Effect of spacer attachment sites and pH-sensitive headgroup expansion on cationic lipid-mediated gene delivery of three novel myristoyl derivatives

Abstract

The transfection activity and physicochemical properties of the dimyristoyl derivatives from three novel series of double-chained tertiary cationic lipids were compared. Two of the derivatives were constructed as isomers with different linkages of the same bis-(2-dimethylaminoethane) polar headgroup and hydrophobic chains to the diaminopropanol backbone, while the third was designed with a hydrophilic region containing only a single ionizable amine group. Such systematic molecular changes offer a great opportunity to delineate factors critical for transfection activity, which in this work include the intramolecular distance between the hydrophobic chains and pH-expandability of the polar headgroup. The physical studies comprised a variety of techniques, including pK a determination, Langmuir monolayer studies, fluorescence anisotropy, gel electrophoresis mobility shift assay, ethidium bromide displacement assay, particle size distribution, and zeta potential. These studies are crucial in the development of lipid-based gene delivery systems with improved efficacy. Physicochemical characterization revealed that a symmetric bivalent pH-expandable polar headgroup in combination with greater intramolecular space between the hydrophobic chains provide for high transfection activity through efficient binding and compaction of pDNA, increased acyl chain fluidity, and high molecular elasticity.

Novel N,N ′‐diacyl‐1,3‐diaminopropyl‐2‐carbamoyl bivalent cationic lipids for gene delivery – synthesis, in vitro transfection activity, and physicochemical characterization

“…Samples were stirred for 30 min before measurement of TNS fluorescence intensity. Nonlinear fitting of the pH titration curves was performed using psi‐plot (version 7.01, Poly Software International, Pearl River, NY, USA) according to a modified version of the Henderson–Hasselbach equation where A is the minimum fluorescence, B is the difference between the maximum and minimum emission intensities, C is a parameter affecting the slope of the transition region, and D is equal to the acid dissociation constant (p K a ) of the cationic lipid [12]. Goodness‐of‐fit statistics were assessed within a 95% confidence interval.…”

“…This work is a continuation of a recent study highlighting the superior gene delivery mediated by the dimyristoyl derivative 1,3lb2 from the aforementioned series as compared to two other cationic lipid vectors, a conformational isomer and a monovalent analog [12]. It was determined that a symmetrical bivalent pH‐expandable polar headgroup, in combination with greater intramolecular space between the hydrophobic chains, promotes highly efficacious in vitro lipofection through efficient binding and compaction of pDNA, increased acyl chain fluidity and high molecular elasticity.…”

Lipid-based vectors for siRNA delivery

“…Tertiary amines have long been used for the delivery of genes, but have been found to have more uses regarding response to the pH of cells. For example, Spelios (2007) synthesized cationic lipids by using bis-(2-dimethylaminoethane) and mono-(2-dimethylaminoethane) as head groups through the linkage of a carbamate bond (Figure 1). The bis-heads lipids were more ionizable than mono-head ones; the pH-expandable polar head-groups and greater intramolecular distance between the hydrophobic chains formed assemblies that resulted in high transfection activity.…”

Physicochemical Characterization, Solubilization, and Stabilization of 9-Nitrocamptothecin Using Pluronic Block Copolymers

“…Measurement of micelle size and size distribution analysis was performed at room temperature by a dynamic light scattering technique with a Malvern Zetasizer Nano ZS particle sizer (Malvern Instruments Inc.). Results are reported as intensity‐weighted hydrodynamic diameters . The effect of dilution on the stability of the drug‐loaded micelles was evaluated by a simple serial dilution precipitation study .…”