A general approach for DNA encapsulation in degradable polymer Microcapsules

We report a general and facile method for the encapsulation of DNA in nanoengineered, degradable polymer microcapsules. Single-stranded (ss), linear double-stranded (ds), and plasmid DNA were encapsulated into disulfide-cross-linked poly(methacrylic acid) (PMA) capsules. The encapsulation procedure involves four steps: adsorption of DNA onto amine-functionalized silica (SiO2+) particles; sequential deposition of thiolated PMA (PMA,,) and poly(vinylpyrrolidone) to form multilayers; cross-linking of the thiol groups of the PMA(SH) in the multilayers into disulfide linkages; and removal of the sacrificial SiO2+ particles. Multilayer growth was dependent on the surface coverage of DNA on the SiO2+ particles, with stable capsules formed from particles with up to 50% DNA surface coverage. The encapsulation strategy applies to nucleic acids with varied size and conformation and allows DNA to be concentrated over 100-fold from dilute solutions into monodisperse, uniformly loaded polymer capsules. The capsule loading can be controlled by the DNA:SiO2+ particle ratio, and for 1 mu m diameter capsules, loadings of similar to 1000 chains of 800 bp dsDNA and more than 10 000 chains of 20-mer ssDNA can be achieved. The encapsulated DNA was released and successfully used in polymerase chain reactions as both templates (linear dsDNA and plasmid DNA) and primer sequences (ssDNA), confirming the functionality and structural integrity of the encapsulated DNA. These DNA-loaded polymer microcapsules hold promise as delivery vehicles for gene therapy and diagnostic applications.