Retention and release of low molecular weight DNA from alginate beads

DNA was encapsulated in alginate beads and retention/release profiles deter mined spectrofluorometrically. A sharp drop in retention occurs within the 24 to 36 kDa range (40 to 60 base pairs). Alginate and calcium concentratio n during gelation appears to have minimal affect on retention. while decrea sing guluronic (G) content of the alginate strongly promotes release. In co ntrast, dextran release was not significantly affected by alginate G-conten t. This dependence of DNA release on alginate composition suggests a DNA-al ginate interaction hindering diffusion, to a larger extent than the effects of DNA molecular weight or alginate matrix permeability. Increased retenti on of oligonucleotides below the molecular weight cutoff was achieved by co valent conjugation of 5' C-12 amine modified DNA to the encapsulating gel m atrix.