DNA encapsulation within co-guanidine membrane coated alginate beads and protection from extracapsular nuclease

Co-guanidine membranes were shown to form intact, ionically complexed membr anes on alginate beads, serving as an alternative to the commonly used poly mers, poly-L-lysine and chitosan. DNA was encapsulated and membrane thickne ss, the level of DNA protection from nuclease diffusion and the degree of D NA-complexation with co-guanidine membranes were all shown to be dependent on both polymer concentration and coating time. The highest level of DNAse exclusion was possible within beads coated with a polymer concentration of 5mg/ml. Recovery of double-stranded DNA after nuclease exposure for 60 min reached 90% of that initially encapsulated. The molecular weight cut-off fo r these co-guanidine membranes was approximately 31kDa, sufficient to exclu de extracapsular nuclease. The level of DNA protection was found to be comp arable to high molecular weight poly-L-lysine membranes (197.1kDa). Intraca psular DNA was accessible to the carcinogen ethidium bromide, which showed a 4-fold increase in uptake in uncoated beads and 2-fold uptake in co-guani dine coated beads compared to beads lacking in DNA. Co-guanidine membranes coating alginate result in a molecular weight cut-off sufficient to retain DNA and exclude 31kDa DNAse, while providing access to the low molecular we ight carcinogen, ethidium bromide.