Electrophoretic extraction and analysis of DNA from chitosan or poly-L-lysine-coated alginate beads

Alginate beads containing entrapped DNA were produced using both external a nd internal calcium sources, and coated with chitosan or poly-L-lysine memb ranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level of DNA protection from nucleic acid h ydrolysis, simulating gastrointestinal exposure. A method was developed to extract and assay intracapsular DNA through a modified agarose electrophore sis system. Both external and internally gelled beads were permeable to DNa se (M-w = 31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic content alginate be ads offered a higher level of DNA protection compared with coated beads wit h low guluronic alginate. No apparent correlation was found with chitosan m embrane molecular weight and degree of deacetylation; however, increasing p oly-L-lysine molecular weight appeared to increase DNase exclusion from bea ds. At elevated levels of DNase exposure, DNA hydrolysis was evident within all coated beads with the exception of those coated with the highest molec ular weight poly-L-lysine (Mw 197.1 kDa), which provided almost total nucle ase protection. Optimal combination then for DNA protection from nucleases is a high guluronic alginate core, coated with high molecular weight poly-L -lysine.