DQAsomes dequalinium

To prepare DQAsomes or vesicles composed of dequalinium derivatives, the appropriate amount of bola-lipid (10 mM final) was dissolved in methanol, dried using a rotary evaporator, suspended in 2.5 mL 5mM N-2-hydroxyethylpiperazine-N -2-ethane sulfonic acid (HEPES), pH 7.4, bath sonicated for about one hour followed by probe sonication for 45 minutes (10 W). The sample was then centrifuged for 30 minutes at 3000 rpm, the clear, or in some cases, opaque supernatant collected and the remaining non-solubilized residue lyophilized. The concentration of solubilized bola-lipid can be determined spectrophotometrically or can be inferred from the amount of recovered compound after lyophilization. 

Based on the intrinsic mitochondriotropism of dequalinium and its unique self-assembly behavior, we have developed a strategy for direct mitochondrial transfection (47-49), which involves the transport of a DNA-mitochondrial leader sequence (MLS) peptide conjugate to mitochondria using DQAsomes, the liberation of this conjugate from the cationic vector upon contact with the mitochondrial outer membrane followed by DNA uptake via the mitochondrial protein import machinery. We have demonstrated that DQAsomes fulfill all essential prerequisites for a mitochondria-specific DNA delivery system they bind and condense pDNA (24), protect it from... 

Dequalinium chloride (10 mM final) and paclitaxel (10 mM final) were dissolved in methanol in a round-bottom flask followed by removing the organic solvent with a rotary evaporator. After adding 5 mM HEPES, pH 7.4, the suspension was sonicated with a probe sonicator until a clear opaque solution of DQAsomes with encapsulated paclitaxel was obtained (usually for about one hour). To remove undissolved material, the preparation was centrifuged for 10 minutes at 3000 rpm. 

The solubility of paclitaxel in water at 25°C at pH 7.4 is 0.172mg/L (0.2 pM), extremely low, making any separation procedure of nonencapsulated paclitaxel from DQAsomes unnecessary i.e., in an aqueous environment, only paclitaxel encapsulated in DQAsomes would stay in colloidal solution. However, for control, a paclitaxel suspension was probe sonicated under identical conditions used for the encapsulation of paclitaxel into DQAsomes, but in the complete absence of dequalinium chloride. As expected, upon centrifugation, no paclitaxel was detectable in the supernatant using ultraviolet (UV) spectroscopy at 230 nm. 

The amount of dequalinium in DQAsomes was measured using fluorescence spectroscopy (ex. 335 nm, em. 360 nm). At these wavelengths, paclitaxel does not display any fluorescence and therefore does not interfere with the determination of dequalinium. For measurements, 3 pL DQAsomes were dissolved in 3mL methanol, resulting in a concentration of dequalinium, which lies within the linear range of a previously determined standard curve. 

In a reproducible way, paclitaxel can be incorporated into DQAsomes at a molar ratio paclitaxel to dequalinium of about 0.6. In comparison to the free drug, encapsulation of paclitaxel into DQAsomes increases the drug s solubility by a factor of about 3000. 

Weissig V, Lasch J, Erdos G, Meyer HW, Rowe TC, Hughes J. DQAsomes a novel potential drug and gene delivery system made from Dequalinium. Pharm Res 1998 15(2) 334-337. 

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