Chitosan chip and application to evaluate DNA loading on the surface of the metal.

The plasmid DNA (pDNA) loading by cationic polymers or/and cationic lipids is essential for gene therapy, especially for metal implants such as stents and artificial joints. Polycations can condense with pDNA by self-assembly, forming polyplexes spontaneously as a result of electrostatic interactions to carry and transfer pDNA in vivo. Cationic polymers, such as chitosan, can also protect pDNA from degradation by DNase. In this study, a chitosan chip was prepared and loaded with pDNA layer-by-layer with polycation/cationic lipids. By real-time surface plasmon resonance (SPR) sensorgram, pDNA loading ability, layer stability and protective effect on pDNA from DNase degradation have been detected. Chitosan can increase the pDNA loading amount of N-(1-(2,3-dioleoyloxy)propyl)-N, N, N-trimethylammonium methyl sulphate (DOTAP) and Lipofectmine 2000 (Lipo) on the chip surface. Different flow rates can affect the pDNA loading on the chitosan chip, and it is not significant at a lower flow rate. The pDNA protection by chitosan with different molecular weights from DNase degradation was also tested. Polycationic chitosan with higher molecular weight (> or =200 kDa) can fulfil the requirements for effective gene protection from DNase degradation. The results of this study present a platform for further optimization studies of polycation-based gene delivery systems.