Gene Therapy Research Characterization Using DLS and Zeta Potential

Abstract

The use of antibodies, either covalently attached onto the surface of neutral and anionic liposomes or used in a complex, is also being investigated. Zeta potential measurements are being used to develop the most efficient formulations of liposomes, peptides, DNA complexes for transfection studies in vivo and in vitro.

Introduction

Gene therapy is the process by which genetic material is delivered, by means of a vector, to patients for a therapeutic purpose. Vectors are delivery vehicles - usually a virus or a liposome - used to transport the genetic material to target cells in the body.

Both cationic and anionic liposomes are currently being investigated as vectors for gene therapy and their effectiveness in transfection is being studied by research groups and pharmaceutical companies.

Cationic liposomes (positively charged) are complexed with DNA (plasmids) Fig. 1. The liposome:DNA ratio is seen to be essential for optimal transfection.

Figure 1 Cationic liposomes (positively charged) are complexed with DNA (plasmids)

Zeta potential measurements can be used to optimise the ratio required for particular liposomes with various plasmids Fig 2. The plot also shows the zaverage diameters of the complex formed at various plasmid:liposome ratios obtained from photon correlation spectroscopy (PCS) measurements. When the complex has either a high negative or positive zeta potential, the size is around 90nm.

Figure 2 Zeta potential measurements can be used to optimise the ratio required for particular liposomes with various plasmids

However, when the zeta potential approaches the iso-electric point, the zaverage diameter increases indicating aggregation of the complex. Zeta potential measurements in conjunction with PCS sizing measurements allows for detailed characterisation of such plasmid: liposome complexes.

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