Gene delivery using non-viral vectors (cyclodextrins) with pluronic-F127 and folic acid

Over the years, gene therapy has gained much attention across the field of research. The ability to deliver genes into cells offers the opportunities to treat various human genetic disease which results from mutation or deletion of gene(s). Effective gene delivery is highly dependent on its stability and ability to transfect across cell membrane and interferes with the host DNA. However, DNA is easily susceptible to enzymatic degradation and its large size and highly negatively charged surface are barriers towards successful transfection (1). Therefore, DNA has to be protected from degradation, neutralised and condensed into appropriate size for effective gene delivery. Currently, non-viral vectors are the preferred carrier systems as they are safer, and easier to manufacture. In this research, the use of β and γ-cyclodextrin as non-viral vectors with the incorporation of two different excipients (Pluronic-F127 and folic acid) at different concentrations to stabilise the formulation was investigated. These formulations were characterised in fresh and freeze dried forms. The freeze dried and fresh solutions of DNA were prepared with cyclodextrins (β or γ), folic acid and Pluronic-F127 as excipients in different ratios [(3:3:1, 10:10:1 and 20:10:1) excipient : cyclodextrin : DNA]. The DNA stability in the formulations was tested by determining the stability of DNA against enzymatic degradation (DNase test) using ultraviolet-visible spectroscopy. The degree of DNA inclusion into cyclodextrins was investigated using fluorescence spectroscopy. Fourier Transform Infrared Spectroscopy (FTIR) was employed to study the interaction between DNA and excipients. Scanning Electron Microscope (SEM) was used in observing the surface morphology and uniformity of formed freeze dried particles and thermal behaviour was studied using Differential Scanning Calorimetry (DSC). The formulations were also stored in high humidity (RH=76%) over 5 weeks to access storage stability. In addition, charge measurement was conducted to figure out the transfection efficiency in vivo. It was observed that incorporation of Pluronic-F127 produced the most stable formulations regarding enzymatic degradation, particularly in the freeze dried formulations. These formulations also show high percentage inclusion (>40%). Shift of peaks in FTIR data, appearance of uniform particulate as detected by SEM and changing in the denaturation temperature as demonstrated by DSC data for Pluronic-F127 containing formulations confirms clear interaction between Pluronic-F127 and the cyclodextrin/DNA complex which exhibits positive overall charge. DNA/cyclodextrin formulations containing Pluronic-F127 also showed high stability and protection for the DNA after storage at 76%RH. Overall, it was noted γ-cyclodextrin provide better protection and inclusion compared to β-cyclodextrin. In summary, Pluronic-F127 with β or γ -cyclodextrins is a promising combination to improve stability and delivery of DNA. References 1. Anchordoquy JT, Allison SD, Lorinda M, Girouard G 2001. Physical stabilization of DNA-based therapeutics. Drug Discovery Today. 6:463-470