Electrochemical sensing of the behaviour of oligonucleotide lipoplexes at charged interfaces

Abstract

Complexes between short oligodeoxynucleotides (ODN) with a variable dG x dC y base composition and liposomes composed of the cationic lipid DOTAP (ODN lipoplexes) were studied by differential pulse voltammetry at a glassy carbon electrode. Since lipoplexes are spontaneously formed by electrostatic interactions, the objective of the voltammetric study was to investigate their behaviour at the electrode surface/solution interface. It was verified that the peak current in the voltammograms for ODN lipoplexes was due to guanosine oxidation and that it was influenced both by the applied adsorption potential and the lipoplex (±) charge ratio used. It was found that for low ODN lipoplexes (±) charge ratios the peak current obtained was enhanced when compared to that registered with free ODN for the same concentration. This allowed a higher sensitivity in the determination of ODN by differential pulse voltammetry and a limit of detection of 5.5 ng/mL was achieved. A model that explains the organisation of ODN lipoplexes at the electrode surface/solution interface is proposed. The electrochemical results presented account for a better physicochemical characterisation of lipoplexes at charged interfaces, which can be important for the understanding and development of gene therapy vectors based on ODN lipoplexes.

Direct Evidence of Multicompartment Aggregates in Polyelectrolyte-Charged Liposome Complexes

“…There is now substantial evidence that, by adding polyions to a suspension of oppositely charged liposomes, polyion chains rapidly adsorb at the liposome surface (30)(31)(32)(33). To gain some energy, the adsorbed chains, repelling each other, reconfigure themselves at the surface in more or less orderly patterns (3,4).…”

An Alternative Approach to Quantify Partition Processes in Confined Environments: The Electrochemical Behavior of PRODAN in Unilamellar Vesicles

“…Another promising method in electrochemical sensing is the detection of molecules by using surface-modified electrodes containing vesicles or giants vesicles. [17][18][19][20][21] The adsorption and adhesion of vesicles play pivotal roles in many biological membrane processes. Also, as they can be doped with receptor moieties, they can mimic cell adhesion and can thus be used as targets to screen for membrane-active peptides.…”