into live cells and animals (Figure 1).