Drying of a plasmid containing formulation: chitosan as a protecting agent

Molecular weight of chitosan was reduced by a chemical reaction and achieved low molecular weight chitosan (LMWC) was complexed with pDNA. Obtained nanocomplex suspensions were diluted by solutions of lactose and leucine, and these formulations were spray dried or freeze dried using a modified technique. Size, polydispersity index, zeta potential, intensity of supercoiled DNA band on gel electrophoresis, and transfection efficiency of reconstituted nanocomplexes were compared with freshly prepared ones.Size distribution profiles of both freeze dried, and 13 out of 16 spray-dried nanocomplexes remained identical to freshly prepared ones. LMWC protected up to 100% of supercoiled structure of pDNA in both processes, although DNA degradation was higher in spray-drying of the nanocomplexes prepared with low N/P ratios. Both techniques preserved transfection efficiency similarly even in lower N/P ratios, where supercoiled DNA content of spray dried formulations was lower than freeze-dried ones. Leucine did not show a significant effect on properties of the processed nanocomplexes. It can be concluded that LMWC can protect DNA structure and transfection efficiency in both processes even in the presence of leucine.While viral gene delivery systems are more efficient and targeted than non-viral gene delivery systems in transducing cells, there are serious concerns about their safety [1]. In addition, they have limited capacity for DNA packing and are not easy to produce. These major shortcomings have become a motive force for research on safe and efficient non-viral gene delivery systems. Polymers have received more attention because their ease of production and modification can be applied to overcome major defects of non-viral gene delivery systems such as low transfection, targeting efficiency and toxicity [2].Alongside efforts to make more safe and efficient gene carriers, it is necessary to make them stable during storage. Stability of non-viral gene delivery systems has