Nontoxic lipid preparation

We showed the existence of a toxic and a nontoxic lipid A fraction in the acid hydrolyzed endotoxin preparation (23). These two fractions were separated and the composition was determined on the purified components so that we could relate specific structural features of lipid A to both toxicity and tumor regression activity (23). 

Figure 1 shows the scheme for the preparation of purified lipid A from endotoxin. S. typhimurium G30/C21 was extracted by the method of Galanos t aK (24) and submitted to one of two different conditions of hydrolysis (a) 0.1 N HC1 [in methanol-water (1 1, v/v)], 100 °C, 45 min, to yield the crude monophosphoryl lipid A (nontoxic), and (b) 0.02 M sodium acetate, pH 4.5, 100 °C for 30 min (two cycles) to yield the crude diphosphoryl lipid A (toxic). The 0.1 N HC1 hydrolysis product was fractionated on a Sephadex LH-20 column (23). Each of these fractions was then separated by preparative thin layer chromatography (TLC) on silica gel H (500 ym), with the solvent system chloroform-methanol-waterconcentrated ammonium hydroxide (50 25 4 2, v/v) as previously described (23) to yield TLC fractions 1-7 and 1-9 respectively. 

In conclusion, we have designed a synthetic vesicular DNA carrier that physically and functionally mimics an enveloped virus particle. To achieve an acceptable degree of encapsulation within the vesicle, we use a process that is essentially inverse to the preparation of cationic lipid-DNA complexes. A suitable DNA condensing agent is introduced that, at a certain critical concentration, conveys a weak net cationic charge to the condensed DNA that then interacts spontaneously with a liposome containing one or more anionic components. These DNA formulations behave distinctly different from classic cationic liposome DNA complexes in vitro in as much as they have been shown to be nontoxic, to display a traditional linear dose response, and to be serum-insensitive. 

Experimental data together with the fact that resorcinolic lipids are nontoxic to higher animals, for example, they are tolerated by rats with an oral intake of 5g/kg ([204] and Kozubek, unpublished work) has resulted in the application of these compounds, as basic components in pharmaceutical and cosmetic preparations. These preparations were found to be useful in the treatment of mouth and gingival infections, as antifungal fluids, in antiacne and also in hair restoration-lotion preparations [309,312,314]. 

Documented effects In experiment on animals (mice and rats), the preparation Dipsacozide (total plant saponins) was nontoxic and caused short-term decrease in arterial pressure. It noticeably raised the animals tolerance to hypoxia, as found in foothill and high mountain conditions. In lipid metabolism Dipsacozide caused results similar to the known preparation Polysponin, and it also had hepatoprotective abilities (Alimbaeva et al. 1986). 

The carrier materials of many microparticle dispersion systems are usually synthesized polymers whose accumulation in vivo could cause possible toxicity. In contrast, stearic acid is a better material for microparticle dispersion system due to its biocompatibility and nontoxicity. Generally, as solid lipid with the above advantages, stearic acid can be used for preparation of solid lipid nanopartical (SLN), which is supposed to be more stable than emulsion or liposome due to solid form of stearic acid at room temperature. 

Sample preparation and extraction methods are critical since they can lead to destruction and/or incomplete extraction of lipids. For example, using acid digestions or nontoxic solvent extractions instead of proven methods with chlorinated solvents should be carefully investigated to ensure quantitative extraction. 

A presynthetic approach has also been used to prepare lipid-conjugated oligonucleotides (LONs) in order to improve cellular uptake and intracellular delivery of various ODNs. Thus, Grijalvo et al. [62] discovered lipid-siRNA with anti-inflammatory properties while Godeau et al. [63] synthesized nontoxic lipid-ON conjugates, which efficiently inhibit HCV internal ribosome entry site-dependent translation in human Huh7 cells. 

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