Design New Model Of Polycation Gene Carrier

In the present study, for one thing, a new type of well-defined WSLP gene carrier consisting of hydrophilic poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) and hydrophobic cholesterol (Chol-PDMAEMA₃₀) was prepared by a one-step synthesis route via oxyanion-initiated polymerization; for another, a facile route for DNA encapsulation in triggered intracellular degradable polymer microcapsules has been achieved via electrostatic interaction, using a polycation, Chol-PDMAEMA₃₀, along with a polyanion named MePEG2000-block-poly- (methacrylic acid) carring partial thiol groups (MePEG2000-b-PMAA_SH), which was also prepared via oxyanion-initiated polymerization. The encapsulation procedure involves three steps: (i) DNA was first complexed with the polycation (Chol-PDMAEMA₃₀); (ii) To overcome the limitations of the positively charged complexes, MePEG2000-b-PMAA_SH, was used to coat the Chol-PDMAEMA₃₀/DNA complexes by electrostatic interaction; and (iii) the complexes were stabilized by oxidizing the thiol groups to form bridging disulfide linkages between the MePEG2000-b-PMAA_SH chains. The properties of Chol-PDMAEMA₃₀, and the interactions between every pair among calf thymus DNA, Chol-PDMAEMA₃₀, and MePEG2000-b-PMAA_SH were studied by critical micelle concentration determination, agarose gel retardation assay and ethidium bromide displacement assay. The results indicate that the prepared microcapsules may remain stable during systemic circulation, but degrade and release the carried DNA in a cellular reducing environment. The studies on chain-exchanging reaction indicate that the excess MePEG2000-b-PMAA_SH will lead to the aborted binding of Chol-PDMAEMA₃₀ with DNA and the amount of MePEG2000-b-PMAA_SH is appropriate when the [MAA]/[DMAEMA] molar ratio is in the range of 1.0-1.5. However, the results of further investigation showed that the exchange reaction may be beneficial for the DNA release when the disulfide linkages are destroyed in cells. Furthermore, the biophysical properties of the microcapsule have been investigated byζ-potential, laser light scattering, and transmission electron microscopy (TEM) measurements.