Lipoplex serum stability

Figure 4 Effect on the serum stability of the incorporation of 5% cholesterol poly(ethy-lene glycol) (PEG) into cationic lipoplexes [hpopolyamine RPR209120/DOPE1/1, ratio (mol) lipid/DNA = 10 in 150 mM NaCl]. Lipoplexes were incubated in DMEM + 10% SVF, at 37°C, aliquots were regularly sampled and monitored by dynamic diffusion. Results represent a mean between three measurements. Error bars are not presented to simplify the graph, but differences among PEG, PEG-1, and PEG-2 are significant. Abbreviations PEG, poly(ethylene glycol) DOPE, dioleylphosphatidylethanolamine DMEM, Dulbecco s Modified Eagle Medium.

Our laboratory mostly works with PEG-cholesterol. It is easily obtained in one step by addition of cholesteryl chloroformate and amino-methoxy-PEG (31). Introduction of a linker between the cholesterol and the PEG part would induce higher membrane fluidity and reduce more efficiently protein interactions as compared to PEG-cholesterol. A diaminobutane spacer was shown to improve significantly the sustained release of calcein from lipoplexes incubated in 30% serum (32). The spacer effect on bicatenar PEG-lipid has not been intensively studied because it can be expected that it would induce less effect on PEG-dioleoyl than on PEG-cholesterol, the lipidic anchor being predominant in the bilayer stabilization (Fig. 2). 

Audouy S, Molema G, de Leij L, Hoekstra D (2000) Serum as a modulator of lipoplex-mediated gene transfection dependence of amphiphile, cell type and complex stability. J Gene Med 2(6) 465 176... 

Aggregation of lipoplexes in polyelectrolyte solutions occurs rapidly, which can result in loss of activity in less than 24 hours thus, strategies are being developed to stabilize the particles and prolong their shelf life. To improve lipoplex stability, PEG-PE has been incorporated into the cationic liposome. PEG containing liposomes are prevented from aggregating and interacting with serum components, which increases their stability [181-183]. Alternatively, new preparation methods... 

A lot of work has been done to find out how lipoplexes and lipoplex-ceU interactions respond to the presence of serum. Many relevant references are cited in a paper published in 2002 that reports how lipoplex stability and processing are affected by serum. The cationic surfactant carrier was SAINT-2 using DOPE as the helper lipid. Previous studies had already shown that transfection efficiencies are reduced in the presence of serum, in... 

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